Thrombocytopenia is both common and multifactorial in the critically ill ( Table 1). The risk of bleeding cannot be directly related to platelet count, but is unlikely until this falls below 80 * 109/l and is increased below 10 to 20 * 109/l. Platelet function (modified by drugs such as aspirin), the integrity of the vessel wall, and the components of the coagulation cascade all contribute to hemorrhagic risk.
Table 1 Pathological classification of causes of thrombocytopenia
The pattern of bleeding due to thrombocytopenia is purpuric and is found on the shins, flexor areas, or pressure areas; small ecchymoses or mucous membrane bleeding are also seen. Subconjunctival and retinal hemorrhage are commonly found in those profoundly thrombocytopenic patients in whom life-threatening intracranial and gastrointestinal hemorrhages are a major risk. Hematomas or hemarthroses are rare unless there is a coexisting hemostatic disorder.
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