Abnormally low platelet counts result from either decreased production or increased consumption of platelets. Although there are numerous causes of thrombocytopenia, most are exceedingly uncommon. Decreased platelet production may be drug induced and is associated with the use of sulfonamides, cinchona alkaloids, thiazide diuretics, NSAIDs, gold salts, penicillamine, anticonvulsants, and heparins (230). Decreased platelet count is a feature of several diseases, including vitamin B12 and folate deficiency, aplastic anemia, myeloproliferative disorders, renal failure, and viral infections. Inherited congenital thrombocytopenia is extremely rare. More commonly, thrombocytopenia results from immune destruction of platelets by diseases such as idiopathic thrombocytopenia purpura and collagen vascular disorders. Consumptive thrombocytopenia is a feature of disseminated intravascular coagulation, which is encountered most frequently in conjunction with sepsis or malignancy in the preoperative population.
Platelet dysfunction most often is acquired, but may be inherited. Occasionally, a patient with von Willebrand disease, the second most common inherited disorder of coagulation, may be encountered in the preoperative setting. More commonly, platelet dysfunction results from the use of drugs (e.g., aspirin and amitriptyline), and in patients with resulting prolonged bleeding time, the drug should be withheld for 7 to 10 days before surgery. Uremia and hepatic diseases can affect platelet function.
Platelet dysfunction is more difficult to diagnose than abnormalities of platelet count. A history of easy bruising, petechiae, bleeding from mucous membranes, or prolonged bleeding from minor wounds may signify an underlying abnormality of platelet function. Such dysfunction can be identified with the help of a bleeding time, but full characterization of the underlying etiology should be carried out with hematologic consultation. If at all possible, surgery should be postponed until therapy is instituted.
Disorders of the coagulation cascade often are diagnosed through a personal or family history of excessive bleeding during minor surgery, childbirth, or menses. Many women with menorrhagia are referred for surgical intervention and require a thorough preoperative evaluation for possible inherited disorders of hemostasis, such as factor VIII (hemophilia), factor IX (Christmas disease), factor XI deficiencies, and von Willebrand disease. Von Willebrand disease is the most common hereditary bleeding disorder, with prevalence in the general population of roughly 1% (231). Seventy percent to 90% of patients with von Willebrand disease have menorrhagia (231). Identified women can be treated effectively with desmopressin nasal spray, avoiding unanticipated or excessive bleeding during surgery (232). In the absence of a genetic diagnosis, the diagnosis of von Willebrand disease is difficult and involves a combination of clinical and laboratory assessments, including von Willebrand factor antigen and von Willebrand factor functional activity or ristocetin cofactor assay (232). Physiologic ﬂuctuations occur with von Willebrand factor levels, requiring repeat testing and consultation or referral to a hematologist. It is recommended that women presenting with menorrhagia without obvious pelvic abnormalities should be routinely screened for inherited bleeding disorders before undergoing invasive procedures.
There are few commonly prescribed drugs that affect coagulation factors, the exceptions being warfarin and heparin. Disease states that may be associated with decreased coagulation factor levels are primarily liver disease, vitamin K deficiency (secondary to obstructive biliary disease, intestinal malabsorption, or antibiotic reduction of bowel ﬂora), and disseminated intravascular coagulation.