RESPIRATORY GAS-EXCHANGE BY HIGH-EFFICIENCY HEMODIALYZERS

The effects of respiratory gas mass-transfer by high-efficiency hemodialyzers with regard to respiratory status and acid-base balance were studied in three groups of patients. Patients dialyzed with acetate dialysate and a single pass delivery system (group I) and those dialyzed with the same dialysate and a recirculating single pass system (group II) had significant intradialytic decreases in PCO2 (p < 0.05), while patients hemodialyzed against a carbon dioxide/bicarbonate dialysate (group III) had no significant alterations in arterial PCO2. The mass-transfer rate of carbon dioxide was 0.3 mM/min in group I and 0.2 mM/min in group II. The hypocapnia caused by dialyzer mass-transfer of carbon dioxide was associated with a significant drop in minute ventilation volume and a decrease in PO2 which was significant in group I (p < 0.05). Although bicarbonate mass-transfer reduced serum bicarbonate levels, the loss of carbon dioxide to the dialysate resulted in an increased arterial pH during dialysis.