Death Risk in Noncardiac Surgery Affected by Anemia

Even mild preoperative anemia appears to be independently associated with an increased mortality risk in patients undergoing major noncardiac surgery, according to a new study.

Researchers at the American University of Beirut Medical Center (AUBMC; Lebanon) analyzed data from The American College of Surgeons (ACS) US national surgical quality improvement program database, involving 227,425 patients undergoing major noncardiac surgery in 2008. Data for 30-day mortality and morbidity, demographics, and preoperative and perioperative risk factors were used to assess the adjusted and modified effect of anemia, which was defined as mild, or moderate-to-severe on postoperative outcomes. The data showed that 69,229 (30.44%) of the patients had preoperative anemia.

The results showed that postoperative mortality at 30 days was higher in patients with anemia than in those without anemia; this difference was consistent in mild anemia and moderate-to-severe anemia. Composite postoperative morbidity at 30 days was also higher in patients with anemia than in those without anemia, again consistent in patients with mild anemia and moderate-to-severe anemia. When compared with patients without anemia or a defined risk factor, patients with anemia and most risk factors had a higher risk for 30-day mortality and morbidity than did patients with either anemia or the risk factor alone.

“The detrimental effects of preoperative anemia may be associated with increased risk for major noncardiac morbidity, including respiratory, urinary, wound, septic, and thromboembolic complications,” concluded lead author Khaled Musallam, MD, and colleagues from the department of internal medicine. “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 anemia after elective major noncardiac surgery.”

Anemia is a decrease in number of red blood cells (RBCs) or less than the normal quantity of hemoglobin in the blood. Because hemoglobin--found inside RBCs-- carries oxygen from the lungs to the tissues, anemia leads to hypoxia in organs. Because all human cells depend on oxygen for survival, varying degrees of anemia can have a wide range of clinical consequences.

Measured by hematocrit concentration, anemia is defined as mild when it was between 29%-39% in men and 29%-36% in women, or moderate-to-severe when it is lower than 29% in both men and women on postoperative outcomes.

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American University of Beirut Medical Center