CAPD patients exhibit a nocturnal fall in blood pressure: a single-centre study

In 29 CAPD (continuous ambulatory peritoneal dialysis) patients the height and diurnal variation of the blood pressure (BP) and heart-rate (HR) were analyzed by means of 24-hour ambulatory blood pressure monitoring (ABPM).

Normal diurnal variation was defined as a fall of 10% or more during nighttime (NT) compared with daytime (DT) BP or HR (DT = 10.00 a.m.-9.00 p.m., NT = midnight-06.00 a.m.). To evaluate high BP in the course of time we used the concept of "whole-day BP load", defined as the percentage of BP readings above 140/90 mmHg during a 24-h period. A "hypertensive BP load" was defined as a systolic BP (SBP) load of more than 50% and/or a diastolic BP (DBP) load in excess of 40%. In addition to analysis of the circadian rhythm of BP and HR and the prevalence of a hypertensive BP load in CAPD patients, the influence of various factors such as gender, creatinine clearance, recombinant human erythropoietin, antihypertensive medication, haematocrit, whole-day BP load, and the nightly dialysis glucose concentration on the diurnal variation of BP and HR were studied.

Based on the 95% confidence intervals for the proportional nocturnal decrease, normal diurnal variation of BP and HR was present in most CAPD patients. No correlation could be demonstrated between a blunted circadian rhythm and the variables mentioned above. However, when other time-period definitions (DT = 6.00 a.m.-11.00 p.m., NT = 11.00-6.00 and DT = 8.00 a.m.-8.00 p.m., NT = 8.00 p.m.-8.00 a.m.) were applied to the data, considerably fewer patients displayed normal diurnal variation. Whereas all patients showed normal home BP readings, ABPM of 21 out of 29 patients displayed a hypertensive BP load.

The majority of our CAPD patients exhibited normal diurnal variation of SBP and DBP depending, however, on the definitions of DT and NT used. The absence of a normal circadian rhythm could not be explained by any of the variables analyzed. Surprisingly, uncontrolled hypertension, as defined by a hypertensive BP load, was found in 72% of the patients.