Dialysis dose and mortality in hemodialysis: Is higher better?

Background The effect of dialysis dose on mortality remains unsettled. Current guidelines recommend to target a spKt/V at 1.20 to 1.40 per tri-weekly dialysis session. However, the optimal dialysis dose remains mostly disputed. Methods In a nationwide registry of all incident patients receiving thrice-weekly hemodialysis, 32 283 patients had available data on dialysis dose, estimated by Kt/V and its variants Kt and Kt/A. Survival was analyzed with a multivariate Cox model and a concurrent risk model accounting for renal transplantation. A predictive model of Kt in the upper quartile was developed. Results Regardless of the indicator, a higher dose of dialysis was consistently associated with better survival. The survival differential of Kt was the most discriminating, but marginally, compared to the survival differential according to Kt/V and Kt/A. Patient survival was higher in the upper quartile of Kt (> 69L/s), then deteriorated as the Kt decreased with a difference in survival between the upper and lower quartile of 23.6% at five years. Survival differences across Kt distribution were similar after accounting for kidney transplantation as a competing risk. Predictive factors for Kt in the upper quartile were arteriovenous fistula versus catheters and graft, hemodiafiltration versus hemodialysis, scheduled dialysis start versus emergency start, long weekly dialysis duration, spKt/V measurement versus double pool eKt/V. Conclusion Our data confirm the existence of a relationship between dialysis dose and survival, which persisted despite correcting for known confounders. A model for predicting a high dose of dialysis is proposed with practical relevance.