Elevated Hematocrit Concentration and the Risk of Mortality and Vascular Events in Patients Undergoing Major Surgery.

Preoperative anemia is associated with adverse outcomes after major surgery. This study evaluates the effect of elevated hematocrit concentration on 30-day postoperative mortality and vascular events in patients undergoing major surgery.

We conducted a cohort study using the American College of Surgeons National Surgical Quality Improvement Program database. Thirty-day mortality and vascular events, demographic, and perioperative risk factors were obtained for 197,469 adult patients undergoing major surgery in nonveteran's administration hospitals across the US, Canada, Lebanon, and the UAE during 2008 and 2009. We assessed the adjusted effect of elevated (>0.50) compared to normal preoperative hematocrit concentration (≥0.41–0.50, American Medical Association reference-range) on postoperative outcomes. Separate sex-specific analysis using hematocrit concentration thresholds commonly used in the diagnosis and management of patients with apparent or absolute erythrocytosis was also done.

A total of 3,961 patients (2.0%) had elevated hematocrit concentration preoperatively. After adjustment, postoperative mortality at 30 days was higher in patients with elevated hematocrit concentration than in those without (odds ratio [OR]: 2.23, 95% CI: 1.77–2.80). 30-day deep vein thrombosis (OR: 1.95, 95% CI: 1.44–2.64) and pulmonary embolism (OR: 1.79, 95% CI: 1.17–2.73), but not myocardial infarction or cerebrovascular events, were also higher in patients with elevated hematocrit concentration than in those without. Similar evaluation of various clinically relevant hematocrit concentrations revealed the following: an effect on mortality was noted beyond the thresholds of 0.48 in women and 0.52 in men, with the effect estimates becoming considerably high for values >0.54. Values between 0.41–0.45 were not associated with increased odds mortality. Similar observations were noted for deep vein thrombosis, although with higher variation and uncertainty especially in women; while the effects on pulmonary embolism were restricted to men.

Elevated hematocrit concentration is associated with an increased risk of 30-day mortality and venous thrombosis following major surgery. Further investigation of the impact of elevated hematocrit concentration and its reduction on surgical outcomes is warranted.

No relevant conflicts of interest to declare.