Whm. Vankuijk et al., INFLUENCE OF CHANGES IN IONIZED CALCIUM ON CARDIOVASCULAR REACTIVITY DURING HEMODIALYSIS, Clinical nephrology, 47(3), 1997, pp. 190-196
In order to prevent hypercalcemia due to the treatment of secondary hy
perparathyroidism the use of low calcium dialysate is advocated. Howev
er, as calcium ions play a pivotal role in both myocardial and vascula
r smooth muscle contraction, lowering the dialysate calcium concentrat
ion might result in a further impairment of the cardiovascular respons
e during dialysis. Therefore, arterial blood pressure, forearm vascula
r resistance (FVR) and venous tone (VT) (straing-gauge plethysmography
) as well as cardiac dimensions and output (echocardiography) were mea
sured in IO hemodynamically stable dialysis patients (ejection fractio
n >30%) during two standardized sessions of three-hour combined ultraf
iltration-hemodialysis (UF+HD) at two different dialysate calcium conc
entrations: 1.25 and 1.75 mmol/l. High calcium UF+HD resulted in a sig
nificant increase in plasma ionized calcium (+0.19 +/- 0.11 mmol/l; p
<0.01) while ionized calcium remained unchanged during low calcium UFHD (-0.02 +/- 0.07 mmol/l). As a result, systolic, diastolic and mean
arterial blood pressure were respectively 14 +/- 10, 5 +/- 7 and 9 +/-
9 mmHg higher during high calcium UF+HD as compared to low calcium UF
+HD (p <0.05). There were no significant differences in FVR and VT bet
ween the two treatments. During both treatments FVR increased while VT
decreased. In addition, there were no differences in calculated syste
mic vascular resistance. However, with comparable end-diastolic dimens
ions, stroke volume (-18 +/- 13 mi) and cardiac output (-1.3 +/- 1.5 l
/min) decreased significantly (p <0.05) only during low calcium UF+HD.
We conclude that even in hemodynamically stable patients changes in p
lasma ionized calcium are an important determinant of the blood pressu
re response during dialysis therapy. Whereas peripheral vascular react
ivity is unaffected by changes in ionized calcium, myocardial contract
ility is improved with higher dialysate calcium concentrations.