High Pre-Tx BMI Increases DGF Risk

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VANCOUVER, B.C.—Pre-transplant overweight and obesity are associated with a higher risk of delayed graft function (DGF) in renal transplant recipients, data suggest.

Researchers led by Kamyar Kalantar-Zadeh, MD, MPH, PhD, studied 11,836 hemodialysis patients who under renal transplantation from July 2001 to June 2007. Subjects had a mean age of 49 years and a mean body mass index (BMI) of 26.8 kg/m2.

Pre-transplant BMI remained an independent predictor of DGF even after adjusting for demographics and other variables. Each standard deviation increment in BMI was associated with a 35% higher risk of DGF. In addition, compared with patients with a pre-transplant BMI of 22-24.99, those with a BMI of 25-29.99 (overweight), 30-34.99 (mild obesity), and 35 or higher had 30%, 42%, and 118% increased risk of DGF, respectively, the investigators reported at the World Congress of Nephrology. In addition, patients with a BMI above 35 had an 87% increased risk of DGF than those with a BMI below 35.

“Despite data indicating an obesity paradox with greater survival of overweight and obese hemodialysis patients, careful trials of closely supervised weight reduction may be indicated to examine whether immediate post-transplant outcomes including risk of DGF can be improved,” said Dr. Kalantar-Zadeh, Associate Professor of Medicine and Pediatrics, and Director, Dialysis Expansion & Epidemiology, Harbor-UCLA Medical Center, Torrance, Calif.

A biologically plausible explanation for the study's findings is that obesity is associated with longer operative time and longer warm ischemic time, which are risk factors of DGF, Dr. Kalantar-Zadeh said.

“Obesity is associated with high sympathetic activity, which results in renal vasoconstriction,” he explained. “Moreover, the prompt administration of calcineurin inhibitors after transplantation, probably in higher doses [because of patient] overweight or obesity, may aggravate vasoconstriction and further compromise graft perfusion, increasing the risk of DGF.”

Another potential explanation is the linkage between obesity and increased pro-thrombotic activity and endothelial dysfunction, he said. “Body fat mass, in particular central obesity, is associated with higher levels of thrombin generation.” Obesity is also a risk factor for venous thromboembolic disease. Increased pro-thrombotic activity and endothelial dysfunction may contribute to the risk of graft microthrombosis, which may play an important role in DGF.

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