Hypoxia-induced vasopressin release and coagulopathy in a normal subject

Humans exposed to hypoxia usually increase their plasma procoagulant VIII activity (VIII:C) with no change in the concentration of VIII related antigen (VIIIR:Ag). This case report describes an apparently normal subject who developed marked qualitative and quantitative changes in all components of the factor VIII complex while inhaling an 11% oxygen/balance nitrogen gas mixture for 2 h. Blood from fresh venepunctures was drawn at baseline, during and after exposure to hypoxia for the following: a partial thromboplastin time, a prothrombin time, fibrin monomer, factor VIII:C, VIII procoagulant antigen (VIII:CAg); ristocetin cofactor activity (VIIIR:Co); VIII von Willebrand factor (VIII:vWF) multimer pattern; and arginine vasopressin. During hypoxia VIII:C, VIII:CAg, VIIIR:Ag and VIIIR:Co increased 4 to 5 fold; the VIII:vWF multimer pattern showed increasing low molecular weight complexes, fibrin monomer appeared and arginine vasopressin (AVP) levels increased from 5.5 pg . ml-1 to 73.8 pg . ml-1. These changes are compatible with both the release of the VIIIR:Ag by AVP and protease induced fragmentation of the VIII complex.