What should be included in the preoperative evaluation?
The goal of the preoperative evaluation is to identify pre-existing conditions that could cause excessive bleeding or thrombosis in the perioperative period. Table 50.1 lists items that should be included. The complete medical history (personal and family), list of recent medications, physical examination results, and preoperative laboratory studies should be reviewed on every patient. In obtaining a med-ical history one must specifically inquire about over-the-counter medications, vitamins, other nutritional supplements, and homeopathic or natural remedies. Many patients do not consider these to be medications and forget to mention them. However, many of these natural reme-dies such as ginkgo biloba, garlic, ginseng, feverfew, and vitamin E inhibit platelet function and may cause bleeding if not discontinued prior to surgery.
The physical examination and blood chemistry profiles may identify other medical problems that could lead to surgical bleeding. Examination of the skin and mucous membranes may provide evidence of a hemorrhagic predisposition (vascular purpura, hereditary hemorrhagic telangiectasia), or collagen vascular disease. Splenomegaly, if present, may be associated with hereditary spherocytosis, myeloproliferative disorders, lymphoma, chronic leukemias, or liver disease with portal hypertension. Renal or liver abnormalities identified in the chemistry profile may sug-gest a need for specialized coagulation tests.
In the absence of a personal or family history of a bleed-ing disorder, coagulation tests are usually confined to a complete blood count, PT, and aPTT. Any abnormalities identified in the screening tests must be investigated and evaluated in terms of the operative procedure that is planned. Preoperative correction is advisable. If that is not possible, plans for intraoperative treatment and management must be developed. If there is a personal history of excessive bleeding, additional studies may be indicated even if screening tests are normal. The most common inherited abnormality of coagulation is von Willebrand disease (vWD), with a preva-lence of 1% in the general population.
Approximately 1:1,000 individuals have clinically significant disease. In the most common form of the disease, the aPTT may be normal and assays for factor VIIIc, von Willebrand antigen, and ristocetin cofactor activity may be necessary to establish the diagnosis.
Medications known to inhibit platelet function should be discontinued in time to insure normal platelet function at the time of surgery. Patients should be advised about over-the-counter medications to avoid in the period immediately before surgery. If patients are on coumadin, vitamin K should be administered. If anticoagulation must continue until sur-gery, coumadin reversal and substitution of low-molecular-weight heparin, or regular heparin, may be advisable.
Finally, consultation with a hematologist to plan the management of patients with significant alterations in hemostasis or a predisposition to thrombosis is advisable.