Here is a puzzler. Blood transfusion rates in patients having hip and knee replacement surgery are dramatically lower in overweight and obese patients than they are in patients of normal weight. That is the result of a study of 2, 399 patients at the Henry Ford Hospital in Detroit, Michigan. Of the 2, 399 patients evaluated, 1, 503 underwent knee replacement and 896 underwent hip surgery between January 1, 2011 and November 1, 2013.
Blood Loss Less in Obese Surgery Patients
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In addition, researchers found no correlation between the heavier patients and post-surgical complications such as blood clots and heart attacks. The patients were divided into three body mass index (BMI) groups: normal which was less than 25 BMI, overweight—25-29.9 BMI, and obese—more than 30 BMI.
The blood transfusion rate for patients with a normal BMI was 34.8% compared to 21.9% for obese BMI patients for hip replacement. For knee replacements, there was a 17.3% blood transfusion rate for normal BMI patients compared to 8.3% for obese BMI patients.
“The results were surprising to us. It goes against the normal thought process, ” said Craig Silverton, D.O., a Henry Ford joint replacement surgeon 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.”
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.
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This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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