Study assesses impact of postoperative nHb and transfusion in patients with PAD

Vascular surgeons from Baylor College of Medicine and the Michael E. DeBakey Veterans' Administration Medical Center in Houston, TX, have released a study about the impact of transfusion and postoperative nadir postoperative hemoglobin (nHb) on short- and long-term outcomes after interventions for peripheral arterial disease (PAD). Their report was presented today at the 66th Vascular Annual Meeting presented by the Society for Vascular Surgery®.

Co-author Panio Kougias, MD, associate professor of surgery at Baylor College of Medicine and chief of vascular surgery at the Michael E. DeBakey Veteran's Administration Medical Center said that controversy surrounds the topic of transfusion policy after noncardiac operations. This new study, he said assessed the combined impact of postoperative nHb levels and blood transfusion on adverse events after open surgical intervention in patients with PAD.

A total of 1,182 consecutive patients who underwent PAD-related operations were matched on propensity scores calculated as their probability to have nHb more or less than 10gm/dl on the basis of operation type, demographics and comorbidities, and the revised cardiac risk index. Logistic and Cox proportional hazards regressions were used to assess the impact of nHb and number of transfused units on a composite endpoint (CE) of death, myocardial infarction and stroke, and respiratory and wound complications.

“After adjusting for nHb level, the number of units transfused was a strong predictor for the perioperative occurrence of the composite outcome(OR: 1.12, p=0.02) and respiratory complications (OR: 1.27, p=0.004),” said Dr. Kougias. “Adjusted for the number of units transfused, nHb had no impact on the perioperative composite outcome (OR: 0.6, p=0.3) or respiratory events (OR: 0.40, p=0.17).”

Dr. Kougias added that an interaction term between transfusion and nHb level remained non-significant (p=0.543), indicating that the impact of blood transfusion was the same regardless of nHb level. Perioperative wound infections were less common in patients with nHb > 10gm/dl (OR: 0.59, p=0.04), whereas transfusion had no impact on wound infection rates (OR: 0.98, p=0.84). During an average follow-up of 24 months transfused patients were more likely to develop the composite outcome of death or adverse cardiovascular events (HR: 1.13, P=0.02), whereas nHb level did not impact the long term adverse event rate (HR: 0.7, P=0.26).

"Blood transfusion appears to increase the incidence of perioperative and long-term mortality and cardiovascular adverse events regardless of the associated minimum postoperative Hb," added Dr. Kougias. "It also increases the risk of perioperative respiratory complications. We believe that a restrictive transfusion strategy is justified in patients with PAD. A randomized controlled trial to definitively settle this topic is needed."