2020

EVIDENCE FOR a gENDER-SPECIFIC Minimum haemodialysis dose

Sridharan, S1, Vilar, E1,2, Davenport, A3, Ashman N4, Almond M5, Banerjee A6, Roberts, J2, Farrington K1,2

1Lister Hospital, 2University of Hertfordshire, 3Royal Free Hospital, 4Royal London Hospital, 5Southend University Hospital, 6Arrowe Park Hospital

Introduction:

Many studies have suggested that women may be under-dialysed with the recommended haemodialysis (HD) target Kt/V of 1.2. There is ongoing debate on utility and reliability of a number of alternate scaling parameters for dialysis dosing. We have previously shown that for a sessional Kt/V of 1.2, the equivalent dialysis dose delivered to women are significantly lower if metabolic parameters such as Resting Energy Expenditure (REE) or Total Energy Expenditure (TEE) are used for dose scaling. We hypothesised that dialysis dose scaled to REE or TEE would associate with improved survival.

Methods:

We recruited 1500 HD patients on thrice weekly maintenance dialysis from 5 centres. Anthropometric and demographic data was collected using direct measurements and medical records at baseline. Information on HD adequacy was collected from medical databases. Each study subject was administered the Recent Physical Activity Questionnaire (RPAQ). Patients were followed-up for at least 12 months from recruitment. Survival and HD adequacy data was collected at various time points during the follow-up. Watson volume (V) was estimated from anthropometric data. REE was estimated using a novel validated predictive equation. Data from RPAQ was used to calculate TEE. Kt was calculated (Kt/V x V). Kt/REE and Kt/TEE was estimated from Kt. Average Kt/V, Kt/REE and Kt/TEE was calculated for the follow-up period.

Results:

1220 patients have completed a minimum of 12-month follow-up and were included in the analyses. 750 were males (62%). Mean age was 64.1 (±15.4) years. There were 167 deaths.

For a target Kt/V of 1.2 per session, the equivalent mean Kt/REE and Kt/TEE in men and women would differ significantly (0.0304 vs. 0.0274 and 0.0256 vs. 0.0235 respectively; p<0.001 in both cases). Increasing the dose delivered to women - based on the parameters Kt/REE or Kt/TEE - to the same level as that of men would require the equivalent minimum mean dose - based on Kt/V - to be increased to at least 1.34 in women.

In these 1220 patients, mean delivered Kt/V was significantly greater in women than in men (1.44 ± 0.25 vs. 1.32 ± 0.2; p<0.001), but there were no gender differences in dialysis dose expressed in terms of Kt/REE (0.033 ± 0.006 vs. 0.033 ± 0.005; p=NS) or Kt/TEE (0.028 ± 0.006 vs. 0.028 ± 0.005; p=NS). Kaplan-Meier survival analyses showed better survival in women compared to men (p=0.034).

Conclusion:

Current clinical practice in participating units delivers a significantly higher dialysis dose - expressed in terms of Kt/V - to women, though the dose expressed as mean Kt/REE and Kt/TEE is similar to that in men. This is associated with a survival benefit in women. This contrasts with previous data showing that the natural survival advantage of women over men is almost completely eradicated in dialysis patients and argues in favour of higher minimum dialysis dose requirements for women, perhaps on the basis of higher rates of metabolic waste generation.