The effect of an alveolar recruitment strategy on oxygenation during laparascopic cholecystectomy

Intraoperative effects of an alveolar recruitment manoeuvre in patients undergoing laparoscopic colon surgery

INTRODUCTION

Pulmonary atelectasis is common in patients undergoing laparoscopic abdominal surgery under general anaesthesia, which increases the risk of perioperative respiratory complications. Alveolar recruitment manoeuvres (ARM) are used to open up the lung parenchyma with atelectasis, although the duration of their benefit has not been clearly established. The aim of this study was to determine the effectiveness of an ARM in laparoscopic colon surgery, the duration of response over time, and its haemodynamic impact.

METHODS

Twenty-five patients undergoing laparoscopic colon surgery were included. After anaesthetic induction and initiation of surgery with pneumoperitoneum, an ARM was performed, and then optimal PEEP determined. Respiratory mechanics and gas exchange variables, and haemodynamic parameters, were analysed before the manoeuvre and periodically over the following 90 min.

RESULTS

Three patients were excluded for surgical reasons. The alveolar arterial oxygen gradient went from 94.3 (62.3-117.8) mmHg before to 60.7 (29.6-91.0) mmHg after the manoeuvre (P < .05). This difference was maintained during the 90 min of the study. Dynamic compliance of the respiratory system went from 31.3 ml/cmH2O (26.1-39.2) before the manoeuvre to 46.1 ml/cmH2O (37.5-53.5) after the manoeuvre (P < .05). This difference was maintained for 60 min. No significant changes were identified in any of the haemodynamic variables studied.

CONCLUSION

In patients undergoing laparoscopic colon surgery, performing an intraoperative ARM improves the mechanics of the respiratory system and oxygenation, without associated haemodynamic compromise. The benefit of these manoeuvres lasts for at least one hour.

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

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

Lung-protective mechanical ventilation for patients undergoing abdominal laparoscopic surgeries: a randomized controlled trial

Background

Pneumoperitoneum and Trendelenburg position in laparoscopic surgeries could contribute to postoperative pulmonary dysfunction. In recent years, intraoperative lung-protective mechanical ventilation (LPV) has been reportedly able to attenuate ventilator-induced lung injuries (VILI). Our objectives were to test the hypothesis that LPV could improve intraoperative oxygenation function, pulmonary mechanics and early postoperative atelectasis in laparoscopic surgeries.

Methods

In this randomized controlled clinical trial, 62 patients indicated for elective abdominal laparoscopic surgeries with an expected duration of greater than 2 h were randomly assigned to receive either lung-protective ventilation (LPV) with a tidal volume (Vt) of 7 ml kg^− 1 ideal body weight (IBW), 10 cmH₂O positive end-expiratory pressure (PEEP) combined with regular recruitment maneuvers (RMs) or conventional ventilation (CV) with a Vt of 10 ml kg^− 1 IBW, 0 cmH₂O in PEEP and no RMs. The primary endpoints were the changes in the ratio of PaO₂ to FiO₂ (P/F). The secondary endpoints were the differences between the two groups in PaO₂, alveolar-arterial oxygen gradient (A-aO₂), intraoperative pulmonary mechanics and the incidence of atelectasis detected on chest x-ray on the first postoperative day.

Results

In comparison to CV group, the intraoperative P/F and PaO₂ in LPV group were significantly higher while the intraoperative A-aO₂ was clearly lower. C_dyn and C_stat at all the intraoperative time points in LPV group were significantly higher compared to CV group (p < 0.05). There were no differences in the incidence of atelectasis on day one after surgery between the two groups.

Conclusions

Lung protective mechanical ventilation significantly improved intraoperative pulmonary oxygenation function and pulmonary compliance in patients experiencing various abdominal laparoscopic surgeries, but it could not ameliorate early postoperative atelectasis and oxygenation function on the first day after surgery.

Trial registration

https://www.clinicaltrials.gov/identifier: NCT04546932 (09/05/2020).

Respiratory and Hemodynamic Effects of Prophylactic Alveolar Recruitment During Liver Transplant: A Randomized Controlled Trial

OBJECTIVES

Prolonged surgical retraction may cause atelectasis. We aimed to recruit collapsed alveoli, stepwise, monitored by lung dynamic compliance and observe effects on arterial oxygenation and systemic and graft hemodynamics. Secondarily, we observed alveolar recruitment effects on postoperative mechanical ventilation, international normalized ratio, and pulmonary complications.

MATERIALS AND METHODS

For 58 recipients (1 excluded), randomized with optimal positive end-expiratory pressure (n = 28) versus control (fixed positive end-expiratory pressure, 5 cm H₂O; n = 29), alveolar recruitment was initiated (pressure-controlled ventilation guided by lung dynamic compliance) to identify optimal conditions. Ventilation shifted to volume-control mode with 0.4 fraction of inspired oxygen, 6 mL/kg tidal volume, and 1:2 inspiratory-to-expiratory ratio. Alveolar recruitment was repeated postretraction and at intensive care unit admission. Primary endpoints were changes in lung dynamic compliance, arterial oxygenation, and hemodynamics (cardiac output, invasive arterial and central venous pressures, graft portal and hepatic vein flows). Secondary endpoints were mechanical ventilation period and postoperative international normalized ratio, aspartate/alanine aminotransferases, lactate, and pulmonary complications.

RESULTS

Alveolar recruitment increased positive end-expiratory pressure, lung dynamic compliance, and arterial oxygenation (P < .01) and central venous pressure (P = .004), without effects on corrected flow time (P = .7). Cardiac output and invasive arterial pressure were stable with (P = .11) and without alveolar recruitment (P = .1), as were portal (P = .27) and hepatic vein flow (P = .30). Alveolar recruitment reduced postoperative pulmonary complications (n = 0/28 vs 8/29; P = .001), without reduction in postoperative mechanical ventilation period (P = .08). International normalization ratio, aspartate/alanine aminotransferases, and lactate were not different from control (P > .05).

CONCLUSIONS

Stepwise alveolar recruitment identified the optimal positive end-expiratory pressure to improve lung mechanics and oxygenation with minimal hemodynamic changes, without liver graft congestion/dysfunction, and was associated with significant reduction in postoperative pulmonary complications.

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.

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.

Application of Positive End-Expiratory Pressure (PEEP) in Patients During Prolonged Gynecological Surgery

Introduction: A lot of clinical studies have shown that during prolonged surgery protective ventilation strategy, including low tidal volume, PEEP and recruitment maneuvers (RM) can reduce the rate of postoperative pulmonary complications, which are the second most common cause for postoperative mortality. Therefore, it is important to investigate clinical methods for preventing them. The strategy of protective ventilation is easy and safe for the patients and inexpensive for application during prolonged surgery.

Aims: The objective of this trial was to study whether application of PEEP in patients during prolonged gynecological surgery could decrease the postoperative complications.

Material and Methods: We compared the rates of postoperative complications in patients after prolonged open gynecological surgery, who were divided into 2 groups – group A, which was the control group on non-protective ventilation (35 patients) and group B on protective ventilation (35 patients). The patients in the control group were ventilated with tidal volume (VT) of 8-10 ml/kg without PEEP and RM; the patients in group B were ventilated with VT = 6-8 ml/kg according to their Predicted Body Weight, with a PEEP of 6 cm H2O and RM, which consisted of applying continuous positive airway pressure of 30 cm H2O for 30 seconds. RM was performed after intubation, after every disconnection from ventilator and before extubation. The study was successfully performed without a need for a change in the type of ventilation strategy because of hypoxia or hemodynamic instability. Statistical nonparametric test (e.g. chi-square) was applied.

Results: Total rate of all postoperative complications observed in both groups was 27,1%. We found a significant relationship between application of PEEP and lower rates of postoperative pulmonary complications in group A (39,4%) compared to group B (12,1%), lower rate of respiratory failure (33,3% in group A vs. 9,1% in group B -) and atelectasis (21,2% in group A vs. 0% in group B).

Conclusion: The protective ventilation strategy (low VT, PEEP and RM) in patients during prolonged gynecological surgery can reduce the rate of postoperative pulmonary complications such as respiratory failure and atelectasis.

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.

Effects of recruitment manoeuvre on perioperative pulmonary complications in patients undergoing robotic assisted radical prostatectomy: A randomised single-blinded trial

Robotic-assisted laparoscopic radical prostatectomy (RARP) needs a steep Trendelenburg position and a relatively high CO2 insufflation pressure, and patients undergoing RARP are usually elderly. These factors make intraoperative ventilatory care difficult and increase the risk of perioperative pulmonary complications. The aim was to determine the efficacy of recruitment manoeuvre (RM) on perioperative pulmonary complications in elderly patients undergoing RARP. A total of 60 elderly patients scheduled for elective RARP were randomly allocated to two groups after induction of anaesthesia; positive end expiratory pressure (PEEP) was applied during the operation without RM in the control group (group C) and after RM in the recruitment group (group R). The total number of patients who developed intraoperative desaturation or postoperative atelectasis was significantly higher in group C compared to group R (43.3% vs. 17.8%, P = 0.034). Intraoperative respiratory mechanics, perioperative blood gas analysis, and pulmonary function testing did not show differences between the groups. Adding RM to PEEP compared to PEEP alone significantly reduced perioperative pulmonary complications in elderly patients undergoing RARP.

Effects of intraoperative protective lung ventilation on postoperative pulmonary complications in patients with laparoscopic surgery: prospective, randomized and controlled trial

BACKGROUND

Respiratory functions are usually impaired during pneumoperitoneum for laparoscopic surgery. This randomized, controlled and single-blinded study was performed to evaluate whether intraoperative protective lung ventilation influences postoperative pulmonary complications after laparoscopic hepatobiliary surgery.

METHODS

Sixty-two patients were randomized to receive either conventional ventilation with alveolar recruitment maneuver (tidal volume of 10 ml/kg with inspiratory pressure of 40 cmH2O for 30 s after the end of pneumoperitoneum, group R), or protective lung ventilation (low tidal volume of 6 ml/kg with positive end-expiratory pressure [PEEP] of 5 cmH2O, group P). Induction and maintenance of anesthesia were done with balanced anesthesia. Respiratory complications such as atelectasis, pneumonia or desaturation were observed postoperatively. The length of hospital stay, arterial blood gas analysis, peak inspiratory pressure and hemodynamic variables were also recorded. Results are presented as mean ± SD or number of patients (%).

RESULTS

Postoperative pulmonary complications (P = 0.023) and desaturation below 90 % (P = 0.016) occurred less frequently in group P than in group R. Eight patients of group R and 3 patients of group P showed atelectasis. Pneumonia was diagnosed in 1 patient of group R. No differences were observed in the length of hospital stay, arterial blood gas analysis (pH, PaO2, PaCO2 and PAO2) and hemodynamic variables except PAO2, AaDO2 and peak inspiratory pressure between the two groups.

CONCLUSION

Protective lung ventilation (low tidal volume with PEEP) during pneumoperitoneum was associated with less incidences of pulmonary complications than conventional ventilation with alveolar recruitment maneuver after laparoscopic hepatobiliary surgery.

Pressure safety range of barotrauma with lung recruitment manoeuvres: a randomised experimental study in a healthy animal model

CONTEXT

Recruitment manoeuvres aim at reversing atelectasis during general anaesthesia but are associated with potential risks such as barotrauma.

OBJECTIVE

To explore the range of pressures that can be used safely to fully recruit the lung without causing barotrauma in an ex-vivo healthy lung rabbit model.

DESIGN

Prospective, randomised, experimental study.

SETTING

Experimental Unit, La Paz University Hospital, Madrid, Spain.

ANIMALS

Fourteen healthy young New Zealand rabbits of 12 weeks of age.

INTERVENTIONS

Animals were euthanised, the thorax and both pleural spaces were opened and the animals were allocated randomly into one of two groups submitted to two distinct recruitment manoeuvre strategies: PEEP-20 group, in which positive end-expiratory pressure (PEEP) was increased in 5-cmH2O steps from 0 to 20 cmH2O and PEEP-50 group, in which PEEP was increased in 5-cmH2O steps from 0 to 50 cmH2O. In both groups, a driving pressure of 15 cmH2O was maintained until maximal PEEP and its corresponding maximal inspiratory pressures (MIPs) were reached. From there on, driving pressure was progressively increased in 5-cmH2O steps until detectable barotrauma occurred. Two macroscopic conditions were defined: anatomically open lung and barotrauma.

MAIN OUTCOME MEASURES

We measured open lung and barotrauma MIP, PEEP and driving pressure obtained using each strategy. A pressure safety range, defined as the difference between barotrauma MIP and anatomically open lung MIP, was also determined in both groups.

RESULTS

Open lung MIP was similar in both groups: 23.6 ± 3.8 and 23.3 ± 4.1 cmH2O in the PEEP-50 and PEEP-20 groups, respectively (P = 0.91). However, barotrauma MIP in the PEEP-50 group was higher (65.7 ± 3.4 cmH2O) than in the PEEP-20 group (56.7 ± 5 0.2 cmH2O) (P = 0.003) resulting in a safety range of pressures of respectively 33.3 ± 8.7 and 42.1 ± 3.9 cmH2O (P = 0.035).

CONCLUSION

In this ex-vivo model, we found a substantial difference between recruitment and barotrauma pressures using both recruitment strategies. However, a higher margin of safety was obtained when a higher PEEP and lower driving pressure strategy was used for recruiting the lung.

Effects of a preemptive alveolar recruitment strategy on arterial oxygenation during one-lung ventilation with different tidal volumes in patients with normal pulmonary function test

BACKGROUND

Hypoxemia during one-lung ventilation (OLV) remains a major concern. The present study compared the effect of alveolar recruitment strategy (ARS) on arterial oxygenation during OLV at varying tidal volumes (Vt) with or without positive end-expiratory pressure (PEEP).

METHODS

In total, 120 patients undergoing wedge resection by video assisted thoracostomy were randomized into four groups comprising 30 patients each: those administered a 10 ml/kg tidal volume with or without preemptive ARS (Group H and Group H-ARS, respectively) and those administered a 6 ml/kg tidal volume and a 8 cmH2O PEEP with or without preemptive ARS (Group L and Group L-ARS, respectively). ARS was performed using pressure-controlled ventilation with a 40 cmH2O plateau airway pressure and a 15 cmH2O PEEP for at least 10 breaths until OLV began.

RESULTS

Preemptive ARS significantly improved the PaO2/FiO2 ratio compared to the groups that did not receive ARS (P < 0.05). The H-ARS group showed a highest PaO2/FiO2 ratio during OLV, the L-ARS and H groups showed similarly improved arterial oxygenation, which was significantly higher than in group L (P < 0.05). The plateau airway pressure in group H-ARS was significantly higher than in group L-ARS (P < 0.05).

CONCLUSIONS

Preemptive ARS can improve arterial oxygenation during OLV. Furthermore, a 6 ml/kg tidal volume combined with 8 cmH2O PEEP after preemptive ARS may reduce the risk of pulmonary injury caused by high tidal volume during one-lung ventilation in patients with normal pulmonary function.

Positive end-expiratory pressure (PEEP) during anaesthesia for prevention of mortality and postoperative pulmonary complications

BACKGROUND

General anaesthesia causes atelectasis, which can lead to impaired respiratory function. Positive end-expiratory pressure (PEEP) is a mechanical manoeuvre that increases functional residual capacity (FRC) and prevents collapse of the airways, thereby reducing atelectasis. It is not known whether intraoperative PEEP alters the risks of postoperative mortality and pulmonary complications. This review was originally published in 2010 and was updated in 2013.

OBJECTIVES

To assess the benefits and harms of intraoperative PEEP in terms of postoperative mortality and pulmonary outcomes in all adult surgical patients.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) 2013, Issue 10, part of The Cochrane Library, as well as MEDLINE (via Ovid) (1966 to October 2013), EMBASE (via Ovid) (1980 to October 2013), CINAHL (via EBSCOhost) (1982 to October 2013), ISI Web of Science (1945 to October 2013) and LILACS (via BIREME interface) (1982 to October 2010). The original search was performed in January 2010.

SELECTION CRITERIA

We included randomized clinical trials assessing the effects of PEEP versus no PEEP during general anaesthesia on postoperative mortality and postoperative respiratory complications in adults, 16 years of age and older.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected papers, assessed trial quality and extracted data. We contacted study authors to ask for additional information, when necessary. We calculated the number of additional participants needed (information size) to make reliable conclusions.

MAIN RESULTS

This updated review includes two new randomized trials. In total, 10 randomized trials with 432 participants and four comparisons are included in this review. One trial had a low risk of bias. No differences were demonstrated in mortality, with risk ratio (RR) of 0.97 (95% confidence interval (CI) 0.20 to 4.59; P value 0.97; 268 participants, six trials, very low quality of evidence (grading of recommendations assessment, development and evaluation (GRADE)), and in pneumonia, with RR of 0.40 (95% CI 0.11 to 1.39; P value 0.15; 120 participants, three trials, very low quality of evidence (GRADE)). Statistically significant results included the following: The PEEP group had higher arterial oxygen pressure (PaO2)/fraction of inspired oxygen (FiO2) on day one postoperatively, with a mean difference of 22.98 (95% CI 4.40 to 41.55; P value 0.02; 80 participants, two trials, very low quality of evidence (GRADE)), and postoperative atelectasis (defined as an area of collapsed lung, quantified by computerized tomography scan) was less in the PEEP group (standard mean difference -1.2, 95% CI -1.78 to -0.79; P value 0.00001; 88 participants, two trials, very low quality of evidence (GRADE)). No adverse events were reported in the three trials that adequately measured these outcomes (barotrauma and cardiac complications). Using information size calculations, we estimated that a further 21,200 participants would have to be randomly assigned to allow a reliable conclusion about PEEP and mortality.

AUTHORS' CONCLUSIONS

Evidence is currently insufficient to permit conclusions about whether intraoperative PEEP alters risks of postoperative mortality and respiratory complications among undifferentiated surgical patients.

Prolonged inspiratory time produces better gas exchange in patients undergoing laparoscopic surgery: A randomised trial

BACKGROUND

Laparoscopic surgery performed with a patient in the Trendelenburg position is known to have adverse effects on pulmonary gas exchange and respiratory mechanics. We supposed that prolonged inspiratory time can improve gas exchange at lower airway pressure.

METHODS

One hundred patients undergoing gynaecologic laparoscopic surgery were randomly assigned to one of four groups: conventional inspiratory-to-expiratory (I : E) ratio (Group 1 : 2), I : E ratio of 1 : 1 (Group 1 : 1), 2 : 1 (Group 2 : 1), or 1 : 2 with external positive end-expiratory pressure (PEEP) of 5 cmH2 O (Group 1 : 2 PEEP). Tidal volume was set to 6 ml/kg, and I : E ratio was adjusted at the onset of pneumoperitoneum. Arterial blood gas analysis with measurements of partial pressure of arterial oxygen/fraction of inspired oxygen (PaO2 /FiO2 ), and physiologic dead space-to-tidal volume ratio (VD /VT ) was performed 15 min after anaesthetic induction (T1), and 30 (T2) and 60 min (T3) after onset of CO2 insufflation.

RESULTS

PaO2 /FiO2 at T3 in Groups 1 : 1, 2 : 1, and 1 : 2 PEEP were higher than Group 1 : 2. The partial pressure of arterial carbon dioxide at T3 in Group 2 : 1 was lower than the other groups. The VD /VT at T2 and T3 were lower in Groups 1 : 1 and 2 : 1 than Groups 1 : 2 and 1 : 2 PEEP. Peak or plateau airway pressure was higher in Group 1 : 2 PEEP than the other groups.

CONCLUSIONS

A prolonged inspiratory time demonstrated a beneficial effect on oxygenation. Furthermore, it showed better CO2 elimination without elevating the peak or plateau airway pressure compared with applying external PEEP. In terms of gas exchange and respiratory mechanics, a prolonged inspiratory time appears to be superior to applying external PEEP in patients undergoing laparoscopic surgery in the Trendelenburg position.

Positive end-expiratory pressure (PEEP) during anaesthesia for the prevention of mortality and postoperative pulmonary complications

BACKGROUND

General anaesthesia causes atelectasis which can lead to impaired respiratory function. Positive end-expiratory pressure (PEEP) is a mechanical manoeuvre which increases functional residual capacity (FRC) and prevents collapse of the airways thereby reducing atelectasis. It is not known whether intra-operative PEEP alters the risk of postoperative mortality and pulmonary complications.

OBJECTIVES

To assess the benefits and harms of intraoperative PEEP, for all adult surgical patients, on postoperative mortality and pulmonary outcomes.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, Issue 4), MEDLINE (via Ovid) (1966 to January 2010), EMBASE (via Ovid) (1980 to January 2010), CINAHL (via EBSCOhost) (1982 to January 2010), ISI Web of Science (1945 to January 2010) and LILACS (via BIREME interface) (1982 to January 2010).

SELECTION CRITERIA

We included randomized clinical trials that evaluated the effect of PEEP versus no PEEP, during general anaesthesia, on postoperative mortality and postoperative respiratory complications. We included studies irrespective of language and publication status.

DATA COLLECTION AND ANALYSIS

Two investigators independently selected papers, extracted data that fulfilled our outcome criteria and assessed the quality of all included trials. We undertook pooled analyses, where appropriate. For our primary outcome (mortality) and two secondary outcomes (respiratory failure and pneumonia), we calculated the number of further patients needed (information size) in order to make reliable conclusions.

MAIN RESULTS

We included eight randomized trials with a total of 330 patients. Two trials had a low risk of bias. There was no difference demonstrated for mortality (relative risk (RR) 0.95, 95% CI 0.14 to 6.39). Two statistically significant results were found: the PEEP group had a higher PaO(2)/FiO(2) on day 1 postoperatively (mean difference (MD) 22.98, 95% CI 4.40 to 41.55) and postoperative atelectasis (defined as an area of collapsed lung, quantified by computerized tomography (CT) scan) was less in the PEEP group (SMD -1.2, 95% CI -1.78 to -0.79). There were no adverse events reported in the three trials that adequately measured these outcomes (barotrauma and cardiac complications). Using information size calculations, we estimated that a further 21,200 patients would need to be randomized in order to make a reliable conclusion about PEEP and mortality.

AUTHORS' CONCLUSIONS

There is currently insufficient evidence to make conclusions about whether intraoperative PEEP alters the risk of postoperative mortality and respiratory complications among undifferentiated surgical patients.

Prevention and reversal of lung collapse during the intra-operative period

General anaesthesia induces ventilation/perfusion mismatch by lung collapse. Such lung collapse predisposes patients to preoperative complications since it can persist for several hours or days after surgery. Atelectasis can be partially prevented by using continuous positive airway pressure (CPAP) and/or by lowering FiO2 during anaesthesia induction. However, these manoeuvres are dangerous for patients presenting with challenging airway or ventilator conditions. Lung recruitment manoeuvres (RMs) are ventilatory strategies that aim to restore the aeration of normal lungs. They consist of a brief and controlled increment in airway pressure to open up collapsed areas of the lungs and sufficient positive end-expiratory pressure (PEEP) to keep them open afterward. The application of RMs during anaesthesia normalises lung function along the intraoperative period. There is physiological evidence that patients of all ages and any kind of surgery benefit from such an active intervention. The effect of RMs on patient outcome in the postoperative period is, however, not yet known.

Effect of Pre-emptive Alveolar Recruitment Strategy before Pneumoperitoneum on Arterial Oxygenation during Laparoscopic Hysterectomy

In a randomised, controlled, single-blind trial, we examined the effect of a pre-emptive alveolar recruitment strategy on arterial oxygenation during subsequent pneumoperitoneum. After intubation, 50 patients were randomly allocated to receive either tidal volume 10 ml/kg with no positive end-expiratory pressure (group C) or alveolar recruitment strategy of 10 manual breaths with peak inspiratory pressure of 40 cmH2O plus positive end-expiratory pressure of 15 cmH2O before gas insufflation (group P). During pneumoperitoneum, group P was ventilated with the same setting as group C (FiO2=0.35, tidal volume 10 ml/kg). PaO2 measured during peumoperitoneum was higher in group P than in group C (166∓32 mmHg vs 145∓34 mmHg at 15 minutes, P=0.028, 155∓30 mmHg vs 136∓32 mmHg at 30 minutes, P=0.035). Alveolar-arterial oxygen gradient in group P increased less after gas insufflation (13∓9 to 60∓34 mmHg vs 10∓9 to 37∓31 mmHg, P=0.013). We conclude that the alveolar recruitment strategy we applied before insufflation of the peritoneal cavity may improve oxygenation during laparoscopic hysterectomy.

Occurrence of iatrogenic pneumothorax during laparoscopy-assisted distal gastrectomy: A case report

The occurrence of a pneumothorax during laparoscopy-assisted distal gastrectomy (LADG) is rare. A pneumothorax was developed during a LADG under general anesthesia in a 67-year-old woman with gastric cancer. About 140 minutes after CO2 insufflation, sudden hemodynamic collapse occurred. A defect was noted in the diaphragm. After immediate repair under laparoscopy, hemodynamic stability was achieved within several minutes. In the anesthetic management of a LADG, the anesthesia provider should be aware of the possible occurrence of a pneumothorax.