ABSTRACT
This chapter focuses on the use of laboratory investigations as an aid to the diagnosis and monitoring of the hemorrhagic state in a patient with a hemorrhagic fever. The mechanisms of bleeding in rickettsial hemorrhagic fevers are largely those of a vasculitis, which may be complicated by thrombocytopenia in 40 to 60% of cases. It is important to consider the physiologic influence of the liver, which is frequently involved directly in the viral hemorrhagic fevers and has an important role in hemostasis, because it is a major site of synthesis of many of the elements of the interacting systems. Most conventional laboratory tests are maximally effective in documenting circulating components of the hemostatic machinery, and seldom reflect this interactive physiology, which is essentially fixed in its local operation. Widespread vascular or endothelial damage has been documented or inferred in most of the disorders encompassed by the term viral hemorrhagic fever, in both experimental animal infections and in man.
