Cardiac surgery patients are prone to complex inflammatory reactions associated with increased microvascular permeability, edema formation, and Capillary Leak Syndrome. Perioperative transfusions have been independently associated with higher risks of complications. This study aimed to investigate the association between transfusion, Capillary Leak Syndrome, and adverse postoperative outcomes in cardiac surgery patients.

A prospective observational cohort of 405 adults undergoing cardiac surgery was enrolled at a tertiary academic center from May 2019 to October 2020. Body impedance electrical analysis and serial serum biomarker measurements were conducted throughout the patients’ peri- and postoperative course. Main outcome measures included inflammatory and endothelial biomarkers (IL-6, IL-8, angiopoietin-2, syndecan-1), body fluid composition assessed by bioelectrical impedance, and clinical outcomes, including acute kidney injury (AKI), ICU length of stay (LOS), and ICU mortality. To study the impact of transfusion on outcomes, statistical analyses including logistic regression, case-matching, and exploratory clustering were performed.

Transfusions of red blood cells, fresh frozen plasma, or platelets were associated with elevated postoperative IL-6 (p < 0.001) and IL-8 (p < 0.001) levels, along with complications in a dose-dependent manner. Higher mortality was observed among patients receiving ≥5 units of each individual component. Transfusions were associated with modest increases in extracellular water and elevated serum levels of angiopoietin-2 and syndecan-1, consistent with Capillary Leak Syndrome, although absolute ECW differences were small. Cluster generation of transfusion-associated capillary leak (TAC) revealed that TAC patients were more frequently prone to death during their ICU stay (p = 0.006), had higher odds of developing AKI (p < 0.001), and a longer ICU LOS (p < 0.001).

Among 405 patients undergoing cardiac surgery, perioperative transfusion was associated with higher inflammatory markers, an increase in extracellular water, and higher risks of AKI and ICU mortality in dose-response analyses, consistent with a transfusion-associated capillary leak phenotype that co-occurs with adverse postoperative outcomes.