Pneumothorax rates following cardiac surgery with versus without continuous serratus anterior plane catheters: a secondary analysis of trial data with propensity score matching to a historic cohort.

PURPOSE: Moderate to severe pain is common after cardiac surgery, especially in the first two postoperative days. Inadequate pain control may prolong intensive care unit (ICU) stay, may increase cost, and contributes to chronic pain. Enhanced Recovery After Cardiac Surgery (ERACS) protocols prioritize multimodal analgesia, including regional anesthesia techniques. In a recent randomized trial with continuous serratus anterior plane (SAP) catheters, we found unexpectedly high pneumothorax rates. To address this, we aimed to design a propensity-score-matched comparison using patients from the same institution to control for institutional practice patterns, surgical techniques, and patient demographics that could confound comparisons with published literature rates from other centres.

METHODS

We conducted a secondary analysis of RCT data with propensity score matching to a historic cohort. We compared the pneumothorax rates in patients receiving continuous SAP catheters in our previous Cardiac-Serratus Anterior Plane (Cardiac-SAP) trial with those in a retrospective institutional database cohort of patients receiving standard care undergoing cardiac surgery via sternotomy. The two groups were propensity score matched in a 1:20 ratio based on age, sex, smoking status, surgery type, and pre-existing respiratory disease. We analyzed univariate comparisons using Fisher's exact test or the percentile bootstrapping method.

RESULTS

We matched 50 patients from the Cardiac-SAP trial to 989 retrospective cohort patients. After matching, the SAP catheter group was associated with a significantly higher risk of pneumothorax (12% vs 3%; odds ratio, 5.3; 95% confidence interval, 2.1 to 13.6; P < 0.001). There were no significant differences for other outcomes, including ICU readmissions, length of ventilation, and length of ICU or hospital stay. Patients who developed a pneumothorax had longer ventilation time and longer hospital stays.

CONCLUSIONS

Our data suggest that SAP catheter use as a part of a randomized trial for cardiac surgery was associated with a higher rate of pneumothorax in trial participants than in a historic cohort of a similar population, though causality is unclear. Differences in monitoring within the trial and the inherent risks in this population may have contributed.