Differences in prescribed Kt/V and delivered haemodialysis dose-why obesity makes a difference to survival for haemodialysis patients when using a 'one size fits all' Kt/V target

Abstract

Background. Morbid obesity is reported to be a survival factor for haemodialysis patients compared with those with a normal body mass index (BMI), yet morbid obesity (BMI >35) is a mortality risk factor for obese patients in the general population. Traditionally, haemodialysis dosing is prescribed to achieve a target Kt/V corrected for total body water (TBW). As obese patients typically have increased body fat, which contains less water than muscle, then obese patients may have lower levels of body water than their slimmer counterparts, and as such delivered Kt/V could be greater than that estimated using standard anthropomorphic equations, and so increased dialysis dose may help explain the increased survival reported for obese patients. Methods. We compared multi-frequency bioelectrical impedance analysis (MF-BIA) measurements of TBW in healthy haemodialysis outpatients, and compared TBW with that calculated from the Watson equation derived from anthropomorphic measurements. © The Author 2013. Published by Oxford University Press on behalf of ERA-EDTA.