According to the World Health Organization (WHO), anemia is defined as a hemoglobin concentration of less than 13 g/dL in men and less than 12 g/dL in women. Anemia is common among hospitalized patients. In this chapter, we focus on the evaluation of acute presentations of anemia in hospitalized patients, outlining a practical approach for assessment with emphasis on differentiating common disorders from rare potentially life-threatening conditions. We also provide case vignettes to illustrate typical presentations of anemia encountered in this setting.
CLASSIFICATION OF ANEMIA IN THE ACUTE CARE SETTING
Anemia can be classified broadly by the underlying pathophysiological mechanism of blood loss, increased RBC destruction, or reduced RBC production (Table 77-1).
TABLE 77-1Classification of Anemia Based on Pathophysiology |Favorite Table|Download (.pdf) TABLE 77-1 Classification of Anemia Based on Pathophysiology
|Decreased RBC Production ||Increased RBC Destruction (Hemolysis) ||Blood Loss |
Substrate deficiency (iron, folate, or vitamin B12 deficiency)
Anemia of chronic inflammation
Bone marrow infiltration (eg, lymphoma, myeloma, leukemia, myelofibrosis, metastatic malignancy)
Bone marrow failure syndrome (congenital or acquired)
Chronic kidney disease
Microangiopathic (TTP/HUS, DIC, HELLP, SRC, malignant hypertension)
Mechanical (eg, cardiac valve hemolysis)
Thermal (eg, burn injury)
RBC membrane defect
Sickle cell anemia
RBC enzyme defect
|Acute or chronic blood loss |
Blood loss leading to anemia may be acute or chronic. With acute bleeding, the initial hemoglobin concentration and hematocrit do not accurately represent the actual volume of blood loss. Reductions in hemoglobin concentration may not become apparent for several hours after the onset of bleeding. Clinical presentation is often characterized by signs of hemodynamic compromise, including hypotension, tachycardia, and hypoperfusion. Acute blood loss may be overt (eg, hematochezia, melena, hematemesis, epistaxis) or occult (eg, retroperitoneal hemorrhage). A high index of suspicion for occult acute bleeding should be maintained in patients receiving antiplatelet or anticoagulant therapies, or those with known bleeding diatheses who present with acute anemia and no obvious source of bleeding. In the perioperative setting, worsening anemia should be investigated for occult bleeding at the operative site (eg, retroperitoneal, intra-abdominal, periprosthetic).
Chronic blood loss causes anemia through depletion of iron, which is required for erythropoiesis. Patients with chronic blood loss may present to hospital with progressive symptoms of anemia such as chest discomfort, palpitation, dyspnea, syncope, or severe fatigue requiring urgent assessment and management. Unexplained iron deficiency anemia requires endoscopic evaluation to exclude occult blood loss from gastrointestinal lesions including malignancy. For patients with prolonged hospital admissions, iatrogenic blood loss ...