Protamine Dosing for Heparin Reversal Following Cardiopulmonary Bypass: A Double-Blinded Prospective Randomized Control Trial Comparing Two Strategies.

Background: Drug shortages are a frequent challenge in current clinical practice. Certain drugs, (e.g., protamine) lack alternatives and inadequate supplies can limit access to services. Conventional protamine dosing uses heparin ratio-based calculations for heparin reversal following CPB and may result in excess protamine utilization, and potential harm due to its intrinsic anticoagulation. We hypothesized that a fixed 250-mg protamine dose would be comparable, as measured by the activated clotting time, to a 1:1 (1 mg for every 100 U) protamine to heparin ratio-based strategy for heparin reversal and that protamine would be conserved.

Methods: In a single-center, double-blinded trial, consenting elective adult cardiac surgical patients without pre-existing coagulopathy or ongoing anticoagulation, and a calculated initial heparin dose of ≥ 27500 U were randomized to receive, following CPB, protamine as a fixed dose (250 mg) or a ratio-based dose (1 mg:100 U heparin). The primary outcome was the activated clotting time following initial protamine administration, assessed by Student's t-test. Secondary outcomes included total protamine, the need for additional protamine, and the cumulative 24-h chest tube output.

Results: There were 62 and 63 patients in the fixed- and ratio-based dose groups, respectively. The mean post-protamine ACT was not different between groups (-2.0 s, 95% CI -7.2 to 3.3 s, P = 0.47). Less total protamine per case was administered in the fixed-dose group (2.1 50-mg vials, 95% CI -2.4 to -1.8, P < 0.0001). There was no difference in the cumulative 24-h chest tube output (difference = -77 ml, 95% CI 220 to 65 ml, P = 0.28).

Conclusions: A 1: 1 heparin ratio-based protamine dosing strategy compared to a fixed 250-mg dose resulted in the administration of a larger total dose of protamine no difference in either the initial ACT or the amount postoperative chest-tube bleeding.