EFFECT OF DIALYSATE CALCIUM CONCENTRATIONS ON INTRADIALYTIC BLOOD-PRESSURE COURSE IN CARDIAC-COMPROMISED PATIENTS

To prevent hypercalcemia in the treatment of secondary hyperparathyroi dism, low calcium (L-Ca) dialysate is advocated. However, changes in i onized calcium (i-Ca) levels have a pivotal role in myocardial contrac tion and could influence blood pressure stability during-dialysis. Rec ently,:our group found in patients with normal cardiac function a sign ificant decrease in blood pressure (decrease in systolic blood pressur e [DSBP]: -13 mm Hg and decrease in mean arterial pressure [DMAP]: -7 mm Hg) during dialysis with L-Ca dialysate compared with high calcium (H-Ca) dialysate, and this was mainly related to a decreased left vent ricular contractility with use of i-Ca dialysate. On the basis of thes e data, it could be expected that changes in i-Ca levels during dialys is are of more clinical importance in cardiac-compromised patients (CC pts), New York Heart Association classifications III and IV. In this s tudy, the effects of i-Ca dialysate (1.25 mmol/L) and H-Ca dialysate ( 1.75 mmol/L) on arterial blood pressure parameters (systolic [SBP], di astolic [DBP], and mean arterial blood pressure [MAP]), heart rate, st roke distance (SDist), and minute distance (MDist) during 3 hours of a standardized ultrafiltration/hemodialysis (UF+HD) in nine CCpts was I nvestigated. i-Ca levels increased significantly with H-Ca dialysate U F+HD, whereas there was no change with L-Ca dialysate. SEP, DBP, and M AP decreased statistically and clinically significantly during UF+HD w ith L-Ca dialysate and were significantly lower with the use of i-Ca d ialysate compared with H-Ca dialysate. SDist and MDist decreased signi ficantly with L-Ca dialysate, whereas there were no changes in SDist a nd MDist with H-Ca dialysate. The predialysis and postdialysis index o f systemic vascular resistance (SVRI) was similar between L-Ca dialysa te and H-Ca dialysate use. Between the two groups, there were no signi ficant differences in changes in SVRI. From this study, we can conclud e that changes in i-Ca levels are a very important determinant of the blood pressure response during UF+HD in CCpts, and this response is me diated by changes in myocardial contractility. (C) 1998 by the Nationa l Kidney Foundation, Inc.