Anemia, Polycythemia, and White Blood Cell Disorders

Anemia is an absolute decrease in the number of circulating red blood cells (RBCs). The diagnosis is made when laboratory measurements fall below accepted normal values (Table 121-1). In emergency medicine, anemia is divided into two broad categories: emergent, having immediate life-threatening complications; and nonemergent, with less imminent danger to the patient. Factors other than the absolute number of circulating RBCs may place the patient in one category or another (e.g., rate of onset and underlying hemodynamic reserve of the patient). Both groups necessitate a sound diagnostic approach, but emergent anemia may require supportive therapy concomitant with or in advance of the definitive diagnosis. Although patients with nonemergent anemia are usually referred to a specialist, they are seen in the hospital often enough to make an understanding of anemia necessary for emergency physicians. The urgency of consultation depends predominantly on the patient’s hemodynamic tolerance of the anemia.