Three of the more common clinical situations faced by the medical consultant are the patient with anemia, the assessment of bleeding risk, and the perioperative management of long-term anticoagulation.
Preoperative anemia is common, with a prevalence of 43% in a large cohort of elderly veterans undergoing surgery. The main goals of the preoperative evaluation of the anemic patient are to determine the need for preoperative diagnostic evaluation and the need for transfusion. When feasible, the diagnostic evaluation of the patient with previously unrecognized anemia should be done prior to surgery because certain types of anemia (particularly those due to sickle cell disease, hemolysis, and acute blood loss) have implications for perioperative management. These types of anemia are typically associated with an elevated reticulocyte count. Preoperative anemia is associated with higher perioperative morbidity and mortality. It is not known whether raising preoperative hemoglobin level to specific targets will improve postoperative outcomes. The clinician determining the need for preoperative transfusion in an individual patient must consider factors other than the absolute hemoglobin level, including the presence of cardiopulmonary disease, the type of surgery, and the likely severity of surgical blood loss. The few studies that have compared different postoperative transfusion thresholds failed to demonstrate improved outcomes with a more aggressive transfusion strategy. One trial randomized hip fracture patients, most with cardiovascular disease, to either transfusion to maintain a hemoglobin level greater than 10 g/dL (100 g/L) or transfusion for symptomatic anemia. Patients receiving symptom-triggered transfusion received far fewer units of packed red blood cells without increased mortality or complication rates. Based on available evidence, the AABB (formerly American Association of Blood Banks) recommends transfusion for a hemoglobin level less than 8 g/dL (80 g/L) or for symptomatic anemia in patients undergoing orthopedic or cardiac surgery.
The most important component of the bleeding risk assessment is a directed bleeding history (see Table 3–1). Patients who provide a reliable history of no abnormal bleeding on directed bleeding history and have no suggestion of abnormal bleeding on physical examination are at very low risk for having an occult bleeding disorder. Laboratory tests of hemostatic parameters in these patients are generally not needed. When the directed bleeding history is unreliable or incomplete, or when abnormal bleeding is suggested, a formal evaluation of hemostasis should be done prior to surgery and should include measurement of the prothrombin time, activated partial thromboplastin time, and platelet count (see Chapter 13-29).
Patients receiving long-term oral anticoagulation are at risk for thromboembolic complications when an operation requires interruption of this therapy. “Bridging anticoagulation,” where unfractionated or low-molecular-weight heparin is administered parenterally while oral anticoagulants are held, is commonly practiced, but its benefit is unproven and there is the potential for harm. A meta-analysis of cohort studies found that approximately 1% of patients who had interruption of anticoagulation for a procedure suffered a thrombotic complication and that bridging anticoagulation did not reduce this risk. In addition, the patients ...