Comparison of intradialytic blood pressure variability between conventional thrice-weekly hemodialysis and short daily hemodialysis

Intradialytic blood pressure (BP) variability may be associated with increased mortality. We examined the effect of short daily hemodialysis (SDHD) on intradialytic BP variability relative to conventional thrice-weekly HD (CHD). This is a retrospective cohort study. Subjects were those converted from CHD to SDHD (n=12). All intradialytic BPs were collected on the last month of CHD, and on month 6 of SDHD. Absolute predialysis BP level and intradialytic BP variability were defined as the intercept and average residual terms, respectively, from a mixed-effects linear regression model of time on BP. Dialysis modality was a predictor variable (CHD vs. SDHD). Outcome variables were intradialytic BP variability and hypotension (BP < 90/55 mmHg at any time during HD). In addition to a predictor and outcomes, the demographics, estimated dry weight, and ultrafiltration ratio were examined. The median (range) age of the patients was 48 (34-77); all had hypertension, and 4 (33%) had diabetes. By a mixed effects linear regression model, the intradialytic systolic BP variability was 13.2 (quartile range 9.5-14.0) mmHg and 10.0 (8.3-10.9) mmHg for CHD and SDHD, respectively (P < 0.006). Intradialytic diastolic BP variability was also significantly reduced (7.7 [6.4-9.2] vs. 6.1 [5.5-6.6] mmHg, P=0.005). Relative to CHD, less hypotension was observed during treatment on SDHD: the odds ratio (95% confidence interval) was 0.36 (0.16-0.81; P=0.008). In this retrospective study, SDHD was associated with less intradialytic BP variability and with fewer episodes of hypotension during treatments. Further studies are necessary to generalize these findings.