INTRODUCTION: Cardiovascular surgery is still associated with significant morbidity and mortality due to bleeding. Several case reports have suggested that a new agent, recombinant Factor VIIa (rVIIa), may reduce bleeding in patients failing conventional treatment (1; 2). The purpose of this study was to determine if adding rVIIa to the already thrombogenic environment of new vascular anastomoses could result in higher incidence of graft occlusion. METHODS: With Animal Care Committee approval, 19 rabbits were anesthesized with ketamine (10mg/kg), xylazine (2mg/kg), and 1-2% isoflurane in 100% oxygen. Through a midline neck incision, the right jugular and both carotid arteries were exposed. The animals were anticoagulated with heparin, and a 2-3 cm section of right jugular vein was then excised and grafted to the right carotid artery with two end to side anastomoses. The left carotid artery was ligated and re-anastomosed in an end to end fashion. Following protamine administration the grafts were inspected before skin closure to ensure adequate flow. Animals then received either placebo or 300ug/kg of rVIIa intravenously. An ultrasound was performed at 3 hours and 24 hours to assess graft flow, and the presence of occlusive clot. On sacrifice, the grafts were visually inspected for thrombus. The primary outcome was ultrasound evidence of no flow or presence of occlusive thrombus in the graft. Data was analyzed using ANOVA, chi-square or fisher's exact test where appropriate, with p<0.05 considered significant. RESULTS: Three animals were excluded for technical reasons. rVIIa treated animals had a significantly higher incidence of graft occlusion (vein 7/8 vs 1/8, p=0.01; artery 7/8 vs 2/8, p<0.05) and lower average vein graft flow (26.7 +/-15.34 vs 5.5 +/-13.47 ml/min, p<0.05). There was no significant difference between the two groups in graft diameter, physiological variables, hemodynamics or anticoagulation. DISCUSSION: This study suggests that high dose rVIIa (300ug/kg) leads to an increased incidence of fresh vascular graft thrombosis. It is still unknown if these results would be obtained with lower doses. Our findings may guide further research and clinical use of rVIIa

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Background Perioperative blood loss is a major contributor to morbidity and mortality in cardiac surgery. Plasma fibrinogen levels play an essential role in hemostasis and deplete quickly during hemorrhage. The objective of this study was to determine whether prophylactic fibrinogen concentrate administration lowers overall blood product transfusion requirements in high‐risk cardiac surgery in patients with low fibrinogen plasma levels. Methods The study was performed in a prospective, randomized, and double‐blinded design. The investigation included 62 patients undergoing elective, high‐risk cardiac surgery. After weaning from cardiopulmonary bypass and reversal of heparin patients received either fibrinogen concentrate or placebo. The primary outcome variable was overall blood product usage 24 hours after intervention. Results The fibrinogen group received numerically fewer total units of blood products than the placebo group, but the difference was not statistically or clinically significant (for groups n = 27; n = 29 and 19 vs 37 units, respectively, P = .908). The overall transfusion rate in both groups was significantly lower than the institutional average suggested (fibrinogen group 26%, placebo group 28%). The fibrinogen group showed significantly higher fibrinogen levels (2.38 vs 1.83 g/L (end of surgery), P < .001; 3.33 vs 2.68 g/L (12 hours after intervention), P = .003) and improved viscoelastic coagulation parameters (FIBTEM MCF, 27 vs 23 mm, P = .022). Conclusion This randomized, controlled trial demonstrates that point‐of‐care guided and prophylactic treatment with fibrinogen concentrate does not reduce transfusion of blood products in a setting of unexpectedly low transfusion rate as tested in this cohort, but may improve coagulation parameters in the setting of high‐risk cardiac surgery.

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