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Influence of changes in ionized calcium on cardiovascular reactivity during hemodialysis
W H van Kuijk1, A W Mulder, C H Peels
1Department of Internal Medicine, University Hospital Maastricht, The Netherlands.
Insights
Lowering dialysate calcium during hemodialysis may impair cardiac function and blood pressure. Higher calcium concentrations improve blood pressure and myocardial contractility in stable dialysis patients.
Area of Science:
- Nephrology
- Cardiovascular Physiology
- Dialysis Therapy
Background:
- Low calcium dialysate is used to prevent hypercalcemia in secondary hyperparathyroidism treatment.
- Calcium ions are crucial for myocardial and vascular smooth muscle contraction.
- Lowering dialysate calcium may negatively impact cardiovascular response during hemodialysis.
Purpose of the Study:
- To investigate the cardiovascular effects of different dialysate calcium concentrations during ultrafiltration-hemodialysis (UF + HD).
- To assess the impact of dialysate calcium on arterial blood pressure, vascular resistance, and cardiac function in stable dialysis patients.
Main Methods:
- 10 hemodynamically stable dialysis patients underwent two 3-hour UF + HD sessions.
- Dialysate calcium concentrations were set at 1.25 mmol/l (low) and 1.75 mmol/l (high).
- Measurements included arterial blood pressure, forearm vascular resistance (FVR), venous tone (VT), cardiac dimensions, and cardiac output via echocardiography.
Main Results:
- High calcium UF + HD significantly increased plasma ionized calcium, while low calcium did not.
- Systolic, diastolic, and mean arterial blood pressure were significantly higher during high calcium UF + HD.
- Stroke volume and cardiac output decreased significantly only during low calcium UF + HD, indicating impaired myocardial contractility.
Conclusions:
- Plasma ionized calcium levels significantly influence blood pressure response during dialysis therapy.
- Peripheral vascular reactivity is not affected by ionized calcium changes.
- Higher dialysate calcium concentrations improve myocardial contractility and cardiovascular stability in hemodynamically stable patients.
Abstract:
In order to prevent hypercalcemia due to the treatment of secondary hyperparathyroidism the use of low calcium dialysate is advocated. However, as calcium ions play a pivotal role in both myocardial and vascular smooth muscle contraction, lowering the dialysate calcium concentration might result in a further impairment of the cardiovascular response during dialysis. Therefore, arterial blood pressure, forearm vascular resistance (FVR) and venous tone (VT) (straing-gauge plethysmography) as well as cardiac dimensions and output (echocardiography) were measured in 10 hemodynamically stable dialysis patients (ejection fraction > 30%) during two standardized sessions of three-hour combined ultrafiltration-hemodialysis (UF + HD) at two different dialysate calcium concentrations: 1.25 and 1.75 mmol/l. High calcium UF + HD resulted in a significant increase in plasma ionized calcium (+0.19 +/- 0.11 mmol/l; p < 0.01) while ionized calcium remained unchanged during low calcium UF + HD (-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 between the two treatments. During both treatments FVR increased while VT decreased. In addition, there were no differences in calculated systemic vascular resistance. However, with comparable end-diastolic dimensions, stroke volume (-18 +/- 13 ml) 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 plasma ionized calcium are an important determinant of the blood pressure response during dialysis therapy. Whereas peripheral vascular reactivity is unaffected by changes in ionized calcium, myocardial contractility is improved with higher dialysate calcium concentrations.