Laboratory heparin resistance in burn injury complicated by venous thrombosis

Anticoagulation with heparin is required in the management of the burn pati ent if their clinical course is complicated by venous thrombosis. Heparin t herapy is commonly monitored by the activated partial thromboplastin time ( APTT) but this assay can be unreliable in patients with acute inflammation because of an increase in plasma factor VIII levels that result in an under estimation of the heparin concentration. We report an example of heparin re sistance that occurred in a patient who developed venous thrombosis followi ng extensive second-degree burns. Heparin doses in excess of 60,000 units p er day were required to produce a significant elevation in the APTT. The pl asma factor VIII level was found to be markedly elevated to 455% and the pl asma heparin concentration as determined by the anti-factor Xa assay was di sproportionately elevated in relation to the APTT. Physicians treating pati ents with burn injury complicated by Venous thrombosis should be aware of t he potential development of factor VIII-related heparin resistance when lar ge amounts of heparin are required to obtain a satisfactory elevation in th e APTT. Measurement of the plasma heparin concentration will avoid excessiv e heparin administration and the serious bleeding which can result. (C) 199 9 Elsevier Science Ltd and ISBI. All rights reserved.