A normal platelet count is 150,000 to 440,000/mm3. Thrombocytopenia is defined as a count of <150,000/mm3. Intraoperative bleeding can be severe with counts of 40,000-to 70,000/mm3, and spontaneous bleeding usually occurs at counts <20,000/mm3. The minimal recommended platelet count before surgery is 75,000/mm3. However, qualitative differences in platelet function make it unwise to rely solely on platelet count. Thrombocytopenic patients with accelerated destruction but active production of platelets have relatively less bleeding than patients with hypoplastic disorders at a given platelet count.
Assessment of preoperative platelet function is further complicated by lack of correlation between bleeding time or any other test of platelet function and a tendency for increased intraoperative bleeding. However, normal bleeding times range from 4 to 9 minutes, and a bleeding time >1.5 times normal (>15 minutes) is considered significantly abnormal.
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