Indexing dialysis dose for gender, body size and physical activity: Impact on survival

Abstract

Current practice basing dialysis dose on urea distribution volume (V) has been questioned. We explored the impact on survival of scaling dialysis dose (Kt) to parameters reflective of metabolic activity. In a multicentre prospective cohort study of 1500 patients on thrice-weekly haemodialysis, body surface area (BSA) and resting energy expenditure (REE) were estimated using validated equations and physical activity by the Recent Physical Activity Questionnaire. Total energy expenditure (TEE) was estimated from REE and physical activity data. Kt was calculated from delivered (single-pool Kt/V)*Watson V. Kt/BSA, Kt/REE and Kt/TEE were then calculated at baseline and 6 monthly during follow-up for 2 years. In adjusted Cox models Kt/TEE, Kt/BSA, Kt/REE, in that order, had lower hazard ratios for death than single-pool Kt/V. On the basis of adjusted survival differences, putative minimum target doses were estimated for Kt/BSA as 27119 ml/m2 and Kt/TEE as 25.79 ml/kcal. We identified spKt/V values equivalent to these estimated targets, ranging from 1.4 to 1.8 in patient groups based on gender, body size and physical activity. For sedentary patients, the minimum target dose was 1.4 for large males, 1.5 for small males and 1.7 for women. For active patients the target was 1.8 irrespective of gender and body-weight. Patients achieving these individualised minimum targets had greater adjusted two-year survival compared to those achieving conventional minimum targets. Metabolic activity related parameters, such as Kt/TEE and Kt/BSA, may have a clinically important role in scaling haemodialysis dose. Using such parameters or their spKt/V equivalents to adjust minimum target doses based on gender, body size and habitual physical activity may have a positive impact on survival.

The effect of gender on survival for hemodialysis patients: Why don't women live longer than men?

“…In this hypothetical example, it is easier to achieve the same target sp Kt / V urea in the smaller women compared to the heavier man, with shorter dialysis sessions and ultrafiltration volume. This is in keeping with previous studies, as to achieve targeted dialysis dose normalized by V , women required less dialysis treatment time compared to men (Figure A,B) …”

“…Creatinine is a breakdown product of muscle metabolism and so depends upon muscle mass and physical activity. Women are likely to have lower muscle mass, lower dietary protein intake and be less physically active compared to aged‐matched men . Moreover, post‐menopausal women experience a greater decrease in lean mass, muscle fiber size, and muscle strength with age .…”

“…Therefore, scaling dialysis dose to V may lead to less dialysis in women. Recent retrospective analysis of a cohort of 1500 hemodialysis patients in the United Kingdom reported greater 2‐year survival outcomes in patients who received urea clearances exceeding both conventional target sp Kt / V urea and adjusted targets based on the Kt /TEE and Kt /BSA (Table ) compared to those who achieved only conventional sp Kt / V urea targets …”

Access to treatment in chronic kidney disease, dialysis and transplantation. Is there gender equality?

“…A study performed by Sridharan et al ( 18 ) in the UK in 2012 which included 1,500 patients on HD, found that women require a higher dialysis dose to improve survival compared to men (Kt/K sp 1.6 vs. 1.4). Also another European study involving 1,247 patients found that dialysis dose was higher in women (Kt/Vsp 1.9 vs. 1.8 and URR 79 vs. 77%) where no differences were found in age, time on dialysis, BMI, Charlson comorbidity index score and proportion of patients with DM or HTN between men and women ( 15 ).…”

Moving Away From Measuring Serum Urea Nitrogen to Estimate Dialyzer Urea Clearance: Technological Panacea or Curio?

“…14 However, more recent studies have suggested that increasing the dialysis sessional clearance for patients with greater metabolism and production of waste products is associated with greater survival. 15 As such, the dialysis community needs to consider moving away from estimates of V when calculating Kt/V urea and instead give thought to adjusting Kt to body composition.…”