You are preparing for an open abdominal procedure in an obese patient (body mass index, 39 kg/m2). In addition to tidal volume ventilation of 7 mL/kg of predicted body weight, you decide to use high positive end-expiratory pressure (PEEP) to minimize postoperative pulmonary complications. Based on a recent randomized clinical trial that compared high PEEP (12 cm H2O) and hourly recruitment maneuvers with low PEEP (4 cm H2O) and no recruitment maneuvers, which of the following outcomes is MOST likely in this patient? Read the discussion.
(A) Similar risk of postoperative respiratory complications
(B) Lower risk of hypotensive episodes intraoperatively
(C) Higher risk of postoperative respiratory complications because this patient’s body mass index is less than 40
Gain insight on this topic, and many others, with Summaries of Emerging Evidence (SEE) 2021 – now available. The content is aggregated from 30 international medical journals to streamline your learning and improve your practice.
With the increasing global prevalence of obesity, there is a high level of interest in identifying perioperative measures to optimize postoperative outcomes in this patient population. The risk of postoperative pulmonary complications is increased in obese patients. A recent international randomized clinical trial, the Protective Intraoperative Ventilation With Higher Versus Lower Levels of Positive End-Expiratory Pressure in Obese Patients (PROBESE) trial, was conducted to determine whether an intraoperative ventilation strategy with higher positive end-expiratory pressure (PEEP) and alveolar recruitment maneuvers reduced the incidence of postoperative pulmonary complications.
The trial included patients with a body mass index (BMI) of 35 kg/m2 or greater undergoing noncardiac surgery that required more than 2 hours of general anesthesia from July 2014 to February 2018. Patients were ventilated on volume-controlled modes with a tidal volume of 7 mL/kg of predicted body weight. Postintubation, patients received the lowest FIO2, but not less than 0.4, to maintain peripheral oxygen saturation (SpO2) greater than 92%. Patients were randomly assigned to the low PEEP group (4 cm H2O) or high PEEP group (12 cm H2O with hourly alveolar recruitment maneuvers). Data from a total of 1,976 patients (low PEEP, n = 987; high PEEP, n = 989) were included in the study analysis. The treatment effect of high versus low PEEP was analyzed in several subgroups:
- Laparoscopic versus nonlaparoscopic surgery
- BMI of 35 to 39 versus BMI of 40 or greater
- Baseline SpO2 less than 96% versus 96% or greater
- Abdominal procedure versus peripheral procedure
- Weight distribution waist-to-hip ratio less than 1.0 versus 1.0 or greater
The findings of the study included:
- Intraoperative use of higher PEEP did not decrease the frequency or severity of postoperative respiratory complications within the first 5 postoperative days compared with lower PEEP levels in all cohorts. The risk of postoperative respiratory complications was similar in the high PEEP group compared to that in the low PEEP group (21.3% vs 23.6%, respectively).
- Patients receiving higher levels of PEEP intraoperatively had a higher incidence of pleural effusion within 5 days postoperatively compared with those receiving lower levels of PEEP (4.3% vs 2.1%, respectively).
- The study did not find that the predefined subgroups benefitted from a specific PEEP level. The risk ratio for postoperative pulmonary complications between high PEEP and low PEEP was not affected by BMI.
The study authors found the intraoperative pattern to be similar between the high and low PEEP groups. Patients in the high PEEP group received the same amount of intravenous fluid (crystalloid, colloid, blood component therapy) compared to those in the low PEEP group. No difference was found in intraoperative urine output between the groups. However, ventilation parameters were found to be different. High PEEP was found to be associated with higher peak airway pressures, lower driving pressures, lower FIO2, and higher SpO2 compared with low PEEP. Hemodynamically, more intraoperative hypotensive events occurred in the high PEEP group than in the low PEEP group (31.6% vs 17.2%, respectively). In addition, the high PEEP group had a higher incidence of bradycardia intraoperatively (9.9% vs 6.0%, respectively). Lastly, the study did not find an increased risk of extrapulmonary complications. The risk of any stage of acute kidney failure was found to be similar in both groups (high PEEP, 3.1% [31 of 989] patients vs low PEEP, 3.2% [32 of 987] patients). Mortality rate was found to be similar between high PEEP and low PEEP (0.5% vs 0.3%, respectively).
In summary, the study findings show that high levels of PEEP in addition to alveolar recruitment maneuvers in obese patients did not reduce the incidence of postoperative pulmonary complications compared to low levels of PEEP. The pragmatic approach of using a high level of PEEP in all obese patients may not be in the best interests of this patient cohort.
- Writing Committee for the PROBESE Collaborative Group of the Protective Ventilation Network (PROVENET) for the Clinical Trial Network of the European Society of Anaesthesiology. Effect of intraoperative high positive end-expiratory pressure (PEEP) with recruitment maneuvers vs low PEEP on postoperative pulmonary complications in obese patients: a randomized clinical trial. JAMA. 2019;321(23):2292-2305. doi:10.1001/jama.2019.7505
- Godet T, Futier E. Setting positive end-expiratory pressure in mechanically ventilated patients undergoing surgery. JAMA. 2019;321(23):2285-2287. doi:10.1001/jama.2019.7540