Differential Effects of Intraoperative Positive End-expiratory Pressure (PEEP) on Respiratory Outcome in Major Abdominal Surgery Versus Craniotomy

Abstract

Objectives: In this study, we examined whether (1) positive end-expiratory pressure (PEEP) has a protective effect on the risk of major postoperative respiratory complications in a cohort of patients undergoing major abdominal surgeries and craniotomies, and (2) the effect of PEEP is differed by surgery type.

Background: Protective mechanical ventilation with lower tidal volumes and PEEP reduces compounded postoperative complications after abdominal surgery. However, data regarding the use of intraoperative PEEP is conflicting.

Methods: In this observational study, we included 5915 major abdominal surgery patients and 5063 craniotomy patients. Analysis was performed using multivariable logistic regression. The primary outcome was a composite of major postoperative respiratory complications (respiratory failure, reintubation, pulmonary edema, and pneumonia) within 3 days of surgery.

Results: Within the entire study population (major abdominal surgeries and craniotomies), we found an association between application of PEEP ≥5 cmH2O and a decreased risk of postoperative respiratory complications compared with PEEP <5 cmH2O. Application of PEEP >5 cmH2O was associated with a significant lower odds of respiratory complications in patients undergoing major abdominal surgery (odds ratio 0.53, 95% confidence interval 0.39 - 0.72), effects that translated to deceased hospital length of stay [median hospital length of stay : 6 days (4-9 days), incidence rate ratios for each additional day: 0.91 (0.84 - 0.98)], whereas PEEP >5 cmH2O was not significantly associated with reduced odds of respiratory complications or hospital length of stay in patients undergoing craniotomy.

Conclusions: The protective effects of PEEP are procedure specific with meaningful effects observed in patients undergoing major abdominal surgery. Our data suggest that default mechanical ventilator settings should include PEEP of 5-10 cmH2O during major abdominal surgery.

Figures

FIGURE 1

Flow diagram of study population.

FIGURE 2

Effect of median intraoperative PEEP on the risk of postoperative respiratory complications in the entire cohort of patients undergoing major abdominal surgery or craniotomy. Multivariable logistic regression analysis, adjusted for: age, sex, body mass index, American Society of Anesthesiologists classification, score for prediction of postoperative respiratory complications, Charlson Comorbidity index, work relative value units, preexisting pulmonary disease, duration of ventilation, units of packed red blood cells, fresh frozen plasma and platelets transfused, urgent/emergent surgery, total fluids administered, type of surgery, and plateau pressure. A PEEP of ≥5 cmH2O is associated with a lower odds of respiratory complications compared with PEEP <5 cmH2O, across surgical services.

FIGURE 3

Respiratory complications as a function of median intraoperative PEEP. Data are shown separated by abdominal surgery and craniotomy. Multivariable logistic regression analysis, adjusted for: age, sex, body mass index, American Society of Anesthesiologists classification, score for prediction of postoperative respiratory complications, Charlson Comorbidity index, work relative value units, preexisting pulmonary disease, duration of ventilation, units of packed red blood cells, fresh frozen plasma and platelets transfused, urgent/emergent surgery, total fluids administered, and plateau pressure. There is a significant reduction in the odds ratio for postoperative respiratory complications for PEEP ≥5 in major abdominal surgery compared with PEEP 5 and PEEP 0, whereas no significant beneficial effect of high PEEP is observed in patients undergoing a craniotomy.