Residual heparinization is a preventable cause of coagulopathy following cardiac surgery. The aim of this work was to assess the proportion of patients with residual heparinization following cardiac surgery and investigate its effect on postsurgical bleeding. Primary outcomes included the proportion of patients with residual heparin activity, measured using thromboelastography. Secondary outcomes include determining the impact of residual heparinization on chest-drain outputs at 24 hours and any factors contributing to residual heparinization.

A prospective observational study.

A quaternary teaching hospital in Melbourne, Australia.

Adult patients undergoing elective or emergency cardiac surgery with cardiopulmonary bypass.

Thromboelastography was performed on all patients 2 hours after returning to the intensive care unit postoperatively.

A total of 99 patients were included in the analysis over the 3-month recruitment period. Residual heparinization was defined by a delta-R value (difference in R-times in the presence and absence of heparinase) of ≥4 minutes and was detected in 27 (27.3%) patients. No differences were detected in bleeding postoperatively when comparing those with and without a residual heparin effect. Higher total intraoperative heparin doses were associated with postoperative heparin activity. Subgroup analysis of only those with residual heparinization (delta-R ≥4 minutes) revealed a significant association with postoperative bleeding.

Residual heparinization occurred frequently following cardiac surgery, without a demonstrated difference in postoperative bleeding compared with control patients. Nevertheless, higher-range delta-R values correlated with increased 24-hour chest drain output. While thromboelastography is a sensitive tool for detecting heparin activity, the level of residual heparinization at which bleeding risk is increased is yet to be established.