VIENNA—Blood transfusion rates in hip and knee replacement surgery are lower in overweight or obese patients than in patients with a normal weight, according to a study presented at the 2015 International Society for Technology in Arthroplasty conference.
In this retrospective study, which included 2,399 participants, researchers sought to evaluate the impact of BMI on blood transfusions and postsurgical complications in hip and knee replacement surgery. In all, 1,503 patients underwent knee replacement and 896 patients underwent hip surgery between January 1, 2011, and November 1, 2013.
Craig Silverton, DO
Patients were classified into groups according to BMI—normal (< 25 BMI), overweight (25 to 29.9 BMI), and obese (> 30 BMI).
Among the study’s findings were:
• A 34.8% blood transfusion rate for normal BMI patients compared with 21.9% for obese BMI patients for hip replacement.
• A 17.3% blood transfusion rate for normal BMI patients compared with 8.3% for obese BMI patients for knee replacement.
• A trend towards increased rates of deep surgical site infections in obese BMI patients.
“The results were surprising to us. It goes against the normal thought process,” said Craig Silverton, DO, a joint replacement surgeon at Henry Ford Hospital in Detroit and the study’s lead author. “It’s hard to explain but one theory could be that heavier patients have larger blood volume than patients of normal weight.”
Researchers also found no correlation between the heavier patients and post-surgical complications such as blood clots and heart attacks.
An estimated 78.6 million adult Americans are obese, and their weight problems are closely linked with an increased demand for hip and knee replacement surgery, according to government and research figures.
Patients who undergo a hip replacement typically lose about 2 pints of blood during surgery. For a knee replacement, patients usually lose about 1 pint of blood.