Intraoperative Ventilation/Perfusion Mismatch and Postoperative Pulmonary Complications after Major non-cardiac surgery: a prospective cohort study.

Abstract

Postoperative pulmonary complications (PPCs) can increase hospital length of stay, postoperative morbidity and mortality. Despite many factors can increase the risk of PPCs, it is not known whether intraoperative ventilation/perfusion (V/Q) mismatch can be associated with an increased risk of PPCs after major non-cardiac surgery. We enrolled patients undergoing general anesthesia for non-cardiac surgery and evaluated intraoperative V/Q distribution using the Automatic Lung Parameter Estimator technique. The assessment was done after anesthesia induction (T1), after 1 hour from surgery start (T2) and at the end of surgery (T3). We collected demographic and procedural information and measured intraoperative ventilatory and hemodynamic parameters at each time-point. Patients were followed up for 7 days after surgery and assessed daily for PPCs occurrence. We enrolled 101 patients with a median age of 71 [62-77] years, a BMI of 25 [22.4-27.9] kg/m 2 and a preoperative ARISCAT score of 41 [34-47]. Of them, 29 (29%) developed PPCs, mainly acute respiratory failure (23%) and pleural effusion (11%). Patients with and without PPCs did not differ in levels of shunt at T1 (PPCs:22.4[10.4-35.9] % vs No PPCs:19.3[9.4-24.1] %, p=0.18) or during the protocol, while significantly different levels of high V/Q were found during surgery (PPCs:13[11-15] mmHg vs No PPCs:10[8-13.5] mmHg, p=0.007) and before extubation (PPCs:13[11-14]mmHg vs No PPCs:10[8-12] mmHg, p=0.006). After adjusting for age, ARISCAT, BMI, smoking, fluid balance, anesthesia type, laparoscopic procedure and surgery duration, high V/Q before extubation was independently associated with the development of PPCs (OR 1.147, CI 95% [1.021-1.289], p=0.02). The sensitivity analysis showed an E-value of 1.35 (CI=1.11). In patients with intermediate/high risk of PPCs undergoing major non-cardiac surgery, intraoperative V/Q mismatch is associated with the development of PPCs. Increased high V/Q before extubation is independently associated with the occurrence of PPCs in the first 7 days after surgery.