Effects of an increase in time vs. frequency on cardiovascular parameters in chronic hemodialysis patients

Cardiovascular mortality is still high and many risk factors are inadequately controlled in patients on conventional chronic hemodialysis. Recent studies on intensified treatment schedules by either increasing length or frequency of dialysis sessions have shown promising results with better control of blood pressure, reduction of left ventricular hypertrophy and easier control of calcium/phosphate metabolism.

The present observational study compared the effect of different forms of "intensified dialysis treatment" i.e. either long nightly intermittent (LNHD, 3 x 7.5 - 8 h) or short daily dialysis sessions (DHD, 6 x 2.5 - 3 h) on cardiovascular parameters, phosphate and anemia control in comparison to standard treatment schedules (SHD, 3 x 4 - 5 h).

All patients stable on hemodialysis between 18 and 80 years of age and with either uncontrolled hypertension and/or left ventricular hypertrophy and/or frequent intradialytic hypotension, were asked to participate in intensified dialysis therapy by either LNHD or DHD. Patients not willing to change their dialysis regime were asked to participate as control group (SHD). Primary end point was 24-h ambulatory blood pressure, secondary end points were predialysis blood pressure, left ventricular mass index (LVMI) and fractional shortening (FS), control of calcium, phosphate and anemia. Patients were followed up for 1 year.

17 patients opted for LNHD, 8 for DHD, 19 patients served as control group. After 1 year of treatment 24-h blood pressure was unchanged in all groups. Predialysis systolic blood pressure decreased in LNHD and DHD, but increased in SHD. Mean LVMI decreased in all treatment groups (DHD -20.1 +/- 24.0%, SHD -13.6 +/- 33.4%, LNHD -6.1 +/- 32.2%). The mean number of antihypertensive tablets/day was reduced in DHD by 3.3 tablet units, in LNHD by 1.2 tablet units, but increased in SHD patients. FS improved in patients on LNHD and DHD, but decreased in patients on SHD. Regression of LVMI was independent of dry weight which was unchanged in LNHD and SHD but increased in DHD. In contrast to SHD, phosphate control and Ca x P product improved in DHD and LNHD with less phosphate binding tablets. Intact PTH did not change in SHD, but decreased in DHD and LNHD. Hemoglobin increased in groups on intensified treatments, but fell in SHD. EPO resistance index fell in LNHD, but increased in DHD and SHD.

While reduction in 24-h blood pressure was not achieved by intensified dialysis, both schedules showed favourable effects on LVMI and FS with less antihypertensive medication. This was independent of reduction in dry weight. These effects were more pronounced in DHD patients. In contrast, in SHD patients, stable 24-h blood pressure and reduction in LVMI were achieved on the expense of an increasing amount of antihypertensive medication and with worsening of FS.