OXYGEN-CONSUMPTION DURING MAINTENANCE HEMODIALYSIS

The influence of hemodialysis on oxygen consumption was studied in 15 patients on maintenance dialysis. Red cell 2,3-DPG, P50, an inverse measure of oxygen affinity of hemoglobin, arterial and central venous blood gases and cardiac index were measured. 2,3-DPG remained unchanged, whereas in vivo P50 fell significantly during dialysis due to a rise of pH (Bohr effect). Arterial Po2 was lower after than before dialysis, but arterial and central venous oxygen saturations did not change significantly. Cardiac index increased from 3.66 to 4.05 liter/min/m2. Oxygen consuption rose from 120.5 to 131.7 ml/min/m2 (p < 0.05), the rise being accounted for by an increase in cardiac index and by a slight postdialysis hemoconcentration. However, even correcting for these parameters did not reveal a decrease in oxygen consumption. It is concluded that, contrary to previous assumptions, the hemodialysis-induced rise in pH with its consequent increase of oxygen hemoglobin affinity did not impair oxygen delivery in this group of patients on maintenance dialysis.