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Increased ionized calcium and left ventricular contractility during hemodialysis
Insights
Routine hemodialysis improves left ventricular contractility, primarily due to increased plasma ionized calcium levels. This finding is crucial for understanding cardiac function during dialysis treatments.
Area of Science:
- Nephrology
- Cardiology
- Physiology
Background:
- Hemodialysis is known to increase left ventricular contractility.
- The underlying mechanisms for this improvement remain unclear.
- Potential factors include uremic toxin removal, increased ionized calcium, and increased bicarbonate.
Purpose of the Study:
- To investigate the specific roles of ionized calcium and bicarbonate in hemodialysis-induced left ventricular contractility changes.
- To determine the primary driver of improved cardiac function during dialysis.
Main Methods:
- Eight stable hemodialysis patients participated.
- Left ventricular contractility was assessed using two-dimensional echocardiography.
- Three dialysate protocols were employed, manipulating ionized calcium and bicarbonate levels.
Main Results:
- Contractility did not improve when neither ionized calcium nor bicarbonate increased.
- Left ventricular contractility significantly increased when ionized calcium rose, while bicarbonate remained constant.
- Increasing bicarbonate alone did not enhance contractility.
Conclusions:
- The rise in plasma ionized calcium concentration during hemodialysis is a key factor responsible for the observed improvement in left ventricular contractility.
- This highlights the importance of calcium balance in cardiac function for patients undergoing dialysis.
Abstract:
Routine hemodialysis is associated with an increase in left ventricular contractility that is independent of a change in preload, but the mechanisms responsible are unknown. We investigated the importance of three distinct effects that regularly occur in hemodialysis and could potentially improve left ventricular contractility: the removal of uremic toxins, the increase in the plasma ionized calcium concentration, and the increase in the plasma bicarbonate concentration. Three different dialysates were used for each of eight stable patients on long-term hemodialysis, and left ventricular contractility was assessed by two-dimensional echocardiography before and after each dialysis. In the first procedure neither the ionized calcium nor the bicarbonate concentration was allowed to increase, and left ventricular contractility did not improve. In the second procedure, ionized calcium increased (from 4.4 to 5.4 mg per deciliter, P less than 0.001), bicarbonate concentration was held constant, and contractility increased (from 0.74 to 0.93 circumferences per second, P less than 0.005). In the third procedure, ionized calcium was kept constant, the bicarbonate concentration increased (from 19 to 24 mmol per liter, P less than 0.001), but contractility did not increase. These results suggest that the increase in ionized calcium that occurs in regular dialysis is a key factor in the improvement in left ventricular contractility observed during the procedure.