The Effect of Perioperative Anemia on Clinical and Functional Outcomes in Patients With Hip Fracture

Anemia is common in the elderly and has been associated with increased mortality.1–3 Among patients with chronic disease or malignancy, hemoglobin levels are often robust predictors of long term survival.4–7 The degree of anemia among patients admitted to the hospital for medical and surgical conditions is associated with higher short term mortality in many,8–12 though not all, studies.13–15 The relationship between hemoglobin levels and surgical outcomes is likely to be complex, and understanding it requires an ability to dissect out several interrelated issues. First, fluctuations in hemoglobin levels during a surgical patient’s hospital course are common, so it is important to distinguish measurements on admission from subsequent ones both before and after surgery.8,9,12–17 Anemia at different points during the hospital course may also reflect different problems with varying implications. Anemia on admission may carry a poor prognosis because it is a physiologic indicator of underlying comorbid illness burden, illness severity (anemia of chronic disease), or prehospital bleeding. For this reason, proper adjustment for comorbidities and severity of illness on admission is imperative. In addition, many elderly patients may be dehydrated on admission, and the initial fluid hydration may decrease hemoglobin levels.18 Many surgical patients who are admitted for urgent or emergent conditions also can have bleeding and fluid shifts before their operation. Drops in hemoglobin levels during surgery can be caused by bleeding and hemodilution from intravenous fluids or fluid shifts.18–20 Finally, inpatients may lose blood through repeated phlebotomy (“hospital-acquired anemia”), though this may be largely a problem of patients requiring intensive care or repeated surgery.21,22 Second, blood transfusions are common among surgical patients and need to be accounted for in studies of anemia.8,9,12–14,16 Indeed, most of the research in this area has predominantly focused on the impact of the blood transfusion itself on outcomes. Unfortunately, the literature examining the impact of transfusion on mortality is quite conflicted.23,24 The majority of studies have reported no effect of transfusion on mortality.13,16,25–34 However, several investigators have reported that transfusion was associated with lower risk of death,10,11 whereas others found it increased death rates.12,35,36 Finally, there has been little investigation of the impact of anemia on nonmortal outcomes.12,14 We sought to characterize variations in hemoglobin levels during the course of hospitalization and examine the prognostic significance of hemoglobin levels measured at different time points during hospitalization using data from a prospective cohort study of patients undergoing surgery for hip fracture in 4 hospitals. The aims of this study were to: 1) describe the epidemiology of anemia during hospitalization; 2) assess the relationship between hemoglobin measurements and clinical and functional outcomes; and 3) determine whether hemoglobin measurements add independent prognostic information after adjusting for risk factors known to influence hip fracture outcomes.