Pulmonary gas exchange during hemodialysis

Pulmonary gas exchange was continuously measured in 13 mechanically ventilated patients during 24 hemodialyses for acute renal failure. Minute-ventilation was maintained constant by controlled ventilation and gas exchange was continuously measured by a mass-spectrometer system. Three groups were compared: a cuprophan membrane with an acetate dialysate; a polyacrilonitrile membrane (PAN) with an acetate dialysate; and PAN with a bicarbonate dialysate. Arterial PO2 and the O2 alveolar-arterial gradient were the same regardless of the membrane used. [H+] mildly decreased with all dialysates used. Arterial PCO2 decreased only with the acetate dialysate. O2 consumption increased, up to 20 +/- 5% of the initial values during hemodialysis, and remained increased during the two hours following the hemodialysis. Respiratory exchange ratio was lower after than before the hemodialysis.the maintenance of a constant minute ventilation prevented hemodialysis induced hypoxemia. VO2 increased during hemodialysis.