(HealthDay News) — For patients undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA), increased body mass index (BMI) is protective against blood transfusions, according to a study presented at the annual meeting of the International Society for Technology in Arthroplasty, held from September 30 to October 1 in Vienna.

Nicholas Frisch, MD, MBA, from Henry Ford Hospital in Detroit, and colleagues examined the impact of BMI on blood transfusions in THA and TKA. Data were included for a retrospective cohort of 2,399 patients (896 with THA and 1,503 with TKA).

The researchers found that in both THA and TKA patients, increased BMI was protective against blood transfusion. Among THA patients, transfusion rates were 34.8% for normal weight, 27.6% for overweight, and 21.9% for obese (P=0.002). The corresponding rates were 17.3, 11.4, and 8.3% for TKA patients (P=0.002). There were no trends for BMI with deep vein thrombosis, pulmonary embolism, myocardial infarction, discharge location, length of stay, 30-day readmission rate, or preoperative hemoglobin level. In THA patients there was a significant trend toward increased deep surgical site infection (P=0.043).

“The results were surprising to us. It goes against the normal thought process,” a coauthor said in a statement. “It’s hard to explain but one theory could be that heavier patients have larger blood volume than patients of normal weight.”

More Information