• continuous infusion;
  • factor concentrate;
  • haemophilia A;
  • haemophilia B;
  • inhibitors;
  • von Willebrand's disease


Inhibitor development against von Willebrand factor, factor VIII or factor IX is one of the most severe complications of treating patients with von Willebrand's disease (VWD), haemophilia A or haemophilia B respectively. Continuous infusion of factor concentrate has been implicated as a risk factor for inhibitor development. This prospective study investigated inhibitor development after continuous infusion of factor concentrate for surgical procedures in subjects with VWD or a severe form of haemophilia (factor activity <1%). Observations were made on the occurrence of inhibitor formation, adverse events and virus seroconversions. Main inclusion criteria comprised a negative history of inhibitors to replacement factor concentrate, ≥50 exposure days to factor concentrate and anticipated surgery requiring replacement factor coverage for ≥3 days. Therapy began with a bolus dose of 30–50 IU kg−1 body weight of factor concentrate followed by continuous infusion with 3–4 IU kg−1 h−1. Continuous infusion dose of factor concentrate was adjusted based on factor levels measured at least once daily. In 46 subjects included in the study to date, no inhibitors have been identified at discharge or follow-up (3–4 weeks after surgery), and no thrombotic events or postoperative wound infections occurred. All subjects underwent surgery without major blood loss, and hemostatic efficacy was generally rated ‘excellent’. The results of the current study are promising, although the number of subjects is too small to make a definitive statement about the incidence of inhibitor development during continuous infusion of factor concentrate. Therefore, this study will be continued.