Impact of zero-positive end-expiratory pressure on blood transfusion rates in off-pump coronary artery bypass surgery: a retrospective cohort study

Background: Bleeding are common in cardiac surgery, with significant impacts on transfusion-related complications and patient prognosis. This study aimed to determine the differences in perioperative blood loss, transfusion rates, and the incidence of postoperative pulmonary complications (PPCs) with and without the use of positive end-expiratory pressure (PEEP) in patients undergoing off-pump coronary artery bypass graft surgery (OPCAB).

Methods: This single-center, retrospective study included 106 adult patients undergoing coronary artery bypass surgery without cardiopulmonary bypass from January 2018 to March 2022. The patients were divided into two groups based on intraoperative ventilator settings: the zero-PEEP (ZEEP) group and the PEEP group. The primary outcome was the perioperative transfusion rate from the intraoperative period to postoperative 7 day. The incidence of PPCs was recorded for 1 week post-operatively. Logistic regression analysis was performed for statistical analysis.

Results: The average PEEP in the PEEP group was 4.92 ± 0.42 cmH₂O. Multiple regression analysis indicated that lower mean airway pressure during surgery tend to associate with intraoperative lower blood loss. The intraoperative transfusion rates in the ZEEP group were significantly lower than those in the PEEP group (ZEEP:14%, PEEP 38.4%, P = 0.02). Logistic regression analysis revealed that ZEEP (adjusted odds ratio [OR] 0.13, 95% confidence interval [CI] 0.04-0.78) and Society of Thoracic Surgeons(STS) scores (adjusted OR 2.31, 95% CI 1.53-3.49) were significantly associated with a reduced requirement for perioperative transfusions. No significant difference was observed between the two groups in terms of PPCs (p = 0.824). Atelectasis was the most common complication in both groups (ZEEP: 35.7%, PEEP: 40%, P = 0.832).

Conclusions: ZEEP and STS scores were associated with significantly reduced requirement for perioperative transfusion rates during elective OPCAB surgery. However, ZEEP did not significantly affect the incidence of PPCs.