Randomized evaluation of fibrinogen versus placebo in complex cardiovascular surgery: post hoc analysis and interpretation of phase III results.

In a multicentre, randomized-controlled, phase III trial in complex cardiovascular surgery (Randomized Evaluation of Fibrinogen vs Placebo in Complex Cardiovascular Surgery: REPLACE), single-dose human fibrinogen concentrate (FCH) was associated with the transfusion of increased allogeneic blood products (ABPs) versus placebo. Post hoc analyses were performed to identify possible reasons for this result. We stratified REPLACE results by adherence to the transfusion algorithm, pretreatment fibrinogen level (≤2 g/l vs >2 g/l) and whether patients were among the first 3 treated at their centre. Patients whose treatment was adherent with the transfusion algorithm [FCH, n = 47 (60.3%); placebo, n = 57 (77.0%); P = 0.036] received smaller quantities of ABPs than those with non-adherent treatment (P < 0.001). Among treatment-adherent patients with pretreatment plasma fibrinogen ≤2 g/l, greater reduction in 5-min bleeding mass was seen with FCH versus placebo (median -22.5 g vs -15.5 g; P = 0.071). Considering patients with the above conditions and not among the first 3 treated at their centre (FCH, n = 15; placebo, n = 22), FCH was associated with trends towards reduced transfusion of ABPs (median 2.0 vs 4.0 units; P = 0.573) and greater reduction in 5-min bleeding mass (median -21.0 g vs -9.5 g; P = 0.173). Differences from a preceding single-centre phase II study with positive outcomes included more patients with pretreatment fibrinogen >2 g/l and fewer patients undergoing thoracoabdominal aortic aneurysm repair. None of the patient stratifications provided a clear explanation for the lack of efficacy seen for FCH in the REPLACE trial versus the positive phase II outcomes. However, together, the 3 factors demonstrated trends favouring FCH. Less familiarity with the protocol and procedures and unavoidable differences in the study populations may explain the differences seen between the phase II study and REPLACE. NCT01475669 https://clinicaltrials.gov/ct2/show/NCT01475669; EudraCT trial no: 2011-002685-20.

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© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.