[Modification of gas exchange and metabolism by various hemodialysis procedures]

We compared the effects of various dialysate composition on pulmonary and transdialyzer gas exchange in patients during hemodialysis. Under acetate hemodialysis there was a permanent loss of CO2 (45-68 ml/min) into the dialysate resulting in a significant decrease of arterial pO2, which can be explained by a reduced alveolar ventilation. The pulmonary oxygen uptake increased up to +20% during treatment, reflecting rising energy metabolism and possibly increased cardiopulmonary instability. Using different concentrates for bicarbonatehemodialysis we saw a moderate to clinical relevant uptake of CO2 (40-60 ml/min) from the dialysate into the blood of the patients, cause the pCO2 in the dialysate varied between 45 and 115 mmHg. Bicarbonate hemodialysis with high pCO2-levels in the dialysate led to hyperventilation and markedly increased oxygen consumption. In critically ill hemodialysis patients the pathophysiologic effects on pulmonary gas exchange of either acetatehemodialysis and bicarbonatehemodialysis with high pCO2 can explain the higher incidence of severe complications.