Anemic patients had a 42% greater risk of 30-day mortality following non-cardiac surgery than those who who had an ample supply of healthy red blood cells (OR 1.42, 95% CI 1.31 to 1.54), Faek Jamali, MD, of American University of Beirut in Lebanon, and colleagues reported online in The Lancet.
That rate "means that around 500 extra people could die from even a mild degree of anemia after elective major non-cardiac surgery," they wrote.
Anemic patients also had a 35% higher risk of a composite of postoperative morbidity at 30 days (OR 1.35, 95% CI 1.30 to 1.40).
Preoperative anemia has been associated with adverse outcomes after cardiac surgery, such as increased perioperative blood transfusion, which is linked with morbidity and mortality. But outcomes after non-cardiac surgery aren't well established, Jamali and colleagues wrote in their introduction.
So they looked at 2008 data on 227,425 patients in the American College of Surgeons' National Surgical Quality Improvement Program database. Patients' mean age was 56.4 and 69,229 had preoperative anemia.
Anemia was defined as "moderate to severe" at a hematocrit concentration of 29% or less and "mild" at a hematocrit of more than 29% and less than 39% in men and 36% in women.
Anemic patients were more likely to be older than 65, be non-Caucasian, and have a higher prevalence of diabetes, sepsis, and cardiovascular, respiratory, hepatobiliary, renal, neurological, and hematological-oncological disorders.
They found that the crude mortality for anemic patients was 4.61% compared with just 0.78% for patients without anemia; the crude composite morbidity was 15.67% versus just 5.33%, respectively.
In adjusted analyses, preoperative anemia remained significantly associated with increased 30-day morbidity and mortality, Jamali and colleagues found (OR 1.42, 95% CI 1.31 to 1.54 for mortality, OR 1.35, 95% CI 1.30 to 1.40 for morbidity).
The mortality difference was consistent in both mild and in moderate-to-severe anemia compared with no anemia (OR 1.41, 95% CI 1.30 to 1.53, and OR 1.44, 95% CI 1.29 to 1.60, respectively).
The same also held true for morbidity (OR 1.31, 95% CI 1.26 to 1.36 for mild anemia and OR 1.56, 95% CI 1.47 to 1.66 for moderate-to-severe anemia).
"Even mild preoperative anemia is independently associated with an increased risk of 30-day morbidity and mortality in patients undergoing major non-cardiac surgery," they wrote.
Patients with anemia also had higher rates of almost all individual morbidities including cardiac, respiratory, urinary tract, and wound events, as well as sepsis and venous thromboembolism, compared with those with a full complement of red blood cells before surgery.
The researchers also found that patients with anemia had higher morbidity after emergency or non-emergency procedures than those without anemia, although the association was only significant for non-emergency cases with regard to mortality.
"Our findings should lead to a careful consideration of appropriate interventions aimed at correction of preoperative anemia in the most patients," they wrote. "At least in elective surgical cases, the treatment of preoperative anemia before surgical intervention should be strongly considered."
The study was limited because the database didn't document use of four or fewer packed red blood cell transfusions in the preoperative or postoperative period.
In an accompanying editorial, Hans Gombotz, MD, of General Hospital Linz in Austria, wrote that the results "could have an enormous effect on healthcare systems worldwide, because preoperative diagnosis and treatment of anemia has almost never been undertaken routinely before surgery."
The condition is easily treatable and less costly than transfusion, Gombotz wrote, and would likely improve outcomes.
He noted, however, that diagnosis and treatment of preoperative anemia is time consuming, and detection should be done close to 28 days before a scheduled surgery.
The study "strongly suggests that implementation of treatment of anemia as part of a universal patient blood management strategy should become standard of care in patients undergoing elective surgery procedures, particularly in those where substantial blood loss is expected," he wrote, though he cautioned that additional studies are needed to assure the efficacy and safety of treating anemia preoperatively.
The study was supported by Vifor Pharma.
The researchers reported relationships with Vifor Pharma, Novo Nordisk, Abbott, AstraZeneca, Bayer, Baxter, B Braun Melsungen, Boehringer Ingelheim, Bristol-Myers Squibb, CSL Behring, Curacyte, Ethicon Biosurgery, Fresenius, Galenica, GlaxoSmithKline, Janssen-Cilag, Octapharma, Organon, Oxygen Biotherapeutics, Roche, and Schering-Plough.
Gombotz reported relationships with Vifor Pharma Osterreich.
Zalman S. Agus, MD Emeritus Professor
University of Pennsylvania School of Medicine and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner
The LancetSource Reference: Musallam KM, et al "Preoperative anemia and postoperative outcomes in non-cardiac surgery: a retrospective cohort study" Lancet 2011; DOI: 10.1016/S0140-6736(11)61381-0.
The LancetSource Reference: Gombotz H, et al "Patient blood management is key before elective surgery" Lancet 2011; DOI: 10.1016/S0140-6736(11)61552-3.