All-cause mortality in relation to changes in relative blood volume during hemodialysis

Background. Relative blood volume (RBV) monitoring is widely used in hemodialysis (HD) patients, yet the association between intradialytic RBV and mortality is unknown.

Methods. Intradialytic RBV was recorded once/min during a 6-month baseline period; all-cause mortality was noted during follow-up. RBV at 1, 2 and 3 h into HD served as a predictor of all-cause mortality during follow-up. We employed Kaplan-Meier analysis, univariate and adjusted Cox proportional hazards models for survival analysis.

Results. We studied 842 patients. During follow-up (median 30.8months), 249 patients (29.6%) died. The following hourly RBV ranges were associated with improved survival: first hour, 93-96% [hazard ratio (HR) 0.58 (95% confidence interval (CI) 0.42-0.79)]; second hour, 89-94% [HR 0.54 (95% CI 0.39-0.75)]; third hour, 86-92% [HR 0.46 (95% CI 0.33-0.65)]. In about onethird of patients the RBV was within these ranges and in twothirds it was above. Subgroup analysis by median age ( 61 years), sex, race (white/nonwhite), predialysis systolic blood pressure (SBP; 130 mmHg) and median interdialytic weight gain ( 2.3 kg) showed comparable favorable RBV ranges. Patients with a 3-h RBV between 86 and 92% were younger, had higher ultrafiltration volumes and rates, similar intradialytic average and nadir SBPs and hypotension rates, lower postdialysis SBP and a lower prevalence of congestive heart failure when compared with patients with an RBV>92%. In themultivariate Cox analysis, RBV ranges remained independent and significant outcome predictors.

Conclusion. Specific hourly intradialytic RBV ranges are associated with lower all-cause mortality in chronic HD patients.