Increased Weight Gain During the Long Interdialytic Period Is Associated with Minor Effects on Blood Pressure Control...

Three-day-a-week chronic haemodialysis (cHD) involves 1 long (72 h) and 2 short (48 h) inter-dialytic periods (IDPs). We aimed to determine whether BP control following the long IDP is inferior to the short IDPs.

All pre- and post-dialysis BP and weight measurements over a 4-week period were retrospectively analyzed among 135 clinically stable cHD patients at 2 academic centres with comparisons between measurements recorded following short and long IDPs. Subsequently, 23 clinically stable cHD patients underwent 24-h ambulatory blood pressure monitoring (ABPM) during the final day/night cycle of the long IDP and 1 short IDP within the same week.

In combined and separate analyses of the 2 retrospective cohorts, pre-dialysis BP parameters were not different following long and short IDPs despite greater inter-dialytic weight gain (IDWG) during the long IDP. Subgroup analyses of the total cohort showed no evidence for inferior BP control during the long IDP among those with high %IDWG. In the ABPM study, nocturnal hypertension and loss of nocturnal dipping were frequent. Furthermore, daytime systolic blood pressure (SBP) and pulse pressure were modestly higher during the last day/night cycle of the long compared with short IDP.

In stable cHD patients, the greater IDWG that occurred during the long IDP was not associated with overtly inferior BP control as reflected in pre-dialysis BP measurements. However, modestly higher daytime SBP was evident towards the end of the long IDP by 24 h ABPM. Thus, while fluid gain has well-documented associations with hypertension and adverse cardiovascular outcomes, the excess IDWG that occurs during the long IDP exerts relatively minor effects on BP control in patients on well-established dialysis regimens that are better identified by ambulatory monitoring.