PHYSIOLOGICAL-MECHANISMS FOR HEMODYNAMIC- CHANGES INDUCED BY DIFFERENT CALCIUM CONCENTRATIONS DURING HEMODIALYSIS

The mechanisms by which variations in blood calcium induce hemodynamic changes during hemodialysis are unknown. To study this issue, quantit ative two-dimensional (2-D) and doppler echocardiography were used to determine the effect of two dialysates differing in calcium concentrat ion (0.5 and 2 mmol/l) on cardiac systolic function (election fraction [EF], cardiac index [CI] and percent fractional shortening), on diast olic function (maximal transmitral early flow [peak E], maximal transm itral late flow [peak A]), and on peripheral resistence (PR). Ionized calcium increased (5.47 +/- 0.17 vs 4.49 +/- 0.16 mg/dl, p < 0.001) wh en patients were dialysed with high calcium bath and decreased (3.26 /- 0.12 vs 4.38 +/- 0.13 mg/dl, p < 0.001) with low calcium bath. Para thyroid hormone levels increased with low calcium bath (271 +/- 37 vs 167 +/- 32 pg/ml, p < 0.001) and decreased with high calcium bath (40 +/- 14 vs 180 +/- 41 pg/ml, p < 0.003). Intradialytic variations of ca techolamines and renin did not differ between the two dialyses. Mean a rterial pressure (MAP) and PR decreased with lower levels of calcium ( 94.2 +/- 3.6 vs 115 +/- 2.6 mmHg, p < 0.003, and 866 +/- 83 vs 1117 +/ - 76 dynes . cm-5, p < 0.005, respectively). Only during dialysis with low calcium bath ed changes in MPA correlate with changes in ionized calcium (r: 0.748, p < 0.05). No significant changes in systolic param eters were observed with either manouvres. Peak E velocity decreased a fter dialysis with high calcium (81.12 +/- 6 vs 98.62 +/- 5 cm/sec, p < 0.001) without significant changes in peak A velocity. Peak E veloci ty did not change during hemodialysis with low calcium. This study sho ws that hypocalcemia during hemodialysis with low calcium dialysate in duces a decrease of arterial pressure through changes in peripheral re sistances. Hemodialysis with high calcium dialysate results in alterat ions in early left ventricular filling.