ABSTRACT
Haemodynamic instability with symptomatic hypotension remains one of the most important complications occuring during HD [20-30% of dialyses]. Calcium ions play a pivotal role in the contractile process of both vascular smooth muscle cells and cardiac myocytes as well as in the release of catecholamines from the synaptic clefts. It has been suggested that the increased clearance of catecholamines by HD may potentiate intradialytic hypotension and that changes in ionized calcium might play an important role in the cardiovascular response during HD. In the present work, we studied the effect of using different dialysate calcium concentrations on the patient serum ionized calcium levels, serum catecholamine levels, haemodynamic data, and echocardiographic parameters before and after HD. Twenty patients [12 males and 8 females], with CRF under chronic regular HD therapy were studied and ten healthy volunteers, matched in age and gender, served as a control group. Patients were dialysed using the standard [low-calcium, 2.5 mEq/L] dialysate for twelve sessions in four weeks, and were then subjected sequentially to the high-calcium [4 mEq/L] dialysate for another twelve sessions in four more weeks. After four weeks of low-calcium dialysis, serum ionized calcium levels showed mild, though statistically significant reduction compared to the predialysis levels. There was no significant change in plasma levels of catecholamines at the end of the four week period. On the other hand, changing to high-calcium dialysate for further four weeks resulted in a very significantly higher post-dialysis levels of ionized calcium compared to predialysis levels. Morever, there was highly significant increase in postdialysis noradrenaline compared to predialysis levels. Low-calcium dialysis resulted in significant reduction in SBP, DBP and mean BP. Regarding vascular reactivity parameters, there was a statistically significant increase in the mean heart rate [HR] and forearm vascular resistance [FVR], while venous tone [VT] was significantly lower in postdialysis compared to predialysis assessment. On the other hand, using high calcium dialysate resulted in minor changes in SBP, DBP, and MBP that did not reach statistical significance. Positive correlation existed between changes in ionized calcium and plasma noradrenaline levels after high-calcium dialysis. No significant changes has been found in the echocardiographic parameters in the pre and post-dialysis assessments, neither in the low-calcium nor in the high-calcium dialysis periods. In conclusion, our study demonstrated that, even in the haemodynamically stable patients, changes in plasma ionized calcium may have an important effect on the blood pressure response during HD. Using high-calcium dialysate solutions may help improving intradialytic hypotension which is the commonest complication occuring during HD