Viscoelastic point-of-care diagnostics are crucial in cardiac surgery. In the FIBTEM assay of rotational thromboelastometry (ROTEM), guidelines suggest target maximum clot firmness values to reduce perioperative bleeding. The fibrinogen doses required to meet these targets remain unclear. This study analyzed the dose-response relationship between fibrinogen concentrate (FC) and clot strength at 5 minutes (A5) and assessed the predictive value of A5 for postoperative hypofibrinogenemia.

Single-center retrospective observational study.

Tertiary academic cardiac hospital.

180 cardiac patients operated on between May 31, 2022, and August 31, 2024.

Patients underwent 2 intraoperative ROTEM examinations and received coagulation factors.

Linear regression was used to examin the relationship between the FC dose and A5 changes. Receiver operating characteristic curves assessed the value of A5 in predicting hypofibrinogenemia and bleeding. Weight-based and estimated blood volume–based FC dosing closely correlated with A5 changes. Each 10 mg/kg increase in FC increased A5 by a mean of 1.37 mm (95% confidence interval [CI], 1.12-1.53 mm) for total body weight, 1.20 mm (95% CI, 1.08-1.33 mm) for ideal body weight, and 1.02 mm (95% CI, 0.9-1.13 mm) for lean body weight, as well as 8.857 mm (95% CI, 7.910-9.818 mm) per mg per mL of estimated blood volume. A5 ≤12 mm predicted hypofibrinogenemia (sensitivity, 77%; specificity, 94%). No thresholds predicted excessive blood loss.

Body weight–based fibrinogen dosing allows predictions of the mean changes in A5. Total, ideal, and lean body weights yielded similar correlation coefficients.