The Role of Bioimpedance Spectroscopy in Predicting Postdischarge Pleural Effusion After Cardiac Surgery

Abstract Fluid overload is a common complication of cardiac surgery but is difficult to measure with traditional clinical tools. This study evaluates the utility of bioimpedance spectroscopy (BIS) in predicting postdischarge fluid overload-related complications in cardiac surgery patients and its potential as a tool to guide postoperative diuresis. Patients undergoing open-heart surgery with cardiopulmonary bypass underwent BIS measurement for determination of fluid status (%extracellular fluid [ECF]/total body water [TBW]). Measurements were conducted on day of discharge and at subsequent postoperative appointments. A retrospective chart review of subjects was conducted to identify occurrences of pleural effusions requiring intervention via thoracentesis or increased diuresis within 35 days of discharge. A total of 93 patients were included. %ECF/TBW on day of discharge was significantly higher in patients who required intervention for a pleural effusion after discharge (n = 7) compared with those who did not (median: 50.7 [interquartile range, IQR: 50.6–51.0] vs. 46.8 [IQR: 45.2–49.3], p = 0.007). %ECF/TBW at the first postoperative appointment was also significantly higher in patients who required intervention for a pleural effusion compared with those who did not (median: 50.2 [IQR: 50.1–51.2] vs. 48.0 [IQR: 46.5–49.8], p = 0.012). A receiver operating characteristics curve was used to determine a cutoff value of 50.6 for the discharge %ECF/TBW for prediction of pleural effusion requiring intervention with a sensitivity of 83% and a specificity of 90%. Patients who developed pleural effusions postdischarge tended to have higher %ECF/TBW. These findings suggest that BIS can identify patients at risk of fluid overload-mediated complications after discharge.