The influence of increasing dialysis treatment time and reducing dry weight on blood pressure control in hemodialysis patients: a prospective study.

A good blood pressure control can be achieved with long hemodialysis sessions (dialysis center of Tassin, France). However, it is not well known whether a higher dialysis dose or a lower dry weight is responsible for this phenomenon. In a preliminary study, 21 hypertensive dialysis patients, dialyzed three times a week for 3-5 h, were randomized into three groups during a 3-month study period. In 6 patients, the dialysis treatment time was increased by 2 h, and the dry weight was gradually decreased (group 1). In 7 patients the dialysis treatment time was increased by 2 h without a change in dry weight (group 2). In 8 patients the dry weight was gradually lowered without changing the dialysis treatment time (group 3). Before and after the study, cardiac index and left ventricular mass index (echocardiography) and forearm vascular resistance (strain gauge plethysmography) were determined on a middialytic day. The blood pressure was assessed by 48-hour ambulatory monitoring. The antihypertensive medication was reduced when the postdialytic blood pressure became <130/80 mm Hg. The dry weight was reduced by 2.6 +/- 1.4 kg in group 1 and by 2.3 +/- 0.8 kg in group 3 (p < 0.05). The number of classes of antihypertensive medication was reduced from 3.3 to 1.8 in group 1 (NS), from 2.4 to 1.7 in group 2 (NS), and from 3.1 to 1.3 in group 3 (p < 0.05). The dose of the remaining antihypertensive drugs was reduced by 50% in group 1 (p < 0.05), by 32% in group 2 (NS), and by 72.2% in group 3 (p < 0.05). The interdialytic systolic blood pressure decreased significantly after increasing the dialysis time without changing the dry weight (group 2: 7 +/- 5 mm Hg; p < 0.05). The systolic blood pressure was also lower in the other patients groups: group 1: 13 +/- 26 mm Hg, group 3 : 7 +/- 16 mm Hg (NS). The pulse pressure decreased significantly in group 2 (7 +/- 5 mm Hg; p < 0.05) and in group 3 (6 +/- 7 mm Hg; p < 0.05) and tended to decrease in group 1 (11 +/- 12 mm Hg; p = 0.08). The diastolic blood pressure and the day-night blood pressure difference did not change significantly, nor did cardiac index and left ventricular mass index. The forearm vascular resistance tended to decrease in the patients on long dialysis sessions. This preliminary study suggests that the dialysis treatment time might have an independent beneficial effect on blood pressure control.