The effect of an alveolar recruitment strategy on oxygenation during laparascopic cholecystectomy. Intraoperative ventilatory strategies for prevention of pulmonary atelectasis in obese patients undergoing laparoscopic bariatric surgery. Mechanical ventilation with lower tidal volumes and positive end-expiratory pressure prevents alveolar coagulation in patients without lung injury. Optimizing peroperative compliance with PEEP during upper abdominal surgery: effects on perioperative oxygenation and complications in patients without preoperative cardiopulmonary dysfunction. 'Alveolar recruitment strategy' improves arterial oxygenation during general anaesthesia. Effects of four intraoperative ventilatory strategies on respiratory compliance and gas exchange during laparoscopic gastric banding in obese patients. Postoperative arterial oxygen tension after peroperative PEEP-ventilation.
This prospective randomized controlled trial examined the effect of an "alveolar recruitment strategy" (ARS) in healthy patients having laparoscopic cholecystectomy. Twenty-four consecutive ASA 1 or 2 patients were randomly allocated to an ARS or control group. All patients were manually ventilated to a maximal airway pressure of 25 to 30 cmH2O or a tidal volume of 10 ml/kg during induction of general anaesthesia. After intubation, the control group was ventilated with standardized mechanical ventilation settings. The ARS group was manually ventilated to an airway pressure of 40 cmH2O for 10 breaths over one minute, followed by mechanical ventilation with similar standardized settings plus 5 cmH2O positive end-expiratory pressure. Blood pressure, heart rate, arterial oxygen and carbon dioxide tension (PaO2 and PaCO2) was measured pre-induction, 20 minutes post induction but before abdominal insufflation, 20 minutes after abdominal insufflation, and 20 minutes after arrival in the recovery room. Demographic and operation data were similar. The ARS group pre-insufflation PaO2 [30.16 (9.43)] was higher than the control group [22.19 (9.08)] (P = 0.047). There was a significant difference in PaO2 between the ARS [23.94 (4.87)] and control [17.26 (3.93)] groups during the post-insufflation period (P = 0.001). There were no significant differences in PaO2 between the groups during baseline and recovery periods. No adverse effects were reported. ARS improved arterial oxygenation intraoperatively in healthy patients having laparoscopic cholecystectomy, without clinical cardiovascular compromise or respiratory complication. We conclude that this alveolar recruitment strategy is a useful method of increasing arterial oxygenation. Atelectasis occurs regularly after induction of general anesthesia, persists postoperatively, and may contribute to significant postoperative morbidity and additional health care costs. Laparoscopic surgery has been reported to be associated with an increased incidence of postoperative atelectasis. It has been shown that during general anesthesia, obese patients have a greater risk of atelectasis than nonobese patients. Preventing atelectasis is important for all patients but is especially important when caring for obese patients.
                We randomly allocated 66 adult obese patients with a body mass index between 30 and 50 kg/m(2) scheduled to undergo laparoscopic bariatric surgery into 3 groups. According to the recruitment maneuver used, the zero end-expiratory pressure (ZEEP) group (n = 22) received the vital capacity maneuver (VCM) maintained for 7-8 s applied immediately after intubation plus ZEEP; the positive end-expiratory pressure (PEEP) 5 group (n = 22) received the VCM maintained for 7-8 s applied immediately after intubation plus 5 cm H(2)O of PEEP; and the PEEP 10 group (n = 22) received the VCM maintained for 7-8 s applied immediately after intubation plus 10 cm H(2)O of PEEP. All other variables (e.g., anesthetic and surgical techniques) were the same for all patients. Heart rate, noninvasive mean arterial blood pressure, arterial oxygen saturation, and alveolar-arterial Pao(2) gradient (A-a Pao(2)) were measured intraoperatively and postoperatively in the postanesthesia care unit (PACU). Length of stay in the PACU and the use of a nonrebreathing O(2) mask (100% Fio(2)) or reintubation were also recorded. A computed tomographic scan of the chest was performed preoperatively and postoperatively after discharge from the PACU to evaluate lung atelectasis.
                Patients in the PEEP 10 group had better oxygenation both intraoperatively and postoperatively in the PACU, lower atelectasis score on chest computed tomographic scan, and less postoperative pulmonary complications than the ZEEP and PEEP 5 groups. There was no evidence of barotrauma in any patient in the 3 study groups.
                Intraoperative alveolar recruitment with a VCM followed by PEEP 10 cm H(2)O is effective at preventing lung atelectasis and is associated with better oxygenation, shorter PACU stay, and fewer pulmonary complications in the postoperative period in obese patients undergoing laparoscopic bariatric surgery. Alveolar fibrin deposition is a hallmark of acute lung injury, resulting from activation of coagulation and inhibition of fibrinolysis. Previous studies have shown that mechanical ventilation with high tidal volumes may aggravate lung injury in patients with sepsis and acute lung injury. The authors sought to determine the effects of mechanical ventilation on the alveolar hemostatic balance in patients without preexistent lung injury.
                Patients scheduled for an elective surgical procedure (lasting > or = 5 h) were randomly assigned to mechanical ventilation with either higher tidal volumes of 12 ml/kg ideal body weight and no positive end-expiratory pressure (PEEP) or lower tidal volumes of 6 ml/kg and 10 cm H2O PEEP. After induction of anesthesia and 5 h later bronchoalveolar lavage fluid and blood samples were obtained, and markers of coagulation and fibrinolysis were measured.
                In contrast to mechanical ventilation with lower tidal volumes and PEEP (n = 21), the use of higher tidal volumes without PEEP (n = 19) caused activation of bronchoalveolar coagulation, as reflected by a marked increase in thrombin-antithrombin complexes, soluble tissue factor, and factor VIIa after 5 h of mechanical ventilation. Mechanical ventilation with higher tidal volumes without PEEP caused an increase in soluble thrombomodulin in lavage fluids and lower levels of bronchoalveolar activated protein C in comparison with lower tidal volumes and PEEP. Bronchoalveolar fibrinolytic activity did not change by either ventilation strategy.
                Mechanical ventilation with higher tidal volumes and no PEEP promotes procoagulant changes, which are largely prevented by the use of lower tidal volumes and PEEP. Late postoperative hypoxaemia after upper abdominal surgery is common even among cardiopulmonary healthy patients. Atelectasis may develop after intubation and persist into or reveal a disposition for atelectasis in the postoperative period. Positive end-expiratory pressure (PEEP) eliminates peroperative atelectasis but the effect on perioperative oxygenation is controversial. This study evaluated the effect of peroperative PEEP optimized pulmonary compliance on perioperative oxygenation and complications.
                Forty patients assessed by electrocardiography, spirometry, functional residual capacity and diffusion capacity were randomly assigned to receive positive end-expiratory pressure (PEEP) or zero end-expiratory pressure (ZEEP) during surgery. PaO2, SPO2 and complications in the postoperative period were evaluated without knowledge of peroperative PEEP or ZEEP application.
                Peroperative arterial oxygenation improved for all patients receiving PEEP, mean 2.1 kPa (0.7-3.5 kPa). There was no difference in postoperative median PaO2 between the groups. The differences in the incidence of late prolonged postoperative hypoxaemia and complications were 25% (-5% to 55%) and -1% (-31% to 29%) between the ZEEP and the PEEP group, but were not statistically significant. Abnormalities in gas exchange during general anaesthesia are caused partly by atelectasis. Inspiratory pressures of approximately 40 cm H2O are required to fully re-expand healthy but collapsed alveoli. However, without PEEP these re-expanded alveoli tend to collapse again. We hypothesized that an initial increase in pressure would open collapsed alveoli; if this inspiratory recruitment is combined with sufficient end-expiratory pressure, alveoli will remain open during general anaesthesia. We tested the effect of an 'alveolar recruitment strategy' on arterial oxygenation and lung mechanics in a prospective, controlled study of 30 ASA II or III patients aged more than 60 yr allocated to one of three groups. Group ZEEP received no PEEP. The second group received an initial control period without PEEP, and then PEEP 5 cm H2O was applied. The third group received an increase in PEEP and tidal volumes until a PEEP of 15 cm H2O and a tidal volume of 18 ml kg-1 or a peak inspiratory pressure of 40 cm H2O was reached. PEEP 5 cm H2O was then maintained. There was a significant increase in median PaO2 values obtained at baseline (20.4 kPa) and those obtained after the recruitment manoeuvre (24.4 kPa) at 40 min. This latter value was also significantly higher than PaO2 measured in the PEEP (16.2 kPa) and ZEEP (18.7 kPa) groups. Application of PEEP also had a significant effect on oxygenation; no such intra-group difference was observed in the ZEEP group. No complications occurred. We conclude that during general anaesthesia, the alveolar recruitment strategy was an efficient way to improve arterial oxygenation. Respiratory function is impaired in obese patients undergoing laparoscopic surgery. This study was performed to determine whether repeated lung recruitment combined with PEEP improves respiratory compliance and arterial partial pressure of oxygen (Pa(O2)) in obese patients undergoing laparoscopic gastric banding.
                Sixty patients with BMI >30 kg m(-2) were randomized, after induction of pneumoperitoneum, to receive either PEEP of 10 cm H2O (Group P), inspiratory pressure of 40 cm H2O for 15 s once (Group R), Group R recruitment followed by PEEP 10 cm H2O (Group RP), or Group RP recruitment but with the inspiratory manoeuvre repeated every 10 min (Group RRP). Static respiratory compliance and Pa(O2) were determined after intubation, 10 min after pneumoperitoneum (before lung recruitment), and every 10 min thereafter (after recruitment). Results are presented as mean (SD).
                Pneumoperitoneum decreased respiratory compliance from 48 (3) to 30 (1) ml cm H2O(-1) and decreased Pa(O2) from 12.4 (0.3) to 8.8 (0.3) kPa in all groups (P<0.01). Immediately after recruitment, compliance was 32 (1), 32 (2), 40 (2), and 40 (1) ml cm H2O(-1) and Pa(O2) was 9.1 (0.3), 9.1 (0.1), 11.9 (0.1), and 11.9 (0.1) kPa in Groups P, R, RP, and RRP, respectively (P<0.01). Ten and 20 min later, Pa(O2) in Group R decreased to 9.2 (0.1) kPa and compliance in Group PR decreased to 33 (2) ml cm H2O(-1), respectively (P<0.01).
                Group RRP recruitment strategy was associated with the best intraoperative respiratory compliance and Pa(O2) in obese patients undergoing laparoscopic gastric banding. Forty otherwise healthy patients (29 women and 11 men), undergoing elective cholecystectomy, were randomly allocated to be ventilated during the operation either with a positive end-expiratory pressure of 1 kPa (10 cmH2O) (PEEP group) or with intermittent positive pressure ventilation without PEEP (control group). During the operation the mean arterial oxygen tension (PaO2) in the PEEP group increased from 14.6 to 16.5 kPa, while no changes occurred in the control group (13.5 and 13.6 kPa). On the first postoperative day, PaO2 decreased by 12% of the preoperative values in the PEEP group; the decrease was 20% in the control group. On the third postoperative day, the PaO2 in the control group was still 9% below the preoperative values, but on the fifth day, both groups had reached their preoperative PaO2 values. In the postoperative period, no statistically significant difference in PaO2 could be demonstrated between the groups. Determinations of the forced vital capacity and forced expiratory volume in the first second showed no difference between the groups pre- or postoperatively. The present study demonstrated no clinically relevant beneficial effect of peroperative PEEP ventilation on the postoperative arterial hypoxaemia after an upper abdominal laparotomy.
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.