Perioperative Positive Pressure Ventilation

Noninvasive ventilation on reintubation in patients with obesity and hypoxemic respiratory failure following abdominal surgery: a post hoc analysis of a randomized clinical trial

PURPOSE

Although noninvasive ventilation (NIV) may reduce reintubation in patients with acute hypoxemic respiratory failure following abdominal surgery, this strategy has not been specifically assessed in patients with obesity.

METHODS

We conducted a post hoc analysis of a multicenter randomized controlled trial comparing NIV delivered via facial mask to standard oxygen therapy among patients with obesity and acute hypoxemic respiratory failure within 7 days after abdominal surgery. The primary outcome was reintubation within 7 days. Secondary outcomes were invasive ventilation-free days at day 30, intensive care unit (ICU)-acquired pneumonia and 30-day survival.

RESULTS

Among 293 patients with hypoxemic respiratory failure following abdominal surgery, 76 (26%) patients had obesity and were included in the intention-to-treat analysis. Reintubation rate was significantly lower with NIV (13/42, 31%) than with standard oxygen therapy (19/34, 56%) within 7 days (absolute difference: - 25%, 95% confidence interval (CI) - 49 to - 1%, p = 0.03). NIV was associated with significantly more invasive ventilation-free days compared with standard oxygen therapy (27.1 ± 8.6 vs 22.7 ± 11.1 days; p = 0.02), while fewer patients developed ICU-acquired pneumonia (1/42, 2% vs 6/34, 18%; p = 0.04). The 30-day survival was 98% in the NIV group (41/42) versus 85% in the standard oxygen therapy (p = 0.08). In patients with body mass index (BMI) < 30 kg/m2, no significant difference was observed between NIV (36/105, 34%) and standard oxygen therapy (47/109, 43%, p = 0.03). An interaction test showed no statistically significant difference between the two subsets (BMI ≥ 30 kg/m2 and BMI < 30 kg/m2).

CONCLUSIONS

Among patients with obesity and hypoxemic respiratory failure following abdominal surgery, use of NIV compared with standard oxygen therapy reduced the risk of reintubation within 7 days, contrary to patients without obesity. However, no interaction was found according to the presence of obesity or not, suggesting either a lack of power to conclude in the non-obese subgroup despite existing differences, or that the statistical difference found in the overall sample was driven by a large effect in the obese subsets.

Use of stepwise lung recruitment maneuver to predict fluid responsiveness under lung protective ventilation in the operating room

Recent research has revealed that hemodynamic changes caused by lung recruitment maneuvers (LRM) with continuous positive airway pressure can be used to identify fluid responders. We investigated the usefulness of stepwise LRM with increasing positive end-expiratory pressure and constant driving pressure for predicting fluid responsiveness in patients under lung protective ventilation (LPV). Forty-one patients under LPV were enrolled when PPV values were in a priori considered gray zone (4% to 17%). The FloTrac-Vigileo device measured stroke volume variation (SVV) and stroke volume (SV), while the patient monitor measured pulse pressure variation (PPV) before and at the end of stepwise LRM and before and 5 min after fluid challenge (6 ml/kg). Fluid responsiveness was defined as a ≥ 15% increase in the SV or SV index. Seventeen were fluid responders. The areas under the curve for the augmented values of PPV and SVV, as well as the decrease in SV by stepwise LRM to identify fluid responders, were 0.76 (95% confidence interval, 0.61-0.88), 0.78 (0.62-0.89), and 0.69 (0.53-0.82), respectively. The optimal cut-offs for the augmented values of PPV and SVV were > 18% and > 13%, respectively. Stepwise LRM -generated augmented PPV and SVV predicted fluid responsiveness under LPV.

Noninvasive respiratory support in the perioperative setting: a narrative review

The application of preoperative noninvasive respiratory support (NRS) has been expanding with increasing recognition of its potential role in this setting as a physiological optimization for patients with a high risk of developing atelectasis and postoperative pulmonary complications (PPC). The increased availability of high-performance anesthesia ventilator machines providing an easy way for NRS support in patients with reduced lung function should not be under-evaluated. This support can reduce hypoxia, restore lung volumes and theoretically reduce atelectasis formation after general anesthesia. Therapeutic purposes should also be considered in the perioperative setting, such as preoperative NRS to optimize treatment of patients' pre-existing diseases, e.g., sleep-disordered breathing. Finally, the recent guidelines for airway management suggest preoperative NRS application before anesthesia induction in difficult airway management to prolong the time needed to secure the airway with an orotracheal tube. This narrative review aims to revise all these aspects and to provide some practical notes to maximize the efficacy of perioperative noninvasive respiratory support.

The effect of inverse ratio ventilation on cardiopulmonary function in obese laparoscopic surgery patients: A systematic review and meta-analysis

This study aimed to evaluate the effect of inverse ratio ventilation (IRV) strategy on cardiopulmonary function in obese patients under general anesthesia. Databases such as China National Knowledge Infrastructure (CNKI), Wangfang, WeiP, Web of Science, the Cochrane Library, and PubMed were systematically searched. All randomized controlled trials' literature on IRV during laparoscopic surgery in obese patients under general anesthesia was collected. After data were extracted and cross-checked, Rev Man 5.3 software was used for meta-analysis. Finally, five randomized controlled clinical trials (RCTs) were included in the meta-analysis, with a total of 312 patients. Compared with the conventional ventilation group, the inspiratory peak pressure was lower at pneumoperitoneum 30 min and pneumoperitoneum 60 min; the PaO2 and oxygenation index were higher at pneumoperitoneum 60 min, and mean airway pressure was higher at pneumoperitoneum 30 min and pneumoperitoneum 60 min; the dynamic lung compliance was superior at pneumoperitoneum 30 min and pneumoperitoneum 60 min. IRV applied to laparoscopic surgery in obese patients under general anesthesia not only reduces peak airway pressure and improves intraoperative oxygenation index and PaO2 but also enhances mean airway pressure and dynamic lung compliance, which has a specific lung protective effect. It can be used as an option for the mechanical ventilation model in obese patients in clinical practice.

Improving Certified Registered Nurse Anesthetists' Adherence to a Standardized Intraoperative Lung Protective Ventilation Protocol

PURPOSE

The use of lung protective ventilation (LPV) during general anesthesia is an effective strategy among certified registered nurse anesthetists (CRNAs) to reduce and prevent the incidence of postoperative pulmonary complications. The purpose of this project was to implement a LPV protocol, assess CRNA provider adherence, and investigate differences in ventilation parameters and postoperative oxygen requirements.

DESIGN

This quality improvement project was conducted using a pre- and postimplementation design.

METHODS

Sixty patients undergoing robotic laparoscopic abdominal surgery and 35 CRNAs at a community hospital participated. An evidence-based intraoperative LPV protocol was developed, CRNA education was provided, and the protocol was implemented. Pre- and postimplementation, CRNA knowledge, and confidence were assessed. Ventilation data were collected at 1-minute intervals intraoperatively and oxygen requirements were recorded in the postanesthesia care unit (PACU).

FINDINGS

Use of intraoperative LPV strategies increased 2.4%. Overall CRNA knowledge (P = .588), confidence (P = .031), and practice (P < .001) improved from pre- to postimplementation. Driving pressures decreased from pre- to postimplementation (P < .001). Supplemental oxygen use on admission to the PACU decreased from 93.3% to 70.0%.

CONCLUSIONS

Educational interventions and implementation of a standardized protocol can improve the use of intraoperative LPV strategies and patient outcomes.

Non-Invasive Ventilation Reduces Postoperative Respiratory Failure in Patients Undergoing Bariatric Surgery: A Retrospective Analysis

Background and Objectives: Postoperative non-invasive ventilation (NIV) has been proposed as an attractive strategy to reduce morbidity in obese subjects undergoing general anaesthesia. The increased body mass index (BMI) correlates with loss of perioperative functional residual capacity, expiratory reserve volume, and total lung capacity. The aim of the current study is to evaluate the efficacy of NIV in a post-anaesthesia care unit (PACU) in reducing post-extubation acute respiratory failure (ARF) after biliointestinal bypass (BIBP) in obese patients. Materials and Methods: A retrospective analysis was conducted from January 2019 to December 2020 to compare acute respiratory failure within the first 72 postoperative hours and oximetry values of obese patients who underwent BIBP after postoperative NIV adoption or conventional Venturi mask. Results: In total, 50 patients who received NIV postoperative protocol and 57 patients who received conventional Venturi mask ventilation were included in the study. After 120 min in PACU pH, pCO2, pO2, and SpO2 were better in the NIV group vs. control group (p < 0.001). Seventy-two hours postoperatively, one patient (2%) in the NIV group vs. seven patients (12.2%) in the control group developed acute respiratory failure. Therefore, conventional Venturi mask ventilation resulted in being significantly associated (p < 0.05) with postoperative ARF with an RR of 0.51 (IC 0.27-0.96). Conclusions: After bariatric surgery, short-term NIV during PACU observation promotes a more rapid recovery of postoperative lung function and oxygenation in obese patients, reducing the necessity for critical care in the days following surgery. Therefore, as day-case surgery becomes more advocated even for morbid obesity, it might be considered a necessary procedure.

Impact of Preemptive Postoperative Pressure Support Ventilation and Physiotherapy on Postoperative Pulmonary Complications after Major Cervicofacial Cancer Surgery: A before and after Study

Introduction: Complex cervicofacial cancer surgery with free flap reconstruction is known to have a high incidence of postoperative pulmonary complications (PPCs). We hypothesized that by implementing an optimized respiratory protocol, including preemptive postoperative pressure support ventilation, physiotherapy, and critical respiratory support and follow-up, we could decrease the incidence of PPCs. Patients and methods: We evaluated the incidence of PPCs over two periods in two groups of patients having a routine or optimized postoperative respiratory protocol: 156 adult patients undergoing major cervicofacial cancer surgery were assessed; 91 were in Group 1 (routine) and 65 were in Group 2 (optimized). In Group 1, no ventilatory support sessions were performed. The incidence of pulmonary complications in both groups was compared using a multivariate analysis. Mortality was also compared until one year postoperatively. Results: In Group 2 with an optimized protocol, the mean number of ventilatory support sessions was 3.7 ± 1 (minimum 2, maximum 6). The incidence of respiratory complications, which was 34% in Group 1 (routine), was reduced by 59% OR = 0.41 (0.16; 0.95), p = 0.043) to 21% for the optimized Group 2. No difference in mortality was found. Conclusions: The present retrospective study showed that using an optimized preemptive respiratory pressure support ventilation combined with physiotherapy after a major cervicofacial surgery could possibly help reduce the incidence of pulmonary complications. Prospective studies are needed to verify these findings.

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.

Effects of ultrasound-guided alveolar recruitment manoeuvres compared with sustained inflation or no recruitment manoeuvres on atelectasis in laparoscopic gynaecological surgery as assessed by ultrasonography: a randomized clinical trial

Background

The majority of patients may experience atelectasis under general anesthesia, and the Trendelenburg position and pneumoperitoneum can aggravate atelectasis during laparoscopic surgery, which promotes postoperative pulmonary complications. Lung recruitment manoeuvres have been proven to reduce perioperative atelectasis, but it remains controversial which method is optimal. Ultrasonic imaging can be conducive to confirming the effect of lung recruitment manoeuvres. The purpose of our study was to assess the effects of ultrasound-guided alveolar recruitment manoeuvres by ultrasonography on reducing perioperative atelectasis and to check whether the effects of recruitment manoeuvres under ultrasound guidance (visual and semiquantitative) on atelectasis are superior to sustained inflation recruitment manoeuvres (classical and widely used) in laparoscopic gynaecological surgery.

Methods

In this randomized, controlled, double-blinded study, women undergoing laparoscopic gynecological surgery were enrolled. Patients were randomly assigned to receive either lung ultrasound-guided alveolar recruitment manoeuvres (UD group), sustained inflation alveolar recruitment manoeuvres (SI group), or no RMs (C group) using a computer-generated table of random numbers. Lung ultrasonography was performed at four predefined time points. The primary outcome was the difference in lung ultrasound score (LUS) among groups at the end of surgery.

Results

Lung ultrasound scores in the UD group were significantly lower than those in both the SI group and the C group immediately after the end of surgery (7.67 ± 1.15 versus 9.70 ± 102, difference, -2.03 [95% confidence interval, -2.77 to -1.29], P < 0.001; 7.67 ± 1.15 versus 11.73 ± 1.96, difference, -4.07 [95% confidence interval, -4.81 to -3.33], P < 0.001;, respectively). The intergroup differences were sustained until 30 min after tracheal extubation (9.33 ± 0.96 versus 11.13 ± 0.97, difference, -1.80 [95% confidence interval, -2.42 to -1.18], P < 0.001; 9.33 ± 0.96 versus 10.77 ± 1.57, difference, -1.43 [95% confidence interval, -2.05 to -0.82], P < 0.001;, respectively). The SI group had a significantly lower LUS than the C group at the end of surgery (9.70 ± 1.02 versus 11.73 ± 1.96, difference, -2.03 [95% confidence interval, -2.77 to -1.29] P < 0.001), but the benefit did not persist 30 min after tracheal extubation.

Conclusions

During general anesthesia, ultrasound-guided recruitment manoeuvres can reduce perioperative aeration loss and improve oxygenation. Furthermore, these effects of ultrasound-guided recruitment manoeuvres on atelectasis are superior to sustained inflation recruitment manoeuvres.

Trial registration

Chictr.org.cn, ChiCTR2100042731, Registered 27 January 2021, www.chictr.org.cn.

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.

Intraoperative Protective Mechanical Ventilation in Dogs: A Randomized Clinical Trial

Objective

To evaluate gas exchange, respiratory mechanics, and hemodynamic impact of mechanical ventilation with low tidal volume (V_T) in dogs with the use of positive end-expiratory pressure (PEEP) or preceded by alveolar recruitment maneuver (ARM).

Study Design

Prospective randomized clinical trial.

Animals

Twenty-one healthy client-owned mesocephalic healthy dogs, 1-7 years old, weighing 10-20 kg, and body condition scores 4-6/9 admitted for periodontal treatment.

Methods

Isoflurane-anesthetized dogs in dorsal recumbency were ventilated until 1 h with a volume-controlled ventilation mode using 8 mL kg^-1 of V_T. The dogs were distributed in 2 groups: in the ARM group, PEEP starts in 0 cmH₂O, increasing gradually 5 cmH₂O every 3 min, until reach 15 cmH₂O and decreasing in the same steps until 5 cmH₂O, maintaining this value until the end; and PEEP group, in which the pressure 5 cmH₂O was instituted from the beginning of anesthesia and maintained the same level up to the end of the anesthesia. Cardiopulmonary, metabolic, oxygenation parameters, and respiratory mechanics were recorded after the anesthesia induction (baseline-BL), 15, 45, and 75 min after BL and during the recovery.

Results

The ARM increased the static compliance (C_st) (15 min after baseline) when compared with baseline moment (24.9 ± 5.8 mL cmH₂0^-1 vs. 20.7 ± 5.4 mL cmH₂0^-1-p = 0.0364), oxygenation index (PaO₂/FIO₂) (505.6 ± 59.2 mmHg vs. 461.2 ± 41.0 mmHg-p = 0.0453) and reduced the shunt fraction (3.4 ± 2.4% vs. 5.5 ± 1.6%-p = 0.062). In the PEEP group, no statistical differences were observed concerning the variables evaluated. At the beginning of the evaluation, the driving pressure (DP) before ARM was significantly greater than all other evaluation time points (6.9 ± 1.8 cmH₂0).

Conclusions and Clinical Relevance

The use of 8 mL kg^-1 of V_T and 5 cmH₂0 PEEP without ARM maintain adequate oxygenation and mechanical ventilation in dental surgeries for up to 1 h. The use of ARM slightly improved compliance and oxygenation during the maneuver.

Complications and Mortality after Surgeries in Patients with Prior Stroke Who Received General and Neuraxial Anesthesia: A Propensity-Score Matched Study

Patients who previously suffered a stroke have increased risks of mortality and complications after surgeries, but the optimal anesthesia method is not fully understood. We aimed to compare the outcomes after surgeries for stroke patients who received general anesthesia (GA) and neuraxial anesthesia (NA). Using health insurance research data, we identified 36,149 stroke patients who underwent surgeries from 1 January 2008 to 31 December 2013. For balancing baseline covariates, the propensity-score-matching procedure was used to select adequate surgical patients who received GA and NA at a case–control ratio of 1:1. Multiple logistic regressions were applied to calculate adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for postoperative mortality and complications between surgical patients with prior stroke who received GA and NA. Among the 4903 matched pairs with prior stroke, patients with GA had higher risks of pneumonia (OR 2.00, 95% CI 1.62–2.46), pulmonary embolism (OR 3.30, 95% CI 1.07–10.2), acute renal failure (OR 3.51, 95% CI 1.13–2.10), intensive care unit stay (OR 3.74, 95% CI 3.17–4.41), and in-hospital mortality (OR 2.02, 95% CI 1.16–3.51) than those who received NA. Postoperative adverse events were associated with GA in patients aged more than 60 years and those who received digestive surgery (OR 3.11, 95% CI 2.08–4.66). We found that stroke patients undergoing GA had increased postoperative complications and mortality after surgery compared with those who received NA. However, these findings need more validation and evaluation by clinical trials.

Perioperative Pulmonary Atelectasis: Part II. Clinical Implications

The development of pulmonary atelectasis is common in the surgical patient. Pulmonary atelectasis can cause various degrees of gas exchange and respiratory mechanics impairment during and after surgery. In its most serious presentations, lung collapse could contribute to postoperative respiratory insufficiency, pneumonia, and worse overall clinical outcomes. A specific risk assessment is critical to allow clinicians to optimally choose the anesthetic technique, prepare appropriate monitoring, adapt the perioperative plan, and ensure the patient's safety. Bedside diagnosis and management have benefited from recent imaging advancements such as lung ultrasound and electrical impedance tomography, and monitoring such as esophageal manometry. Therapeutic management includes a broad range of interventions aimed at promoting lung recruitment. During general anesthesia, these strategies have consistently demonstrated their effectiveness in improving intraoperative oxygenation and respiratory compliance. Yet these same intraoperative strategies may fail to affect additional postoperative pulmonary outcomes. Specific attention to the postoperative period may be key for such outcome impact of lung expansion. Interventions such as noninvasive positive pressure ventilatory support may be beneficial in specific patients at high risk for pulmonary atelectasis (e.g., obese) or those with clinical presentations consistent with lung collapse (e.g., postoperative hypoxemia after abdominal and cardiothoracic surgeries). Preoperative interventions may open new opportunities to minimize perioperative lung collapse and prevent pulmonary complications. Knowledge of pathophysiologic mechanisms of atelectasis and their consequences in the healthy and diseased lung should provide the basis for current practice and help to stratify and match the intensity of selected interventions to clinical conditions.

Quantitative Lung Ultrasound: Technical Aspects and Clinical Applications

Lung ultrasound is increasingly used in emergency departments, medical wards, and critical care units-adult, pediatric, and neonatal. In vitro and in vivo studies show that the number and type of artifacts visualized change with lung density. This has led to the idea of a quantitative lung ultrasound approach, opening up new prospects for use not only as a diagnostic but also as a monitoring tool. Consequently, the multiple scoring systems proposed in the last few years have different technical approaches and specific clinical indications, adaptable for more or less time-dependent patients. However, multiple scoring systems may generate confusion among physicians aiming at introducing lung ultrasound in their clinical practice. This review describes the various lung ultrasound scoring systems and aims to clarify their use in different settings, focusing on technical aspects, validation with reference techniques, and clinical applications.

Prediction of fluid responsiveness using lung recruitment manoeuvre in paediatric patients receiving lung-protective ventilation: A prospective observational study

BACKGROUND

Pressure-based dynamic variables are poor predictors of fluid responsiveness in children, and their predictability is expected to reduce further during lung-protective ventilation with a low tidal volume.

OBJECTIVE

We hypothesised that lung recruitment manoeuvre (LRM)-induced changes in dynamic variables improve their ability to predict fluid responsiveness in children.

DESIGN

Prospective observational study.

SETTING

Tertiary care children's hospital, single-centre study performed from June 2017 to May 2019.

PATIENTS

We included patients less than 7 years of age undergoing cardiac surgery. Neonates and patients with pulmonary hypertension, significant dysrhythmia, ventricular ejection fraction of less than 30% or pulmonary disease were excluded.

INTERVENTION

All patients were provided with lung-protective volume-controlled ventilation (tidal volume 6 ml kg-1, positive end-expiratory pressure 6 cmH2O). A LRM was applied with a continuous inspiratory pressure of 25 cmH2O for 20 s.

MAIN OUTCOME MEASURE

The ability of dynamic variables to predict fluid responsiveness was evaluated by the area under the receiver operating characteristic curve [area under the curve (AUC)]. Fluid responsiveness was defined as an increase in the cardiac index by more than 15% with crystalloid administration (10 ml kg-1).

RESULTS

Thirty patients were included in the final analysis, of whom 19 were responders. The baseline pleth variability index (PVI) (AUC 0.794, 95% confidence interval 0.608 to 0.919, P < 0.001) and LRM-induced PVI (AUC 0.711, 95% confidence interval 0.517 to 0.861, P = 0.026) could predict fluid responsiveness. The respiratory variation of pulse oximetry photoplethysmographic waveform and pulse pressure variation did not predict fluid responsiveness regardless of the LRM.

CONCLUSION

The PVI is effective in predicting fluid responsiveness in paediatric patients with lung-protective ventilation regardless of a LRM. However, the LRM did not improve the ability of the other dynamic variables to predict fluid responsiveness in these patients.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov identifier: NCT03184961.

Ultrasound-guided versus conventional lung recruitment manoeuvres in laparoscopic gynaecological surgery: A randomised controlled trial

BACKGROUND

Pneumoperitoneum and steep Trendelenburg position promote the formation of pulmonary atelectasis during laparoscopic gynaecological surgery.

OBJECTIVE

To determine whether lung ultrasound-guided alveolar recruitment manoeuvres could reduce peri-operative atelectasis compared with conventional recruitment manoeuvres during laparoscopic gynaecological surgery.

DESIGN

Randomised controlled trial.

SETTING

Tertiary hospital, Republic of Korea, from August 2018 to January 2019.

PATIENTS

Adult patients scheduled for laparoscopic gynaecological surgery under general anaesthesia.

INTERVENTION

Forty patients were randomised to receive either ultrasound-guided recruitment manoeuvres (manual inflation until no visibly collapsed area was seen with lung ultrasonography; intervention group) or conventional recruitment manoeuvres (single manual inflation with 30 cmH2O pressure; control group). Recruitment manoeuvres were performed 5 min after induction and at the end of surgery in both groups. All patients received volume-controlled ventilation with a tidal volume of 8 ml kg-1 and a positive end-expiratory pressure of 5 cmH2O.

MAIN OUTCOME MEASURES

The primary outcome was the lung ultrasound score at the end of surgery; a higher score indicates worse lung aeration.

RESULTS

Lung ultrasound scores at the end of surgery were significantly lower in the intervention group compared with control group (median [IQR], 7.5 [6.5 to 8.5] versus 9.5 [8.5 to 13.5]; difference, -2 [95% CI, -4.5 to -1]; P = 0.008). The intergroup difference persisted in the postanaesthesia care unit (7 [5 to 8.8] versus 10 [7.3 to 12.8]; difference, -3 [95% CI, -5.5 to -1.5]; P = 0.005). The incidence of atelectasis was lower in the intervention group compared with control group at the end of surgery (35 versus 80%; P = 0.010) but was comparable in the postanaesthesia care unit (40 versus 55%; P = 0.527).

CONCLUSIONS

The use of ultrasound-guided recruitment manoeuvres improves peri-operative lung aeration; these effects may persist in the postanaesthesia care unit. However, the long-term effects of ultrasound-guided recruitment manoeuvres on clinical outcomes should be the subject of future trials.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT03607240).

Effects of lung-protective ventilation strategy on lung aeration loss and postoperative pulmonary complications in moderate-risk patients undergoing abdominal surgery

BACKGROUND

There is a controversy about whether the use of a lung-protective ventilation strategy(LPVS) can reduce the incidence of postoperative pulmonary complications (PPCs) and improve the clinical outcomes in moderate-risk patients were assessed by the Assess Respiratory Risk in Surgical Patients in Catalonia(ARISCAT).

METHODS

One hundred moderate-risk patients predicted by the ARISCAT, scheduled to undergo abdominal surgery were randomized into two groups: conventional ventilation strategy group (G<inf>0</inf>) and lung-protective ventilation strategy group (G<inf>1</inf>). Lung ultrasonography (LUS) and the LUS score were performed before induction of anesthesia (T<inf>0</inf>), 30min after extubation (T<inf>1</inf>), and 24h (T<inf>2</inf>), 72h (T<inf>3</inf>) after surgery. The incidence and severity of PPCs within the postoperative 7 days, the duration of postoperative oxygen supplementation, and postoperative hospital stay (PHS) were recorded.

RESULTS

The LUS score of both groups at T<inf>1-3</inf> was higher than those at T<inf>0</inf> (P<0.05), moreover, the LUS score of G<inf>1</inf> was lower than that of G<inf>0</inf> at T<inf>1-3</inf>. The incidence of PPCs of G<inf>1</inf> (10.9%) was lower than that of G<inf>0</inf> (29.8%) (relative risk, 0.37; 95% confidence interval [CI], 0.14 to 0.93; P=0.02) and the severity of PPCs of G<inf>1</inf> were lower than those of G<inf>0</inf> (P<0.05). The PHS of G<inf>1</inf> was less than that of G<inf>0</inf> (8[7-10] vs. 9[8-11], P<0.05).

CONCLUSIONS

The LPVS can decrease lung aeration loss assessed by LUS and reduce the incidence of PPCs in moderate-risk patients.

Perioperative Open-lung Approach, Regional Ventilation, and Lung Injury in Cardiac Surgery

BACKGROUND

In the Protective Ventilation in Cardiac Surgery (PROVECS) randomized, controlled trial, an open-lung ventilation strategy did not improve postoperative respiratory outcomes after on-pump cardiac surgery. In this prespecified subanalysis, the authors aimed to assess the regional distribution of ventilation and plasma biomarkers of lung epithelial and endothelial injury produced by that strategy.

METHODS

Perioperative open-lung ventilation consisted of recruitment maneuvers, positive end-expiratory pressure (PEEP) = 8 cm H2O, and low-tidal volume ventilation including during cardiopulmonary bypass. Control ventilation strategy was a low-PEEP (2 cm H2O) low-tidal volume approach. Electrical impedance tomography was used serially throughout the perioperative period (n = 56) to compute the dorsal fraction of ventilation (defined as the ratio of dorsal tidal impedance variation to global tidal impedance variation). Lung injury was assessed serially using biomarkers of epithelial (soluble form of the receptor for advanced glycation end-products, sRAGE) and endothelial (angiopoietin-2) lung injury (n = 30).

RESULTS

Eighty-six patients (age = 64 ± 12 yr; EuroSCORE II = 1.65 ± 1.57%) undergoing elective on-pump cardiac surgery were studied. Induction of general anesthesia was associated with ventral redistribution of tidal volumes and higher dorsal fraction of ventilation in the open-lung than the control strategy (0.38 ± 0.07 vs. 0.30 ± 0.10; P = 0.004). No effect of the open-lung strategy on the dorsal fraction of ventilation was noted at the end of surgery after median sternotomy closure (open-lung = 0.37 ± 0.09 vs. control = 0.34 ± 0.11; P = 0.743) or in extubated patients at postoperative day 2 (open-lung = 0.63 ± 0.18 vs. control = 0.59 ± 0.11; P > 0.999). Open-lung ventilation was associated with increased intraoperative plasma sRAGE (7,677 ± 3,097 pg/ml vs. 6,125 ± 1,400 pg/ml; P = 0.037) and had no effect on angiopoietin-2 (P > 0.999).

CONCLUSIONS

In cardiac surgery patients, open-lung ventilation provided larger dorsal lung ventilation early during surgery without a maintained benefit as compared with controls at the end of surgery and postoperative day 2 and was associated with higher intraoperative plasma concentration of sRAGE suggesting lung overdistension.

EDITOR’S PERSPECTIVE

Alveolar recruitment manoeuvre results in improved pulmonary function in obese patients undergoing bariatric surgery: a randomised trial

Perioperative ventilation is an important challenge of anaesthesia, especially in obese patients: body mass index is correlated with reduction of the pulmonary volume and they develop significantly more perioperative atelectasis and pulmonary complications. The alveolar recruitment manoeuvre is the most effective technique to reverse atelectasis. However, the clinical benefit on lung function in the perioperative period is not clear. The aim of the present study is to assess the perioperative clinical results of systematic alveolar recruitment manoeuvre associated with protective ventilation in patients undergoing laparoscopic bariatric surgery. It was a single-centre, randomised, double blind, superiority trial: control group with standard protective ventilation and recruitment group with protective ventilation and systematic recruitment manoeuvre. The primary outcome was a composite clinical criterion of pulmonary dysfunction including oxygen saturation, oxygen needs and dyspnoea in recovery room and at day 1. Secondary outcomes were recruitment manoeuvre tolerance, pulmonary and non-pulmonary complications, length of hospital stay and proportion of Intensive Care Unit admission. Two hundred and thirty patients were included: 115 in the recruitment manoeuvre group and 115 in the control group, 2 patients were excluded from the analysis in the control group. Patients in the recruitment manoeuvre group had significantly lower rate of pulmonary dysfunction in the recovery room (73% versus 84% (p =  0.043) and 77% versus 88% at postoperative day 1 (p =  0.043)). No significant differences were found for secondary outcomes. No patient was excluded from the recruitment manoeuvre group for intolerance to the manoeuvre. Recruitment manoeuvre is safe and effective in reducing early pulmonary dysfunction in obese patients undergoing bariatric surgery.

Evaluation of alveolar recruitment maneuver on respiratory resistance during general anesthesia: a prospective observational study

Background

Alveolar recruitment maneuvers enable easily reopening nonaerated lung regions via a transient elevation in transpulmonary pressure. To evaluate the effect of these maneuvers on respiratory resistance, we used an oscillatory technique during mechanical ventilation. This study was conducted to assess the effect of the alveolar recruitment maneuvers on respiratory resistance under routine anesthesia. We hypothesized that respiratory resistance at 5 Hz (R5) after the maneuver would be decreased after the lung aeration.

Methods

After receiving the ethics committee’s approval, we enrolled 33 patients who were classified with an American Society of Anesthesiologists physical status of 1, 2 or 3 and were undergoing general anesthesia for transurethral resection of a bladder tumor within a 12-month period from 2017 to 2018. The recruitment maneuver was performed 30 min after endotracheal intubation. The maneuver consisted of sustained manual inflation of the anesthesia reservoir bag to a peak inspiratory pressure of 40 cmH₂O for 15 s, including 5 s of gradually increasing the peak inspiratory pressure. Respiratory resistance was measured using the forced oscillation technique before and after the maneuver, and the mean R5 was calculated during the expiratory phase. The respiratory resistance and ventilator parameter results were analyzed using paired Student’s t-tests, and p < 0.05 was considered statistically significant.

Results

We analyzed 31 patients (25 men and 6 women). R5 was 7.3 ± 1.6 cmH₂O/L/sec before the recruitment maneuver during mechanical ventilation and was significantly decreased to 6.4 ± 1.7 cmH₂O/L/sec after the maneuver. Peak inspiratory pressure and plateau pressure were significantly decreased, and pulmonary compliance was increased, although the values were not clinically relevant.

Conclusion

The recruitment maneuver decreased respiratory resistance and increased lung compliance during mechanical ventilation.

Trial registration

Name of registry: Japan Medical Association Center for Clinical Trials.

Trial registration number: reference JMA-IIA00136.

Date of registration: 2 September 2013.

URL of trial registry record: https://dbcentre3.jmacct.med.or.jp/JMACTR/App/JMACTRE02_04/JMACTRE02_04.aspx?kbn=3&seqno=3582

Intraoperative mechanical ventilation practice in thoracic surgery patients and its association with postoperative pulmonary complications: results of a multicenter prospective observational study

Background

Intraoperative mechanical ventilation may influence postoperative pulmonary complications (PPCs). Current practice during thoracic surgery is not well described.

Methods

This is a post-hoc analysis of the prospective multicenter cross-sectional LAS VEGAS study focusing on patients who underwent thoracic surgery. Consecutive adult patients receiving invasive ventilation during general anesthesia were included in a one-week period in 2013. Baseline characteristics, intraoperative and postoperative data were registered. PPCs were collected as composite endpoint until the 5th postoperative day. Patients were stratified into groups based on the use of one lung ventilation (OLV) or two lung ventilation (TLV), endoscopic vs. non-endoscopic approach and ARISCAT score risk for PPCs. Differences between subgroups were compared using χ² or Fisher exact tests or Student’s t-test. Kaplan–Meier estimates of the cumulative probability of development of PPC and hospital discharge were performed. Cox-proportional hazard models without adjustment for covariates were used to assess the effect of the subgroups on outcome.

Results

From 10,520 patients enrolled in the LAS VEGAS study, 302 patients underwent thoracic procedures and were analyzed. There were no differences in patient characteristics between OLV vs. TLV, or endoscopic vs. open surgery. Patients received V_T of 7.4 ± 1.6 mL/kg, a PEEP of 3.5 ± 2.4 cmH₂O, and driving pressure of 14.4 ± 4.6 cmH₂O. Compared with TLV, patients receiving OLV had lower V_T and higher peak, plateau and driving pressures, higher PEEP and respiratory rate, and received more recruitment maneuvers. There was no difference in the incidence of PPCs in OLV vs. TLV or in endoscopic vs. open procedures. Patients at high risk had a higher incidence of PPCs compared with patients at low risk (48.1% vs. 28.9%; hazard ratio, 1.95; 95% CI 1.05–3.61; p = 0.033). There was no difference in the incidence of severe PPCs. The in-hospital length of stay (LOS) was longer in patients who developed PPCs. Patients undergoing OLV, endoscopic procedures and at low risk for PPC had shorter LOS.

Conclusion

PPCs occurred frequently and prolonged hospital LOS following thoracic surgery. Proportionally large tidal volumes and high driving pressure were commonly used in this sub-population. However, large RCTs are needed to confirm these findings.

Trial registration

This trial was prospectively registered at the Clinical Trial Register (www.clinicaltrials.gov; NCT01601223; registered May 17, 2012.)

Effects of intraoperative positive end-expiratory pressure optimization on respiratory mechanics and the inflammatory response: a randomized controlled trial

Applying lung protective mechanical ventilation (LPV) during general anaesthesia even in patients with non-injured lungs is recommended. However, the effects of an individual PEEP-optimisation on respiratory mechanics, oxygenation and their potential correlation with the inflammatory response and postoperative complications have not been evaluated have not been compared to standard LPV in patients undergoing major abdominal surgery. Thirty-nine patients undergoing open radical cystectomy were enrolled in this study. In the study group (SG) optimal PEEP was determined by a decremental titration procedure and defined as the PEEP value resulting the highest static pulmonary compliance. In the control group (CG) PEEP was set to 6 cmH2O. Primary endpoints were intraoperative respiratory mechanics and gas exchange parameters. Secondary outcomes were perioperative procalcitonin kinetics and postoperative pulmonary complications. Optimal PEEP levels (median = 10, range: 8–14 cmH2O), PaO2/FiO2 (451.24 ± 121.78 mmHg vs. 404.15 ± 115.87 mmHg, P = 0.005) and static pulmonary compliance (52.54 ± 13.59 ml cmH2O-1 vs. 45.22 ± 9.13 ml cmH2O-1, P < 0.0001) were significantly higher, while driving pressure (8.26 ± 1.74 cmH2O vs. 9.73 ± 4.02 cmH2O, P < 0.0001) was significantly lower in the SG as compared to the CG. No significant intergroup differences were found in procalcitonin kinetics (P = 0.076). Composite outcome results indicated a non-significant reduction of postoperative complications in the SG. Intraoperative PEEP-optimization resulted in significant improvement in gas exchange and pulmonary mechanics as compared to standard LPV. Whether these have any effect on short and long term outcomes require further investigations. Trial registration: Clinicaltrials.gov, identifier: NCT02931409.

Protective ventilation during anaesthesia reduces major postoperative complications after lung cancer surgery: A double-blind randomised controlled trial

BACKGROUND

Thoracic surgery for lung resection is associated with a high incidence of postoperative pulmonary complications. Controlled ventilation with a large tidal volume has been documented to be a risk factor for postoperative respiratory complications after major abdominal surgery, whereas the use of low tidal volumes and positive end-expiratory pressure (PEEP) has a protective effect.

OBJECTIVE

To evaluate the effects of ventilation with low tidal volume and PEEP on major complications after thoracic surgery.

DESIGN

A double-blind, randomised controlled study.

SETTING

A multicentre trial from December 2008 to October 2011.

PATIENTS

A total of 346 patients undergoing lobectomy or pneumonectomy for lung cancer.

MAIN OUTCOME MEASURES

The primary outcome was the occurrence of major postoperative complications (pneumonia, acute lung injury, acute respiratory distress syndrome, pulmonary embolism, shock, myocardial infarction or death) within 30 days after surgery.

INTERVENTIONS

Patients were randomly assigned to receive either lung-protective ventilation (LPV group) [tidal volume 5 ml kg ideal body weight + PEEP between 5 and 8 cmH2O] or nonprotective ventilation (control group) (tidal volume 10 ml kg ideal body weight without PEEP) during anaesthesia.

RESULTS

The trial was stopped prematurely because of an insufficient inclusion rate. Major postoperative complications occurred in 23/172 patients in the LPV group (13.4%) vs. 38/171 (22.2%) in the control group (odds ratio 0.54, 95% confidence interval, 0.31 to 0.95, P = 0.03). The incidence of other complications (supraventricular cardiac arrhythmia, bronchial obstruction, pulmonary atelectasis, hypercapnia, bronchial fistula and persistent air leak) was also lower in the LPV group (37.2 vs. 49.4%, odds ratio 0.60, 95% confidence interval, 0.39 to 0.92, P = 0.02).The duration of hospital stay was shorter in the LPV group, 11 [interquartile range, 9 to 15] days vs. 12 [9 to 16] days, P = 0.048.

CONCLUSION

Compared with high tidal volume and no PEEP, LPV combining low tidal volume and PEEP during anaesthesia for lung cancer surgery seems to improve postoperative outcomes.

TRIALS REGISTRATION

ClinicalTrials.gov number: NCT00805077.

Effect of open-lung vs conventional perioperative ventilation strategies on postoperative pulmonary complications after on-pump cardiac surgery: the PROVECS randomized clinical trial

PURPOSE

To evaluate whether a perioperative open-lung ventilation strategy prevents postoperative pulmonary complications after elective on-pump cardiac surgery.

METHODS

In a pragmatic, randomized, multicenter, controlled trial, we assigned patients planned for on-pump cardiac surgery to either a conventional ventilation strategy with no ventilation during cardiopulmonary bypass (CPB) and lower perioperative positive end-expiratory pressure (PEEP) levels (2 cm H₂O) or an open-lung ventilation strategy that included maintaining ventilation during CPB along with perioperative recruitment maneuvers and higher PEEP levels (8 cm H₂O). All study patients were ventilated with low-tidal volumes before and after CPB (6 to 8 ml/kg of predicted body weight). The primary end point was a composite of pulmonary complications occurring within the first 7 postoperative days.

RESULTS

Among 493 randomized patients, 488 completed the study (mean age, 65.7 years; 360 (73.7%) men; 230 (47.1%) underwent isolated valve surgery). Postoperative pulmonary complications occurred in 133 of 243 patients (54.7%) assigned to open-lung ventilation and in 145 of 245 patients (59.2%) assigned to conventional ventilation (p = 0.32). Open-lung ventilation did not significantly reduce the use of high-flow nasal oxygenotherapy (8.6% vs 9.4%; p = 0.77), non-invasive ventilation (13.2% vs 15.5%; p = 0.46) or new invasive mechanical ventilation (0.8% vs 2.4%, p = 0.28). Mean alive ICU-free days at postoperative day 7 was 4.4 ± 1.3 days in the open-lung group vs 4.3 ± 1.3 days in the conventional group (mean difference, 0.1 ± 0.1 day, p = 0.51). Extra-pulmonary complications and adverse events did not significantly differ between groups.

CONCLUSIONS

A perioperative open-lung ventilation including ventilation during CPB does not reduce the incidence of postoperative pulmonary complications as compared with usual care. This finding does not support the use of such a strategy in patients undergoing on-pump cardiac surgery.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT02866578. https://clinicaltrials.gov/ct2/show/NCT02866578.

Positive End-Expiratory Pressure During Anesthesia for Prevention of Postoperative Pulmonary Complications: A Meta-analysis With Trial Sequential Analysis of Randomized Controlled Trials

BACKGROUND

Whether intraoperative positive end-expiratory pressure (PEEP) can reduce the risk of postoperative pulmonary complications remains controversial. We performed a systematic review of currently available literature to investigate whether intraoperative PEEP decreases pulmonary complications in anesthetized patients undergoing surgery.

METHODS

We searched PubMed, Embase, and the Cochrane Library to identify randomized controlled trials (RCTs) that compared intraoperative PEEP versus zero PEEP (ZEEP) for postoperative pulmonary complications in adults. The prespecified primary outcome was postoperative pulmonary atelectasis.

RESULTS

Fourteen RCTs enrolling 1238 patients met the inclusion criteria. Meta-analysis using a random-effects model showed a decrease in postoperative atelectasis (relative risk [RR], 0.51; 95% confidence interval [CI], 0.35-0.76; trial sequential analyses [TSA]-adjusted CI, 0.10-2.55) and postoperative pneumonia (RR, 0.48; 95% CI, 0.27-0.84; TSA-adjusted CI, 0.05-4.86) in patients receiving PEEP ventilation. However, TSA showed that the cumulative Z-curve of 2 outcomes crossed the conventional boundary but did not cross the trial sequential monitoring boundary, indicating a possible false-positive result. We observed no effect of PEEP versus ZEEP ventilation on postoperative mortality (RR, 1.78; 95% CI, 0.55-5.70).

CONCLUSIONS

The evidence that intraoperative PEEP reduces postoperative pulmonary complications is suggestive but too unreliable to allow definitive conclusions to be drawn.

Ventilatory support after extubation in critically ill patients

The periextubation period represents a crucial moment in the management of critically ill patients. Extubation failure, defined as the need for reintubation within 2-7 days after a planned extubation, is associated with prolonged mechanical ventilation, increased incidence of ventilator-associated pneumonia, longer intensive care unit and hospital stays, and increased mortality. Conventional oxygen therapy is commonly used after extubation. Additional methods of non-invasive respiratory support, such as non-invasive ventilation and high-flow nasal therapy, can be used to avoid reintubation. The aim of this Review is to describe the pathophysiological mechanisms of postextubation respiratory failure and the available techniques and strategies of respiratory support to avoid reintubation. We summarise and discuss the available evidence supporting the use of these strategies to achieve a tailored therapy for an individual patient at the bedside.

Effect of the pulmonary recruitment maneuver on pain after laparoscopic gynecological oncologic surgery: a prospective randomized trial

OBJECTIVE

To evaluate the effectiveness of the pulmonary recruitment maneuver (PRM) at the end of the operation to decrease laparoscopy-induced abdominal or shoulder pain after gynecological oncologic surgery.

METHODS

In total, 113 women undergoing laparoscopic surgery for malignant or premalignant gynecological lesions were assigned randomly to two groups: the PRM group (the patient was placed in the Trendelenburg position (30°) and the PRM, consisting of two manual pulmonary inflations to a maximum pressure of 40 cmH₂O) (n=54) and the control group (n=52). Postoperative shoulder and abdominal pain was assessed 12, 24, and 48 hours later using a visual analog scale (0-10). In addition, the incidence of post-discharge nausea and vomiting was recorded until 48 hours after discharge.

RESULTS

Postoperative shoulder pain at 12 and 24 hours was significantly less severe in the PRM group (2.2±0.5 and 2.0±0.4) than in the control group (4.0±0.5 and 3.9±0.4; both p<0.001). The PRM significantly reduced the severity of upper abdominal pain at 12 and 24 h compared with the control group (3.1±0.4 and 2.9±0.4 vs. 5.9±0.5 and 4.9±0.5; both p<0.001). The analgesic requirement during the postoperative period was similar in the two groups (control group, 78.8%; PRM group, 75.9%; p=0.719).

CONCLUSION

The PRM effectively and safely reduced postoperative shoulder and upper abdominal pain levels in patients undergoing laparoscopic gynecological oncologic surgery. Trial registry at ClinicalTrials.gov, NCT01940042.

Perioperative Lung Protective Ventilatory Management During Major Abdominal Surgery: A Hungarian Nationwide Survey

Lung protective mechanical ventilation (LPV) even in patients with healthy lungs is associated with a lower incidence of postoperative pulmonary complications (PPC). The pathophysiology of ventilator-induced lung injury and the risk factors of PPCs have been widely identified, and a perioperative lung protective concept has been elaborated. Despite the well-known advantages, results of recent studies indicated that intraoperative LPV is still not widely implemented in current anaesthesia practice.

No nationwide surveys regarding perioperative pulmonary protective management have been carried out previously in Hungary. This study aimed to evaluate the routine anaesthetic care and adherence to the LPV concept of Hungarian anaesthesiologists during major abdominal surgery.

A questionnaire of 36 questions was prepared, and anaesthesiologists were invited by an e-mail and a newsletter to participate in an online survey between January 1st to March 31st, 2018.

A total of one hundred and eleven anaesthesiologists participated in the survey; 61 (54.9%), applied low tidal volumes, 30 (27%) applied the entire LPV concept, and only 6 (5.4%) regularly applied alveolar recruitment manoeuvres (ARM). Application of low plateau and driving pressures were 40.5%. Authoritatively written protocols were not available resulting in markedly different perioperative pulmonary management. According to respondents, the most critical risk factors of PPCs are chronic obstructive pulmonary diseases (103; 92.8%); in contrast malnutrition, anaemia or prolonged use of nasogastric tube were considered negligible risk factors. Positive end-expiratory pressure (PEEP) and regular ARM are usually ignored. Based on the survey, more attention should be given to the use of LPV.

Changes in stroke volume during an alveolar recruitment maneuvers through a stepwise increase in positive end expiratory pressure and transient continuous positive airway pressure in anesthetized patients. A prospective observational pilot study

Background and Aims:

Recruitment maneuvers may be used during anesthesia as part of perioperative protective ventilation strategy. However, the hemodynamic effect of recruitment maneuvers remain poorly documented in this setting.

Material and Methods:

This was a prospective observational study performed in operating theatre including patients scheduled for major vascular surgery. Patients were monitored with invasive arterial pressure and esophageal doppler. After induction of general anesthesia, before surgery began, preload optimization based on stroke volume (SV) variation following fluid challenge was performed. Then, an alveolar recruitment maneuver (ARM) through stepwise increase in positive end expiratory pressure (PEEP) or continuous positive airway pressure (CPAP) was performed. Hemodynamic data were noted before, during, and after the alveolar recruitment maneuver.

Results:

ARM through stepwise increase in PEEP and CPAP were applied in 22 and 14 preload independent patients, respectively. Relative changes in SV during ARMs were significantly greater in the ARM_CPAP group (-39 ± 20%) as compared to the ARM_PEEP group (-15 ± 22%; P = 0.002). The difference (95% CI) in relative decrease in SV between ARM_CPAP and ARM_PEEP groups was -24% (-38 to -9; P = 0.001). Changes in arterial pressure, cardiac index, pulse pressure variation, peak velocity, and corrected flow time measures were not different between groups.

Conclusion:

During anesthesia, in preload independent patients, ARMs through CPAP resulted in a significantly greater decrease in SV than stepwise increase in PEEP. During anesthesia, ARM should be used cautiously.

High flow nasal therapy in perioperative medicine: from operating room to general ward

BACKGROUND

High flow nasal therapy (HFNT) is a technique in which humidified and heated gas is delivered to the airways through the nose via small nasal prongs at flows that are higher than the rates generally applied during conventional oxygen therapy. The delivered high flow rates combine mixtures of air and oxygen and enable different inspired oxygen fractions ranging from 0.21 to 1. HFNT is increasingly used in critically ill adult patients, especially hypoxemic patients in different clinical settings.

MAIN BODY

Noninvasive ventilation delivers positive pressure (end-expiratory and inspiratory pressures or continuous positive airway pressure) via different external interfaces. In contrast, HFNT produces different physiological effects that are only partially linked to the generation of expiratory positive airway pressure. HFNT and noninvasive ventilation (NIV) are interesting non-invasive supports in perioperative medicine. HFNT exhibits some advantages compared to NIV because HFNT is easier to apply and requires a lower nursing workload. Tolerance of HFNT remains a matter of intense debate, and it may be related to selected parameters. Patients receiving HFNT and their respiratory patterns should be closely monitored to avoid delays in intubation despite correct oxygenation parameters.

CONCLUSION

HFNT seems to be an interesting noninvasive support in perioperative medicine. The present review provides anesthesiologists with an overview of current evidence and practical advice on the application of HFNT in perioperative medicine in adult patients.

Ventilation With High or Low Tidal Volume With PEEP Does Not Influence Lung Function After Spinal Surgery in Prone Position: A Randomized Controlled Trial

BACKGROUND

Spinal surgery in the prone position is accompanied by increased intrathoracic pressure and decreased respiratory compliance. This study investigated whether intraoperative lung protective mechanical ventilation improved lung function evaluated with pulmonary function tests in patients at risk of postoperative pulmonary complications (PPCs) after major spinal surgery in the prone position.

METHODS

Seventy-eight patients at potential risk of PPCs were randomly assigned to the protective group (tidal volume; 6 mL/kg predicted body weight, 6 cm H2O positive end-expiratory pressure with recruitment maneuvers) or the conventional group (10 mL/kg predicted body weight, no positive end-expiratory pressure). The primary efficacy variables were assessed by pulmonary function tests, performed before surgery, and 3 and 5 days afterward.

RESULTS

Postoperative forced vital capacity (2.17±0.1 L vs. 1.91±0.1 L, P=0.213) and forced expiratory volume in 1 second (1.73±0.08 L vs. 1.59±0.08 L, P=0.603) at postoperative day (POD) 3 in the protective and conventional groups, respectively, were similar. Trends of a postoperative decrease in forced vital capacity (P=0.586) and forced expiratory volume in 1 second (P=0.855) were similar between the groups. Perioperative blood-gas analysis variables were comparable between the groups. Patients in the protective and conventional groups showed similar rates of clinically significant PPCs (8% vs. 10%, P>0.999).

CONCLUSIONS

In patients at potential risk of developing PPCs undergoing major spinal surgery, we did not find evidence indicating any difference between the lung protective and conventional ventilation in postoperative pulmonary function and oxygenation.

Perioperative lung protective ventilation

Perioperative lung injury is a major source of postoperative morbidity, excess healthcare use, and avoidable mortality. Many potential inciting factors can lead to this condition, including intraoperative ventilator induced lung injury. Questions exist as to whether protective ventilation strategies used in the intensive care unit for patients with acute respiratory distress syndrome are equally beneficial for surgical patients, most of whom do not present with any pre-existing lung pathology. Studied both individually and in combination as a package of intraoperative lung protective ventilation, the use of low tidal volumes, moderate positive end expiratory pressure, and recruitment maneuvers have been shown to improve oxygenation and pulmonary physiology and to reduce postoperative pulmonary complications in at risk patient groups. Further work is needed to define the potential contributions of alternative ventilator strategies, limiting excessive intraoperative oxygen supplementation, use of non-invasive techniques in the postoperative period, and personalized mechanical ventilation. Although the weight of evidence strongly suggests a role for lung protective ventilation in moderate risk patient groups, definitive evidence of its benefit for the general surgical population does not exist. However, given the shift in understanding of what is needed for adequate oxygenation and ventilation under anesthesia, the largely historical arguments against the use of intraoperative lung protective ventilation may soon be outdated, on the basis of its expanding track record of safety and efficacy in multiple settings.

Dual effects of leptin in perioperative gas exchange of morbidly obese patients

Leptin has shown positive effects on respiratory function in experimental settings. The role of leptin on perioperative respiratory function in morbidly obese patients has not been established. We performed a retrospective analysis of morbidly obese patients undergoing laparoscopic sleeve gastrectomy. Fasting serum leptin and interleukin (IL)-6 were measured preoperatively, and arterial blood gases were obtained pre- and postoperatively. Outcome variables were arterial partial pressure of oxygen (PaO₂), arterial partial pressure of carbon dioxide (PaCO₂), and differences in PaO₂ and PaCO₂ between pre- and postoperative values (ΔPaO₂, ΔPaCO₂; postoperative minus preoperative). Patients with lower (<40 μg/L) and higher (≥40 μg/L) leptin levels were compared. Bravais-Pearson’s correlation, multiple linear regression, and logistic regression analysis were performed. A total of 112 morbidly obese patients were included. Serum leptin was significantly higher in females than in males (42.86±12.89 vs. 30.67±13.39 μg/L, p<0.0001). Leptin was positively correlated with body mass index (r = 0.238; p = 0.011), IL-6 (r = 0.473; p<0.0001), and ΔPaO₂ (r = 0.312; p = 0.0008). Leptin was negatively correlated with preoperative PaO₂ (r = -0.199; p = 0.035). Preoperative PaO₂ was lower, ΔPaCO₂ was smaller, and ΔPaO₂ was greater in the high leptin group than in the low leptin group. In multiple regression analysis, leptin was negatively associated with preoperative PaO₂ (estimate coefficient = -0.147; p = 0.023). In logistic regression analysis, leptin was associated with improved ΔPaO₂ (odds ratio [OR] = 1.104; p = 0.0138) and ΔPaCO₂ (OR = 0.968; p = 0.0334). Leptin appears to have dual effects related to perioperative gas exchange in obese patients undergoing bariatric surgery. It is associated with worse preoperative oxygenation but improved respiratory function after surgery.

Recruitment manoeuvres in anaesthesia: How many more excuses are there not to use them?

Pulmonary recruitment manoeuvres (RM) are intended to reopen collapsed lung areas. RMs are present in nature as a physiological mechanism to get a newborn to open their lungs for the first time at birth, and we also use them, in our usual anaesthesiological clinical practice, after induction or during general anaesthesia when a patient is desaturated. However, there is much confusion in clinical practice regarding their safety, the best way to perform them, when to do them, in which patients they are indicated, and in those where they are totally contraindicated. There are important differences between RM in the patient with adult respiratory distress syndrome, and in a healthy patient during general anaesthesia. Our intention is to review, from a clinical and practical point of view, the use of RM, specifically in anaesthesia.

Individualised perioperative open-lung approach versus standard protective ventilation in abdominal surgery (iPROVE): a randomised controlled trial

BACKGROUND

The effects of individualised perioperative lung-protective ventilation (based on the open-lung approach [OLA]) on postoperative complications is unknown. We aimed to investigate the effects of intraoperative and postoperative ventilatory management in patients scheduled for abdominal surgery, compared with standard protective ventilation.

METHODS

We did this prospective, multicentre, randomised controlled trial in 21 teaching hospitals in Spain. We enrolled patients who were aged 18 years or older, were scheduled to have abdominal surgery with an expected time of longer than 2 h, had intermediate-to-high-risk of developing postoperative pulmonary complications, and who had a body-mass index less than 35 kg/m². Patients were randomly assigned (1:1:1:1) online to receive one of four lung-protective ventilation strategies using low tidal volume plus positive end-expiratory pressure (PEEP): open-lung approach (OLA)-iCPAP (individualised intraoperative ventilation [individualised PEEP after a lung recruitment manoeuvre] plus individualised postoperative continuous positive airway pressure [CPAP]), OLA-CPAP (intraoperative individualised ventilation plus postoperative CPAP), STD-CPAP (standard intraoperative ventilation plus postoperative CPAP), or STD-O₂ (standard intraoperative ventilation plus standard postoperative oxygen therapy). Patients were masked to treatment allocation. Investigators were not masked in the operating and postoperative rooms; after 24 h, data were given to a second investigator who was masked to allocations. The primary outcome was a composite of pulmonary and systemic complications during the first 7 postoperative days. We did the primary analysis using the modified intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT02158923.

FINDINGS

Between Jan 2, 2015, and May 18, 2016, we enrolled 1012 eligible patients. Data were available for 967 patients, whom we included in the final analysis. Risk of pulmonary and systemic complications did not differ for patients in OLA-iCPAP (110 [46%] of 241, relative risk 0·89 [95% CI 0·74-1·07; p=0·25]), OLA-CPAP (111 [47%] of 238, 0·91 [0·76-1·09; p=0·35]), or STD-CPAP groups (118 [48%] of 244, 0·95 [0·80-1·14; p=0·65]) when compared with patients in the STD-O₂ group (125 [51%] of 244). Intraoperatively, PEEP was increased in 69 (14%) of patients in the standard perioperative ventilation groups because of hypoxaemia, and no patients from either of the OLA groups required rescue manoeuvres.

INTERPRETATION

In patients who have major abdominal surgery, the different perioperative open lung approaches tested in this study did not reduce the risk of postoperative complications when compared with standard lung-protective mechanical ventilation.

FUNDING

Instituto de Salud Carlos III of the Spanish Ministry of Economy and Competitiveness, and Grants Programme of the European Society of Anaesthesiology.

Respiratory System Mechanics During Low Versus High Positive End-Expiratory Pressure in Open Abdominal Surgery: A Substudy of PROVHILO Randomized Controlled Trial

BACKGROUND

In the 2014 PROtective Ventilation using HIgh versus LOw positive end-expiratory pressure (PROVHILO) trial, intraoperative low tidal volume ventilation with high positive end-expiratory pressure (PEEP = 12 cm H2O) and lung recruitment maneuvers did not decrease postoperative pulmonary complications when compared to low PEEP (0-2 cm H2O) approach without recruitment breaths. However, effects of intraoperative PEEP on lung compliance remain poorly understood. We hypothesized that higher PEEP leads to a dominance of intratidal overdistension, whereas lower PEEP results in intratidal recruitment/derecruitment (R/D). To test our hypothesis, we used the volume-dependent elastance index %E2, a respiratory parameter that allows for noninvasive and radiation-free assessment of dominant overdistension and intratidal R/D. We compared the incidence of intratidal R/D, linear expansion, and overdistension by means of %E2 in a subset of the PROVHILO cohort.

METHODS

In 36 patients from 2 participating centers of the PROVHILO trial, we calculated respiratory system elastance (E), resistance (R), and %E2, a surrogate parameter for intratidal overdistension (%E2 > 30%) and R/D (%E2 < 0%). To test the main hypothesis, we compared the incidence of intratidal overdistension (primary end point) and R/D in higher and lower PEEP groups, as measured by %E2.

RESULTS

E was increased in the lower compared to higher PEEP group (18.6 [16…22] vs 13.4 [11.0…17.0] cm H2O·L; P < .01). %E2 was reduced in the lower PEEP group compared to higher PEEP (-15.4 [-28.0…6.5] vs 6.2 [-0.8…14.0] %; P < .05). Intratidal R/D was increased in the lower PEEP group (61% vs 22%; P = .037). The incidence of intratidal overdistension did not differ significantly between groups (6%).

CONCLUSIONS

During mechanical ventilation with protective tidal volumes in patients undergoing open abdominal surgery, lung recruitment followed by PEEP of 12 cm H2O decreased the incidence of intratidal R/D and did not worsen overdistension, when compared to PEEP ≤2 cm H2O.

Protective intraoperative ventilation with higher versus lower levels of positive end-expiratory pressure in obese patients (PROBESE): study protocol for a randomized controlled trial

BACKGROUND

Postoperative pulmonary complications (PPCs) increase the morbidity and mortality of surgery in obese patients. High levels of positive end-expiratory pressure (PEEP) with lung recruitment maneuvers may improve intraoperative respiratory function, but they can also compromise hemodynamics, and the effects on PPCs are uncertain. We hypothesized that intraoperative mechanical ventilation using high PEEP with periodic recruitment maneuvers, as compared with low PEEP without recruitment maneuvers, prevents PPCs in obese patients.

METHODS/DESIGN

The PRotective Ventilation with Higher versus Lower PEEP during General Anesthesia for Surgery in OBESE Patients (PROBESE) study is a multicenter, two-arm, international randomized controlled trial. In total, 2013 obese patients with body mass index ≥35 kg/m² scheduled for at least 2 h of surgery under general anesthesia and at intermediate to high risk for PPCs will be included. Patients are ventilated intraoperatively with a low tidal volume of 7 ml/kg (predicted body weight) and randomly assigned to PEEP of 12 cmH₂O with lung recruitment maneuvers (high PEEP) or PEEP of 4 cmH₂O without recruitment maneuvers (low PEEP). The occurrence of PPCs will be recorded as collapsed composite of single adverse pulmonary events and represents the primary endpoint.

DISCUSSION

To our knowledge, the PROBESE trial is the first multicenter, international randomized controlled trial to compare the effects of two different levels of intraoperative PEEP during protective low tidal volume ventilation on PPCs in obese patients. The results of the PROBESE trial will support anesthesiologists in their decision to choose a certain PEEP level during general anesthesia for surgery in obese patients in an attempt to prevent PPCs.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02148692. Registered on 23 May 2014; last updated 7 June 2016.

Influence of intraoperative positive end-expiratory pressure level on pulmonary complications in emergency major trauma surgery

INTRODUCTION

Pulmonary complications have a major impact on the morbidity and mortality of critically ill patients with multiple trauma. Intraoperative protective ventilation with low tidal volume may prevent lung injury and infection, whereas the role of positive end-expiratory pressure (PEEP) levels is unclear. The aim of this study was to evaluate the influence of different intraoperative PEEP levels on incidence of pulmonary complications after emergency trauma surgery.

MATERIAL AND METHODS

We retrospectively analysed data of multiple trauma patients who underwent emergency surgery within 24 h after injury in our level I trauma centre (n = 86). On the basis of their intraoperative PEEP level, patients were divided into a low PEEP group with a PEEP of < 8 mbar and a high PEEP group with a PEEP of 8 mbar or higher.

RESULTS

Besides differences in body mass index and preoperative oxygenation, there were no differences in patients' baseline data. There was a significant difference between incidence of pneumonia within 7 days after trauma surgery, with an incidence 26.7% in the low PEEP group and 7.3% in the high PEEP group (p = 0.02). The low PEEP group had higher pulmonary infection scores at days 3 and 5 after surgery. Oxygenation was better in the higher PEEP group postoperatively. There was no difference with respect to the incidence of acute respiratory distress syndrome, the mortality up until hospital discharge or haemodynamic parameters between groups.

CONCLUSIONS

Higher PEEP levels were associated with perioperative improvement of oxygenation and a lower incidence of pneumonia, without impairment of haemodynamics. Additional studies should be initiated to confirm these observations.

Changes in Stroke Volume Induced by Lung Recruitment Maneuver Predict Fluid Responsiveness in Mechanically Ventilated Patients in the Operating Room

Background

Lung recruitment maneuver induces a decrease in stroke volume, which is more pronounced in hypovolemic patients. The authors hypothesized that the magnitude of stroke volume reduction through lung recruitment maneuver could predict preload responsiveness.

Methods

Twenty-eight mechanically ventilated patients with low tidal volume during general anesthesia were included. Heart rate, mean arterial pressure, stroke volume, and pulse pressure variations were recorded before lung recruitment maneuver (application of continuous positive airway pressure of 30 cm H2O for 30 s), during lung recruitment maneuver when stroke volume reached its minimal value, and before and after volume expansion (250 ml saline, 0.9%, infused during 10 min). Patients were considered as responders to fluid administration if stroke volume increased greater than or equal to 10%.

Results

Sixteen patients were responders. Lung recruitment maneuver induced a significant decrease in mean arterial pressure and stroke volume in both responders and nonresponders. Changes in stroke volume induced by lung recruitment maneuver were correlated with those induced by volume expansion (r2 = 0.56; P &lt; 0.0001). A 30% decrease in stroke volume during lung recruitment maneuver predicted fluid responsiveness with a sensitivity of 88% (95% CI, 62 to 98) and a specificity of 92% (95% CI, 62 to 99). Pulse pressure variations more than 6% before lung recruitment maneuver discriminated responders with a sensitivity of 69% (95% CI, 41 to 89) and a specificity of 75% (95% CI, 42 to 95). The area under receiver operating curves generated for changes in stroke volume induced by lung recruitment maneuver (0.96; 95% CI, 0.81 to 0.99) was significantly higher than that for pulse pressure variations (0.72; 95% CI, 0.52 to 0.88; P &lt; 0.05).

Conclusions

The authors’ study suggests that the magnitude of stroke volume decrease during lung recruitment maneuver could predict preload responsiveness in mechanically ventilated patients in the operating room.