Risk for perioperative myocardial infarction and mortality in patients undergoing hip or knee arthroplasty: the role of anemia

Abstract

Anemia is common in patients undergoing surgery. This study was designed to determine whether preoperative anemia represents an independent risk factor for 30-day mortality and nonfatal myocardial infarction (death/MI) in patients undergoing major orthopedic arthroplasty surgery. Between January 1987 and December 2006 at the Mayo Clinic, 391 orthopedic patients experienced death/MI within 30 days of the index surgery. For each patient included in the event cohort (case), one control patient (1:1 ratio) was identified matched according to sex, age, type of joint operation (hip vs. knee vs. bilateral knee), primary operation versus revision, emergent versus elective, and date of surgery. Association of preoperative hemoglobin (Hb) with death/MI was assessed by multiple linear regression including preoperative Hb and all other characteristics and comorbid conditions found to have some evidence (p<0.10) of univariate association with death/MI. After adjusting for other perioperative risk factors, anemia (Hb<12.0 g/dL for females and<13.0 g/dL for males) was not a significant independent risk factor for death/MI (odds ratio [OR], 0.81; 95% confidence interval [CI], 0.54-1.20; p=0.286), nor was Hb when treated as a continuous variable (OR, 0.98; 95% CI, 0.81-1.19 per 1.0 g/dL decrease below 13.0 g/dL; p=0.868). Cardiovascular, cerebrovascular, or pulmonary disease and history of recent malignancy were found to be the most important risk factors for death/MI. Existing comorbidities, rather than preoperative anemia, were independently associated with major morbidity and mortality in patients undergoing major orthopedic arthroplasty.