Although protamine induces cardiotoxicity, ulinastatin has been shown to attenuate protamine-induced cardiotoxicity in rats. However, whether ulinastatin alleviates protamine-induced cardiac depression during cardiac surgery remains unclear. This study aimed to evaluate the degree of protamine-induced hypotension in patients undergoing cardiac surgery who received ulinastatin.

This post hoc exploratory analysis included patients undergoing scheduled cardiac surgery. Patients were divided into 2 groups: ulinastatin and control. Patients in the ulinastatin group received 300,000 U of ulinastatin before cardiopulmonary bypass, while those in the control group did not receive ulinastatin. Propensity score matching was performed. Arterial blood pressure (ABP), pulmonary artery pressure, continuous cardiac index, systemic vascular resistance index, and vasopressor use were recorded. The primary outcome was the change in mean ABP after protamine administration.

After propensity score matching, 30 patients were included in each of the control and ulinastatin groups. Patient characteristics were comparable between the 2 groups. The protamine-induced decrease in mean ABP was significantly lower in the ulinastatin group than in the control group (4 [0–9] vs 8 [4–13] mm Hg, median [interquartile range], P = .015). There were no significant differences in pulmonary artery pressure and vasopressor use between the groups. While the continuous cardiac index was comparable between the groups after protamine administration, systemic vascular resistance index was significantly higher in the ulinastatin group than in the control group (2090.1 [342.5] vs 1616.2 [644.4] dynes*sec/cm⁵/m², mean [standard deviation], P = .022).

Ulinastatin mitigates protamine-induced hypotension, maintaining systemic vascular resistance.