Impact of lower delivered Kt/V on the survival of overweight patients on hemodialysis

Background. A recent study suggests that overweight (OW) patients on hemodialysis are more likely to receive inadequate doses of dialysis. Because underdialysis is associated with higher mortality, OW patients might be at risk for higher mortality. This is in contrast with our recent observation in which survival was better in OW patients on hemodialysis. The objective of this study was to verify whether being OW was associated with underdialysis and to determine the influence of underdialysis on the survival of OW patients. Method. Kt/V measurements were obtained in 1151 patients on hemodialysis for two consecutive months, and their survival was prospectively followed for nine months. Body weights were defined by body mass index (BMI): OW if BMI was >27.5, underweight (UW) if BMI was <20, and normal weight (NW) if BMI was 20 to 27.5. Results. The Kt/V was inversely related to BMI (r = - 0.30, P < 0.0001). Kt/V in the OW patients was significantly lower than Kt/V in the NW or UW patients. By using a Kt/V threshold of 1.2, more patients were underdialyzed in the OW group (24%) than in the NW (15%) or UW (7%) groups. Underdialysis in the whole study group was associated with a 1.6-fold increase in the relative risk (RR) for mortality. The risk was more pronounced (RR, 2.6) in the underdialyzed OW patients compared with adequately dialyzed OW patients. In multivariate analysis, underdialysis in OW patients (RR, 4.3), but not in UW or NW patients, was a significant and independent risk factor for mortality. Conclusion. Our results verify that in the current practice of dialysis prescription, OW patients are less likely to receive adequate dialysis, and, to our knowledge for the first time, suggest that such underdialysis in OW patients might exert a negative influence on their survival. Prospective studies are required to test whether ensuring adequate delivery of dialysis in the OW patients might further improve their survival.