Chapter 16. Anesthetic Considerations for the Patient with Anemia and Coagulation Disorders

1. Anemia is common in perioperative patients.

2. Hemoglobin (Hb) concentration or hematocrit (HCT) level can be used to rapidly assess the severity of anemia.

3. Treatment of anemia should be based on the physiology and etiology of anemia. Maintenance and restoration of normovolemia and cardiac output (CO) are necessary but insufficient aims in treating anemia.

4. Tachycardia and hypotension are important clinical signs of hypovolemia and anemia, but compensatory increases in heart rate and CO may be impeded by an insufficient cardiac reserve or anesthetic-induced sympathectomy.

5. Consideration of the physiologic signs and laboratory evidence for inadequate tissue oxygen delivery is mandatory before making a decision to transfuse red blood cells (RBCs).

6. Evidence-based outcomes supporting a specific transfusion trigger level of Hb or HCT do not yet exist for perioperative patients; however, the limited present information suggests that Hb levels as low as 7 to 8 g/dL may be as safe as higher levels of Hb in cardiac surgical and critically ill patients without clinical evidence of ischemia. Further clinical investigations are needed to guide transfusion decisions in critically ill patients.

7. Alternatives to transfusion of allogeneic RBCs are available and should be integrated into a blood-conservation strategy for selected surgical patients.

8. Goals of the perioperative management of patients with sickle cell disease are focused on clinical measures to avoid precipitating a vaso-occlusive crisis and include avoiding hypoxia, hypothermia, and dehydration.

9. Implementation of standard or exchange transfusions for sickle cell patients with the goal of reducing Hb S concentration to less than 30% to 40% can be helpful to reduce the incidence of a perioperative vaso-occlusive crisis.

Anemia is a common blood disorder of perioperative patients.1 The primary physiologic consequence of severe anemia to the surgical patient is inadequate tissue oxygen delivery, which may lead to tissue hypoxia, biochemical imbalances, organ dysfunction, and ultimately organ damage.2 Mismanagement of the anemic surgical patient can adversely affect perioperative outcomes.3 Understanding the laboratory techniques used to assess anemia, the various anemia classifications, and the physiology and appropriate treatment of anemia permits the anesthesiologist to provide better perioperative care for anemic patients.

Anemia Defined and Measured

Anemia is defined as a reduction in the total red cell mass (RCM). Both hematocrit (HCT) level and hemoglobin (Hb) concentration measurements reflect the body's RCM but do not define it. The HCT level, defined as the fractional volume of sampled blood that erythrocytes occupy, is an indirect measurement of the body's RCM (Fig. 16-1). The HCT is a simple, commonly used test to indirectly assess the severity of anemia as well as estimate whole-blood viscosity, oxygen-carrying capacity, and RCM.4 Hb is the predominant protein component of blood and serves as the major carrier transporting oxygen, carbon dioxide, and some nitric oxide.4,5 Hb concentration is a directly measured value that is commonly used to indirectly assess RCM. An isotopic dilution assay of tagged red cells can provide a more accurate assessment ...