This study investigates whether on-pump FIBTEM-A5 values measured during cardiopulmonary bypass (CPB) accurately predict post-protamine administration values. Conducted at a single cardiac center, the retrospective analysis of 70 patients found a strong correlation (R² = 0.813) between the two measurements. Despite a statistically significant but clinically negligible difference, the findings support using on-pump FIBTEM-A5 to guide fibrinogen supplementation in cardiac surgery.