Blood pH measurement with the glass electrode; study of venous and fingertip blood.

BSERVATIONS MADE DURING the routine estimation of blood pH with the glass electrode noted that specimens of fingertip blood often tended to drift rapidly toward the alkaline side when exposed to air at 370 or showed a slower drift in this direction under oil. This change was noted to be slower with specimens of venous blood. The pH of blood taken from fingertip or vein under oil and cooled rapidly to room temperature, did not tend to drift. When exposed to air at room temperature, the pH of fingertip blood drifted more rapidly to the alkaline side, than did venous blood. In patients with acidemia, with low CO2 plasma levels, this drift was not marked or did not occur at room temperature or at 37#{176}, either under oil or exposed to air. It was suspected that, since with fingertip blood the tendency to nipture erythrocytes is greater than when blood is drawn from the vein and the proportion of tissue juice is greater in fingertip blood than in venous blood, the difference between venous and fingertip blood lay in their respective carbonic anhydrase content. A study was therefore set up to test the effect of carbonic anhydrase and its inhibitor, Diamox (1) (2-acetylamino-l ,3 ,4-thiadiazole-5sulfonamide), on the drift of pH in the blood and plasma from normal individuals.