Perioperative anemia: an independent risk factor for infection, mortality, and resource utilization in surgery

Background: Previous studies on patients with hip fractures and in patients with colorectal cancer have documented that perioperative transfusion is associated with a significant increase in postoperative infection rate. Therefore, we sought to investigate the incidence of preoperative and postoperative anemia in noncardiac surgical patients and to determine if transfusion is an independent risk factor for infection and adverse outcome postoperatively.

Methods: Prospective data from the National Veterans Administration Surgical Quality Improvement Program (NSQIP) was collected on 6301 noncardiac surgical patients at the Veterans Affairs Maryland Healthcare System from 1995 to 2000.

Results: The mean age of the study cohort was 61 +/- 13. Descriptive data revealed 95% were male, 44% used tobacco, 19% were diabetic, 9% had COPD, 9% used alcohol, 3% used steroids, 1.7% had a diagnosis of cancer, and 1.2% had ascites. Preoperative anemia (hematocrit less than 36) was found in 33.9% and postoperative anemia was found in 84.1% of the study cohort. In the postoperative period, 32.5% of patients had a hematocrit of 26-30, and 26.5% had a hematocrit of 21-25. Mean units of blood transfused in the perioperative period ranged from 0.1 +/- 0.9 in patients without anemia to 2.7 +/- 2.9 in those with anemia. Incidence of pneumonia increased from 2.6 to 5% with increasing degree of anemia. Multiple logistic regression analysis documented that low preoperative hematocrit, low postoperative hematocrit, and increased blood transfusion rates were associated with increased mortality (P < 0.01), increased postoperative pneumonia (P < or = 0.05), and increased hospital length of stay (P < 0.05).

Conclusion: There is a high incidence of preoperative and postoperative anemia in surgical patients, with a coincident increase in blood utilization. These factors are associated with increased risk for perioperative infection and adverse outcome (mortality) in surgical patients. Consideration should be given to preoperative diagnosis and correction of anemia with iron, vitamin B12, folate supplementation, or administration of recombinant human erythropoietin.