Even Mild Anemia Linked to Death Risk in Noncardiac Surgery

Emma Hitt, PhD

October 06, 2011

October 6, 2011 — In patients undergoing major noncardiac surgery, even mild preoperative anemia appears to be independently associated with an increased risk for 30-day morbidity and mortality, according to new study findings.

Khaled M. Musallam, MD, from the Department of Internal Medicine at the American University of Beirut Medical Center, Lebanon, and colleagues published their findings online October 6 in The Lancet.

According to the researchers, "[a]lthough haematocrit concentrations are almost always measured before major non-cardiac surgery, few studies have explored the implications of preoperative anaemia on postoperative outcomes."

The current study sought to determine outcomes of survival and complications based on anemia status in patients with preoperative anemia undergoing major noncardiac surgery. The researchers evaluated a large dataset from the 2008 American College of Surgeons' National Surgical Quality Improvement Program, which they describe as "a prospective validated outcomes registry from 211 hospitals worldwide."

A total of 227,425 patients were included in the database and had undergone major noncardiac surgery in 2008. Of those, 69,229 patients (30.44%) had preoperative anemia. Information on 30-day mortality and morbidity, demographics, and preoperative and perioperative risk factors was assessed. Morbidities considered included cardiac, respiratory, central nervous system, urinary tract, wound, sepsis, and venous thromboembolism outcomes.

Anemia was defined as mild if the hematocrit concentration was between 30% and 38% in men and 30% and 35% in women; moderate to severe anemia was defined as a hematocrit concentration of 29% or less in both men and women.

After adjusting for confounding factors, the researchers found that the presence of anemia was associated with a more than 40% increased risk for postoperative mortality at 30 days (odds ratio [OR], 1.42, 95% confidence interval [CI], 1.31 - 1.54). Notably, the odds ratio was similar for mild and moderate to severe anemia, at 1.41 (95% CI, 1.30 - 1.53) and 1.44 (95% CI, 1.29 - 1.60), respectively.

Risk for postoperative morbidity at 30 days was also higher in patients with anemia (adjusted OR, 1.35; 95% CI, 1.30 - 1.40), as well as being higher in patients with either mild anemia (adjusted OR, 1.31; 95% CI, 1.26 - 1.36) or moderate to severe anemia (adjusted OR, 1.56; 95% CI, 1.47 - 1.66).

The researchers also found that when anemia was present concomitantly with a known preoperative risk factor, the risk for 30-day morbidity or mortality was greatly increased compared with when only anemia or a risk factor was present.

The authors suggest that the detrimental effects of preoperative anemia may be associated with increased risk for major noncardiac morbidity, including "respiratory, urinary, wound, septic, and thromboembolic complications."

They add that "a 42% adjusted increase in death rate in such a large sample size means that around 500 extra people could die from even a mild degree of anaemia after elective major non-cardiac surgery."

Physicians "need to consider preoperative treatment of anaemia when possible," Dr. Musallam and colleagues conclude.

In a related editorial, Hans Gombotz, MD, PhD, from the Department of Anaesthesiology and Intensive Care, General Hospital Linz, in Austria, noted that the current study did not assess the cause of anemia, but "a third of patients with anaemia probably would have had nutritional deficiencies, a third probably would have had chronic disease, and a third would have had anaemia from an unknown cause," he writes.

According to Dr. Gombotz, the study "strongly suggests that implementation of treatment of anaemia as part of a universal patient blood management strategy should become standard of care in patients undergoing elective surgical procedures, particularly in those where substantial blood loss is expected."

Independent commentator Gregory M.T. Hare, MD, PhD, a scientist in the Keenan Research Centre at St. Michael's Hospital in Toronto, Ontario, Canada, notes that these findings add to our current understanding about the risk for anemia in perioperative patients.

Dr. Hare told Medscape Medical News that the database used by the researchers represents patients from more than 200 centers, and therefore the findings may be broadly applicable to medical practice in North America.

"It remains to be demonstrated that treatment of anemia will reduce postoperative mortality," he added. "This study strongly supports the need to perform appropriately powered randomized studies to address this important clinical question."

The study was supported by Vifor Pharma. Some of the study authors receive consultancy fees, research funding, and other support from Vifor Pharma. Dr. Gombotz reports that he has given lectures for Vifor Pharma Österreich. Dr. Hare has disclosed no relevant financial relationships.

Lancet. Published online October 6, 2011. Article abstract, Editorial extract