Background: Hemodialysis patients have a steady increase in blood pressure (BP) during the 44-hour interdialytic interval when ambulatory BP monitoring is used. Home BP recording allows for a longer period of monitoring between dialysis treatments and may better define the chronobiological characteristics of arterial hypertension. This study sought to determine the optimal time to perform home BP monitoring in hemodialysis patients to improve the strength of prediction of 44-hour interdialytic ambulatory BP.
Study design: Diagnostic test study.
Setting & participants: This is an ancillary analysis of patients participating in the Dry-weight Reduction in Hypertensive Hemodialysis Patients (DRIP) trial.
Index test: Home BP measured 3 times daily for 1 week by using a validated oscillometric monitor on 3 occasions at 4-week intervals after randomization. Home BP measured during the first third, second third, and last third of time elapsed after the dialysis treatment, as well as each third of the dialysis treatment, was compared with the overall ambulatory BP.
Reference tests: Interdialytic ambulatory BP measured on 3 occasions at 4-week intervals after randomization.
Results: During the interdialytic interval, we found an increase in systolic ambulatory BP of 0.30 +/- 0.36 mm Hg/h and an increase in systolic home BP of 0.40 +/- 0.25 mm Hg/h. This relationship in home BP reached a plateau after approximately 48 hours. A similar pattern was seen for diastolic home BP. Probing dry weight steepened the slope of ambulatory BP, but did not alter the time-dependent relationship of home BP. Home BP was on average higher (bias) by 14.1 (95% confidence interval, 12.0 to 16.2)/5.7 mm Hg (95% confidence interval, 4.6 to 6.9). The SD of differences between methods (precision) was 4.6/2.8 mm Hg. Measurement of BP during each third of the interdialytic interval gave the best precision, measured by using model fit compared with ambulatory BP measurements.
Limitations: Our cohort was overrepresented by African American hemodialysis patients. Whether African American participants have a different pattern of BP response than non-African American participants in the interdialytic period is not known.
Conclusions: Our findings suggest that time elapsed after a dialysis treatment must be considered in interpreting home BP recordings in hemodialysis patients. Home BP measured in each third of the interdialytic interval is likely to yield the most reliable BP estimate.
Trial registration: ClinicalTrials.gov NCT00067665.