Hemodialysis with acetate, DL-lactate and bicarbonate: a hemodynamic and gasometric study.

Using invasive techniques we have studied various hemodynamic and gasometric parameters in the course of hemodialysis (HD) with different buffers in an animal model. HD sessions of 180 minutes at zero ultrafiltration were carried out on three groups of eight uremic dogs each, under anesthesia and constant mechanical ventilation. The three groups differed only in the buffer used: acetate (Group AC), equal proportions of DL-lactate and acetate (Group AC+LA), and bicarbonate (Group BC). No hemodynamic changes were seen in Group BC. In the AC and AC+LA groups we observed on minute 1 a decrease of the mean blood pressure (MBP) and of the systemic vascular resistances (SVR). These parameters returned to baseline values within the first 30 minutes in Group AC+LA. In Group AC the SVR also returned to baseline values after the minute 30, but the MBP remained below baseline throughout the study period, together with cardiac index and left ventricular stroke work index decreases. Only in Group AC did we see a flattening of the ventricular function curves. Only in this Group was there a decrease of the arterial oxygen pressure (PaO2) with an associated increase of the alveolo-arterial and arterio-venous O2 differences. The O2 consumption was not modified in any of the groups. Acetate as a single buffer induces hemodynamic instability through peripheral vasodilation and reduction of myocardial contractility. The myocardial depression induced by acetate, in its turn, causes a reduction in PaO2. The mixed acetate+lactate buffer is hemodynamically better tolerated than acetate as single buffer, as it induces only vasodilation.