Prospective study of continuous infusion with Beriate® P in patients with severe haemophilia A undergoing surgery - a subgroup analysis.

INTRODUCTION: Inhibitor development in severe haemophilia A patients is currently the most serious complication of factor VIII (FVIII) treatment. Although continuous infusion (CI) of FVIII concentrate during surgical procedures in haemophilia A patients has been shown to be beneficial, some publications suggest that CI increases the risk of inhibitor generation. We conducted a prospective subgroup analysis to investigate if CI of the high-purity, pasteurized, plasma-derived FVIII concentrate Beriate(®) P during surgery increases the risk of inhibitor formation. MATERIALS AND METHODS: Patients with severe haemophilia A (FVIII:C <1%) were included if they presented with a negative history of previous inhibitors, had ≥ 50 exposure days, and had been scheduled for a planned surgical procedure. A bolus infusion (30-50 IU/kg body weight) of Beriate(®) P was administered intravenously and followed by CI at a rate of 3-4 IU/kg body weight/hour. Dose adjustments were subsequently made based on daily measurements of plasma FVIII activity. RESULTS: Five patients (aged 8-34 years) with severe haemophilia A were included. The surgical procedures ranged from teeth extraction to internal fixation of a fracture. There was no inhibitor generation with CI of Beriate(®) P in patients undergoing surgery, and we did not observe any complications due to re-bleeding or virus transmission. CONCLUSION: Beriate(®) P was efficacious, safe, and well tolerated during CI.

Platelets promote coagulation factor XII-mediated proteolytic cascade systems in plasma.

Blood coagulation factor XII (FXII, Hageman factor) is a plasma serine protease which is autoactivated following contact with negatively charged surfaces in a reaction involving plasma kallikrein and high-molecular-weight kininogen (contact phase activation). Active FXII has the ability to initiate blood clotting via the intrinsic pathway of coagulation and inflammatory reactions via the kallikrein-kinin system. Here we have determined FXII-mediated bradykinin formation and clotting in plasma. Western blotting analysis with specific antibodies against various parts of the contact factors revealed that limited activation of FXII is sufficient to promote plasma kallikrein activation, resulting in the conversion of high-molecular-weight kininogen and bradykinin generation. The presence of platelets significantly promoted FXII-initiated bradykinin formation. Similarly, in vitro clotting assays revealed that platelets critically promoted FXII-driven thrombin and fibrin formation. In summary, our data suggest that FXII-initiated protease cascades may proceed on platelet surfaces, with implications for inflammation and clotting.