Monitoring incomplete heparin reversal and heparin rebound after cardiac surgery.

OBJECTIVES: To assess the incidence of incomplete heparin reversal and heparin rebound after cardiac surgery with cardiopulmonary bypass (CPB) and the ability of the activated coagulation time (ACT) and thromboelastography (TEG) to detect these phenomena.
DESIGN: Prospective single-center study.
SETTING: University hospital. PARTICIPANTS: Forty-one patients undergoing elective cardiac surgery with CPB and with normal preoperative TEG parameters.
INTERVENTIONS: ACT, TEG, and plasma heparin levels were measured in all patients at 5 different times between 20 minutes and 3 hours after protamine administration. The variability of TEG reaction time (R) with and without heparinase (delta-R [DR]) was used to detect the presence of residual heparin.
MEASUREMENTS AND MAIN RESULTS: Plasma heparin expressed as anti-FXa activity was detected in 180 (88%) samples. At univariate analysis, ACT, R-kaolin (R-k), and DR significantly correlated with plasma heparin concentration (respectively, p = 0.007, p = 0.006, and p = 0.002). At multivariate analysis, R-k and DR remained associated with plasma heparin concentration (respectively, p = 0.014 and p = 0.004). Greater quartiles of heparin were associated with higher values of R-k and DR. Combined procedures had significantly lower DR than isolated procedures (p = 0.017), and CPB time and heparinization time positively correlated with R-k (respectively, p = 0.044 and p = 0.022). No association was observed between heparin concentration, ACT, and TEG parameters with postoperative bleeding and need for blood and blood components transfusions.
CONCLUSIONS: Heparin rebound and incomplete heparin reversal are very common phenomena after cardiac surgery with CPB; ACT is not able to detect residual heparin activity, whereas TEG analysis with and without heparinase allows the diagnosis of heparin rebound.