Thromboelastometry and two activated clotting tests in detecting residual heparin after protamine in cardiac surgical patients: A prospective cohort study

Abstract

Background: After cardiac surgery, complete heparin reversal with protamine is essential. Accordingly, there is a need for an accurate and precise point-of-care device to detect possible residual heparin after protamine administration.

Objectives: To compare two different activated clotting time (ACT) tests and thromboelastometry in detecting postprotamine heparin activity after cardiac surgery.

Design: A single-centre prospective, observational study.

Setting: University Hospital from September 2021 to February 2023.

Participants: Fifty-five adult, elective cardiac surgical patients.

Interventions: The ACT-LR and ACT+ tests of Hemochron Signature Elite device, and the coagulation time (CT) ratio from INTEM and HEPTEM tests of ROTEM Sigma device, were analysed after protamine administration and compared to baseline values.

Main outcome measures: Based on postprotamine antifactor Xa (anti-fXa) activity, the patients were divided into heparin (anti-fXa ≥0.2 IU ml -1 ) and no heparin (anti-fXa ≤0.1 IU ml -1 ) groups.

Results: There was a mean bias of 44 [95% confidence interval (CI) 40 to 47] celite seconds between ACT-LR and ACT+ measurements. The absolute changes in ACT-LR, ACT+ and INTEM:HEPTEM CT ratio were variable and did not differ between the groups. The mean ± SD percentage changes between postprotamine and baseline ACT-LR and ACT+ values were 5.9 ± 17.5 and 5.9 ± 16.9% in the no residual heparin group, compared to 1.4 ± 8.4 and 9.9 ± 12.5% in the residual heparin group. Receiver operator characteristic curves for postprotamine INTEM:HEPTEM CT ratio and for percentage changes in ACT-LR and ACT+ to detect an anti-fXa at least 0.2 IU ml -1 had areas under the curve of 0.496 (95% CI, 0.329 to 0.663), 0.425 (95% CI, 0.260 to 0.591) and 0.583 (95% CI, 0.417 to 0.749), respectively.

Conclusion: Both the ACT-LR and ACT+ tests of Hemochron Signature Elite device and the INTEM:HEPTEM CT ratio of ROTEM Sigma device have poor ability to detect residual heparin shortly after protamine administration.