Risk Associated with Preoperative Anemia in Noncardiac Surgery. A Single-center Cohort Study

Preoperative anemia is an important risk factor
for perioperative red blood cell transfusions and has been
shown to be independently associated with adverse outcomes
after noncardiac surgery. The objective of this observational
study was to measure the prevalence of preoperative anemia
and assess the relationship between preoperative anemia and
postoperative mortality.
Methods: Data were retrospectively collected on 7,759 consecutive
noncardiac surgical patients at the University Health Network
between 2003 and 2006. Preoperative anemia was defined as
a hemoglobin concentration less than 12.0 g/dl for women and
less than 13.0 g/dl for men. The unadjusted and adjusted relationship
between preoperative anemia and mortality was assessed
using logistic regression and propensity analyses.
Results: Preoperative anemia was common and equal between
genders (39.5% for men and 39.9% for women) and was
associated with a nearly five-fold increase in the odds of postoperative
mortality. After adjustment for major confounders
using logistic regression, anemia was still associated with increased
mortality (odds ratio, 2.36; 95% confidence interval,
1.57–3.41). This relationship was unchanged after elimination
of patients with severe anemia and patients who received transfusions.
In a propensity-matched cohort of patients, anemia
was associated with increased mortality (odds ratio, 2.29; 95%
confidence interval, 1.45–3.63).
Conclusions: Anemia is a common condition in surgical patients
and is independently associated with increased mortality.
Although anemia increases mortality independent of transfusion,
it is associated with increased requirement for transfusion,
which is also associated with increased mortality. Treatment
of preoperative anemia should be the focus of
investigations for the reduction of perioperative risk.