Protective mechanical ventilation during general anesthesia for open abdominal surgery improves postoperative pulmonary function. Anesthesiology. 2013;118:1307-1321. [PMID: 23542800 DOI: 10.1097/aln.0b013e31829102de]

Determination of optimal positive end-expiratory pressure using electrical impedance tomography in infants under general anesthesia: Comparison between supine and prone positions

AIMS

This study determined the optimal positive end-expiratory pressure levels in infants in supine and prone positions under general anesthesia using electrical impedance tomography (EIT).

METHODS

This prospective observational single-centre study included infants scheduled for surgery in the prone position. An electrical impedance tomography sensor was applied after inducing general anesthesia. The optimal positive end-expiratory pressure in the supine position was determined in a decremental trial based on EIT and compliance. Subsequently, the patient's position was changed to prone. Electrical impedance tomography parameters, including global inhomogeneity index, regional ventilation delay, opening pressure, the centre of ventilation, and pendelluft volume, were continuously obtained up to 1 h after prone positioning. The optimal positive end-expiratory pressure in the prone position was similarly determined.

RESULTS

Data from 30 infants were analyzed. The mean value of electrical impedance tomography-based optimal positive end-expiratory pressure in the prone position was significantly higher than that in the supine position [10.9 (1.6) cmH2O and 6.1 (0.9) cmH2O, respectively (p < .001)]. Significant differences were observed between electrical impedance tomography- and compliance-based optimal positive end-expiratory pressure. Peak and mean airway, plateau, and driving pressures increased 1 h after prone positioning compared with those in the supine position. In addition, the centre of ventilation for balance in ventilation between the ventral and dorsal regions improved.

CONCLUSION

The prone position required higher positive end-expiratory pressure than the supine position in mechanically ventilated infants under general anesthesia. EIT is a promising tool to find the optimal positive end-expiratory pressure, which needs to be individualized.

Effect of postoperative intermittent boluses of subcostal quadratus lumborum block on pulmonary function recovery and analgesia after gastrectomy: a randomized controlled clinical trial

BACKGROUND

Following the gastrectomy, the reduction in pulmonary function is partly attributed to postoperative pain. Subcostal quadratus lumborum block (QLB) has recently emerged as a promising component in multimodal analgesia. We aimed to assess the impact of intermittent boluses of subcostal QLB on pulmonary function recovery and analgesic efficacy after gastrectomy.

METHODS

Sixty patients scheduled for gastrectomy were randomly assigned to either control group (multimodal analgesia) or intervention group (intermittent boluses of subcostal QLB plus multimodal analgesia). Two primary outcomes included the preservation of forced expiratory volume in the first second (FEV1) and the pain scores (0-10 cm visual analog score) on coughing 24 h postoperatively. We assessed the pulmonary function parameters, pain score, morphine consumption and number of rescue analgesia at a 24-h interval up to 72 h (Day1, Day2, Day3 respectively) as secondary outcomes.

RESULTS

59 patients were analyzed in a modified intention-to-treat set. The preservation of FEV1 (median difference: 4.0%, 97.5% CI: -5.7 to 14.9, P = 0.332) and pain scores on coughing (mean difference: 0.0 cm, 97.5% CI: -1.1 to 1.2, P = 0.924) did not differ significantly between two groups. In the intervention group, the recovery of forced vital capacity (FVC) was faster 72 h after surgery (interaction effect of group*(Day3-Day0): estimated effect (β) =0.30 L, standard error (SE) =0.13, P = 0.025), pain scores at rest were lower in the first 3 days (interaction effect of group*(Day1-Day0): β = - 0.8 cm, SE = 0.4, P = 0.035; interaction effect of group*(Day2-Day0): β = - 1.0 cm, SE = 0.4, P = 0.014; and interaction effect of group*(Day3-Day0): β = - 1.0 cm, SE = 0.4, P values = 0.009 respectively), intravenous morphine consumption was lower during 0-24 h (median difference: -3 mg, 95% CI -6 to -1, P = 0.014) and in total 72 h (median difference: -5 mg, 95% CI -10 to -1, P = 0.019), and the numbers of rescue analgesia was fewer during 24-48 h (median difference: 0, 95% CI 0 to 0, P = 0.043). Other outcomes didn't show statistical differences.

CONCLUSION

Postoperative intermittent boluses of subcostal QLB did not confer advantages in terms of the preservation of FEV1 or pain scores on coughing 24 h after gastrectomy. However, notable effects were observed in analgesia at rest and FVC recovery.

Semirecumbent Positioning During Anesthesia Recovery and Postoperative Hypoxemia: A Randomized Clinical Trial

Importance

The efficacy of a semirecumbent position (SRP) in reducing postoperative hypoxemia during anesthesia emergence is unclear despite its widespread use.

Objective

To determine the differences in postoperative hypoxemia between patients in an SRP and a supine position.

Design, Setting, and Participants

This randomized clinical trial was performed at a tertiary hospital in China between March 20, 2021, and May 10, 2022. Patients scheduled to undergo laparoscopic upper abdominal surgery under general anesthesia were enrolled. Study recruitment and follow-up are complete.

Interventions

Patients were randomized to 1 of the following positions at the end of the operation until leaving the postanesthesia care unit: supine (group S), 15° SRP (group F), or 30° SRP (group T).

Main Outcomes and Measures

The primary outcome was the incidence of postoperative hypoxemia in the postanesthesia care unit. Severe hypoxemia was also evaluated.

Results

Out of 700 patients (364 men [52.0%]; mean [SD] age, 47.8 [11.3] years), 233 were randomized to group S (126 men [54.1%]; mean [SD] age, 48.2 [10.9] years), 233 to group F (122 men [52.4%]; mean [SD] age, 48.1 [10.9] years), and 234 to group T (118 women [50.4%]; mean [SD] age, 47.2 [12.1] years). Postoperative hypoxemia differed significantly among the 3 groups (group S, 109 of 233 [46.8%]; group F, 105 of 233 [45.1%]; group T, 76 of 234 [32.5%]; P = .002). This difference was statistically significant for groups T vs S (risk ratio [RR], 0.69 [95% CI, 0.55-0.87]; P = .002) and groups T vs F (RR, 0.72 [95% CI, 0.57-0.91]; P = .007), but not for groups F vs S (RR, 0.96 [95% CI, 0.79-1.17]; P = .78). Severe hypoxemia also differed among the 3 groups (group S, 61 of 233 [26.2%]; group F, 53 of 233 [22.7%]; group T, 36 of 234 [15.4%]; P = .01). This difference was statistically significant for groups T vs S (RR, 0.59 [95% CI, 0.41-0.85]; P = .005).

Conclusions and Relevance

In this randomized clinical trial of SRP during anesthesia recovery in patients undergoing laparoscopic upper abdominal surgery, postoperative hypoxemia was significantly reduced in group T compared with group F or group S.

Trial Registration

Chinese Clinical Trial Registry Identifier: ChiCTR2100045087.

Comparison of lung aeration loss in open abdominal oncologic surgeries after ventilation with electrical impedance tomography-guided PEEP versus conventional PEEP: a pilot feasibility study

BACKGROUND

Existing literature lacks high-quality evidence regarding the ideal intraoperative positive end-expiratory pressure (PEEP) to minimize postoperative pulmonary complications (PPCs). We hypothesized that applying individualized PEEP derived from electrical impedance tomography would reduce the severity of postoperative lung aeration loss, deterioration in oxygenation, and PPC incidence.

METHODS

A pilot feasibility study was conducted on 36 patients who underwent open abdominal oncologic surgery. The patients were randomized to receive individualized PEEP or conventional PEEP at 4 cmH2O. The primary outcome was the impact of individualized PEEP on changes in the modified lung ultrasound score (MLUS) derived from preoperative and postoperative lung ultrasonography. A higher MLUS indicated greater lung aeration loss. The secondary outcomes were the PaO2/FiO2 ratio and PPC incidence.

RESULTS

A significant increase in the postoperative MLUS (12.0 ± 3.6 vs 7.9 ± 2.1, P < 0.001) and a significant difference between the postoperative and preoperative MLUS values (7.0 ± 3.3 vs 3.0 ± 1.6, P < 0.001) were found in the conventional PEEP group, indicating increased lung aeration loss. In the conventional PEEP group, the intraoperative PaO2/FiO2 ratios were significantly lower but not the postoperative ratios. The PPC incidence was not significantly different between the groups. Post-hoc analysis showed the increase in lung aeration loss and deterioration of intraoperative oxygenation correlated with the deviation from the individualized PEEP.

CONCLUSIONS

Individualized PEEP appears to protect against lung aeration loss and intraoperative oxygenation deterioration. The advantage was greater in patients whose individualized PEEP deviated more from the conventional PEEP.

Positive end-expiratory pressure and the incidence of postoperative pulmonary complications in patients undergoing general anaesthesia

AIM OF THE STUDY

To evaluate the effect of intraoperative positive end-expiratory pressure and driving pressure on the development of postoperative pulmonary complications.

METHOD

The prospective study included 83 patients undergoing abdominal surgery and receiving general anaesthesia. Patients were divided into two groups: with low intraoperative positive end-expiratory pressure (0-2cm H2O) and with high intraoperative positive end-expiratory pressure (8-10cm H2O). The primary endpoint is the development of postoperative pulmonary complications during follow-up.

RESULTS

The incidence of postoperative pulmonary complications in the group of low intraoperative positive end-expiratory pressure was 9.8%, while in the group of high positive end-expiratory pressure was 7.1% (p = 0.6), demonstrating that high positive end-expiratory pressure used during general anaesthesia does not affect the frequency of complications (odds ratio = 0.71, p = 0.6). In the multivariate analysis that controls for all confounders, driving pressure resulted in a significant and independent risk factor for complications.

CONCLUSION

High intraoperative positive end-expiratory pressure does not affect the frequency of postoperative pulmonary complications. The increase in driving pressure is a risk factor for complications. Positive end-expiratory pressure is easily implemented, and its use does not result in significant economic costs.

Intraoperative lung protection: strategies and their impact on outcomes

PURPOSE OF REVIEW

The present review summarizes the current knowledge and the barriers encountered when implementing tailoring lung-protective ventilation strategies to individual patients based on advanced monitoring systems.

RECENT FINDINGS

Lung-protective ventilation has become a pivotal component of perioperative care, aiming to enhance patient outcomes and reduce the incidence of postoperative pulmonary complications (PPCs). High-quality research has established the benefits of strategies such as low tidal volume ventilation and low driving pressures. Debate is still ongoing on the most suitable levels of positive end-expiratory pressure (PEEP) and the role of recruitment maneuvers. Adapting PEEP according to patient-specific factors offers potential benefits in maintaining ventilation distribution uniformity, especially in challenging scenarios like pneumoperitoneum and steep Trendelenburg positions. Advanced monitoring systems, which continuously assess patient responses and enable the fine-tuning of ventilation parameters, offer real-time data analytics to predict and prevent impending lung complications. However, their impact on postoperative outcomes, particularly PPCs, is an ongoing area of research.

SUMMARY

Refining protective lung ventilation is crucial to provide patients with the best possible care during surgery, reduce the incidence of PPCs, and improve their overall surgical journey.

Effect of incremental PEEP titration on postoperative pulmonary complications in patients undergoing emergency laparotomy: a randomized controlled trial

Postoperative pulmonary complications (PPC) has a significant negative impact and are associated with increased length of hospital stay and cost of care. Emergency surgery is a well-established risk factor for PPC. Previous studies reported that personalized positive end-expiratory pressure (PEEP) might reduce postoperative atelectasis and postoperative pulmonary complications. N = 168 adult patients undergoing major emergency laparotomy under general anesthesia were recruited in this study. A minimum driving pressure based incremental PEEP titration was compared to a fixed PEEP of 5 cmH2O. The primary outcome was PPC up to postoperative day 7. The mean (standard deviation) of the recruited patients was 41.7(16.1)y, and 48.8% (82 of 168 patients) were female. The risk of PPC at postoperative day 7 was similar in both the study groups [Relative risk (RR) (95% Confidence interval, CI) 0.81 (0.58, 1.13); p = 0.25]. In addition, the incidence of intraoperative hypotension [p = 0.75], oxygen-free days at day 28 [p = 0.27], duration of postoperative hospital stay [p = 0.50], length of postoperative intensive care unit stay [p = 0.28], and in-hospital mortality [p = 0.38] were similar in two groups. Incidence of PPC was not reduced with the use of an individualized PEEP strategy based on lowest driving pressure. However, the incidence of hypotension and bradycardia was also not increased with titrated PEEP.Trial Registration: www.ctri.nic.in ; CTRI/2020/12/029765.

Perioperative Care in Cardiac Surgery: A Joint Consensus Statement by the Enhanced Recovery After Surgery (ERAS) Cardiac Society, ERAS International Society, and The Society of Thoracic Surgeons (STS)

Enhanced Recovery After Surgery (ERAS) programs have been shown to lessen surgical insult, promote recovery, and improve postoperative clinical outcomes across a number of specialty operations. A core tenet of ERAS involves the provision of protocolized evidence-based perioperative interventions. Given both the growing enthusiasm for applying ERAS principles to cardiac surgery and the broad scope of relevant interventions, an international, multidisciplinary expert panel was assembled to derive a list of potential program elements, review the literature, and provide a statement regarding clinical practice for each topic area. This article summarizes those consensus statements and their accompanying evidence. These results provide the foundation for best practice for the management of the adult patient undergoing cardiac surgery.

Intraoperative mechanical power and postoperative pulmonary complications in low-risk surgical patients: a prospective observational cohort study

BACKGROUND

Inadequate intraoperative mechanical ventilation (MV) can lead to ventilator-induced lung injury and increased risk for postoperative pulmonary complications (PPCs). Mechanical power (MP) was shown to be a valuable indicator for MV outcomes in critical care patients. The aim of this study is to assess the association between intraoperative MP in low-risk surgical patients undergoing general anesthesia and PPCs.

METHODS

Two-hundred eighteen low-risk surgical patients undergoing general anesthesia for elective surgery were included in the study. Intraoperative mechanical ventilatory support parameters were collected for all patients. Postoperatively, patients were followed throughout their hospital stay and up to seven days post discharge for the occurrence of any PPCs.

RESULTS

Out of 218 patients, 35% exhibited PPCs. The average body mass index, tidal volume per ideal body weight, peak inspiratory pressure, and MP were significantly higher in the patients with PPCs than in the patients without PPCs (30.3 ± 8.1 kg/m2 vs. 26.8 ± 4.9 kg.m2, p < 0.001; 9.1 ± 1.9 ml/kg vs. 8.6 ± 1.4 ml/kg, p = 0.02; 20 ± 4.9 cmH2O vs. 18 ± 3.7 cmH2O, p = 0.001; 12.9 ± 4.5 J/min vs. 11.1 ± 3.7 J/min, p = 0.002). A multivariable regression analysis revealed MP as the sole significant predictor for the risk of postoperative pulmonary complications [OR 1.1 (95% CI 1.0-1.2, p = 0.036].

CONCLUSIONS

High intraoperative mechanical power is a risk factor for developing postoperative pulmonary complications. Furthermore, intraoperative mechanical power is superior to other traditional mechanical ventilation variables in identifying surgical patients who are at risk for developing postoperative pulmonary complications.

CLINICAL TRIAL REGISTRATION

NCT03551899; 24/02/2017.

Mechanical Ventilation, Past, Present, and Future

Mechanical ventilation (MV) has played a crucial role in the medical field, particularly in anesthesia and in critical care medicine (CCM) settings. MV has evolved significantly since its inception over 70 years ago and the future promises even more advanced technology. In the past, ventilation was provided manually, intermittently, and it was primarily used for resuscitation or as a last resort for patients with severe respiratory or cardiovascular failure. The earliest MV machines for prolonged ventilatory support and oxygenation were large and cumbersome. They required a significant amount of skills and expertise to operate. These early devices had limited capabilities, battery, power, safety features, alarms, and therefore these often caused harm to patients. Moreover, the physiology of MV was modified when mechanical ventilators moved from negative pressure to positive pressure mechanisms. Monitoring systems were also very limited and therefore the risks related to MV support were difficult to quantify, predict and timely detect for individual patients who were necessarily young with few comorbidities. Technology and devices designed to use tracheostomies versus endotracheal intubation evolved in the last century too and these are currently much more reliable. In the present, positive pressure MV is more sophisticated and widely used for extensive period of time. Modern ventilators use mostly positive pressure systems and are much smaller, more portable than their predecessors, and they are much easier to operate. They can also be programmed to provide different levels of support based on evolving physiological concepts allowing lung-protective ventilation. Monitoring systems are more sophisticated and knowledge related to the physiology of MV is improved. Patients are also more complex and elderly compared to the past. MV experts are informed about risks related to prolonged or aggressive ventilation modalities and settings. One of the most significant advances in MV has been protective lung ventilation, diaphragm protective ventilation including noninvasive ventilation (NIV). Health care professionals are familiar with the use of MV and in many countries, respiratory therapists have been trained for the exclusive purpose of providing safe and professional respiratory support to critically ill patients. Analgo-sedation drugs and techniques are improved, and more sedative drugs are available and this has an impact on recovery, weaning, and overall patients' outcome. Looking toward the future, MV is likely to continue to evolve and improve alongside monitoring techniques and sedatives. There is increasing precision in monitoring global "patient-ventilator" interactions: structure and analysis (asynchrony, desynchrony, etc). One area of development is the use of artificial intelligence (AI) in ventilator technology. AI can be used to monitor patients in real-time, and it can predict when a patient is likely to experience respiratory distress. This allows medical professionals to intervene before a crisis occurs, improving patient outcomes and reducing the need for emergency intervention. This specific area of development is intended as "personalized ventilation." It involves tailoring the ventilator settings to the individual patient, based on their physiology and the specific condition they are being treated for. This approach has the potential to improve patient outcomes by optimizing ventilation and reducing the risk of harm. In conclusion, MV has come a long way since its inception, and it continues to play a critical role in anesthesia and in CCM settings. Advances in technology have made MV safer, more effective, affordable, and more widely available. As technology continues to improve, more advanced and personalized MV will become available, leading to better patients' outcomes and quality of life for those in need.

Intraoperative individualization of positive-end-expiratory pressure through electrical impedance tomography or esophageal pressure assessment: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

This systematic review of randomized-controlled trials (RCTs) with meta-analyses aimed to compare the effects on intraoperative arterial oxygen tension to inspired oxygen fraction ratio (PaO2/FiO2), exerted by positive end-expiratory pressure (PEEP) individualized trough electrical impedance tomography (EIT) or esophageal pressure (Pes) assessment (intervention) vs. PEEP not tailored on EIT or Pes (control), in patients undergoing abdominal or pelvic surgery with an open or laparoscopic/robotic approach.

METHODS

PUBMED®, EMBASE®, and Cochrane Controlled Clinical trials register were searched for observational studies and RCTs from inception to the end of August 2022. Inclusion criteria were: RCTs comparing PEEP titrated on EIT/Pes assessment vs. PEEP not individualized on EIT/Pes and reporting intraoperative PaO2/FiO2. Two authors independently extracted data from the enrolled investigations. Data are reported as mean difference and 95% confidence interval (CI).

RESULTS

Six RCTs were included for a total of 240 patients undergoing general anesthesia for surgery, of whom 117 subjects in the intervention group and 123 subjects in the control group. The intraoperative mean PaO2/FiO2 was 69.6 (95%CI 32.-106.4 ) mmHg higher in the intervention group as compared with the control group with 81.4% between-study heterogeneity (p < 0.01). However, at meta-regression, the between-study heterogeneity diminished to 44.96% when data were moderated for body mass index (estimate 3.45, 95%CI 0.78-6.11, p = 0.011).

CONCLUSIONS

In patients undergoing abdominal or pelvic surgery with an open or laparoscopic/robotic approach, PEEP personalized by EIT or Pes allowed the achievement of a better intraoperative oxygenation compared to PEEP not individualized through EIT or Pes.

PROSPERO REGISTRATION NUMBER

CRD 42021218306, 30/01/2023.

Pulmonary response prediction through personalized basis functions in a virtual patient model

BACKGROUND AND OBJECTIVE

Recruitment maneuvers with subsequent positive-end-expiratory-pressure (PEEP) have proven effective in recruiting lung volume and preventing alveoli collapse. However, determining a safe, effective, and patient-specific PEEP is not standardized, and this more optimal PEEP level evolves with patient condition, requiring personalised monitoring and care approaches to maintain optimal ventilation settings.

METHODS

This research examines 3 physiologically relevant basis function sets (exponential, parabolic, cumulative) to enable better prediction of elastance evolution for a virtual patient or digital twin model of MV lung mechanics, including novel elements to model and predict distension elastance. Prediction accuracy and robustness are validated against recruitment maneuver data from 18 volume-controlled ventilation (VCV) patients at 7 different baseline PEEP levels (0 to 12 cmH2O) and 14 pressure-controlled ventilation (PCV) patients at 4 different baseline PEEP levels (6 to 12 cmH2O), yielding 623 and 294 prediction cases, respectively. Predictions were made up to 12 cmH2O of added PEEP ahead, covering 6 × 2 cmH2O PEEP steps.

RESULTS

The 3 basis function sets yield median absolute peak inspiratory pressure (PIP) prediction error of 1.63 cmH2O for VCV patients, and median peak inspiratory volume (PIV) prediction error of 0.028 L for PCV patients. The exponential basis function set yields a better trade-off of overall performance across VCV and PCV prediction than parabolic and cumulative basis function sets from other studies. Comparing predicted and clinically measured distension prediction in VCV demonstrated consistent, robust high accuracy with R2 = 0.90-0.95.

CONCLUSIONS

The results demonstrate recruitment mechanics are best captured by an exponential basis function across different mechanical ventilation modes, matching physiological expectations, and accurately capture, for the first time, distension mechanics to within 5-10 % accuracy. Enabling the risk of lung injury to be predicted before changing ventilator settings. The overall outcomes significantly extend and more fully validate this digital twin or virtual mechanical ventilation patient model.

High Mechanical Power and Driving Pressures are Associated With Postoperative Respiratory Failure Independent From Patients' Respiratory System Mechanics

OBJECTIVES

High mechanical power and driving pressure (ΔP) have been associated with postoperative respiratory failure (PRF) and may be important parameters guiding mechanical ventilation. However, it remains unclear whether high mechanical power and ΔP merely reflect patients with poor respiratory system mechanics at risk of PRF. We investigated the effect of mechanical power and ΔP on PRF in cohorts after exact matching by patients' baseline respiratory system compliance.

DESIGN

Hospital registry study.

SETTING

Academic hospital in New England.

PATIENTS

Adult patients undergoing general anesthesia between 2008 and 2020.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

The primary exposure was high (≥ 6.7 J/min, cohort median) versus low mechanical power and the key-secondary exposure was high (≥ 15.0 cm H 2 O) versus low ΔP. The primary endpoint was PRF (reintubation or unplanned noninvasive ventilation within seven days). Among 97,555 included patients, 4,030 (4.1%) developed PRF. In adjusted analyses, high intraoperative mechanical power and ΔP were associated with higher odds of PRF (adjusted odds ratio [aOR] 1.37 [95% CI, 1.25-1.50]; p < 0.001 and aOR 1.45 [95% CI, 1.31-1.60]; p < 0.001, respectively). There was large variability in applied ventilatory parameters, dependent on the anesthesia provider. This facilitated matching of 63,612 (mechanical power cohort) and 53,260 (ΔP cohort) patients, yielding identical baseline standardized respiratory system compliance (standardized difference [SDiff] = 0.00) with distinctly different mechanical power (9.4 [2.4] vs 4.9 [1.3] J/min; SDiff = -2.33) and ΔP (19.3 [4.1] vs 11.9 [2.1] cm H 2 O; SDiff = -2.27). After matching, high mechanical power and ΔP remained associated with higher risk of PRF (aOR 1.30 [95% CI, 1.17-1.45]; p < 0.001 and aOR 1.28 [95% CI, 1.12-1.46]; p < 0.001, respectively).

CONCLUSIONS

High mechanical power and ΔP are associated with PRF independent of patient's baseline respiratory system compliance. Our findings support utilization of these parameters for titrating mechanical ventilation in the operating room and ICU.

Bibliometric Evaluation of the 100 Top-Cited Articles on Anesthesiology

This review is a bibliometric analysis based on anesthesiology, which is a medical specialty that deals with a patient's complete preoperative, intraoperative, and postoperative care. The objective of the review attempts to analyze the bibliometric characteristics of the 100 most top-cited articles on anesthesiology. The meta-data of the study were collected from the Core Collection of Web of Science database. A title search option was employed, and "Anesthesia" and "Anesthesiology" were typed in two different search boxes separated with the Boolean operator ''OR''. Further, the data were sorted by highest citation order; later, "article" was selected from the filter of document type, and all other types of documents were excluded. Finally, downloaded the bibliographic details of the 100 top-cited articles. VOSviewer Software (version 1.6.10 by van Eck and Waltman) was used for bibliometric network analysis for co-authors and keywords. Pearson chi-square test was used for statistical analysis. The 100 top-cited articles were published between the years of 1971 and 2018. These articles gained a maximum of 1006 to a minimum of 276 citations with an average of 384.57 cites/article. Open accessed articles gained a slightly higher ratio of citations, while more than half of the articles were published in the two leading journals of "Anesthesiology" and "Anesthesia and Analgesia". There was no statistically significant difference in both citation analysis among open and closed access journals and Anesthesia vs Non-Anesthesia journals. Thirty-six articles were published in journals not specifically related to Anesthesia. Most of the top-cited articles were contributed by the United States, whereas Surgery and General Anesthesia were the two most occurred keywords.  We conclude that all the top-cited articles in anesthesiology were contributed by authors who belonged to the developed nations and the United States outclassed the rest of the world. This bibliometric analysis would be valuable to practitioners, academics, researchers, and students to understand the dynamics of progress in the field of anesthesiology.

A 20-year bibliometric analysis of postoperative pulmonary complications: 2003-2022

Background

Postoperative pulmonary complications (PPCs) are known to adversely affect surgical outcomes and patient prognoses, yet no published study provides a qualitative and quantitative analysis of the latest trends and developments in the field of PPCs. Therefore, we conducted a bibliometric analysis of 20 years of publications related to PPCs.

Methods

We examined publications on PPCs published between 2003 and 2022 in the Web of Science Core Collection database to assess trends in the field in four dimensions: trends in publications, major research power, keywords, and co-cited publications.

Results

A total of 1881 articles were analyzed using CiteSpace and VOSviewer. Overall, the number of publications on PPCs has increased in the last two decades, with 42.72% of the publications being produced in the last five years. The United States of America had the highest number of articles, accounting for 21.91% of the total. The institution with the highest number of publications was the University of Genoa, which published 54 articles and showed a general lack of inter-institutional collaboration. The most productive author was Paolo Pelosi, with no core group of authors identified in the field of PPCs. The keyword co-occurrence analysis indicated that the focus of research has shifted over the past 20 years in terms of risk factors, type of surgery, and so on, while "enhanced recovery", "prehabilitation", "driving pressure" and "sugammadex" have received the most recent attention. In the analysis of co-cited literature, the most recent clusters that received attention were driving pressure, lung cancer patient, enhanced recovery, and neuromuscular blockade.

Conclusion

This bibliometric study suggests that pulmonary protective ventilation strategies, neuromuscular blockade reversal, and pulmonary prehabilitation strategy will be the focus of attention in the coming period. More large-scale studies and strengthened institutional collaboration are necessary to generate robust evidence for guiding individualized prevention of PPCs.

Effect of individualized positive end-expiratory pressure based on electrical impedance tomography guidance on pulmonary ventilation distribution in patients who receive abdominal thermal perfusion chemotherapy

Background

Electrical impedance tomography (EIT) has been shown to be useful in guiding individual positive end-expiratory pressure titration for patients with mechanical ventilation. However, the appropriate positive end-expiratory pressure (PEEP) level and whether the individualized PEEP needs to be adjusted during long-term surgery (>6 h) were unknown. Meanwhile, the effect of individualized PEEP on the distribution of pulmonary ventilation in patients who receive abdominal thermoperfusion chemotherapy is unknown. The primary aim of this study was to observe the effect of EIT-guided PEEP on the distribution of pulmonary ventilation in patients undergoing cytoreductive surgery (CRS) combined with hot intraperitoneal chemotherapy (HIPEC). The secondary aim was to analyze their effect on postoperative pulmonary complications.

Methods

A total of 48 patients were recruited and randomly divided into two groups, with 24 patients in each group. For the control group (group A), PEEP was set at 5 cm H2O, while in the EIT group (group B), individual PEEP was titrated and adjusted every 2 h with EIT guidance. Ventilation distribution, respiratory/circulation parameters, and PPC incidence were compared between the two groups.

Results

The average individualized PEEP was 10.3 ± 1.5 cm H2O, 10.2 ± 1.6 cm H2O, 10.1 ± 1.8 cm H2O, and 9.7 ± 2.1 cm H2O at 5 min, 2 h, 4 h, and 6 h after tracheal intubation during CRS + HIPEC. Individualized PEEP was correlated with ventilation distribution in the regions of interest (ROI) 1 and ROI 3 at 4 h mechanical ventilation and ROI 1 at 6 h mechanical ventilation. The ventilation distribution under individualized PEEP was back-shifted for 6 h but moved to the control group's ventral side under PEEP 5 cm H2O. The respiratory and circulatory function indicators were both acceptable either under individualized PEEP or PEEP 5 cm H2O. The incidence of total PPCs was significantly lower under individualized PEEP (66.7%) than PEEP 5 cm H2O (37.5%) for patients with CRS + HIPEC.

Conclusion

The appropriate individualized PEEP was stable at approximately 10 cm H2O during 6 h for patients with CRS + HIPEC, along with better ventilation distribution and a lower total PPC incidence than the fixed PEEP of 5 cm H2O.Clinical trial registration: identifier ChiCTR1900023897.

Perioperative Pulmonary Complications in the Elderly: The Forgotten System

With a rapidly aging population and increasing global surgical volumes, managing the elevated risk of perioperative pulmonary complications has become an expanding focus for quality improvement in health care. In this narrative review, we will analyze the evidence-based literature to provide high-quality and actionable management strategies to better detect, stratify risk, optimize, and manage perioperative pulmonary complications in geriatric populations.

Effect of Lung Compliance-Based Optimum Pressure Versus Fixed Positive End-Expiratory Pressure on Lung Atelectasis Assessed by Modified Lung Ultrasound Score in Laparoscopic Gynecological Surgery: A Prospective Randomized Controlled Trial

BACKGROUND

 Lung protective ventilation during the intraoperative period is now well established. However, the additional role of positive end-expiratory pressure (PEEP) during the intraoperative period remains uncertain in major laparoscopic gynecological surgery. The authors hypothesized that compliance-based optimum PEEP titration reduces postoperative lung atelectasis and improves outcomes.

METHODS

 Patients undergoing major laparoscopic pelvic gynecological surgeries with healthy lungs were randomized to the fixed PEEP group (PEEP 5 cm H₂O and recruitment maneuver {RM}) and optimum PEEP group (compliance-based PEEP and RM). Lung ultrasound and arterial blood gas analysis were performed at four time points. Modified lung ultrasound scoring was done, and the same was used as means of assessing lung aeration and the amount of lung atelectasis. Postoperative supplemental oxygen requirement and duration were also assessed and compared.

RESULTS

Lung ultrasound score (LUS) 30 minutes after extubation in fixed (Group F) and optimum (Group O) PEEP groups were median (interquartile range {IQR}) 3 (2-3) versus 1 (1-2), p=0.0001. Ventilatory parameters between Group F and Group O after lung recruitment were tidal volume (mean 357 mL {SD: 35} versus 362 mL {SD: 22}, p=0.46), PEEP (median, 5 cm H₂O {IQR: 5-5} versus median 16 cm H₂O {IQR: 14-18}), peak airway pressure (median 26 cm H₂O {IQR: 24-28} versus median 30 cm H₂O {IQR: 28-32} p<0.0001), plateau pressure (median 22 cm H₂O {IQR: 20-24} versus median 26 cm H₂O {IQR: 24-28} p<0.0001), static compliance (32.07±8.36 mL cm H₂O-1 versus 39.58±8.99 mL cm H₂O-1, p=0.0002). The number of patients requiring postoperative oxygen therapy to maintain SpO₂ >94% after extubation in postanesthesia care unit (PACU) was statistically significantly greater in group F (39/41 {95%} versus 30/41 {73%}, p=0.007). Median (IQR) duration of oxygenation therapy in the first 24 hours of the postoperative period between Group F and Group O differed with statistical significance, with the median (IQR) values being 25 (20-30) minutes versus 10 (0-15) minutes (p<0.0001).

CONCLUSIONS

 The modified lung ultrasound score significantly differed intraoperatively between the two groups, with lower scores in the optimum PEEP group. This has reflected improved postoperative outcomes in optimum PEEP group patients, with fewer patients requiring postoperative oxygen supplementation and reduced supplemental oxygen requirement duration.

Effect of protective lung ventilation on pulmonary complications after laparoscopic surgery: a meta-analysis of randomized controlled trials

Introduction

Compared with traditional open surgery, laparoscopic surgery is widely used in surgery, with the advantages of being minimally invasive, having good cosmetic effects, and having short hospital stays, but in laparoscopic surgery, pneumoperitoneum and the Trendelenburg position can cause complications, such as atelectasis. Recently, several studies have shown that protective lung ventilation strategies are protective for abdominal surgery, reducing the incidence of postoperative pulmonary complications (PPCs). Ventilator-associated lung injury can be reduced by protective lung ventilation, which includes microtidal volume (4-8 mL/kg) ventilation and positive end-expiratory pressure (PEEP). Therefore, we used randomized, controlled trials (RCTs) to assess the results on this topic, and RCTs were used for meta-analysis to further evaluate the effect of protective lung ventilation on pulmonary complications in patients undergoing laparoscopic surgery.

Methods

In this meta-analysis, we searched the relevant literature contained in six major databases-CNKI, CBM, Wanfang Medical, Cochrane, PubMed, and Web of Science-from their inception to October 15, 2022. After screening the eligible literature, a randomized, controlled method was used to compare the occurrence of postoperative pulmonary complications when a protective lung ventilation strategy and conventional lung ventilation strategy were applied to laparoscopic surgery. After statistical analysis, the results were verified to be statistically significant.

Results

Twenty-three trials were included. Patients receiving protective lung ventilation were 1.17 times less likely to develop pulmonary complications after surgery than those receiving conventional lung ventilation (hazard ratio [RR] 0.18, 95% confidence interval [CI] 1.13-1.22; I² = 0%). When tested for bias (P = 0.36), the result was statistically significant. Patients with protective lung ventilation were less likely to develop pulmonary complications after laparoscopic surgery.

Conclusion

Compared with conventional mechanical ventilation, protective lung ventilation reduces the incidence of postoperative pulmonary complications. For patients undergoing laparoscopic surgery, we suggest the use of protective lung ventilation, which is effective in reducing the incidence of lung injury and pulmonary infection. Implementation of a low tidal volume plus moderate positive end-expiratory pressure strategy reduces the risk of postoperative pulmonary complications.

Driving Pressure-Guided Ventilation in Obese Patients Undergoing Laparoscopic Sleeve Gastrectomy: A Randomized Controlled Trial

Purpose

This study aims to compare the conventional lung protective ventilation strategy (LPVS) with driving pressure-guided ventilation in obese patients undergoing laparoscopic sleeve gastrectomy (LSG).

Methods

Forty-five patients undergoing elective LSG under general anesthesia were randomly assigned to the conventional LPVS group (group L) or the driving pressure-guided ventilation group (group D) using random numbers generated by Excel. The primary outcome was the driving pressure of both groups 90 min after pneumoperitoneum.

Results

After 30 min of pneumoperitoneum, 90 min of pneumoperitoneum, 10 min of closing the pneumoperitoneum, and restoring the supine position, the driving pressure of group L and group D were 20.0 ± 2.9 cm H2O vs 16.6 ± 3.0 cm H2O (P < 0.001), 20.7 ± 3.2 cm H2O vs 17.3 ± 2.8 cm H2O (P < 0.001), and 16.3 ± 3.1 cm H2O vs 13.3 ± 2.5 cm H2O (P = 0.001), respectively; the respiratory compliance of groups L and D were 23.4 ± 3.7 mL/cm H2O vs 27.6 ± 5.1 mL/cm H2O (P = 0.003), 22.7 ± 3.8 mL/cm H2O vs 26.4 ± 3.5 mL/cm H2O (P = 0.005), and 29.6 ± 6.8 mL/cm H2O vs 34.7 ± 5.3 mL/cm H2O (P = 0.007), respectively. The intraoperative PEEP in groups L and group D was 5 (5-5) cm H2O vs 10 (9-11) cm H2O (P < 0.001).

Conclusion

An individualized peep-based driving pressure-guided ventilation strategy can reduce intraoperative driving pressure and increase respiratory compliance in obese patients undergoing LSG.

Lung-protective ventilation during Trendelenburg pneumoperitoneum surgery: A randomized clinical trial

Study objective To assess the effects of a protective ventilation strategy during Trendelenburg pneumoperitoneum surgery on postoperative oxygenation.

DESIGNS

Parallel-group, randomized trial.

SETTING

Operating room of a university hospital, Italy.

PATIENTS

Morbidly obese patients undergoing Trendelenburg pneumoperitoneum gynaecological surgery.

INTERVENTIONS

Participants were randomized to standard (SV: tidal volume = 10 ml/kg of predicted body weight, PEEP = 5 cmH₂O) or protective (PV: tidal volume = 6 ml/kg of predicted body weight, PEEP = 10 cmH₂O, recruitment maneuvers) ventilation during anesthesia.

MEASUREMENTS

Primary outcome was PaO₂/FiO₂ one hour after extubation. Secondary outcomes included day-1 PaO₂/FiO₂, day-2 respiratory function and intraoperative respiratory/lung mechanics, assessed through esophageal manometry, end-expiratory lung volume (EELV) measurement and pressure-volume curves.

MAIN RESULTS

Sixty patients were analyzed (31 in SV group, 29 in PV group). Median [IqR] tidal volume was 350 ml [300-360] in PV group and 525 [500-575] in SV group. Median PaO₂/FiO₂ one hour after extubation was 280 mmHg [246-364] in PV group vs. 298 [250-343] in SV group (p = 0.64). Day-1 PaO₂/FiO_2, day-2 forced vital capacity, FEV-1 and Tiffenau Index were not different between groups (all p > 0.10). Intraoperatively, 59% of patients showed complete airway closure during pneumoperitoneum, without difference between groups: median airway opening pressure was 17 cmH₂O. In PV group, airway and transpulmonary driving pressure were lower (12 ± 5 cmH₂O vs. 17 ± 7, p < 0.001; 9 ± 4 vs. 13 ± 7, p < 0.001), PaCO₂ and respiratory rate were higher (48 ± 8 mmHg vs. 42 ± 12, p < 0.001; 23 ± 5 breaths/min vs. 16 ± 4, p < 0.001). Intraoperative EELV was similar between PV and SV group (1193 ± 258 ml vs. 1207 ± 368, p = 0.80); ratio of tidal volume to EELV was lower in PV group (0.45 ± 0.12 vs. 0.32 ± 0.09, p < 0.001).

CONCLUSIONS

In obese patients undergoing Trendelenburg pneumoperitoneum surgery, PV did not improve postoperative oxygenation nor day-2 respiratory function. PV was associated with intraoperative respiratory mechanics indicating less injurious ventilation. The high prevalence of complete airway closure may have affected study results.

TRIAL REGISTRATION

Prospectively registered on http://clinicaltrials.govNCT03157479 on May 17th, 2017.

Dexmedetomidine improves lung compliance in patients undergoing lateral decubitus position of shoulder arthroscopy: A randomized controlled trial

BACKGROUND

The improvement of oxygenation and pulmonary mechanics in patients under general anesthesia can be achieved by dexmedetomidine (DEX) infusion. However, its role in patients undergoing lateral supine shoulder arthroscopy has not been thoroughly studied. This study aimed to evaluate the effect of DEX on lung compliance in patients undergoing shoulder arthroscopic surgery in a lateral decubitus position.

METHODS

The patients who underwent lateral recumbent shoulder arthroscopy under general anesthesia were randomly divided into the DEX group (group D) and the control group (group N). At the start of the trial, group D was given 0.5 μg/kg/hours continuous pumping until 30 minutes before the end of anesthesia; Group N was injected with normal saline at the same volume. The patients were recorded at each time point after intubation: supine position for 5 minutes (T0), lateral position for 5 minutes (T1), lateral position for 1 hour (T2), lateral position for 2 hours (T3), airway peak pressure, platform pressure, dynamic lung compliance, and static lung compliance, etc.

RESULTS

At the end of the drug infusion, the DEX group showed significant improved pulmonary mechanics and higher lung compliance than the control group. Compared with group N, group D's heart rate and mean arterial pressure were lower at all time points; there was no statistical difference in Tidal volume and Pressure end-tidal carbon dioxide data at each time point in Group D.

CONCLUSION

DEX can improve lung compliance and reduce airway pressure and platform pressure of patients undergoing shoulder arthroscopy in the lateral position under general anesthesia.

Pulmonary Recruitment Prior to Intraoperative Multiple Pulmonary Ground-Glass Nodule Localization Increases the Localization Accuracy-A Retrospective Study

The standard treatment for early-stage lung cancer is complete tumor excision by limited resection of the lung. Preoperative localization is used before video-assisted thoracoscopic surgery (VATS) to improve the accuracy of pulmonary nodule excision. However, lung atelectasis and hypoxia resulting from controlling apnea during the localization procedure may affect the localization accuracy. Pre-procedural pulmonary recruitment may improve the respiratory mechanics and oxygenation during localization. In this study, we investigated the potential benefits of pre-localization pulmonary recruitment prior to pulmonary ground-glass nodule localization in a hybrid operating room. We hypothesized that pre-localization pulmonary recruitment would increase the localization accuracy, improve oxygenation, and prevent the need for re-inflation during the localization procedure. We retrospectively enrolled patients with multiple pulmonary nodule localizations before surgical intervention in our hybrid operating room. We compared the localization accuracy between patients who had undergone pre-procedure pulmonary recruitment and patients who had not. Saturation, re-inflation rate, apnea time, procedure-related pneumothorax, and procedure time were also recorded as secondary outcomes. The patients who had undergone pre-procedure recruitment had better saturation, shorter procedure time, and higher localization accuracy. The pre-procedure pulmonary recruitment maneuver was effective in increasing regional lung ventilation, leading to improved oxygenation and localization accuracy.

Spin and fragility in anaesthesia studies: when sirens sing into anaesthetists' ears

Spin and fragility are common in randomised controlled trials published in anaesthesia journals. Staying with the facts and addressing only the primary endpoint in the conclusion of clinical research reports might help reduce spin. Routinely reporting the fragility index, in turn, could deliver information about robustness, enhancing the transparency of positive dichotomous results. It is in the best interest of clinical research that authors, reviewers, and journals come together to reduce spin and address the fragility of randomised controlled trials.

Low tidal volume ventilation for patients undergoing laparoscopic surgery: a secondary analysis of a randomised clinical trial

BACKGROUND

We recently reported the results for a large randomized controlled trial of low tidal volume ventilation (LTVV) versus conventional tidal volume (CTVV) during major surgery when positive end expiratory pressure (PEEP) was equal between groups. We found no difference in postoperative pulmonary complications (PPCs) in patients who received LTVV. However, in the subgroup of patients undergoing laparoscopic surgery, LTVV was associated with a numerically lower rate of PPCs after surgery. We aimed to further assess the relationship between LTVV versus CTVV during laparoscopic surgery.

METHODS

We conducted a post-hoc analysis of this pre-specified subgroup. All patients received volume-controlled ventilation with an applied PEEP of 5 cmH₂O and either LTVV (6 mL/kg predicted body weight [PBW]) or CTVV (10 mL/kg PBW). The primary outcome was the incidence of a composite of PPCs within seven days.

RESULTS

Three hundred twenty-eight patients (27.2%) underwent laparoscopic surgeries, with 158 (48.2%) randomised to LTVV. Fifty two of 157 patients (33.1%) assigned to LTVV and 72 of 169 (42.6%) assigned to conventional tidal volume developed PPCs within 7 days (unadjusted absolute difference, - 9.48 [95% CI, - 19.86 to 1.05]; p = 0.076). After adjusting for pre-specified confounders, the LTVV group had a lower incidence of the primary outcome than patients receiving CTVV (adjusted absolute difference, - 10.36 [95% CI, - 20.52 to - 0.20]; p = 0.046).

CONCLUSION

In this post-hoc analysis of a large, randomised trial of LTVV we found that during laparoscopic surgeries, LTVV was associated with a significantly reduced PPCs compared to CTVV when PEEP was applied equally between both groups.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry no: 12614000790640.

The association of intraoperative low driving pressure ventilation and nonhome discharge: a historical cohort study

PURPOSE

To evaluate whether intraoperative ventilation using lower driving pressure decreases the risk of nonhome discharge.

METHODS

We conducted a historical cohort study of patients aged ≥ 60 yr who were living at home before undergoing elective, noncardiothoracic surgery at two tertiary healthcare networks in Massachusetts between 2007 and 2018. We assessed the association of the median driving pressure during intraoperative mechanical ventilation with nonhome discharge using multivariable logistic regression analysis, adjusted for patient and procedural factors. Contingent on the primary association, we assessed effect modification by patients' baseline risk and mediation by postoperative respiratory failure.

RESULTS

Of 87,407 included patients, 12,584 (14.4%) experienced nonhome discharge. In adjusted analyses, a lower driving pressure was associated with a lower risk of nonhome discharge (adjusted odds ratio [aOR], 0.88; 95% confidence interval [CI], 0.83 to 0.93, per 10 cm H2O decrease; P < 0.001). This association was magnified in patients with a high baseline risk (aOR, 0.77; 95% CI, 0.73 to 0.81, per 10 cm H2O decrease, P-for-interaction < 0.001). The findings were confirmed in 19,518 patients matched for their baseline respiratory system compliance (aOR, 0.90; 95% CI, 0.81 to 1.00; P = 0.04 for low [< 15 cm H2O] vs high [≥ 15 cm H2O] driving pressures). A lower risk of respiratory failure mediated the association of a low driving pressure with nonhome discharge (20.8%; 95% CI, 15.0 to 56.8; P < 0.001).

CONCLUSIONS

Intraoperative ventilation maintaining lower driving pressure was associated with a lower risk of nonhome discharge, which can be partially explained by lowered rates of postoperative respiratory failure. Future randomized controlled trials should target driving pressure as a potential intervention to decrease nonhome discharge.

Electric impedance tomography and protective mechanical ventilation in elective robotic-assisted laparoscopy surgery with steep Trendelenburg position: a randomized controlled study

Electrical impedance tomography (EIT) reconstructs functional lung images and evaluates the variations of impedance during the breathing cycle. The aim of this study was to evaluate the effect of protective mechanical ventilation on ventilation distributions recorded by the EIT during elective robotic-assisted laparoscopy surgery with steep Trendelenburg position. This prospective, randomized single center study included patients with healthy lungs undergoing elective robot-assisted laparoscopic urological surgery in general anesthesia. Patients were randomly assigned to either protective lung ventilation or conventional ventilation. In the protective ventilation group, tidal volume (TV) was set at 6 ml/Kg predicted body weight (PBW), with PEEP 6 cmH₂O, and recruitment maneuvers (RM) as needed. In the conventional ventilation group, TV was set at 9 ml/Kg PBW, with PEEP 2 cmH₂O and RM only as needed. Ventilation distribution was assessed using an EIT device. This study included 40 patients in the functional image analysis. Significant differences were found in ventilation distribution in the region of interest (p < 0.05). Driving pressure was significantly lower in protective ventilation group (p < 0.05). Peak and plateau pressures were not different between the groups while statical significance was found in tidal volume and respiratory rate. EIT may be a valuable tool for monitoring lung function during general anesthesia. During elective robotic-assisted laparoscopy surgery with steep Trendelenburg position, protective mechanical ventilation may have a more homogenous distribution of intraoperative and postoperative ventilation. Larger sample size and long-term evaluation are needed in future studies to assess the benefit of EIT monitoring in operation room.Clinical trial registration ClinicalTrials.gov Identifier: NCT04194177 registered at 11th December 2019.

Individualized positive end-expiratory pressure guided by respiratory mechanics during anesthesia for the prevention of postoperative pulmonary complications: a systematic review and meta-analysis

The optimization of positive end-expiratory pressure (PEEP) according to respiratory mechanics [driving pressure or respiratory system compliance (Crs)] is a simple and straightforward strategy. However, its validity to prevent postoperative pulmonary complications (PPCs) remains unclear. Here, we performed a meta-analysis to assess such efficacy. We searched PubMed, Embase, and the Cochrane Library to identify randomized controlled trials (RCTs) that compared personalized PEEP based on respiratory mechanics and constant PEEP to prevent PPCs in adults. The primary outcome was PPCs. Fourteen studies with 1105 patients were included. Compared with those who received constant PEEP, patients who received optimized PEEP exhibited a significant reduction in the incidence of PPCs (RR = 0.54, 95% CI 0.42 to 0.69). The results of commonly happened PPCs (pulmonary infections, hypoxemia, and atelectasis but not pleural effusion) also supported individualized PEEP group. Moreover, the application of PEEP based on respiratory mechanics improved intraoperative respiratory mechanics (driving pressure and Crs) and oxygenation. The PEEP titration method based on respiratory mechanics seems to work positively for lung protection in surgical patients undergoing general anesthesia.

The respiratory and hemodynamic effects of alveolar recruitment in cirrhotic patients undergoing liver resection surgery: A randomized controlled trial

Background and Aims

Extensive surgical retraction combined with general anesthesia increase alveolar collapse. The primary aim of our study was to investigate the effect of alveolar recruitment maneuver (ARM) on arterial oxygenation tension (PaO2). The secondary aim was to observe its effect on hemodynamics parameters in hepatic patients during liver resection, to investigate its impact on blood loss, postoperative pulmonary complications (PPC), remnant liver function tests, and on the outcome.

Material and Methods

Adult patients scheduled for liver resection were randomized into two groups: ARM (n = 21) and control (C) (n = 21). Stepwise ARM was initiated after intubation and was repeated post-retraction. Pressure-control ventilation mode was adjusted to deliver a tidal volume (Vt) of 6 mL/kg and an inspiratory-to-expiratory time (I:E) ratio of 1:2 with an optimal positive end-expiratory pressure (PEEP) for the ARM group. In the C group, a fixed PEEP (5 cmH2O) was applied. Invasive intra-arterial blood pressure (IBP), central venous pressure (CVP), electrical cardiometry (EC), alanine transaminase (ALT, U/L), and aspartate aminotransferase (AST, U/L) blood levels were monitored.

Results

ARM increased PEEP, dynamic compliances, and arterial oxygenation, but reduced ventilator driving pressure compared to group C (P < 0.01). IBP, cardiac output (CO), and stroke volume variation were not affected by the higher PEEP in the ARM group (P > 0.05) but the CVP increased significantly (P = 0.001). Blood loss was not different between the ARM and C groups (1700 (1150-2000) mL vs 1110 (900-2400) mL, respectively and P = 0.57). ARM reduced postoperative oxygen desaturation; however, it did not affect the increase in remnant liver enzymes and was comparable to group C (ALT, P = 0.54, AST, P = 0.41).

Conclusions

ARM improved intraoperative lung mechanics and reduced oxygen desaturation episodes in recovery, but not PPC or ICU stay. ARM was tolerated with minimal cardiac and systemic hemodynamic effects.

Beyond audit: Embracing QI methodology to drive improvements in lung-protective ventilation

BACKGROUND

Mechanical ventilation supports patients with respiratory failure during critical illness. Evidence suggests that excessive tidal volumes (regarded as >8 mL/kg predicted body weight [PBW]) cause lung damage through increased lung stretch and alveolar inflammation. Lung-protective ventilation strategies have been shown to decrease morbidity and mortality, and that all patients should receive tidal volumes between 6 and 8 mls/kg PBW. Despite this, studies demonstrate that fewer than half of patients in critical care successfully receive lung-protective ventilation.

AIM

The primary aim was to reduce tidal volumes delivered to all patients receiving mandatory ventilation, with a target of >85% of tidal volumes delivered to be compliant with lung-protective ventilation strategies by the end of November 2019.

METHODS

A multidisciplinary team of nurses and doctors, based in a UK tertiary hospital, utilized the Institute for Healthcare Improvement's (IHI) quality improvement methodology to improve compliance with lung-protective ventilation.

RESULTS

Baseline data demonstrated that only 60.1% of tidal volumes recorded were compliant with lung-protective ventilation. Quality improvement (QI) methodology was utilized to systematically diagnose the aetiology of poor compliance and to produce and implement solutions. Real-time data collection and reporting were utilized to monitor and report improvement. Following 8 months of continuous data collection and repeated PDSA cycles, sustainable compliance with lung-protective ventilation for >85% of tidal volumes was achieved.

CONCLUSIONS

The use of QI methodology to implement low tidal volume ventilation has shown a significant improvement in the delivery of lung-protective ventilation. Using QI methodology is central to this sustained improvement and offers a useful tool to systematically approach complex clinical problems.

RELEVANCE TO CLINICAL PRACTICE

Lung protective ventilation is critically important in the management of ventilated patients, although compliance in intensive care is variable. Here, we describe how quality improvement methodology can lead to consistent and sustainable improvement in the delivery of lung protective ventilation.

Anesthesia Machine and New Modes of Ventilation

Mechanical ventilation is ubiquitous in the operating room. This article explores the anesthesia machine as a ventilator, examining its unique features and differences from ventilators designed for long-term use. It will describe standard and nonstandard modes of ventilation. The reader will develop a more nuanced understanding of how to tailor ventilation and oxygenation strategies based on patient and anesthetic scenarios as well as with the assistance of new technologies.

Airway driving pressure is associated with postoperative pulmonary complications after major abdominal surgery: a multicentre retrospective observational cohort study

Background

High airway driving pressure is associated with adverse outcomes in critically ill patients receiving mechanical ventilation, but large multicentre studies investigating airway driving pressure during major surgery are lacking. We hypothesised that increased driving pressure is associated with postoperative pulmonary complications in patients undergoing major abdominal surgery.

Methods

In this preregistered multicentre retrospective observational cohort study, the authors reviewed major abdominal surgical procedures in 11 hospitals from 2004 to 2018. The primary outcome was a composite of postoperative pulmonary complications, defined as postoperative pneumonia, unplanned tracheal intubation, or prolonged mechanical ventilation for more than 48 h. Associations between intraoperative dynamic driving pressure and outcomes, adjusted for patient and procedural factors, were evaluated.

Results

Among 14 218 qualifying cases, 389 (2.7%) experienced postoperative pulmonary complications. After adjustment, the mean dynamic driving pressure was associated with postoperative pulmonary complications (adjusted odds ratio for every 1 cm H₂O increase: 1.04; 95% confidence interval [CI], 1.02-1.06; P<0.001). Neither tidal volume nor PEEP was associated with postoperative pulmonary complications. Increased BMI, shorter height, and female sex were predictors for higher dynamic driving pressure (β=0.35, 95% CI 0.32-0.39, P<0.001; β=-0.01, 95% CI -0.02 to 0.00, P=0.005; and β=0.74, 95% CI 0.63-0.86, P<0.001, respectively).

Conclusions

Dynamic airway driving pressure, but not tidal volume or PEEP, is associated with postoperative pulmonary complications in models controlling for a large number of risk predictors and covariates. Such models are capable of risk prediction applicable to individual patients.

Effect of ventilation mode on postoperative pulmonary complications following lung resection surgery: a randomised controlled trial

The effect of intra-operative mechanical ventilation modes on pulmonary outcomes after thoracic surgery with one-lung ventilation has not been well established. We evaluated the impact of three common ventilation modes on postoperative pulmonary complications in patients undergoing lung resection surgery. In this two-centre randomised controlled trial, 1224 adults scheduled for lung resection surgery with one-lung ventilation were randomised to one of three groups: volume-controlled ventilation; pressure-controlled ventilation; and pressure-control with volume guaranteed ventilation. Enhanced recovery after surgery pathways and lung-protective ventilation protocols were implemented in all groups. The primary outcome was a composite of postoperative pulmonary complications within the first seven postoperative days. The outcome occurred in 270 (22%), with 87 (21%) in the volume control group, 89 (22%) in the pressure control group and 94 (23%) in the pressure-control with volume guaranteed group (p = 0.831). The secondary outcomes also did not differ across study groups. In patients undergoing lung resection surgery with one-lung ventilation, the choice of ventilation mode did not influence the risk of developing postoperative pulmonary complications. This is the first randomised controlled trial examining the effect of three ventilation modes on pulmonary outcomes in patients undergoing lung resection surgery.

Ventilation Strategies During General Anesthesia for Noncardiac Surgery: A Systematic Review and Meta-Analysis

BACKGROUND

The optimal ventilation strategy during general anesthesia is unclear. This systematic review investigated the relationship between ventilation targets or strategies (eg, positive end-expiratory pressure [PEEP], tidal volume, and recruitment maneuvers) and postoperative outcomes.

METHODS

PubMed and Embase were searched on March 8, 2021, for randomized trials investigating the effect of different respiratory targets or strategies on adults undergoing noncardiac surgery. Two investigators reviewed trials for relevance, extracted data, and assessed risk of bias. Meta-analyses were performed for relevant outcomes, and several subgroup analyses were conducted. The certainty of evidence was evaluated using Grading of Recommendations Assessment, Development and Evaluation (GRADE).

RESULTS

This review included 63 trials with 65 comparisons. Risk of bias was intermediate for all trials. In the meta-analyses, lung-protective ventilation (ie, low tidal volume with PEEP) reduced the risk of combined pulmonary complications (odds ratio [OR], 0.37; 95% confidence interval [CI], 0.28-0.49; 9 trials; 1106 patients), atelectasis (OR, 0.39; 95% CI, 0.25-0.60; 8 trials; 895 patients), and need for postoperative mechanical ventilation (OR, 0.36; 95% CI, 0.13-1.00; 5 trials; 636 patients). Recruitment maneuvers reduced the risk of atelectasis (OR, 0.44; 95% CI, 0.21-0.92; 5 trials; 328 patients). We found no clear effect of tidal volume, higher versus lower PEEP, or recruitment maneuvers on postoperative pulmonary complications when evaluated individually. For all comparisons across targets, no effect was found on mortality or hospital length of stay. No effect measure modifiers were found in subgroup analyses. The certainty of evidence was rated as very low, low, or moderate depending on the intervention and outcome.

CONCLUSIONS

Although lung-protective ventilation results in a decrease in pulmonary complications, randomized clinical trials provide only limited evidence to guide specific ventilation strategies during general anesthesia for adults undergoing noncardiac surgery.

Optimal anesthetic conduct regarding immediate and short-term outcomes after liver transplantation - Systematic review of the literature and expert panel recommendations

BACKGROUND

In the era of enhanced recovery after surgery, there is significant discussion regarding the impact of intraoperative anesthetic management on short-term outcomes following liver transplantation (LT), with no clear consensus in the literature.

OBJECTIVES

To identify whether or not intraoperative anesthetic management affects short-term outcomes after liver transplantation.

DATA SOURCES

Ovid MEDLINE, Embase, Scopus, Google Scholar, and Cochrane Central.

METHODS

A systematic review following PRISMA guidelines was undertaken. The systematic review was registered on PROSPERO (CRD42021239758). An international expert panel made recommendations for clinical practice using the GRADE approach.

RESULTS

After screening, 14 studies were eligible for inclusion in this systematic review. Six were prospective randomized clinical trials, three were prospective nonrandomized clinical trials, and five were retrospective studies. These manuscripts were reviewed to look at five questions regarding anesthetic care and its impact on short term outcomes following liver transplant. After review of the literature, the quality of evidence according to the following outcomes was as follows: intraoperative and postoperative morbidity and mortality (low), early allograft dysfunction (low), and hospital and ICU length of stay (moderate).

CONCLUSIONS

For optimal short term outcomes after liver transplantation, the panel recommends the use of volatile anesthetics in preference to total intravenous anesthesia (TIVA) (Level of Evidence: Very low; Strength of Recommendation: Weak) and minimum alveolar concentration (MAC) versus bispectral index (BIS) for depth of anesthesia monitoring (Level of Evidence: Very low; Strength of Recommendation: Weak). Regarding ventilation and oxygenation, the panel recommends a restrictive oxygenation strategy targeting a PaO₂ of 70-120 mmHg (10-14 kPa), a tidal volume of 6-8 ml/kg ideal body weight (IBW), administration of positive end expiratory pressure (PEEP) tailored to patient intraoperative physiology, and recruitment maneuvers. (Level of evidence: Very low; Strength of Recommendation: Strong). Finally, the panel recommends the routine use of antiemetic prophylaxis. (Level of evidence: low; Strength of Recommendation: Strong).

Individualised positive end-expiratory pressure in abdominal surgery: a systematic review and meta-analysis

BACKGROUND

Individualised PEEP may optimise pulmonary compliance, thereby potentially mitigating lung injury. This meta-analysis aimed to determine the impact of individualised PEEP vs fixed PEEP during abdominal surgery on postoperative pulmonary outcomes.

METHODS

Medical databases (PubMed, Embase, Web of Science, ScienceDirect, Google Scholar, and the China National Knowledge Infrastructure) were searched for RCTs comparing fixed vs individualised PEEP. The composite primary outcome of pulmonary complications comprised hypoxaemia, atelectasis, pneumonia, and acute respiratory distress syndrome. Secondary outcomes included oxygenation (P_aO₂/FiO₂) and systemic inflammatory markers (interleukin-6 [IL-6] and club cell protein-16 [CC16]). We calculated risk ratios (RRs) and mean differences (MDs) with 95% confidence interval (CI) using DerSimonian and Laird random effects models. Cochrane risk-of-bias tool was applied.

RESULTS

Ten RCTs (n=1117 patients) met the criteria for inclusion, with six reporting the primary endpoint. Individualised PEEP reduced the incidence of overall pulmonary complications (141/412 [34.2%]) compared with 183/415 (44.1%) receiving fixed PEEP (RR 0.69 [95% CI: 0.51-0.93]; P=0.016; I²=43%). Risk-of-bias analysis did not alter these findings. Individualised PEEP reduced postoperative hypoxaemia (74/392 [18.9%]) compared with 110/395 (27.8%) participants receiving fixed PEEP (RR 0.68 [0.52-0.88]; P=0.003; I²=0%) but not postoperative atelectasis (RR 0.93 [0.81-1.07]; P=0.297; I²=0%). Individualised PEEP resulted in higher P_aO₂/FiO₂ (MD 20.8 mm Hg [4.6-36.9]; P=0.012; I²=80%) and reduced systemic inflammation (lower plasma IL-6 [MD -6.8 pg ml^-1; -11.9 to -1.7]; P=0.009; I²=6%; and CC16 levels [MD -6.2 ng ml^-1; -8.8 to -3.5]; P<0.001; I²=0%) at the end of surgery.

CONCLUSIONS

Individualised PEEP may reduce pulmonary complications, improve oxygenation, and reduce systemic inflammation after abdominal surgery.

CLINICAL TRIAL REGISTRATION

CRD42021277973.

Effects of two alveolar recruitment maneuvers in an “open-lung” approach during laparoscopy in dogs

Objectives

The aim of this study was to compare the effects of a sustained inflation alveolar recruiting maneuver (ARM) followed by 5 cmH₂O of PEEP and a stepwise ARM, in dogs undergoing laparoscopic surgery.

Materials and methods

Twenty adult dogs were enrolled in this prospective randomized clinical study. Dogs were premedicated with methadone intramuscularly (IM); anesthesia was induced with propofol intravenously (IV) and maintained with inhaled isoflurane in pure oxygen. The baseline ventilatory setting (BVS) was as follows: tidal volume of 15 mL/kg, inspiratory pause of 25%, inspiratory to expiratory ratio of 1:2, and the respiratory rate to maintain the end-tidal carbon dioxide between 45 and 55 mmHg. 10 min after pneumoperitoneum, randomly, 10 dogs underwent sustained inflation ARM followed by 5 cmH₂O of PEEP (ARMi), while 10 dogs underwent a stepwise recruitment maneuver followed by the setting of the “best PEEP” (ARMc). Gas exchange, respiratory system mechanics, and hemodynamic were evaluated before the pneumoperitoneum induction (BASE), 10 min after the pneumoperitoneum (PP), 10 min after the recruitment (ARM), and 10 min after the pneumoperitoneum resolution (PostPP). Statistical analysis was performed with the ANOVA test (p < 0.05).

Results

Static compliance decreased in both groups at PP (ARMc = 1.35 ± 0.21; ARMi = 1.16 ± 0.26 mL/cmH₂O/kg) compared to BASE (ARMc = 1.78 ± 0.60; ARMi = 1.66 ± 0.66 mL/cmH₂O/kg) and at ARM (ARMc = 1.71 ± 0.41; ARMi = 1.44 ± 0.84 mL/cmH₂O/kg) and PostPP (ARMc = 1.75 ± 0.45; ARMi = 1.89 ± 0.59 mL/cmH₂O/kg), and it was higher compared to PP and similar to BASE. The PaO₂/FiO₂, in both groups, was higher at ARM (ARMc = 455.11 ± 85.90; ARMi = 505.40 ± 31.70) and PostPP (ARMc = 521.30 ± 66.20; ARMi = 450.90 ± 70.60) compared to PP (ARMc = 369.53 ± 49.31; ARMi = 394.32 ± 37.72).

Conclusion and clinical relevance

The two ARMs improve lung function in dogs undergoing laparoscopic surgery similarly. Application of PEEP at the end of the ARMs prolonged the effects of the open-lung strategy.

How traditional and digital analytics interventions can enhance lung-protective ventilation strategies during general anaesthesia: A two-year quality improvement project analysis

PURPOSE

This quality improvement project evaluated interventions implemented to enhance individual adherence to a lung-protective ventilation strategy and its triad: low tidal volume, PEEP ≥ 5, recruitment manoeuvres.

METHODS

For two years, nine anaesthesia workstations were connected to an automated cloud- based analytics software tool, which automatically recorded ventilation parameters as soon as a new patient case was opened. Four quality improvement periods were determined over the first year: baseline, intervention, no intervention, intervention + digital. In the second year, the digital strategy was continued for nine months, followed by a final "overtime" period. Baseline and no intervention periods included no training. The intervention period included both conventional and educational programs. The digital period included pop-up messages, which automatically appeared on the screen of the anaesthesia data management system when patients were intubated. The primary endpoint was provider adherence to the recommended triad.

RESULTS

From October 2018 to December 2020, 12,883 procedures were performed. Data were available for 8,968 procedures: baseline (n = 2361), intervention (n = 2423), no intervention (n = 1064), intervention + digital (n = 1862), overtime (n = 1258). Age, Predicted Body Weight, ASA score, type of surgery and airway management were similar between periods. At baseline, 75.2 % of procedures reported low tidal volume but only 6.9% involved the complete triad. At over time, Triad was 22% (p <  0.001). Over study period, each parameter of the Triad (RM, Vt and Peep) increased (p < 0.001 vs. baseline), driving pressure decreased although EtCO₂ and plateau pressure had not changed.

CONCLUSION

Training with the help of digital apps improved LPV adherence over time.

Intraoperative Respiratory and Hemodynamic Strategies for Reducing Nausea, Vomiting, and Pain after Surgery: Systematic Review and Meta-Analysis

BACKGROUND

Despite improved medical treatment strategies, post-operative pain, nausea, and vomiting remain major challenges. This systematic review investigated the relationship between perioperative respiratory and hemodynamic interventions and postoperative pain, nausea, and vomiting.

METHODS

PubMed and Embase were searched on March 8, 2021 for randomized clinical trials investigating the effect of perioperative respiratory or hemodynamic interventions in adults undergoing non-cardiac surgery. Investigators reviewed trials for relevance, extracted data, and assessed risk of bias. Meta-analyses were performed when feasible. GRADE was used to assess the certainty in the evidence.

RESULTS

This review included 65 original trials; of these 48% had pain, nausea and/or vomiting as the primary focus. No reduction of postoperative pain was found in meta-analyses when comparing recruitment maneuvers with no recruitment, high (80%) to low (30%) fraction of oxygen, low (5-7 ml/kg) to high (9-12 ml/kg) tidal volume, or goal-directed hemodynamic therapy to standard care. In the meta-analysis comparing recruitment maneuvers with no recruitment maneuvers, patients undergoing laparoscopic gynecological surgery had less shoulder pain 24 hours postoperatively (mean difference in the numeric rating scale from 0 to 10: -1.1, 95% CI: -1.7, -0.5). In meta-analyses, comparing high to low fraction of inspired oxygen and goal-directed hemodynamic therapy to standard care in patients undergoing abdominal surgery, the risk of postoperative nausea and vomiting was reduced (odds ratio: 0.45, 95% CI: 0.24, 0.87 and 0.48, 95% CI: 0.27, 0.85). The certainty in the evidence was mostly very low to low. The results should be considered exploratory given the lack of pre-specified hypotheses and corresponding risk of Type 1 errors.

CONCLUSION

There is limited evidence regarding the impact of intraoperative respiratory and hemodynamic interventions on postoperative pain or nausea and vomiting. More definitive trials are needed to guide clinical care within this area. This article is protected by copyright. All rights reserved.

An Updated Review of Driving-Pressure Guided Ventilation Strategy and Its Clinical Application

Traditional lung-protective ventilation strategies (LPVS) are currently used to reduce the incidence of postoperative pulmonary complications (PPCs), including low tidal volume (VT), positive end-expiratory pressure (PEEP), low inspiratory plateau pressure (Pplat), permissive hypercapnia, and recruitment maneuver (RM). However, a meta-analysis showed that high driving pressure was closely associated with the incidence of PPCs, but not with PEEP or VT, which led to the driving pressure-guided ventilation strategy. Some studies have proved that the driving pressure-guided ventilation strategy is superior to the traditional LPVS in reducing the incidence of PPCs. The purpose of this review is to present the current research progress and application of driving pressure-guided ventilation strategy.

Association between intraoperative tidal volume and postoperative respiratory complications is dependent on respiratory elastance: a retrospective, multicentre cohort study

BACKGROUND

The impact of high vs low intraoperative tidal volumes on postoperative respiratory complications remains unclear. We hypothesised that the effect of intraoperative tidal volume on postoperative respiratory complications is dependent on respiratory system elastance.

METHODS

We retrospectively recorded tidal volume (Vt; ml kg^-1 ideal body weight [IBW]) in patients undergoing elective, non-cardiothoracic surgery from hospital registry data. The primary outcome was respiratory failure (requiring reintubation within 7 days of surgery, desaturation after extubation, or both). The primary exposure was defined as the interaction between Vt and standardised respiratory system elastance (driving pressure divided by Vt; cm H₂O/[ml kg^-1]). Multivariable logistic regression models, with and without interaction terms (which categorised Vt as low [Vt ≤8 ml kg^-1] or high [Vt >8 ml kg^-1]), were adjusted for potential confounders. Additional analyses included path mediation analysis and fractional polynomial modelling.

RESULTS

Overall, 10 821/197 474 (5.5%) patients sustained postoperative respiratory complications. Higher Vt was associated with greater risk of postoperative respiratory complications (adjusted odds ratio=1.42 per ml kg^-1; 95% confidence interval [CI], 1.35-1.50]; P<0.001). This association was modified by respiratory system elastance (P<0.001); in patients with low compliance (<42.4 ml cm H₂O^-1), higher Vt was associated with greater risk of postoperative respiratory complications (adjusted risk difference=0.3% [95% CI, 0.0-0.5] at 41.2 ml cm H₂O^-1 compliance, compared with 5.8% [95% CI, 3.8-7.8] at 14 ml cm H₂O^-1 compliance). This association was absent when compliance exceeded 41.2 ml cm H₂O^-1. Adverse effects associated with high Vt were entirely mediated by driving pressures (P<0.001).

CONCLUSIONS

The association of harm with higher tidal volumes during intraoperative mechanical ventilation is modified by respiratory system elastance. These data suggest that respiratory elastance should inform the design of perioperative trials testing intraoperative ventilatory strategies.

Effects of Driving Pressure-Guided Ventilation on Postoperative Pulmonary Complications in Prone-Positioned Patients Undergoing Spinal Surgery: A Randomized Controlled Clinical Trial

BACKGROUND

Prolonged spinal surgery in the prone position may lead to postoperative pulmonary complications (PPCs). We aimed to compare the effects of driving pressure-guided ventilation versus conventional protective ventilation on postoperative pulmonary complications in patients undergoing spinal surgery in the prone position. We hypothesized that driving pressure-guided ventilation would be associated with a decreased incidence of PPC.

METHODS

We enrolled 78 patients into this single-center, double-blind, randomized controlled trial. The driving pressure (DP) group (n = 40) received a tidal volume of 6 ml/kg of predicted body weight, individualized positive end-expiratory pressure (PEEP) which produced the lowest driving pressure (plateau pressure-PEEP), and a recruitment maneuver. The protective ventilation (PV) group (n = 38) received the same tidal volume and recruitment maneuver but with a fixed PEEP of 5 cm H₂O. Our primary outcome was postoperative pulmonary complications based on Lung Ultrasound Scores (LUS) at the end of the surgery and the simplified Clinical Pulmonary Infection Score (sCPIS) on postoperative days (POD) 1 and 3.

RESULTS

DP patients had lower LUS and POD1 sCPIS than the PV group (p < 0.01). DP patients had lower driving pressure during the surgery than PV patients (p < 0.01). Perioperative arterial blood gases and hemodynamic parameters were comparable between the two groups (p > 0.05). The visual pain score (VAS) in postoperative days, drainage, and lengths of stay (LOS) were also similar between the two groups (p > 0.05).

CONCLUSIONS

Driving pressure-guided ventilation during spinal surgery with a prolonged prone patient position may reduce the incidence of early postoperative pulmonary complications, compared with conventional protective ventilation.

Effect of intraoperative alveolar recruitment maneuver on intraoperative oxygenation and postoperative pulmonary function tests in patients undergoing robotic-assisted hysterectomy: a single-blind randomized study

BACKGROUND

Robotic-Assisted Hysterectomies (RAH) require Trendelenburg positioning and pneumoperitoneum, which further accentuate alteration in respiratory mechanics induced by general anesthesia. The role of Recruitment Maneuver (RM) as a lung-protective strategy during intraoperative surgical settings has not been much studied. We planned this study to evaluate the effect of RM on perioperative oxygenation and postoperative spirometry using PaO₂/FiO₂ and FEV1/FVC, respectively in patients undergoing RAH.

METHODS

Sixty-six ASA I‒II female patients scheduled for elective RAH were randomized into group R (recruitment maneuver, n = 33) or group C (control, n = 33). Portable spirometry was done one day before surgery. Patients were induced with general anesthesia, and mechanical ventilation started with volume control mode, with Tidal Volume (TV) of 6-8 mL.kg^-1, Respiratory Rate (RR) of 12 min, inspiratory-expiratory ratio (I: E ratio) of 1:2, FiO₂ of 0.4, and Positive End-Expiratory Pressure (PEEP) of 5 cmH₂O. Patients in group R received recruitment maneuvers of 30 cmH₂O every 30 minutes following tracheal intubation. The primary objectives were comparison of oxygenation and ventilation between two groups intraoperatively and portable spirometry postoperatively. Postoperative pulmonary complications, like desaturation, pulmonary edema, pneumonia, were monitored.

RESULTS

Patients who received RM had significantly higher PaO₂ (mmHg) (203.2+-24.3 vs. 167.8+-27.3, p < 0.001) at T2 (30 min after the pneumoperitoneum). However, there was no significant difference in portable spirometry between the groups in the postoperative period (FVC, 1.40 ± 0.5 L vs. 1.32 ± 0.46 L, p = 0.55).

CONCLUSION

This study concluded that intraoperative recruitment did not prevent deterioration of postoperative spirometry values; however, it led to improved oxygenation intraoperatively.

The Influence of Positive End-Expiratory Pressure on Leakage and Oxygenation Using a Laryngeal Mask Airway: A Randomized Trial

BACKGROUND

The value of positive end-expiratory pressure (PEEP) in maintaining oxygenation during ventilation with a laryngeal mask airway (LMA) mask is unclear. To clarify the potential benefit or harm to PEEP application during positive pressure ventilation with a ProSeal LMA® mask, we compared the effect of PEEP versus zero end-expiratory pressure (ZEEP) on gas leakage and oxygenation. We hypothesized that a PEEP of 8 mbar (8.2 cm H2O) would be associated with an increased incidence of gas leakage compared to ZEEP.

METHODS

We designed a prospective, controlled, randomized, single-blinded, multicenter clinical trial. Patients >18 years of age with an American Society of Anesthesiologists (ASA) physical status I/II without increased risk of aspiration were enrolled if they were scheduled for elective surgery under general anesthesia with an LMA mask. Patients were randomized to a control group managed with ZEEP or an intervention group managed with a PEEP of 8 mbar. Both groups received positive pressure ventilation. The primary end point was the occurrence of gas leakage. The Student t test and χ2 test were used for statistical analysis.

RESULTS

A total of 174 patients were enrolled in the ZEEP group, and 208 were enrolled in the PEEP group. The incidence of gas leakage did not differ between the 2 groups (ZEEP: 23/174, 13.2%; PEEP: 42/208, 20.2%; P = .071; odds ratio [OR], 1.611; 95% confidence interval [CI], 0.954-2.891). However, more patients required reseating of the LMA mask in the PEEP group (ZEEP: 5/174, 2.9%; PEEP: 18/208, 8.7%; P = .018; OR, 3.202; 95% CI, 1.164-8.812). The need for endotracheal intubation did not differ between groups (ZEEP: 2/174, 1.1%; PEEP: 7/208, 3.4%; P = .190; OR, 2.995; 95% CI, 0.614-14.608). After positive pressure ventilation for 25 minutes, the mean peripheral oxygen saturation (Spo2) was higher in the PEEP than in the ZEEP group (98.5 [1.9]% vs 98.0 [1.4]%; P = .01). Peak inspiratory pressure (PIP; 16 [2] vs 12 [4] mbar; P < .001) and dynamic compliance (57 [14] vs 49 [14] mL/mbar; P < .001) were both higher in the PEEP group than in the ZEEP group.

CONCLUSIONS

Use of PEEP did not affect the overall incidence of gas leakage. However, PEEP did result in a higher incidence of attempts to reseat the LMA mask compared to ZEEP, whereas the incidence of rescue intubation did not differ between groups. We concluded that a PEEP of 8 mbar did not increase overall gas leakage during positive pressure ventilation with an LMA mask, but it did slightly improve gas exchange and compliance. Overall, our study does not provide strong arguments for using PEEP during ventilation with an LMA mask in elective surgery.

Outcomes and risk factors for delayed-onset postoperative respiratory failure: a multi-center case-control study by the University of California Critical Care Research Collaborative (UC3RC)

BACKGROUND

Few interventions are known to reduce the incidence of respiratory failure that occurs following elective surgery (postoperative respiratory failure; PRF). We previously reported risk factors associated with PRF that occurs within the first 5 days after elective surgery (early PRF; E-PRF); however, PRF that occurs six or more days after elective surgery (late PRF; L-PRF) likely represents a different entity. We hypothesized that L-PRF would be associated with worse outcomes and different risk factors than E-PRF.

METHODS

This was a retrospective matched case-control study of 59,073 consecutive adult patients admitted for elective non-cardiac and non-pulmonary surgical procedures at one of five University of California academic medical centers between October 2012 and September 2015. We identified patients with L-PRF, confirmed by surgeon and intensivist subject matter expert review, and matched them 1:1 to patients who did not develop PRF (No-PRF) based on hospital, age, and surgical procedure. We then analyzed risk factors and outcomes associated with L-PRF compared to E-PRF and No-PRF.

RESULTS

Among 95 patients with L-PRF, 50.5% were female, 71.6% white, 27.4% Hispanic, and 53.7% Medicare recipients; the median age was 63 years (IQR 56, 70). Compared to 95 matched patients with No-PRF and 319 patients who developed E-PRF, L-PRF was associated with higher morbidity and mortality, longer hospital and intensive care unit length of stay, and increased costs. Compared to No-PRF, factors associated with L-PRF included: preexisiting neurologic disease (OR 4.36, 95% CI 1.81-10.46), anesthesia duration per hour (OR 1.22, 95% CI 1.04-1.44), and maximum intraoperative peak inspiratory pressure per cm H₂0 (OR 1.14, 95% CI 1.06-1.22).

CONCLUSIONS

We identified that pre-existing neurologic disease, longer duration of anesthesia, and greater maximum intraoperative peak inspiratory pressures were associated with respiratory failure that developed six or more days after elective surgery in adult patients (L-PRF). Interventions targeting these factors may be worthy of future evaluation.

Intraoperative protective mechanical ventilation in patients requiring emergency abdominal surgery: the multicentre prospective randomised IMPROVE-2 study protocol

IntroductionEmergency abdominal surgery is associated with a high risk of postoperative complications. One of the most serious is postoperative respiratory failure (PRF), with reported rates up to 20%-30% and attributable 30-day mortality that can exceed 20%.Lung-protective ventilation, especially the use of low tidal volume, may help reducing the risk of lung injury. The role of positive end-expiratory pressure (PEEP) and recruitment manoeuvre (RM) remains however debated. We aim to evaluate whether a strategy aimed at increasing alveolar recruitment by using higher PEEP levels and RM could be more effective at reducing PRF and mortality after emergency abdominal surgery than a strategy aimed at minimising alveolar distension by using lower PEEP levels without RM.

METHODS AND ANALYSIS

The IMPROVE-2 study is a multicentre randomised, parallel-group clinical trial of 680 patients requiring emergency abdominal surgery under general anaesthesia. Patients will be randomly allocated in a 1:1 ratio to receive either low PEEP levels (≤5 cm H₂O) without RM or high PEEP levels individually adjusted according to driving pressure in addition to RM, stratified by centre and according to the presence of shock and hypoxaemia at randomisation. The primary endpoint is a composite of PRF and all-cause mortality by day 30 or hospital discharge. Data will be analysed on the intention-to-treat principle and a per-protocol basis.

ETHICS AND DISSEMINATION

IMPROVE-2 trial has been approved by an independent ethics committee for all study centres. Participant recruitment began in February 2021. Results will be submitted for publication in international peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03987789.

Mechanical power during general anesthesia and postoperative respiratory failure: A multicenter retrospective cohort study

BACKGROUND

Mechanical power during ventilation estimates the energy delivered to the respiratory system through integrating inspiratory pressures, tidal volume and respiratory rate into a single value. It has been linked to lung injury and mortality in the acute respiratory distress syndrome, but little evidence exists whether the concept relates to lung injury in patients with healthy lungs. We hypothesized that higher mechanical power is associated with more postoperative respiratory failure requiring reintubation in patients undergoing general anesthesia.

METHODS

In this multicenter, retrospective study, 230,767 elective, non-cardiac adult surgical out- and inpatients undergoing general anesthesia between 2008 and 2018 at two academic hospital networks in Boston, MA, were included. The risk-adjusted association between the median intraoperative mechanical power (MP), calculated from median values of tidal volume (Vt), respiratory rate (RR), positive end-expiratory pressure (PEEP), plateau pressure (Pplat), and peak inspiratory pressure (Ppeak), using the formula MP (J/min)= 0.098*RR*Vt*[PEEP+½(Pplat-PEEP)+(Ppeak-Pplat)], and postoperative respiratory failure requiring reintubation within 7 days was assessed.

RESULTS

The median intraoperative mechanical power was 6.63 (interquartile range: 4.62-9.11) J/min. Postoperative respiratory failure occurred in 2,024 (0.9%) patients. The median (IQR) intraoperative mechanical power was higher in patients with postoperative respiratory failure than in patients without (7.67 [5.64-10.11] vs. 6.62 [4.62-9.10] J/min; p<0.001). In adjusted analyses, a higher mechanical power was associated with greater odds of postoperative respiratory failure (adjusted odds ratio [ORadj] 1.31 per 5 J/min increase; 95%CI 1.21-1.42; p<0.001). The association between mechanical power and postoperative respiratory failure was robust to additional adjustment for known drivers of ventilator-induced lung injury, including tidal volume, driving pressure and respiratory rate, and driven by the dynamic elastic component (ORadj 1.35 per 5 J/min; 95%CI 1.05-1.73; p=0.02).

CONCLUSIONS

Higher mechanical power during ventilation is statistically associated with a greater risk of postoperative respiratory failure requiring reintubation.

Intraoperative positive end-expiratory pressure and postoperative pulmonary complications: a patient-level meta-analysis of three randomised clinical trials

BACKGROUND

High intraoperative PEEP with recruitment manoeuvres may improve perioperative outcomes. We re-examined this question by conducting a patient-level meta-analysis of three clinical trials in adult patients at increased risk for postoperative pulmonary complications who underwent non-cardiothoracic and non-neurological surgery.

METHODS

The three trials enrolled patients at 128 hospitals in 24 countries from February 2011 to February 2018. All patients received volume-controlled ventilation with low tidal volume. Analyses were performed using one-stage, two-level, mixed modelling (site as a random effect; trial as a fixed effect). The primary outcome was a composite of postoperative pulmonary complications within the first week, analysed using mixed-effect logistic regression. Pre-specified subgroup analyses of nine patient characteristics and seven procedure and care-delivery characteristics were also performed.

RESULTS

Complete datasets were available for 1913 participants ventilated with high PEEP and recruitment manoeuvres, compared with 1924 participants who received low PEEP. The primary outcome occurred in 562/1913 (29.4%) participants randomised to high PEEP, compared with 620/1924 (32.2%) participants randomised to low PEEP (unadjusted odds ratio [OR]=0.87; 95% confidence interval [95% CI], 0.75-1.01; P=0.06). Higher PEEP resulted in 87/1913 (4.5%) participants requiring interventions for desaturation, compared with 216/1924 (11.2%) participants randomised to low PEEP (OR=0.34; 95% CI, 0.26-0.45). Intraoperative hypotension was associated more frequently (784/1913 [41.0%]) with high PEEP, compared with low PEEP (579/1924 [30.1%]; OR=1.87; 95% CI, 1.60-2.17).

CONCLUSIONS

High PEEP combined with recruitment manoeuvres during low tidal volume ventilation in patients undergoing major surgery did not reduce postoperative pulmonary complications.

CLINICAL TRIAL REGISTRATION

NCT03937375 (Clinicaltrials.gov).