The relationship between angiography, intraerythrocytic pH and hemoglobin oxygen equilibrium

The acute effects of an injection of contrast material (Renovist) on intraerythrocytic and extracellular pH was studied at cardiac catheterization in 72 patients with congenital heart disease. A decrease in mean extracellular (plasma) pH (7.444 plus or minus .006 to 7.419 plus or minus 0.009) and an increase in mean intraerythrocytic pH (7.204 plus or minus .005 to 7.232 plus or minus .006) were observed within minutes after injection (p smaller than .01). In 17/72 patients, simultaneous measurements of oxygen affinity for hemoglobin as characterized by P50 (oxygen tension at 50% O-2 saturation) corrected to in vivo arterial pH decreased from a mean of 26.4 to 25.2 mm Hg (p smaller than .01). It is postulated that the acute increase in intraerythrocyte pH and increased affinity of hemoglobin for oxygen are due to a decrease in intracellular hydrogen ion concentration induced by the increase in plasma osmolality with subsequent shift of hemoglobin oxygen equilibrium via the Bohr effect.