Activated F IX concentrate (FEIBA) used in the treatment of haemophilic patients with antibody to F VIII

First 20 years with recombinant FVIIa (NovoSeven)

This review describes the background for the development of recombinant FVIIa (rFVIIa; NovoSeven) for use in haemophilic patients with inhibitors. The first proof of principle for using pharmacological doses of FVIIa as a haemostatic agent was obtained by producing small amounts of pure plasma-derived FVIIa, which showed encouraging effect in two patients with haemophilia A and inhibitors. To make pure FVIIa available for use in a larger number of patients, rFVIIa was produced that was approved for use in patients with inhibitors against coagulation factors (congenital haemophilia and acquired haemophilia) in 1996 (EU), 1999 (USA) and 2000 (Japan). The efficacy rate in severe bleedings and in major surgery including major orthopaedic surgery has been found to be around 90% in controlled studies, and no serious safety concerns have been demonstrated. The availability of rFVIIa has facilitated the performance of elective major surgery in haemophilia patients with inhibitors. Further steps along the vision of providing a treatment for inhibitor patients similar to non-inhibitor patients have been the efficacy of rFVIIa in home-treatment and recently the encouraging experience in prophylaxis. The concept of using pharmacological doses of rFVIIa as a haemostatic agent is a new one, which has caused difficulties in finding the correct dose. A step forward has been the demonstration that similar efficacy can be achieved after one single dose of 270 μg kg(-1) instead of three injections of a dose of 90 μg kg(-1). The higher clearance rate in children suggests that higher doses may be beneficial in children. The availability of rFVIIa has made advances in the understanding of coagulation processes possible. In a cell-based in vitro model, it has been shown that rFVIIa binds to preactivated platelets if present in concentrations of 30 nm or higher. By doing so, it activates FX into FXa and enhances the thrombin generation on the activated platelet surface in the absence of FVIII/FIX. Through the increased thrombin generation, a firm, well-structured fibrin haemostatic plug, which is resistant to premature lysis, is formed. By exploiting this mechanism of action, rFVIIa may also be effective in situations other than haemophilia, characterized by an impaired thrombin generation.

Prothrombin complex concentrates for clinical use

Prothrombin complex concentrates prepared for clinical use are reviewed with emphasis on frequently observed adverse reactions such as viral hepatitis and thromboembolic complications. Preparation procedures and quality control are described briefly, and the use of these concentrates in the treatment of hemophilia A patients who develop factor VIII inhibitors is also described. The causes of and methods for the detection of potential thrombogenicity are discussed and suggestions which may result in a safer product are made.

Heparin levels and activated clotting time (ACT) during open heart surgery

Heparin levels were followed by an amidolytic method during open heart surgery in 10 adult patients and correlated to the activated clotting time (ACT) (Haemochron). There was a good correlation between the 2 parameters when the ACT was below 600 s. Based on the present and previous studies of the ACT the authors conclude that the ACT is a useful tool in control of heparinization during open heart surgery.

Evaluation of the activated whole blood clotting time (ACT) in vitro

The activated whole blood clotting time (ACT) was analyzed in vitro using blood samples from normal individuals and from patients with heart disease, scheduled for open heart surgery. The ACT was found to be normally distributed in a group of normal individuals with a mean of 135 sec. In patients with heart diseases, the average ACT was slightly shorter than in normal individuals. A linear relationship between ACT and heparin concentrations was established. Haemodilution and depletion of platelets did not significantly influence the ACT. When a clean venipuncture with disposable needles is used, ACT is a reliable, uncomplicated bedside technique by which heparinisation can be monitored.