Preoperative Anemia Linked With Increased Risk of Death After Cardiac Bypass

Patients with preoperative hemoglobin concentrations of 100 g/L or less are at increased risk for death after coronary artery bypass grafting (CABG), even if the level is corrected with transfusions, according to a report published in the May 18th issue of The Lancet.

Previous reports have suggested that for many surgical procedures mild anemia is acceptable and does not require transfusion. However, patients with coronary artery disease may be more susceptible to the effects of anemia. Furthermore, it was unclear whether preoperative anemia was a risk factor for poor outcomes following CABG.

To answer this question, Dr. Jens Peder Bagger and colleagues, from Hammersmith Hospital in London, evaluated the outcomes of all patients who underwent isolated CABG at their hospital between 1993 and 1997. The study included 2059 patients, 53 of whom had preoperative hemoglobin concentrations of 100 g/L or less.

According to surgical protocol, when the preoperative level was less than 100 g/L the bypass pump was primed with blood. If the level was below 90 g/L, a preoperative blood transfusion was given.

Compared with patients with higher hemoglobin levels, those with low levels were significantly more likely to have higher serum creatinine values and lower ejection fractions, the authors note.

The in-hospital mortality rate was five times higher for patients with low hemoglobin levels than for patients with higher levels. The preoperative hemoglobin level was a predictor of mortality among men, but not among women, the authors note. However, only 335 of the 2059 patients were women, so the study may not have been powered to detect a difference.

On multivariate analysis, preoperative hemoglobin and serum creatinine concentrations were found to be independently associated with mortality.

“Our findings suggest that a low hemoglobin concentration is a marker of disease severity or comorbidity that has a major effect on survival rate,” Dr. Bagger’s team states. “Since perioperative correction of anemia did not improve survival rate, our findings suggest that patients who present with anemia should be further investigated before surgery whenever possible.”

Lancet 2002;359:1747-1748.