Dose-dependent Effects of Four-factor Prothrombin Complex Concentrate on Clotting Time in Rotational Thromboelastometry—A Retrospective Cohort Study

OBJECTIVES: To determine whether four-factor prothrombin complex concentrate (PCC) dosing produces a predictable, dose-dependent reduction in EXTEM clotting time (CT) and to evaluate the ability of EXTEM-CT to predict severe postoperative bleeding after cardiac surgery. DESIGN: Single-center retrospective cohort study. SETTING: A high-volume tertiary academic cardiac center. PARTICIPANTS: Adult patients undergoing cardiac or aortic surgery between May 2022 and August 2024 who received a single PCC dose between two rotational thromboelastometry (ROTEM) assessments. INTERVENTIONS: Administration of a single dose of four-factor PCC guided by viscoelastic testing (ROTEM). MEASUREMENTS AND MAIN RESULTS: The primary outcome was the change in EXTEM-CT (ΔCT) between pre- and post-PCC ROTEM measurements. Robust linear regression adjusted for on-pump EXTEM-CT assessed the causal effect of PCC dose (IU/kg) on ΔCT. Among 175 patients (median PCC dose 3,000 IU, 36 IU/kg), median EXTEM-CT decreased from 104 seconds pre-PCC to 76 seconds post-PCC. On-pump EXTEM-CT was the strongest predictor of ΔCT (β = -0.91; p < 0.001), while the adjusted effect of PCC dose was modest and not statistically significant (β = 0.11; p = 0.14). Post-PCC EXTEM-CT showed poor discrimination for severe postoperative bleeding (area under the curve = 0.486). CONCLUSIONS: Weight-based PCC dosing yields inconsistent reductions in ROTEM-measured CT after cardiac surgery. EXTEM-CT is an unreliable predictor of severe postoperative bleeding, and PCC dosing should not be escalated solely based on EXTEM-CT prolongation.