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Effect of dialysate calcium concentrations on intradialytic blood pressure course in cardiac-compromised patients
F M van der Sande1, E C Cheriex, W H van Kuijk
1Department of Internal Medicine, academisch ziekenhuis Maastricht, The Netherlands. fvs@sint.azm.nl
Insights
Low calcium dialysate may cause significant blood pressure drops in cardiac patients due to reduced myocardial contractility. High calcium dialysate maintains blood pressure stability during hemodialysis in these vulnerable individuals.
Area of Science:
- Nephrology
- Cardiology
- Internal Medicine
Background:
- Low calcium (L-Ca) dialysate is used to prevent hypercalcemia in secondary hyperparathyroidism.
- Ionized calcium (i-Ca) levels significantly impact myocardial contractility and blood pressure during dialysis.
Purpose of the Study:
- To investigate the effects of L-Ca and high calcium (H-Ca) dialysate on hemodynamics in cardiac-compromised patients (CCpts).
- To determine if i-Ca level changes during dialysis influence blood pressure stability in CCpts.
Main Methods:
- Nine CCpts (NYHA class III-IV) underwent 3-hour ultrafiltration/hemodialysis (UF+HD) using either L-Ca (1.25 mmol/L) or H-Ca (1.75 mmol/L) dialysate.
- Monitored arterial blood pressure (SBP, DBP, MAP), heart rate, stroke distance (SDist), and minute distance (MDist).
- Assessed changes in ionized calcium (i-Ca) and systemic vascular resistance index (SVRI).
Main Results:
- L-Ca dialysate showed no change in i-Ca levels, while H-Ca dialysate significantly increased i-Ca.
- Significant decreases in SBP, DBP, MAP, SDist, and MDist were observed with L-Ca dialysate.
- Blood pressure and cardiac contractility parameters were significantly lower with L-Ca compared to H-Ca dialysate.
- No significant differences in SVRI changes were noted between the two dialysate types.
Conclusions:
- Changes in i-Ca levels are critical determinants of blood pressure response during UF+HD in CCpts.
- The blood pressure response in CCpts is mediated by alterations in myocardial contractility.
- H-Ca dialysate appears to offer better hemodynamic stability during dialysis for CCpts.
Abstract:
To prevent hypercalcemia in the treatment of secondary hyperparathyroidism, low calcium (L-Ca) dialysate is advocated. However, changes in ionized calcium (i-Ca) levels have a pivotal role in myocardial contraction and could influence blood pressure stability during dialysis. Recently, our group found in patients with normal cardiac function a significant decrease in blood pressure (decrease in systolic blood pressure [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 ventricular contractility with use of L-Ca dialysate. On the basis of these data, it could be expected that changes in i-Ca levels during dialysis are of more clinical importance in cardiac-compromised patients (CCpts), New York Heart Association classifications III and IV. In this study, the effects of L-Ca dialysate (1.25 mmol/L) and H-Ca dialysate (1.75 mmol/L) on arterial blood pressure parameters (systolic [SBP], diastolic [DBP], and mean arterial blood pressure [MAP]), heart rate, stroke distance (SDist), and minute distance (MDist) during 3 hours of a standardized ultrafiltration/hemodialysis (UF+HD) in nine CCpts was investigated. i-Ca levels increased significantly with H-Ca dialysate UF+HD, whereas there was no change with L-Ca dialysate. SBP, DBP, and MAP decreased statistically and clinically significantly during UF+HD with L-Ca dialysate and were significantly lower with the use of L-Ca dialysate compared with H-Ca dialysate. SDist and MDist decreased significantly with L-Ca dialysate, whereas there were no changes in SDist and MDist with H-Ca dialysate. The predialysis and postdialysis index of systemic vascular resistance (SVRI) was similar between L-Ca dialysate and H-Ca dialysate use. Between the two groups, there were no significant differences in changes in SVRI. From this study, we can conclude 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 mediated by changes in myocardial contractility.