Ventilation with low tidal volumes during upper abdominal surgery does not improve postoperative lung function

Association of Mechanical Energy and Power with Postoperative Pulmonary Complications in Lung Resection Surgery: A Post Hoc Analysis of Randomized Clinical Trial Data

BACKGROUND

Mechanical power (MP), the rate of mechanical energy (ME) delivery, is a recently introduced unifying ventilator parameter consisting of tidal volume, airway pressures, and respiratory rates, which predicts pulmonary complications in several clinical contexts. However, ME has not been previously studied in the perioperative context, and neither parameter has been studied in the context of thoracic surgery utilizing one-lung ventilation.

METHODS

The relationships between ME variables and postoperative pulmonary complications were evaluated in this post hoc analysis of data from a multicenter randomized clinical trial of lung resection surgery conducted between 2020 and 2021 (n = 1,170). Time-weighted average MP and ME (the area under the MP time curve) were obtained for individual patients. The primary analysis was the association of time-weighted average MP and ME with pulmonary complications within 7 postoperative days. Multivariable logistic regression was performed to examine the relationships between energy variables and the primary outcome.

RESULTS

In 1,055 patients analyzed, pulmonary complications occurred in 41% (431 of 1,055). The median (interquartile ranges) ME and time-weighted average MP in patients who developed postoperative pulmonary complications versus those who did not were 1,146 (811 to 1,530) J versus 924 (730 to 1,240) J (P < 0.001), and 6.9 (5.5 to 8.7) J/min versus 6.7 (5.2 to 8.5) J/min (P = 0.091), respectively. ME was independently associated with postoperative pulmonary complications (ORadjusted, 1.44 [95% CI, 1.16 to 1.80]; P = 0.001). However, the association between time-weighted average MP and postoperative pulmonary complications was time-dependent, and time-weighted average MP was significantly associated with postoperative pulmonary complications in cases utilizing longer periods of mechanical ventilation (210 min or greater; ORadjusted, 1.46 [95% CI, 1.11 to 1.93]; P = 0.007). Normalization of ME and time-weighted average MP either to predicted body weight or to respiratory system compliance did not alter these associations.

CONCLUSIONS

ME and, in cases requiring longer periods of mechanical ventilation, MP were independently associated with postoperative pulmonary complications in thoracic surgery.

EDITOR’S PERSPECTIVE

The effect of goal-directed crystalloid versus colloid administration on postoperative spirometry parameters: a substudy of a randomized controlled clinical trial

BACKGROUND

Pulmonary function is impaired after major abdominal surgery and might be less impaired by restrictive fluid administration. Under the assumption of a fluid-sparing effect of colloids, we tested the hypothesis that an intraoperative colloid-based goal-directed fluid management strategy impairs postoperative pulmonary function parameters less compared to goal-directed crystalloid administration.

METHODS

We performed a preplanned, single-center substudy within a recently published trial evaluating the effect of goal-directed crystalloids versus colloids on a composite of major complications. Sixty patients undergoing major open abdominal surgery were randomized to Doppler-guided intraoperative fluid replacement therapy with lactated Ringer's solution (n = 31) or unbalanced 6% hydroxyethyl starch 130/0.4 (n = 29). A blinded investigator performed bedside spirometry (Spirobank-G, Medical International Research, Rome, Italy) preoperatively as well as 6, 24, and 48 h postoperatively.

RESULTS

Median total intraoperative fluid requirements were significantly higher during crystalloid administration compared to patients receiving colloids (4567 ml vs. 3044 ml, p = 0.01). Six hours after surgery, pulmonary function parameters did not differ significantly between the crystalloid - and the colloid group: forced vital capacity (FVC): 1.6 l (1.2-2 l) vs. 1.9 l (1.5-2.4 l), p = 0.15; forced expiratory volume in 1 second (FEV1): 1.1 l (0.9-1.6 l) vs. 1.4 l (1.2-1.7 l), p = 0.18; and peak expiratory flow (PEF): 2 l.sec-1 (1.5 - 3.6 l.sec -1) vs. 2.3 l.sec -1 (1.8 - 3.4 l.sec -1), p = 0.23. Moreover, postoperative longitudinal time × group interactions of FVC, FEV1, and PEF between 6 and 48 postoperative hours did not differ significantly.

CONCLUSION

Postoperative pulmonary function parameters were similarly impaired in patients receiving goal-directed crystalloid administration as compared to goal-directed colloid administration during open abdominal surgery.

TRIAL REGISTRATION

ClinicalTrials.gov ( NCT00517127 , registered on August 16, 2007) and EudraCT (2005-004602-86).

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.

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.

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.

Effect of electrical impedance-guided PEEP in reducing pulmonary complications after craniotomy: study protocol for a randomized controlled trial

Objective

The purpose of this study is to explore whether electrical impedance tomography (EIT)-guided individualized positive end-expiratory pressure (PEEP) can reduce the incidence of pulmonary complications within 1 week following a craniotomy compared with a single PEEP (PEEP = 6 cmH₂O) from dura suturing to extubation.

Methods

A randomized controlled trial will be conducted at the Second Affiliated Hospital of Soochou University. Five hundred forty patients undergoing a craniotomy in the supine position will be randomly allocated into the P6 (PEEP = 6 cmH₂O) or Pi (individualized PEEP) group. Both groups of patients will receive a lung recruitment maneuver before suturing the dura. Then, the P6 group will receive 6 cmH₂O PEEP, and the Pi group will receive EIT-guided individualized PEEP. The incidence and severity score of pulmonary complications within 1 week following surgery, the lung ultrasound score (LUS), regional cerebral oxygen saturation (rScO₂), and PaO₂/FiO₂ before anesthesia (T0), 10 min after extubation (T1), 24 h after extubation (T2), and 72 h after extubation (T3) will be compared between the two groups. The duration of surgery and anesthesia, the level and duration of PEEP during surgery, the volume of liquid intake and output during surgery, and the postoperative ICU and hospital stays will be recorded. The main outcome of this study will be the incidence of pulmonary complications within 1 week after surgery.

Discussion

The purposes of this study are to determine whether EIT-guided individualized PEEP from the beginning of dura suturing to extubation reduces the incidence of pulmonary complications within 1 week after a craniotomy compared with a single constant PEEP and to evaluate the length of ICU and hospital stays. If our results are positive, this study will show that EIT-guided individualized PEEP is better than a single constant PEEP and can further improve the prognosis of neurosurgical patients and reduce hospitalization costs, which will promote the wide application of individualized PEEP in clinical anesthesia.

Trial registration

Chinese Clinical Trial Registry CHiCTR2100051200. Registered on 15 September 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06751-6.

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.

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.

Ultrasonographic Assessment of Diaphragmatic Inspiratory Amplitude and Its Association with Postoperative Pulmonary Complications in Upper Abdominal Surgery: A Prospective, Longitudinal, Observational Study

Background

Diaphragmatic dysfunction following upper abdominal surgery is less recognized due to a lack of diagnostic modality for bedside evaluation. We used point-of-care ultrasound to evaluate the diaphragmatic inspiratory amplitude (DIA) in upper abdominal surgery for cancer. Our primary hypothesis was DIA would be reduced in the immediate postoperative period in patients with postoperative pulmonary complications (PPCs). Our aim was to identify an optimal cutoff of DIA for the diagnosis of PPCs.

Methods

We conducted a prospective, observational study in patients aged 18-75 years undergoing elective, upper abdominal oncological surgeries under combined general and epidural anesthesia. Ultrasound evaluation of the diaphragm was done by measuring the DIA in the right and left hemidiaphragms during quiet and deep breathing on the day before surgery and postoperative days (PODs) 1, 2, and 3. Patients were followed up for PPCs until POD 7. The linear mixed-effects model examined the association between DIA and PPCs and other perioperative factors. Receiver-operating characteristics analysis was done to determine the optimal cutoff of DIA in diagnosing PPCs.

Results

DIA measured in the 162 patients showed a significant decrease in their absolute values postoperatively from its preoperative baseline measurement. This decrease in DIA was significantly associated with PPC [right hemidiaphragm, β = -0.17, 95% confidence interval (CI) -0.31 to -0.02, p = 0.001 during quiet breathing; left hemidiaphragm, β = -0.24, 95% CI = -0.44 to -0.04, p = 0.018 and β = -0.40, 95% CI = -0.71 to -0.09, p = 0.012 during quiet and deep breathing, respectively]. A cutoff value of DIA of left hemidiaphragm at 1.3 cm during quiet breathing and 1.6 cm during deep breathing had a sensitivity of 77 and 75%, respectively, in their ability to diagnose PPCs [left hemidiaphragm quiet breathing, area under the curve (AUC): 0.653, 95% CI 0.539-0.768, p = 0.015; left hemidiaphragm deep breathing, AUC: 0.675, 95% CI 0.577-0.773, p = 0.007].

Conclusion

Following upper abdominal surgery, the DIA is decreased and associated with PPCs. DIA of left hemidiaphragm less than 1.3 cm during quiet breathing and 1.6 cm during deep breathing has a sensitivity of 77 and 75%, respectively, in diagnosing PPCs following upper abdominal surgery.

How to cite this article

Vanamail PV, Balakrishnan K, Prahlad S, Chockalingam P, Dash R, Soundararajan DK. Ultrasonographic Assessment of Diaphragmatic Inspiratory Amplitude and Its Association with Postoperative Pulmonary Complications in Upper Abdominal Surgery: A Prospective, Longitudinal, Observational Study. Indian J Crit Care Med 2021;25(9):1031-1039.

Effect of Intraoperative Ventilation Strategies on Postoperative Pulmonary Complications: A Meta-Analysis

Introduction: The role of intraoperative ventilation strategies in subjects undergoing surgery is still contested. This meta-analysis study was performed to assess the relationship between the low tidal volumes strategy and conventional mechanical ventilation in subjects undergoing surgery. Methods: A systematic literature search up to December 2020 was performed in OVID, Embase, Cochrane Library, PubMed, and Google scholar, and 28 studies including 11,846 subjects undergoing surgery at baseline and reporting a total of 2,638 receiving the low tidal volumes strategy and 3,632 receiving conventional mechanical ventilation, were found recording relationships between low tidal volumes strategy and conventional mechanical ventilation in subjects undergoing surgery. Odds ratio (OR) or mean difference (MD) with 95% confidence intervals (CIs) were calculated between the low tidal volumes strategy vs. conventional mechanical ventilation using dichotomous and continuous methods with a random or fixed-effect model. Results: The low tidal volumes strategy during surgery was significantly related to a lower rate of postoperative pulmonary complications (OR, 0.60; 95% CI, 0.44-0.83, p < 0.001), aspiration pneumonitis (OR, 0.63; 95% CI, 0.46-0.86, p < 0.001), and pleural effusion (OR, 0.72; 95% CI, 0.56-0.92, p < 0.001) compared to conventional mechanical ventilation. However, the low tidal volumes strategy during surgery was not significantly correlated with length of hospital stay (MD, -0.48; 95% CI, -0.99-0.02, p = 0.06), short-term mortality (OR, 0.88; 95% CI, 0.70-1.10, p = 0.25), atelectasis (OR, 0.76; 95% CI, 0.57-1.01, p = 0.06), acute respiratory distress (OR, 1.06; 95% CI, 0.67-1.66, p = 0.81), pneumothorax (OR, 1.37; 95% CI, 0.88-2.15, p = 0.17), pulmonary edema (OR, 0.70; 95% CI, 0.38-1.26, p = 0.23), and pulmonary embolism (OR, 0.65; 95% CI, 0.26-1.60, p = 0.35) compared to conventional mechanical ventilation. Conclusions: The low tidal volumes strategy during surgery may have an independent relationship with lower postoperative pulmonary complications, aspiration pneumonitis, and pleural effusion compared to conventional mechanical ventilation. This relationship encouraged us to recommend the low tidal volumes strategy during surgery to avoid any possible complications.

Effect of High-Flow Nasal Cannula for Hypoxemia Following Sun's Procedure in Acute Aortic Dissection Type a Patients

Background: Patients with acute aortic dissection type A (AADA) often have hypoxemia (partial pressure of oxygen [PaO₂]/fraction of inspired oxygen [FiO₂] <300 mmHg) before weaning in the intensive care unit (ICU). This study compared the efficacy of high-flow nasal cannula (HFNC) with that of conventional oxygen therapy (COT) in patients with AADA following Sun's procedure.

Methods: The medical records of 87 adult patients with AADA who underwent Sun's procedure and met the inclusion criteria (PaO₂/FiO₂ <300 mmHg before weaning) were retrospectively analyzed. After surgery, 41 patients were treated with HFNC and 46 were treated with COT. The oxygenation level, FiO₂, partial pressure of carbon dioxide, heart rate, respiratory rate, subjective discomfort, and reintubation rate were recorded. The difference in lung volume loss between the HFNC and COT groups was assessed using the radiological atelectasis score (chest radiograph) or calculated from three-dimensional (3D) reconstructed computed tomography (CT) images.

Results: From day 1 to day 5 after weaning, there was no significant difference in PaO₂/FiO₂ between the HFNC and COT groups, although the FiO₂ was significantly lower in the HFNC group than in the COT group (P < 0.05). Further studies indicated that the percentage of lung volume loss (pleural effusion and/or pulmonary atelectasis) by 3D reconstruction of CT images at 4–8 days post-operation was significantly lower in the HFNC group (P < 0.05). The subjective experience of breathing discomfort, reintubation rate, and length of stay in the ICU were significantly reduced in the HFNC group (P < 0.05). There was no significant difference in readmission to the ICU and in-hospital mortality between the two groups.

Conclusions: HFNC can be used as an effective oxygen therapy for AADA patients with hypoxemia after Sun's procedure.

Intraoperative lung protective ventilation in peritonitis patients undergoing emergency laparotomy: A randomised controlled trial

Background and Aims:

Lung protective ventilation (LPV) is recommended in acute respiratory distress syndrome. However, role of intraoperative LPV in elective laparotomy is controversial and it has not been evaluated in emergency laparotomy (EL). The aim of the study was to identify whether use of intraoperative LPV in EL in peritonitis patients reduces postoperative pulmonary complications (POPC).

Methods:

After institutional ethics committee approval and informed written consent, 98 adult patients undergoing EL for peritonitis were randomised into two groups. Patients in group 1 received LPV (tidal volume 6–8 ml/kg, positive end expiratory pressure (PEEP) 6–8 cm H₂O and recruitment manoeuvre every 30 min) and patients in group 2 received conventional ventilation (tidal volume 10-12 ml/kg, without PEEP/recruitment). Primary outcome was incidence of POPC on day 7.

Results:

Data of 94 patients (n = 45 in group 1 & n = 49 in group 2) were available. Baseline demographic & laboratory parameters were comparable. Incidence of POPC was similar in both the groups [42.9% in group 1 vs. 53.3% in group 2; risk difference -10.4% (-30.6%, 9.6%); P = 0.31]. Mortality during hospital stay was 26.7% patients in group 1 and 26.5% patients in group 2 [risk difference (95% CI) 0.14%, (-17.7, 18.0); P = 0.98]. Length of hospital stay [median interquartile range (IQR) 13 (9–18) days in group 1 vs. 13 (8–21) days in group 2; P = 0.82] and length of intensive care unit stay [median (IQR) 7 (4–10) days vs. 6 (3–12) days; P = 0.88] were also similar in both groups.

Conclusion:

LPV during EL in peritonitis patients does not reduce the incidence of POPC compared to conventional ventilation.

Individualized PEEP ventilation between tumor resection and dural suture in craniotomy

OBJECTIVE

Atelectasis, which affects oxygenation, is always occurred after craniotomy under general anesthesia. The commonly used protective ventilation strategy, which includes recruitment maneuver and higher level of positive end-expiratory pressure (PEEP), can effectively reduce atelectasis after heart and abdominal surgery, but increase intracranial pressure and reduce cerebral perfusion in patients undergoing craniotomy. We hypothesized individualized PEEP ventilation between tumor resection and dural suture in craniotomy could effectively reduce postoperative atelectasis, improve PaO₂/FiO₂ ratio, and without reducing the regional cerebral oxygen saturation (rScO₂).

PATIENTS AND METHODS

96 patients underwent tumor craniotomy in supine position were randomized into the control group (C group) and individualized PEEP group (P group). In the C group, the tidal volume (VT) was set at 8 mL/kg of predicted body weight, but PEEP were not used. In the P group, VT was set at 6 mL/kg of predicted body weight combined with individualized PEEP between tumor resection and dural suture, while in other periods of general anesthesia, VT was set at 8 mL/kg of predicted body weight. PaO₂/FiO₂ ratio, lung ultrasound score (LUS) and rScO₂ were measured before induction, 1 h and 24 h after extubation.

RESULTS

Individual PEEP in the P group was 7.0 (4.0-9.0). The PaO₂/FiO₂ ratio and rScO₂ in the P group were significantly higher than that of the C group (395 ± 62 vs. 344 ± 40, 67 ± 5 vs. 61 ± 4, respectively, p < 0.05) and the LUS of the experimental group was significantly lower than that of the C group [7.5 (5.3-8.3) vs. 10.0 (9.0-12.0), p < 0.05] 1 h after extubation.

CONCLUSION

Mechanical ventilation with individualized PEEP between tumor resection and dural suture in craniotomy can reduce atelectasis, improve PaO₂/FiO₂ ratio and rScO₂ 1 h after extubation.

Association of Intraoperative Ventilator Management With Postoperative Oxygenation, Pulmonary Complications, and Mortality

BACKGROUND

"Lung-protective ventilation" describes a ventilation strategy involving low tidal volumes (VTs) and/or low driving pressure/plateau pressure and has been associated with improved outcomes after mechanical ventilation. We evaluated the association between intraoperative ventilation parameters (including positive end-expiratory pressure [PEEP], driving pressure, and VT) and 3 postoperative outcomes: (1) PaO2/fractional inspired oxygen tension (FIO2), (2) postoperative pulmonary complications, and (3) 30-day mortality.

METHODS

We retrospectively analyzed adult patients who underwent major noncardiac surgery and remained intubated postoperatively from 2006 to 2015 at a single US center. Using multivariable regressions, we studied associations between intraoperative ventilator settings and lowest postoperative PaO2/FIO2 while intubated, pulmonary complications identified from discharge diagnoses, and in-hospital 30-day mortality.

RESULTS

Among a cohort of 2096 cases, the median PEEP was 5 cm H2O (interquartile range = 4-6), median delivered VT was 520 mL (interquartile range = 460-580), and median driving pressure was 15 cm H2O (13-19). After multivariable adjustment, intraoperative median PEEP (linear regression estimate [B] = -6.04; 95% CI, -8.22 to -3.87; P < .001), median FIO2 (B = -0.30; 95% CI, -0.50 to -0.10; P = .003), and hours with driving pressure >16 cm H2O (B = -5.40; 95% CI, -7.2 to -4.2; P < .001) were associated with decreased postoperative PaO2/FIO2. Higher postoperative PaO2/FIO2 ratios were associated with a decreased risk of pulmonary complications (adjusted odds ratio for each 100 mm Hg = 0.495; 95% CI, 0.331-0.740; P = .001, model C-statistic of 0.852) and mortality (adjusted odds ratio = 0.495; 95% CI, 0.366-0.606; P < .001, model C-statistic of 0.820). Intraoperative time with VT >500 mL was also associated with an increased likelihood of developing a postoperative pulmonary complication (adjusted odds ratio = 1.06/hour; 95% CI, 1.00-1.20; P = .042).

CONCLUSIONS

In patients requiring postoperative intubation after noncardiac surgery, increased median FIO2, increased median PEEP, and increased time duration with elevated driving pressure predict lower postoperative PaO2/FIO2. Intraoperative duration of VT >500 mL was independently associated with increased postoperative pulmonary complications. Lower postoperative PaO2/FIO2 ratios were independently associated with pulmonary complications and mortality. Our findings suggest that postoperative PaO2/FIO2 may be a potential target for future prospective trials investigating the impact of specific ventilation strategies for reducing ventilator-induced pulmonary injury.

Perioperative interventions for prevention of postoperative pulmonary complications: systematic review and meta-analysis

OBJECTIVE

To identify, appraise, and synthesise the best available evidence on the efficacy of perioperative interventions to reduce postoperative pulmonary complications (PPCs) in adult patients undergoing non-cardiac surgery.

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

DATA SOURCES

Medline, Embase, CINHAL, and CENTRAL from January 1990 to December 2017.

ELIGIBILITY CRITERIA

Randomised controlled trials investigating short term, protocolised medical interventions conducted before, during, or after non-cardiac surgery were included. Trials with clinical diagnostic criteria for PPC outcomes were included. Studies of surgical technique or physiological or biochemical outcomes were excluded.

DATA EXTRACTION AND SYNTHESIS

Reviewers independently identified studies, extracted data, and assessed the quality of evidence. Meta-analyses were conducted to calculate risk ratios with 95% confidence intervals. Quality of evidence was summarised in accordance with GRADE methods. The primary outcome was the incidence of PPCs. Secondary outcomes were respiratory infection, atelectasis, length of hospital stay, and mortality. Trial sequential analysis was used to investigate the reliability and conclusiveness of available evidence. Adverse effects of interventions were not measured or compared.

RESULTS

117 trials enrolled 21 940 participants, investigating 11 categories of intervention. 95 randomised controlled trials enrolling 18 062 participants were included in meta-analysis; 22 trials were excluded from meta-analysis because the interventions were not sufficiently similar to be pooled. No high quality evidence was found for interventions to reduce the primary outcome (incidence of PPCs). Seven interventions had low or moderate quality evidence with confidence intervals indicating a probable reduction in PPCs: enhanced recovery pathways (risk ratio 0.35, 95% confidence interval 0.21 to 0.58), prophylactic mucolytics (0.40, 0.23 to 0.67), postoperative continuous positive airway pressure ventilation (0.49, 0.24 to 0.99), lung protective intraoperative ventilation (0.52, 0.30 to 0.88), prophylactic respiratory physiotherapy (0.55, 0.32 to 0.93), epidural analgesia (0.77, 0.65 to 0.92), and goal directed haemodynamic therapy (0.87, 0.77 to 0.98). Moderate quality evidence showed no benefit for incentive spirometry in preventing PPCs. Trial sequential analysis adjustment confidently supported a relative risk reduction of 25% in PPCs for prophylactic respiratory physiotherapy, epidural analgesia, enhanced recovery pathways, and goal directed haemodynamic therapies. Insufficient data were available to support or refute equivalent relative risk reductions for other interventions.

CONCLUSIONS

Predominantly low quality evidence favours multiple perioperative PPC reduction strategies. Clinicians may choose to reassess their perioperative care pathways, but the results indicate that new trials with a low risk of bias are needed to obtain conclusive evidence of efficacy for many of these interventions.

STUDY REGISTRATION

Prospero CRD42016035662.

The effects of protective lung ventilation on regional cerebral oxygen saturation in intracranial tumor operation during dura opening: study protocol for a randomized controlled trial

Objective

The objective of this trial is to investigate the effects of protective lung ventilation on regional cerebral oxygen saturation (rSO₂) during dura opening, that is from Ta (after dura opening) to Tb (before dura closing), in patients undergoing intracranial tumor surgery.

Methods

This is a randomized controlled trial which will be carried out at the Second Affiliated Hospital of Soochow University. Fifty-four patients undergoing intracranial tumor surgery will be randomly allocated to the control group (C group) or the protective lung ventilation group (P group). In the C group, the tidal volume (VT) will be set at 8 ml/kg of predicted body weight, but positive end-expiratory pressure (PEEP) and recruitment maneuvers will not be used. In the P group, VT will be set at 6 ml/kg of predicted body weight combined with individualized PEEP during dura opening, while in other periods of general anesthesia, VT will be set at 8 ml/kg of predicted body weight. The level of rSO₂, partial pressures of oxygen and carbon dioxide, oxygenation index, lactic acid level in arterial blood, and mean arterial pressure will be compared before anesthesia (T0), before dura opening (T1), after dura closing (T2), and 24 h after surgery (T3). Lung ultrasound scores will be measured at T0 and T3. The degree of brain relaxation at T1 and T2 will be evaluated by the surgeon using the brain relaxation scale. The amount of vasoactive drugs used and blood loss will be recorded during surgery. The duration of operation and reoperation rate will be recorded. The primary outcome of this study is the changes in rSO₂ within 24 h postoperatively.

Discussion

This study aims to determine whether protective lung ventilation during dura opening can improve rSO₂ and the state of pulmonary ventilation in patients undergoing intracranial tumor surgery, and to investigate whether this strategy affects the degree of brain tissue swelling and the reoperation rate after operation. If our results are positive, this study will show that protective lung ventilation during dura opening can be used effectively and safely in neurosurgical patients undergoing craniotomy for tumor resection.

Trial registration

Chinese Clinical Trial Registry, ChiCTR1900025632. Registered on 3 September 2019. chictr.org.cn.

Temporal Changes in Ventilator Settings in Patients With Uninjured Lungs: A Systematic Review

In patients with uninjured lungs, increasing evidence indicates that tidal volume (VT) reduction improves outcomes in the intensive care unit (ICU) and in the operating room (OR). However, the degree to which this evidence has translated to clinical changes in ventilator settings for patients with uninjured lungs is unknown. To clarify whether ventilator settings have changed, we searched MEDLINE, Cochrane Central Register of Controlled Trials, and Web of Science for publications on invasive ventilation in ICUs or ORs, excluding those on patients <18 years of age or those with >25% of patients with acute respiratory distress syndrome (ARDS). Our primary end point was temporal change in VT over time. Secondary end points were changes in maximum airway pressure, mean airway pressure, positive end-expiratory pressure, inspiratory oxygen fraction, development of ARDS (ICU studies only), and postoperative pulmonary complications (OR studies only) determined using correlation analysis and linear regression. We identified 96 ICU and 96 OR studies comprising 130,316 patients from 1975 to 2014 and observed that in the ICU, VT size decreased annually by 0.16 mL/kg (-0.19 to -0.12 mL/kg) (P < .001), while positive end-expiratory pressure increased by an average of 0.1 mbar/y (0.02-0.17 mbar/y) (P = .017). In the OR, VT size decreased by 0.09 mL/kg per year (-0.14 to -0.04 mL/kg per year) (P < .001). The change in VTs leveled off in 1995. Other intraoperative ventilator settings did not change in the study period. Incidences of ARDS (ICU studies) and postoperative pulmonary complications (OR studies) also did not change over time. We found that, during a 39-year period, from 1975 to 2014, VTs in clinical studies on mechanical ventilation have decreased significantly in the ICU and in the OR.

Effect of Thoracic Epidural Anesthesia in a Rat Model of Phrenic Motor Inhibition after Upper Abdominal Surgery

WHAT WE ALREADY KNOW ABOUT THIS TOPIC

WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: One important example of impaired motor function after surgery is diaphragmatic dysfunction after upper abdominal surgery. In this study, the authors directly recorded efferent phrenic nerve activity and determined the effect of the upper abdominal incision. The authors hypothesized that phrenic motor output would be decreased after the upper abdominal incision; it was also hypothesized that blocking sensory input from the incision using thoracic epidural anesthesia would diminish this incision-induced change in phrenic motor activity.

METHODS

Efferent phrenic activity was recorded 1 h to 10 days after upper abdominal incision in urethane-anesthetized rats. Ventilatory parameters were measured in unanesthetized rats using whole-body plethysmography at multiple time points after incision. The authors then determined the effect of thoracic epidural anesthesia on phrenic nerve activity and ventilatory parameters after incision.

RESULTS

Phrenic motor output remained reduced by approximately 40% 1 h and 1 day after incision, but was not different from the sham group by postoperative day 10. One day after incision (n = 9), compared to sham-operated animals (n = 7), there was a significant decrease in spike frequency area-under-the-curve (median [interquartile range]: 54.0 [48.7 to 84.4] vs. 97.8 [88.7 to 130.3]; P = 0.0184), central respiratory rate (0.71 [0.63 to 0.79] vs. 0.86 [0.82 to 0.93]/s; P = 0.0460), and inspiratory-to-expiratory duration ratio (0.46 [0.44 to 0.55] vs. 0.78 [0.72 to 0.93]; P = 0.0023). Unlike humans, a decrease, not an increase, in breathing frequency has been observed after the abdominal incision in whole-body plethysmography. Thoracic epidural anesthesia attenuated the incision-induced changes in phrenic motor output and ventilatory parameters.

CONCLUSIONS

Upper abdominal incision decreased phrenic motor output and ventilatory parameters, and this incision-induced impairment was attenuated by thoracic epidural anesthesia. The authors' results provide direct evidence that afferent inputs from the upper abdominal incision induce reflex inhibition of phrenic motor activity.

Perioperative redistribution of regional ventilation and pulmonary function: a prospective observational study in two cohorts of patients at risk for postoperative pulmonary complications

Background

Postoperative pulmonary complications (PPCs) increase morbidity and mortality of surgical patients, duration of hospital stay and costs. Postoperative atelectasis of dorsal lung regions as a common PPC has been described before, but its clinical relevance is insufficiently examined. Pulmonary electrical impedance tomography (EIT) enables the bedside visualization of regional ventilation in real-time within a transversal section of the lung. Dorsal atelectasis or effusions might cause a ventral redistribution of ventilation. We hypothesized the existence of ventral redistribution in spontaneously breathing patients during their recovery from abdominal and peripheral surgery and that vital capacity is reduced if regional ventilation shifts to ventral lung regions.

Methods

This prospective observational study included 69 adult patients undergoing elective surgery with an expected intermediate or high risk for PPCs. Patients undergoing abdominal and peripheral surgery were recruited to obtain groups of equal size. Patients received general anesthesia with and without additional regional anesthesia. On the preoperative, the first and the third postoperative day, EIT was performed at rest and during spirometry (forced breathing). The center of ventilation in dorso-ventral direction (COVy) was calculated.

Results

Both groups received intraoperative low tidal volume ventilation. Postoperative ventral redistribution of ventilation (forced breathing COVy; preoperative: 16.5 (16.0–17.3); first day: 17.8 (16.9–18.2), p < 0.004; third day: 17.4 (16.2–18.2), p = 0.020) and decreased forced vital capacity in percentage of predicted values (FVC%predicted) (median: 93, 58, 64%, respectively) persisted after abdominal surgery. In addition, dorsal to ventral shift was associated with a decrease of the FVC%predicted on the third postoperative day (r = − 0.66; p < 0.001). A redistribution of pulmonary ventilation was not observed after peripheral surgery. FVC%predicted was only decreased on the first postoperative day (median FVC%predicted on the preoperative, first and third day: 85, 81 and 88%, respectively). In ten patients occurred pulmonary complications after abdominal surgery also in two patients after peripheral surgery.

Conclusions

After abdominal surgery ventral redistribution of ventilation persisted up to the third postoperative day and was associated with decreased vital capacity. The peripheral surgery group showed only minor changes in vital capacity, suggesting a role of the location of surgery for postoperative redistribution of pulmonary ventilation.

Trial registration

This prospective observational single centre study was submitted to registration prior to patient enrollment at ClinicalTrials.gov (NCT02419196, Date of registration: December 1, 2014). Registration was finalized at April 17, 2015.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0805-8) contains supplementary material, which is available to authorized users.

Effects of neuromuscular block reversal with sugammadex versus neostigmine on postoperative respiratory outcomes after major abdominal surgery: a randomized-controlled trial

PURPOSE

Postoperative pulmonary complications may be better reduced by reversal of neuromuscular block with sugammadex than by reversal with neostigmine because the incidence of residual block after sugammadex application is lower and diaphragm function is less impaired than after neostigmine administration. The aim of the study was to compare the effect of reversal of neuromuscular block with sugammadex or neostigmine on lung function after major abdominal surgery.

METHODS

One hundred and thirty adults scheduled for major abdominal surgery under combined general and epidural anesthesia were randomly allocated to receive 40 µg of neostigmine or 4 mg·kg^-1 of sugammadex to reverse neuromuscular block. Two blinded researchers performed spirometry and lung ultrasound before the surgery, as well as 1 hr and 24 hr postoperatively. Differences in mean changes from baseline were analyzed with repeated measures analysis of variance. Forced vital capacity (FVC) loss one hour after surgery was the main outcome. Secondary outcomes were differences in rate and size of atelectasis one hour and 24 hr after surgery.

RESULTS

One hundred twenty-six patients were included in the main analysis. In the neostigmine group (n = 64), mean (95% confidence interval [95% CI]) reduction in FVC after one hour was 0.5 (0.4 to 0.6) L. In the sugammadex group (n = 62), the mean (95% CI) reduction in FVC during the first hour was 0.5 (95% CI, 0.3 to 0.6) L. Thirty-nine percent of patients in the neostigmine group and 29% in the sugammadex group had visible atelectasis. Median [interquartile range (IQR)] atelectasis area was 9.7 [4.7-13.1] cm² and 6.8 [3.6-12.5] cm², respectively.

CONCLUSION

We found no differences in pulmonary function in patients reversed with sugammadex or neostigmine in a high-risk population.

TRIAL REGISTRATION

EudraCT 2014-005156-26; registered 27 May, 2015.

Low tidal volume ventilation strategy and organ functions in patients with pre-existing systemic inflammatory response

Background and Aims

Ventilation can induce increase in inflammatory mediators that may contribute to systemic organ dysfunction. Ventilation-induced organ dysfunction is likely to be accentuated if there is a pre-existing systemic inflammatory response.

Material and Methods

Adult patients suffering from intestinal perforation peritonitis-induced systemic inflammatory response syndrome and scheduled for emergency laparotomy were randomized to receive intraoperative ventilation with 10 ml.kg^-1 tidal volume (Group H) versus lower tidal volume of 6 ml.kg^-1 along with positive end-expiratory pressure (PEEP) of 10 cmH₂O (Group L), (n = 45 each). The primary outcome was postoperative organ dysfunction evaluated using the aggregate Sepsis-related Organ Failure Assessment (SOFA) score. The secondary outcomes were, inflammatory mediators viz. interleukin-6, tumor necrosis factor-α, procalcitonin, and C-reactive protein, assessed prior to (basal) and 1 h after initiation of mechanical ventilation, and 18 h postoperatively.

Results

The aggregate SOFA score (3[1-3] vs. 1[1-3]); and that on the first postoperative day (2[1-3] vs. 1[0-3]) were higher for group L as compared to group H (P < 0.05). All inflammatory mediators were statistically similar between both groups at all time intervals (P > 0.05).

Conclusions

Mechanical ventilation with low tidal volume of 6 ml/kg^-1 along with PEEP of 10 cmH₂O is associated with significantly worse postoperative organ functions as compared to high tidal volume of 10 ml.kg^-1 in patients of perforation peritonitis-induced systemic inflammation undergoing emergency laparotomy.

Management of 1-Lung Ventilation-Variation and Trends in Clinical Practice: A Report From the Multicenter Perioperative Outcomes Group

BACKGROUND

Lung-protective ventilation (LPV) has been demonstrated to improve clinical outcomes in surgical patients. There are very limited data on the current use of LPV for patients undergoing 1-lung ventilation (1LV) despite evidence that 1LV may be a particularly important setting for its use. In this multicenter study, we report trends in ventilation practice for patients undergoing 1LV.

METHODS

The Multicenter Perioperative Outcomes Group database was used to identify patients undergoing 1LV. We retrieved and calculated median initial and overall tidal volume (VT) for the cohort and for high-risk subgroups (female sex, obesity [body mass index >30 kg/m], and short stature), percentage of patients receiving positive end-expiratory pressure (PEEP) ≥5 cm H2O, LPV during 1LV (VT ≤ 6 mL/kg predicted body weight [PBW] and PEEP ≥5 cm H2O), and ventilator driving pressure (ΔP; plateau airway pressure - PEEP).

RESULTS

Data from 5609 patients across 4 institutions were included in the analysis. Median VT was calculated for each case and since the data were normally distributed, the mean is reported for the entire cohort and subgroups. Mean of median VT during 1LV for the cohort was 6.49 ± 1.82 mL/kg PBW. VT (mL/kg PBW) for high-risk subgroups was significantly higher; 6.86 ± 1.97 for body mass index ≥30 kg/m, 7.05 ± 1.92 for female patients, and 7.33 ± 2.01 for short stature patients. Mean of the median VT declined significantly over the study period (from 6.88 to 5.72; P < .001), and the proportion of patients receiving LPV increased significantly over the study period (from 9.1% to 54.6%; P < .001). These changes coincided with a significant decrease in ΔP during the study period, from 19.4 cm H2O during period 1 to 17.3 cm H2O in period 12 (P = .003).

CONCLUSIONS

Despite a growing awareness of the importance of protective ventilation, a large proportion of patients undergoing 1LV continue to receive VT PEEP levels outside of recommended thresholds. Moreover, VT remains higher and LPV less common in high-risk subgroups, potentially placing them at elevated risk for iatrogenic lung injury.

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.

Ventilation with high versus low peep levels during general anaesthesia for open abdominal surgery does not affect postoperative spirometry: A randomised clinical trial

BACKGROUND

Invasive mechanical ventilation during general anaesthesia for surgery typically causes atelectasis and impairs postoperative lung function.

OBJECTIVE

We investigated the effect of intraoperative ventilation with high positive end-expiratory pressure (PEEP) and recruitment manoeuvres (RMs) on postoperative spirometry.

DESIGN

This was a preplanned, single-centre substudy of an international multicentre randomised controlled trial, the PROVHILO trial.

SETTING

University hospital from November 2011 to January 2013.

PATIENTS

Nonobese patients scheduled for major abdominal surgery at a high risk of postoperative pulmonary complications (PPCs).

INTERVENTION

Intraoperative low tidal volume ventilation with PEEP levels of 12 cmH2O and RM (the high PEEP group) or with PEEP levels of 2 cmH2O or less without RM (the low PEEP group).

MAIN OUTCOME MEASURES

Time-weighted averages (TWAs) of the forced expiratory volume in 1 s (FEV1) and the forced vital capacity (FVC) up to postoperative day five.

RESULTS

Thirty-one patients were allocated to the high PEEP group and 32 to the low PEEP group. No postoperative spirometry test results were available for 6 patients. In both groups, TWA of FEV1 and FVC until postoperative day five were lower than preoperative values. Postoperative spirometry test results were not different between the high and low PEEP group; Data are median [interquartile range], TWA FVC 1.8 [1.6 to 2.4] versus 1.7 [1.2 to 2.4] l (P = NS) and TWA FEV1 1.2 [1.1 to 2.5] versus 1.2 [0.9 to 1.9] l (P = NS). Patients who developed PPCs had lower FEV1 and FVC on postoperative day five; 1.1 [0.9 to 1.6] versus 1.6 [1.4 to 1.9] l (P = 0.001) and 1.6 [1.2 to 2.6] versus 2.3 [1.7 to 2.6] l (P = 0.036), respectively.

CONCLUSION

Postoperative spirometry is not affected by PEEP and RM during intraoperative ventilation for open abdominal surgery in nonobese patients at a high risk of PPCs, but rather is associated with the development of PPCs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01441791.

Intraoperative use of low volume ventilation to decrease postoperative mortality, mechanical ventilation, lengths of stay and lung injury in adults without acute lung injury

BACKGROUND

Since the 2000s, there has been a trend towards decreasing tidal volumes for positive pressure ventilation during surgery. This an update of a review first published in 2015, trying to determine if lower tidal volumes are beneficial or harmful for patients.

OBJECTIVES

To assess the benefit of intraoperative use of low tidal volume ventilation (less than 10 mL/kg of predicted body weight) compared with high tidal volumes (10 mL/kg or greater) to decrease postoperative complications in adults without acute lung injury.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2017, Issue 5), MEDLINE (OvidSP) (from 1946 to 19 May 2017), Embase (OvidSP) (from 1974 to 19 May 2017) and six trial registries. We screened the reference lists of all studies retained and of recent meta-analysis related to the topic during data extraction. We also screened conference proceedings of anaesthesiology societies, published in two major anaesthesiology journals. The search was rerun 3 January 2018.

SELECTION CRITERIA

We included all parallel randomized controlled trials (RCTs) that evaluated the effect of low tidal volumes (defined as less than 10 mL/kg) on any of our selected outcomes in adults undergoing any type of surgery. We did not retain studies with participants requiring one-lung ventilation.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the quality of the retained studies with the Cochrane 'Risk of bias' tool. We analysed data with both fixed-effect (I² statistic less than 25%) or random-effects (I² statistic greater than 25%) models based on the degree of heterogeneity. When there was an effect, we calculated a number needed to treat for an additional beneficial outcome (NNTB) using the odds ratio. When there was no effect, we calculated the optimum information size.

MAIN RESULTS

We included seven new RCTs (536 participants) in the update.In total, we included 19 studies in the review (776 participants in the low tidal volume group and 772 in the high volume group). There are four studies awaiting classification and three are ongoing. All included studies were at some risk of bias. Participants were scheduled for abdominal surgery, heart surgery, pulmonary thromboendarterectomy, spinal surgery and knee surgery. Low tidal volumes used in the studies varied from 6 mL/kg to 8.1 mL/kg while high tidal volumes varied from 10 mL/kg to 12 mL/kg.Based on 12 studies including 1207 participants, the effects of low volume ventilation on 0- to 30-day mortality were uncertain (risk ratio (RR) 0.80, 95% confidence interval (CI) 0.42 to 1.53; I² = 0%; low-quality evidence). Based on seven studies including 778 participants, lower tidal volumes probably reduced postoperative pneumonia (RR 0.45, 95% CI 0.25 to 0.82; I² = 0%; moderate-quality evidence; NNTB 24, 95% CI 16 to 160), and it probably reduced the need for non-invasive postoperative ventilatory support based on three studies including 506 participants (RR 0.31, 95% CI 0.15 to 0.64; moderate-quality evidence; NNTB 13, 95% CI 11 to 24). Based on 11 studies including 957 participants, low tidal volumes during surgery probably decreased the need for postoperative invasive ventilatory support (RR 0.33, 95% CI 0.14 to 0.77; I² = 0%; NNTB 39, 95% CI 30 to 166; moderate-quality evidence). Based on five studies including 898 participants, there may be little or no difference in the intensive care unit length of stay (standardized mean difference (SMD) -0.06, 95% CI -0.22 to 0.10; I² = 33%; low-quality evidence). Based on 14 studies including 1297 participants, low tidal volumes may have reduced hospital length of stay by about 0.8 days (SMD -0.15, 95% CI -0.29 to 0.00; I² = 27%; low-quality evidence). Based on five studies including 708 participants, the effects of low volume ventilation on barotrauma (pneumothorax) were uncertain (RR 1.77, 95% CI 0.52 to 5.99; I² = 0%; very low-quality evidence).

AUTHORS' CONCLUSIONS

We found moderate-quality evidence that low tidal volumes (defined as less than 10 mL/kg) decreases pneumonia and the need for postoperative ventilatory support (invasive and non-invasive). We found no difference in the risk of barotrauma (pneumothorax), but the number of participants included does not allow us to make definitive statement on this. The four studies in 'Studies awaiting classification' may alter the conclusions of the review once assessed.

Adoption of Lung Protective ventilation IN patients undergoing Emergency laparotomy: the ALPINE study. A prospective multicentre observational study

BACKGROUND

Emergency abdominal surgery is associated with a high risk of postoperative pulmonary complications (PPCs). The primary aim of this study was to determine whether patients undergoing emergency laparotomy are ventilated using a lung-protective ventilation strategy employing tidal volume ≤8 ml kg^-1 ideal body weight^-1, PEEP >5 cm H₂O, and recruitment manoeuvres. The secondary aim was to investigate the association between ventilation factors (lung-protective ventilation strategy, intraoperative FiO₂, and peak inspiratory pressure) and the occurrence of PPCs.

METHODS

Data were collected prospectively in 28 hospitals across London as part of routine National Emergency Laparotomy Audit (NELA). Patients were followed for 7 days. Complications were defined according to the European Perioperative Clinical Outcome definition.

RESULTS

Data were collected from 568 patients. The median [inter-quartile range (IQR)] tidal volume observed was 500 ml (450-540 ml), corresponding to a median tidal volume of 8 ml kg^-1 ideal body weight^-1 (IQR: 7.2-9.1 ml). A lung-protective ventilation strategy was employed in 4.9% (28/568) of patients, and was not protective against the occurrence of PPCs in the multivariable analysis (hazard ratio=1.06; P=0.69). Peak inspiratory pressure of <30 cm H₂O was protective against development of PPCs (hazard ratio=0.46; confidence interval: 0.30-0.72; P=0.001). Median FiO₂ was 0.5 (IQR: 0.44-0.53), and an increase in FiO₂ by 5% increased the risk of developing a PPC by 8% (2.6-14.1%; P=0.008).

CONCLUSIONS

Both intraoperative peak inspiratory pressure and FiO₂ are independent factors significantly associated with development of a postoperative pulmonary complication in emergency laparotomy patients. Further studies are required to identify causality and to demonstrate if their manipulation could lead to better clinical outcomes.

Short-term one-lung ventilation does not influence local inflammatory cytokine response after lung resection

Background

One-lung ventilation (OLV) is a ventilation procedure used for pulmonary resection which may results in lung injury. The aim of this study was to evaluate the local inflammatory cytokine response from the dependent lung after OLV and its correlation to VT. The secondary aim was to evaluate the clinical outcome of each patient.

Methods

Twenty-eight consecutive patients were enrolled. Ventilation was delivered in volume-controlled mode with a VT based on predicted body weight (PBW). 5 cmH₂O positive end-expiratory pressure (PEEP) and FiO₂ 0.5 were applied. Bronchoalveolar lavage (BAL) was performed in the dependent lung before and after OLV. The levels of pro-inflammatory interleukins (IL-1α, IL-1β, IL-6, IL-8), tumor necrosis factor alpha (TNFα), vascular endothelial growth factor (VEGF), endothelial growth factor (EGF), monocyte chemoattractant protein-1 (MCP-1) and anti-inflammatory cytokines, such as interleukins (IL-2, IL-4, IL-10) and interferon (IFN-γ), were evaluated. Subgroup analysis: to analyze the VT setting during OLV, all patients were ventilated within a range of 5-10 mL/kg. Thirteen patients, classified as a conventional ventilation (CV) subgroup, received 8-10 mL/kg, while 15 patients, classified as a protective ventilation (PV) subgroup, received 5-7 mL/kg.

Results

Cytokine BAL levels after surgery showed no significant increase after OLV, and no significant differences were recorded between the two subgroups. The mean duration of OLV was 64.44±21.68 minutes. No postoperative respiratory complications were recorded. The mean length of stay was for 4.00±1.41 days in the PV subgroup and 4.45±2.07 days in the CV group; no statistically significant differences were recorded between the two subgroups (P=0.511).

Conclusions

Localized inflammatory cytokine response after OLV was not influenced by the use of different VT. Potentially, the application of PEEP in both ventilation strategies and the short duration of OLV could prevent postoperative complications.

The effect of an intraoperative, lung-protective ventilation strategy in neurosurgical patients undergoing craniotomy: study protocol for a randomized controlled trial

BACKGROUND

Ventilator-induced lung injury is a major cause of postoperative pulmonary complications (PPCs) in patients undergoing neurosurgery after general anesthesia. However, there is no study on the effect of a lung-protective ventilation strategy in patients undergoing neurosurgery.

METHODS

This is a single-center, randomized, parallel-group controlled trial which will be carried out at Beijing Tiantan Hospital, Capital Medical University. Three hundred and thirty-four patients undergoing intracranial tumor surgery will be randomly allocated to the control group and the protective-ventilation strategy group. In the control group, tidal volume (VT) will be set at 10-12 ml/kg of predicted body weight but PEEP and recruitment maneuvers will not be used. In the protective group, VT will be set at 6-8 ml/kg of predicted body weight, PEEP at 6-8 cmH₂O, and a recruitment maneuver will be used intermittently. The primary outcome is pulmonary complications within 7 days postoperatively. Secondary outcomes include intraoperative brain relaxation, the postoperative complications within 30 days and the cost analysis.

DISCUSSION

This study aims to determine if the protective, pulmonary-ventilation strategy decreases the incidence of PPCs in patients undergoing neurosurgical anesthesia. If our results are positive, the study will indicate whether the protective, pulmonary-ventilation strategy is efficiently and safely used in neurosurgical patients undergoing the craniotomy.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT02386683 . Registered on 18 October 2014.

Improving Adherence to Intraoperative Lung-Protective Ventilation Strategies at a University Medical Center

BACKGROUND

Intraoperative lung-protective ventilation (ILPV) is defined as tidal volumes <8 mL/kg ideal bodyweight and is increasingly a standard of care for major abdominal surgical procedures performed under general anesthesia. In this study, we report the result of a quality improvement initiative targeted at improving adherence to ILPV guidelines in a large academic teaching hospital.

METHODS

We performed a time-series study to determine whether anesthesia provider adherence to ILPV was affected by certain improvement interventions and patient ideal body weight (IBW). Tidal volume data were collected at 3 different time points for 191 abdominal surgical cases from June 2014 through April 2015. Improvement interventions during that period included education at departmental grand rounds, creation of a departmental ILPV policy, feedback of tidal volume and failure rate data at grand rounds sessions, and reducing default ventilator settings for tidal volume. Mean tidal volume per kilogram of ideal body weight (VT/kg IBW) and rates of noncompliance with ILPV were analyzed before and after the interventions. A survey was administered to assess provider attitudes after implementation of improvement interventions. Responses before and after interventions and between physician and nonphysician providers were analyzed.

RESULTS

Reductions in mean VT/kg IBW and rates of failure for providers to use ILPV occurred after improvement interventions. Patients with IBW <65 kg received higher VT/kg IBW and had higher rates of failure to use ILPV than patients with IBW >65 kg. Surveyed providers demonstrated stronger agreement to having knowledge and practice consistent with ILPV after interventions.

CONCLUSIONS

Our interventions improved anesthesia provider adherence to low tidal volume ILPV. IBW was found to be an important factor related to provider adherence to ILPV. Provider attitudes about their knowledge and practice consistent with ILPV also changed with our interventions.

Interaction between peri-operative blood transfusion, tidal volume, airway pressure and postoperative ARDS: an individual patient data meta-analysis

Background

Transfusion of blood products and mechanical ventilation with injurious settings are considered risk factors for postoperative lung injury in surgical Patients.

Methods

A systematic review and individual patient data meta-analysis was done to determine the independent effects of peri-operative transfusion of blood products, intra-operative tidal volume and airway pressure in adult patients undergoing mechanical ventilation for general surgery, as well as their interactions on the occurrence of postoperative acute respiratory distress syndrome (ARDS). Observational studies and randomized trials were identified by a systematic search of MEDLINE, CINAHL, Web of Science, and CENTRAL and screened for inclusion into a meta-analysis. Individual patient data were obtained from the corresponding authors. Patients were stratified according to whether they received transfusion in the peri-operative period [red blood cell concentrates (RBC) and/or fresh frozen plasma (FFP)], tidal volume size [≤7 mL/kg predicted body weight (PBW), 7-10 and >10 mL/kg PBW] and airway pressure level used during surgery (≤15, 15-20 and >20 cmH₂O). The primary outcome was development of postoperative ARDS.

Results

Seventeen investigations were included (3,659 patients). Postoperative ARDS occurred in 40 (7.2%) patients who received at least one blood product compared to 40 patients (2.5%) who did not [adjusted hazard ratio (HR), 2.32; 95% confidence interval (CI), 1.25-4.33; P=0.008]. Incidence of postoperative ARDS was highest in patients ventilated with tidal volumes of >10 mL/kg PBW and having airway pressures of >20 cmH₂O receiving both RBC and FFP, and lowest in patients ventilated with tidal volume of ≤7 mL/kg PBW and having airway pressures of ≤15 cmH₂O with no transfusion. There was a significant interaction between transfusion and airway pressure level (P=0.002) on the risk of postoperative ARDS.

Conclusions

Peri-operative transfusion of blood products is associated with an increased risk of postoperative ARDS, which seems more dependent on airway pressure than tidal volume size.

Protective Lung Ventilation and Morbidity After Pulmonary Resection: A Propensity Score-Matched Analysis

BACKGROUND

Protective lung ventilation (PLV) during one-lung ventilation (OLV) for thoracic surgery is frequently recommended to reduce pulmonary complications. However, limited outcome data exist on whether PLV use during OLV is associated with less clinically relevant pulmonary morbidity after lung resection.

METHODS

Intraoperative data were prospectively collected in 1080 patients undergoing pulmonary resection with OLV, intentional crystalloid restriction, and mechanical ventilation to maintain inspiratory peak airway pressure <30 cm H2O. Other ventilator settings and all aspects of anesthetic management were at the discretion of the anesthesia care team. We defined PLV and non-PLV as <8 or ≥8 mL/kg (predicted body weight) mean tidal volume. The primary outcome was the occurrence of pneumonia and/or acute respiratory distress syndrome (ARDS). Propensity score matching was used to generate PLV and non-PLV groups with comparable characteristics. Associations between outcomes and PLV status were analyzed by exact logistic regression, with matching as cluster in the anatomic and nonanatomic lung resection cohorts.

RESULTS

In the propensity score-matched analysis, the incidence of pneumonia and/or ARDS among patients who had an anatomic lung resection was 9/172 (5.2%) in the non-PLV compared to the PLV group 7/172 (4.1%; odds ratio, 1.29; 95% confidence interval, 0.48-3.45, P= .62). The incidence of pneumonia and/or ARDS in patients who underwent nonanatomic resection was 3/118 (2.5%) in the non-PLV compared to the PLV group, 1/118 (0.9%; odds ratio, 3.00; 95% confidence interval, 0.31-28.84, P= .34).

CONCLUSIONS

In this prospective observational study, we found no differences in the incidence of pneumonia and/or ARDS between patients undergoing lung resection with tidal volumes <8 or ≥8 mL/kg. Our data suggest that when fluid restriction and peak airway pressures are limited, the clinical impact of PLV in this patient population is small. Future randomized trials are needed to better understand the benefits of a small tidal volume strategy during OLV on clinically important outcomes.

Ventilation in Trauma Patients: The First 24 h is Different!

INTRODUCTION

Ventilation of major trauma patients is often needed in both the acute (emergency department and early ICU phase) and subsequent phases of trauma care for those who need ICU admission. What is unclear is whether ICU ventilation strategies should be directly extrapolated to the acute phase of treatment.

METHODS

This paper reviews the ARDS.net study, highlights recent developments in ventilation strategies, and provides practical ventilation guidance to the trauma surgeon for acute phase (in the ED or ICU) and the subsequent phase of ICU care.

RESULTS

The acute phase of care in the ED and the ICU is different from the subsequent phases of ICU care as the lung is more recruitable and there are other aspects of resuscitation from metabolic acidosis and traumatic brain injury, which require a different ventilation strategy to the traditional ARDS.net approach.

DISCUSSION AND CONCLUSION

The acute phase is different from the subsequent phase of care and there appears to be some inappropriate extrapolation of ICU practice to the acute phase. Application of the proposed ventilation strategies should ensure an optimal outcome. It is important to treat patients as individuals during assessment and treatment.

Management of One-lung Ventilation: Impact of Tidal Volume on Complications after Thoracic Surgery

BACKGROUND

The use of lung-protective ventilation (LPV) strategies may minimize iatrogenic lung injury in surgical patients. However, the identification of an ideal LPV strategy, particularly during one-lung ventilation (OLV), remains elusive. This study examines the role of ventilator management during OLV and its impact on clinical outcomes.

METHODS

Data were retrospectively collected from the hospital electronic medical record and the Society of Thoracic Surgery database for subjects undergoing thoracic surgery with OLV between 2012 and 2014. Mean tidal volume (VT) during two-lung ventilation and OLV and ventilator driving pressure (ΔP) (plateau pressure - positive end-expiratory pressure [PEEP]) were analyzed for the 1,019 cases that met the inclusion criteria. Associations between ventilator parameters and clinical outcomes were examined by multivariate linear regression.

RESULTS

After the initiation of OLV, 73.3, 43.3, 18.8, and 7.2% of patients received VT greater than 5, 6, 7, and 8 ml/kg predicted body weight, respectively. One hundred and eighty-four primary and 288 secondary outcome events were recorded. In multivariate logistic regression modeling, VT was inversely related to the incidence of respiratory complications (odds ratio, 0.837; 95% CI, 0.729 to 0.958), while ΔP predicted the development of major morbidity when modeled with VT (odds ratio, 1.034; 95% CI, 1.001 to 1.068).

CONCLUSIONS

Low VT per se (i.e., in the absence of sufficient PEEP) has not been unambiguously demonstrated to be beneficial. The authors found that a large proportion of patients continue to receive high VT during OLV and that VT was inversely related to the incidence of respiratory complications and major postoperative morbidity. While low (physiologically appropriate) VT is an important component of an LPV strategy for surgical patients during OLV, current evidence suggests that, without adequate PEEP, low VT does not prevent postoperative respiratory complications. Thus, use of physiologic VT may represent a necessary, but not independently sufficient, component of LPV.

Intraoperative low tidal volume ventilation strategy has no benefits during laparoscopic cholecystectomy

Background and Aims:

Benefits of intraoperative low tidal volume ventilation during laparoscopic surgery are not conclusively proven, even though its advantages were seen in other situations with intraoperative respiratory compromise such as one-lung ventilation. The present study compared the efficacy of intraoperative low tidal volume ventilatory strategy (6 ml/kg along with positive end-expiratory pressure [PEEP] of 10 cmH₂O) versus one with higher tidal volume (10 ml/kg with no PEEP) on various clinical parameters and plasma levels of interleukin (IL)-6 in patients undergoing laparoscopic cholecystectomy.

Material and Methods:

A total of 58 adult patients with American Society of Anesthesiologists physical status I or II, undergoing laparoscopic cholecystectomy were randomized to receive the low or higher tidal volume strategy as above (n = 29 each). The primary outcome measure was postoperative PaO₂. Systemic levels of IL-6 along with clinical indices of intraoperative gas exchange, pulmonary mechanics, and hemodynamic consequences were measured as secondary outcome measures.

Results:

There was no statistically significant difference in oxygenation; intraoperative dynamic compliance, peak airway pressures, or hemodynamic parameters, or the IL-6 levels between the two groups (P > 0.05). Low tidal volume strategy was associated with significantly higher mean airway pressure, lower airway resistance, greater respiratory rates, and albeit clinically similar, higher PaCO₂and lower pH (P < 0.05).

Conclusion:

Strategy using 6 ml/kg tidal volume along with 10 cmH₂O of PEEP was not associated with any significant improvement in gas exchange, hemodynamic parameters, or systemic inflammatory response over ventilation with 10 ml/kg volume without PEEP during laparoscopic cholecystectomy.

Protective Ventilation Improves Gas Exchange, Reduces Incidence of Atelectases, and Affects Metabolic Response in Major Pancreatoduodenal Surgery

Background

Protective perioperative ventilation has been shown to improve outcomes and reduce the incidence of postoperative pulmonary complications. The goal of this study was to assess the effects of ventilation with low tidal volume (V_T) either alone or in a combination with moderate permissive hypercapnia in major pancreatoduodenal interventions.

Materials and methods

Sixty adult patients scheduled for elective pancreatoduodenal surgery with duration >2 h were enrolled into a prospective single-center study. All patients were randomized to three groups receiving high V_T [10 mL/kg of predicted body weight (PBW), the HVT group, n = 20], low V_T (6 mL/kg PBW, the LVT group, n = 20), and low V_T combined with a moderate hypercapnia and hypercapnic acidosis (6 mL/kg PBW, PaCO₂ 45–60 mm Hg, the LVT + HC group, n = 20). Cardiopulmonary parameters and the incidence of complications were registered during surgery and postoperatively.

Results and discussion

The values of V_T were 610 (563–712), 370 (321–400), and 340 (312–430) mL/kg for the HVT, the LVT, and the LVT + HC groups, respectively (p < 0.001). Compared to the HVT group, PaO₂/FiO₂ ratio was increased in the LVT group by 15%: 333 (301–381) vs. 382 (349–423) mm Hg at 24 h postoperatively (p < 0.05). The HVT group had significantly higher incidence of atelectases (n = 6), despite lower incidence of smoking compared with the LVT (n = 1) group (p = 0.017) and demonstrated longer length of hospital stay. The patients of the LVT + HC group had lower arterial lactate and bicarbonate excess values by the end of surgery.

Conclusion

In major pancreatoduodenal interventions, preventively protective V_T improves postoperative oxygenation, reduces the incidence of atelectases, and shortens length of hospital stay. The combination of low V_T and permissive hypercapnia results in hypercapnic acidosis decreasing the lactate concentration but adding no additional benefits and warrants further investigations.

Mechanical ventilation strategies for intensive care unit patients without acute lung injury or acute respiratory distress syndrome: a systematic review and network meta-analysis

Background

It has been shown that the application of a lung-protective mechanical ventilation strategy can improve the prognosis of patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). However, the optimal mechanical ventilation strategy for intensive care unit (ICU) patients without ALI or ARDS is uncertain. Therefore, we performed a network meta-analysis to identify the optimal mechanical ventilation strategy for these patients.

Methods

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, EMBASE, MEDLINE, CINAHL, and Web of Science for studies published up to July 2015 in which pulmonary compliance or the partial pressure of arterial oxygen/fraction of inspired oxygen (PaO₂/FIO₂) ratio was assessed in ICU patients without ALI or ARDS, who received mechanical ventilation via different strategies. The data for study characteristics, methods, and outcomes were extracted. We assessed the studies for eligibility, extracted the data, pooled the data, and used a Bayesian fixed-effects model to combine direct comparisons with indirect evidence.

Results

Seventeen randomized controlled trials including a total of 575 patients who received one of six ventilation strategies were included for network meta-analysis. Among ICU patients without ALI or ARDS, strategy C (lower tidal volume (VT) + higher positive end-expiratory pressure (PEEP)) resulted in the highest PaO₂/FIO₂ ratio; strategy B (higher VT + lower PEEP) was associated with the highest pulmonary compliance; strategy A (lower VT + lower PEEP) was associated with a shorter length of ICU stay; and strategy D (lower VT + zero end-expiratory pressure (ZEEP)) was associated with the lowest PaO₂/FiO₂ ratio and pulmonary compliance.

Conclusions

For ICU patients without ALI or ARDS, strategy C (lower VT + higher PEEP) was associated with the highest PaO₂/FiO₂ ratio. Strategy B (higher VT + lower PEEP) was superior to the other strategies in improving pulmonary compliance. Strategy A (lower VT + lower PEEP) was associated with a shorter length of ICU stay, whereas strategy D (lower VT + ZEEP) was associated with the lowest PaO₂/FiO₂ ratio and pulmonary compliance.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1396-0) contains supplementary material, which is available to authorized users.

Preventing Ventilator-Associated Lung Injury: A Perioperative Perspective

Introduction

Research into the prevention of ventilator-associated lung injury (VALI) in patients with acute respiratory distress syndrome (ARDS) in the intensive care unit (ICU) has resulted in the development of a number of lung protective strategies, which have become commonplace in the treatment of critically ill patients. An increasing number of studies have applied lung protective ventilation in the operating room to otherwise healthy individuals. We review the history of lung protective strategies in patients with acute respiratory failure and explore their use in patients undergoing mechanical ventilation during general anesthesia. We aim to provide context for a discussion of the benefits and drawbacks of lung protective ventilation, as well as to inform future areas of research.

Methods

We completed a database search and reviewed articles investigating lung protective ventilation in both the ICU and in patients receiving general anesthesia through May 2015.

Results

Lung protective ventilation was associated with improved outcomes in patients with acute respiratory failure in the ICU. Clinical evidence is less clear regarding lung protective ventilation for patients undergoing surgery.

Conclusion

Lung protective ventilation strategies, including low tidal volume ventilation and moderate positive end-expiratory pressure, are well established therapies to minimize lung injury in critically ill patients with and without lung disease, and may provide benefit to patients undergoing general anesthesia.

Postoperative pulmonary complications following major elective abdominal surgery: a cohort study

Background

Postoperative pulmonary complications (PPC) are an under-reported but major cause of perioperative morbidity and mortality. The aim of this prospective, contemporary, multicentre cohort study of unselected patients undergoing major elective abdominal surgery was to determine the incidence and effects of PPC.

Methods

Data on all major elective abdominal operations performed over a 2-week period in December 2014 were collected in six hospitals. The primary outcome measure of PPC at 7 days was used. Univariate and multivariate analyses were performed to investigate how different factors were associated with PPC and the effects of such complications.

Results

Two hundred sixty-eight major elective abdominal operations were performed, and the internal validation showed that the data set was 99 % accurate. Thirty-two (11.9 %) PPC were reported at 7 days. PPC was more common in patients with a history of chronic obstructive pulmonary disease compared to those with no history (26.7 vs. 10.2 %, p < 0.001). PPC was not associated with other patient factors (e.g. age, gender, body mass index or other comorbidities), type/method of operation or postoperative analgesia. The risk of PPC appeared to increase with every additional minute of operating time independent of other factors (odds ratio 1.01 (95 % confidence intervals 1.00–1.02), p = 0.007). PPC significantly increase the length of hospital stay (10 vs. 3 days). Attendance to the emergency department within 30 days (27.3 vs. 10.6 %), 30-day readmission (21.7 vs. 9.9 %) and 30-day mortality (12.5 vs. 0.0 %) was higher in those with PPC.

Conclusions

PPC are common and have profound effects on outcomes. Strategies need to be considered to reduce PPC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13741-016-0037-0) contains supplementary material, which is available to authorized users.

A systematic review and meta-analysis of perioperative oral decontamination in patients undergoing major elective surgery

Background

Oral antiseptics reduce nosocomial infections and ventilator-associated pneumonia in critically ill medical and surgical patients intubated for prolonged periods. However, the role of oral antiseptics given before and after planned surgery is not clear. The aim of this systematic review and meta-analysis is to determine the effect of oral antiseptics (chlorhexidine or povidone–iodine) when administered before and after major elective surgery.

Methods

Searches were conducted of the MEDLINE, EMBASE and Cochrane databases. The analysis was performed using the random-effects method and the risk ratio (RR) with 95 % confidence interval (CI).

Results

Of 1114 unique identified articles, perioperative chlorhexidine was administered to patients undergoing elective surgery in four studies. This identified 2265 patients undergoing elective cardiac surgery, of whom 1093 (48.3 %) received perioperative chlorhexidine. Postoperative pneumonia and nosocomial infections were observed in 5.3 and 20.2 % who received chlorhexidine compared to 10.4 and 31.3 % who received a control preparation, respectively. Oral perioperative chlorhexidine significantly reduced the risk of postoperative pneumonia (RR = 0.52; 95 % CI 0.39–0.71; p < 0.01) and overall nosocomial infections (RR = 0.65; 95 % CI 0.52–0.81; p < 0.01), with no effect on in-hospital mortality (RR = 1.01; 95 % CI 0.49–2.09; p = 0.98).

Conclusions

Perioperative oral chlorhexidine significantly decreases the incidence of nosocomial infection and postoperative pneumonia in patients undergoing elective cardiac surgery. There are no randomised controlled studies of this simple and cheap intervention in patients undergoing elective non-cardiac surgery.

Trial Registration

This systematic review was registered with the International prospective register of systematic reviews (PROSPERO). The registration number is CRD42015016063.