Dialysis Dose Scaled to Body Surface Area and Size-Adjusted, Sex-Specific Patient Mortality

Abstract

SummaryBackground and objectives When hemodialysis dose is scaled to body water (V), women typically receive a greater dose than men, but their survival is not better given a similar dose. This study sought to determine whether rescaling dose to body surface area (SA) might reveal different associations among dose, sex, and mortality.Design, setting, participants, & measurements Single-pool Kt/V (spKt/V), equilibrated Kt/V, and standard Kt/V (stdKt/V) were computed using urea kinetic modeling on a prevalent cohort of 7229 patients undergoing thriceweekly hemodialysis. Data were obtained from the Centers for Medicare & Medicaid Services 2008 ESRD Clinical Performance Measures Project. SA-normalized stdKt/V (SAN-stdKt/V) was calculated as stdKt/V 3 ratio of anthropometric volume to SA/17.5. Patients were grouped into sex-specific dose quintiles (reference: quintile 1 for men). Adjusted hazard ratios (HRs) for 1-year mortality were calculated using Cox regression.Results spKt/V was higher in women (1.760.3) than in men (1.560.2; P,0.001), but SAN-stdKt/V was lower (women: 2.360.2; men: 2.560.3; P,0.001). For both sexes, mortality decreased as spKt/V increased, until spKt/V was 1.6-1.7 (quintile 4 for men: HR, 0.62; quintile 3 for women: HR, 0.64); no benefit was observed with higher spKt/V. HR for mortality decreased further at higher SAN-stdKt/V in both sexes (quintile 5 for men: HR, 0.69; quintile 5 for women: HR, 0.60).Conclusions SA-based dialysis dose results in dose-mortality relationships substantially different from those with volume-based dosing. SAN-stdKt/V analyses suggest women may be relatively underdosed when treated by V-based dosing. SAN-stdKt/V as a measure for dialysis dose may warrant further study.

Scaling Hemodialysis Target Dose to Reflect Body Surface Area, Metabolic Activity, and Protein Catabolic Rate: A Prospective, Cross-sectional Study

“…Daugirdas et al have shown that BSA-based dialysis dosing will result in higher delivered dialysis doses to women and small men 23 . A recent study has also shown a better relationship with survival for the BSA-based dosing compared to current practice 24 . On the other hand, Morton and Singer have argued that the dialysis dose should be based on metabolic rate because of the non-linear correlation between body mass and metabolic rate 25 .…”

The Effects of Racial Differences on Body Composition and Total Body Water Measured by Multifrequency Bioelectrical Impedance Analysis Influence Delivered Kt/V Dialysis Dosing

“…The greatest differences between measured TBW by MF-BIA and that estimated by anthropometric equations occurred in patients with similar BMI, but with more fat and reduced muscle mass. This may help to explain the apparent paradox of increased survival for the very obese haemodialysis patients in North America compared to those with a normal BMI [36], as the patients have proportionately much more fat and so to achieve an adequate Kt/V based on anthropometric equations, they require more prolonged dialysis sessions, potentially increasing sodium and middle molecular weight clearances [37]. On the other hand, underdosing of various groups could also occur, because on multiple regression analysis, the difference between measured and calculated TBW was affected by pre-dialysis serum albumin, BMI and percentage skeletal muscle mass as well as diabetic status, sex and ethnicity.…”

Optimizing the Measurement of Dialysis

“…Many studies, including HEMO and the study by Ramirez et al (see their Figure 2), show that larger patients have lower mortality rates independent of dialysis dose and often attributed to better nutrition (3,(11)(12)(13). When corrected for this effect, Kt/V shows an even steeper relationship to mortality (14).…”

“…When corrected for this effect, Kt/V shows an even steeper relationship to mortality (14). Ramirez et al corrected for this effect using an anthropometric estimate of V (Vant) and found little influence on survival in their cohort (3). Regardless of the reason for the effect of size on outcome, any attempt to normalize the dialysis dose to body size must take into consideration this potential confounder.…”

“…Comparisons of outcomes in men versus women undergoing chronic maintenance hemodialysis have shown differences usually favoring men despite larger doses given to women (1)(2)(3). All agree that larger doses are given to women because of their smaller size, which allows delivery of more dialysis within a short time frame.…”