Unilateral postoperative pulmonary edema after minimally invasive cardiac surgical procedures: A case-control study

Background Unilateral postoperative pulmonary edema is an underreported adverse event after a minimally invasive cardiac surgical procedure that combines right minithoracotomy with cardiopulmonary bypass. We sought to characterize its incidence, risk factors, and morbidity. Methods We conducted a retrospective case-control study of all cardiac surgical procedures that combined right-sided minithoracotomy with cardiopulmonary bypass at our institution over 8 consecutive years. Unilateral postoperative pulmonary edema was defined on the chest radiograph taken on the first postoperative day as relatively increased opacification of the right versus left hemithorax involving at least 20% of the hemithorax, not better explained by atelectasis. Baseline characteristics, potential risk factors, and outcomes were subject to univariable and multivariable analysis. Results Radiographs were available for 277 of 278 patients; of those, 68 (25%) met our definition of unilateral postoperative pulmonary edema. Patients with unilateral postoperative pulmonary edema had higher mortality and were more likely to have a lower postoperative PaO₂/F_IO₂ ratio, to require vasoactive medications and mechanical ventilation for longer than 24 hours, and to have longer lengths of stay in the intensive care unit and the hospital. Unilateral postoperative pulmonary edema was independently associated with chronic obstructive pulmonary disease (odds ratio [OR] 4.79; 95% confidence interval [CI] 1.28 to 18.0; p = 0.02); pulmonary hypertension, right-ventricular dysfunction, or both (OR 2.92; 95% CI 1.41 to 6.03; p = 0.004); and increasing cardiopulmonary bypass time (OR 1.019; 95% CI 1.011 to 1.027 per additional minute; p <0.001). Conclusions Unilateral postoperative pulmonary edema after minimally invasive cardiac surgical procedures is common, carries significant morbidity, and has identifiable risk factors. Further research is needed to enable a better understanding of the pathophysiology and clinical implications of unilateral postoperative pulmonary edema.