Postoperative use of rFVIIa by continuous infusion in a haemophilic boy

Continuous infusion of coagulation factor concentrates has proved to be safe and effective. Because rFVIIa (NovoSeven(R)) is a very expensive product and very frequent doses are needed, continuous infusion is expected to be highly cost-effective. The postoperative use of continuous infusion of rFVIIa in a haemophilic boy with a high titre FVIII inhibitor is reported. He presented with a large right knee haemarthrosis and was treated with intermittent doses of rFVIIa. After a transient improvement the haemarthrosis became worse and an open evacuation of the joint had to be made under treatment with bolus injections of rFVIIa for 3 days (120 mu g kg(-1) every 2 h). A previous pharmacokinetic evaluation in this patient had showed that FVIIa recovery and half-life were less than expected. Continuous infusion of rFVIIa (20 mu g kg(-1) h(-1)), with added low molecular heparin to prevent local thrombophlebitis, was started on the fourth postoperative day and maintained unchanged for 7 days. Four additional single bolus injections were given for early joint mobilization. The intervals between replacements of the pump syringes were progressively increased from 6 to 12 h and then up to 24 h. FVIIa plasma levels during continuous infusion ranged between 6.3 and 10.4 IU mL(-1). Although FVIIa assays seemed to show good stability, we observed the formation of precipitates inside the syringes. The precipitates seemed to contain FVIIa. We concluded that FVIIa plasma levels of 6-10 IU mL(-1) were safe and effective to prevent postoperative haemorrhage in this patient. The addition of heparin to the rFVIIa concentrates, however, may cause precipitation and should be avoided. Individual pharmacokinetic evaluation may be useful to select the appropriate initial doses, especially in young patients.