ORLANDO — Anemia is a potent risk factor for patients undergoing surgery.
Patients who were anemic just prior to coronary artery surgery, elective vascular surgery, or endovascular aortic aneurysm repair had a significantly increased risk of death or major cardiac events in results from three separate studies reported at the annual scientific sessions of the American Heart Association.
One possible explanation for these findings is that anemia is a marker for inflammation and frailty in surgery patients, said Dr. Nicolas A. Diehm, a vascular physician at the Swiss Cardiovascular Center in Bern, Switzerland, who presented one of the studies. None of the studies addressed whether treatments that resolve anemia might reduce the risk, but Dr. Diehm was skeptical whether interventions could lead to any rapid improvements in a patient's prognosis. “Treatment does not reduce the inflammatory burden,” he said in an interview.
“Treatment of preoperative anemia has not been shown to reduce risk [following surgery], so this is not yet a standard procedure,” agreed Dr. Martin Dunkelgrun, a vascular surgeon at Erasmus Medical Center, in Rotterdam, the Netherlands, who presented another one of the studies at the meeting. The best approach to take today for patients with significant anemia prior to surgery is to reconsider the need for surgery, if the operation is elective, or to give patients who are proceeding to surgery “the best work-up they can get,” Dr. Dunkelgrun said.
Dr. Dunkelgrun's study reviewed records for 1,211 patients who underwent elective, open vascular surgery at Erasmus Medical Center during 1990–2006. Preoperatively, 399 patients had anemia, defined as a serum hemoglobin level of less that 13 g/dL in men and less than 12 g/dL in women. The average age of all 1,211 patients was 68 years, and 77% were men.
The prevalence of heart failure (a left ventricular ejection fraction of less than 35%) in the total group was 21%, 30% had chronic kidney disease (defined as an estimated glomerular filtration rate of less than 60 mL/min per 1.73 m
To analyze the impact of anemia on adverse outcomes—cardiovascular death or myocardial infarction—the patients with anemia were divided into tertiles of mild, moderate, or severe anemia. All patients with severe anemia had serum hemoglobin levels of less than 9.0 g/dL.
The incidence of an adverse outcome during both the first 30 days after surgery and throughout an average follow-up of 3.8 years was significantly worse in the patients with anemia than in patients with normal hemoglobin levels. The rate of death or MI also increased as the severity of anemia worsened.
In multivariate analyses that controlled for patients' age, gender, and clinical parameters at baseline, patients with anemia had a significantly increased risk for adverse outcomes, both perioperatively and long term. The relative risk for patients with severe anemia was comparable to the increased risk for death or MI faced by patients with heart failure or chronic kidney disease (see box).
The study presented by Dr. Diehm on patients undergoing endovascular repair of abdominal aortic aneurysms used data collected on 711 consecutive patients who underwent endovascular aneurysm repair (EVAR) during March 1994-November 2006 at the Baptist Cardiac and Vascular Institute in Miami. Anemia was defined by the same criteria used in Dr. Dunkelgrun's study, and was present in 218 patients. The average age of all patients in the study was about 76 years. The patients in the anemia group were significantly older and were more likely to have concurrent cardiac, renal, and pulmonary disease.
The rates of death, aneurysm rupture, or need for follow-up open surgery during the first 30 days after EVAR were not significantly different between the anemic and normal patients. But during an average long-term follow-up of 48 months, patients with anemia were significantly more likely to die. In a multivariable analysis that controlled for baseline demographic and clinical differences, patients had about a 13% increased risk of long-term mortality for each 1-g/dL reduction in their serum hemoglobin level, Dr. Diehm said.
The third reported study on anemia and surgical risk reviewed data collected on 14,574 patients who were entered in the Coronary Artery Surgery Study (CASS) registry during 1974–1979. These patients, a subgroup of the more than 25,000 patients in the registry, all had data available on their hematocrit and serum creatinine levels at baseline. The average age of all patients was about 53 years, and about three-quarters were men.
The study group included 2,338 patients (19%) with anemia, defined as a serum hematocrit of less than 39% in men and less than 36% in women. The patients with anemia had a significantly lower level of creatinine clearance, compared with the nonanemic patients.