Principles of Critical Care > Part VII. Hematologic and Oncologic Disorders > Chapter 68. Anemia and Blood Transfusion Judith A. Luce

Anemia in the ICU

"The frequency of anemia in critically ill patients has been studied in a variety of settings, all with the conclusion that it is a common problem that tends to worsen with severity of illness and duration of stay in the ICU. Up to 40% of patients admitted to the ICU in one large sequential cohort study were bleeding on admission,² and 40% to 50% require blood transfusion during their ICU stay.³ By day two in the ICU, nearly 95% of patients are anemic.⁴ Trauma patients are subject to higher rates of transfusion, 55%, than medical patients in one comparative study, even though these patients had lower rates of comorbid illnesses.⁵Hemorrhage is the most common cause of anemia in the ICU; those losses arise from surgical intervention or from medical causes of bleeding, and are the sole contributor to anemia in up to 20% of anemic patients in the ICU (Table 68-1).⁴ The severity of red cell loss, and the resultant need for transfusion, is also dependent on the degree of underlying illness in a particular patient, as well as the type of surgery being performed, and the exact medical cause of bleeding. Underlying conditions such as renal failure, nutritional failure, liver disease, and drug effects have been shown to increase the risk of bleeding in critically ill patients.²In spite of a long tradition of transfusion of red blood cells in critically ill patients, the precise indications for transfusion remain a source of controversy, and specific transfusion practices may vary..."