Oxygen and Carbon Dioxide Dissociation Studies on Blood Drawn after Intravenous Injection of Pitressin. ∗

Abstract

In previous communications 1 , 2 , 3 it was pointed out that certain well defined circulatory and respiratory changes are elicited by the intravenous injection of moderate doses of pituitrin or pitressin into unanesthetized human beings or dogs. For a brief period (5 to 10 minutes) immediately following the administration of the drugs, the venous blood draining the limbs becomes arterial in color and shows a high oxygen content, a rapidly rising lactic acid concentration, and a concomitantly lowered carbon dioxide content. There is at the same time a precipitous decrease in total oxygen consumption and a lowering of the cardiac output. In the immediately ensuing recovery period, which persists for 1 1/2 to 2 hours after the injection, the physiological picture is reversed. An abnormally dark venous blood is found, indicating increased oxygen utilization by the “starved” tissues; a further rise in lactic acid is followed by a gradual return to the pre-injection level; the carbon dioxide content returns slowly to a slightly sub-basal value. Total oxygen consumption and cardiac output show parallel increases above their pre-injection values and then gradually return to the basal level.

A temporary inability of the blood to give up its oxygen is one cause which might account for the arterial character of the venous blood drawn from the leg 5 to 10 minutes after the intravenous injection of pitressin. To ascertain whether such a factor comes into play, oxygen and carbon dioxide dissociation studies were made on this blood and the results obtained are recorded in the present communication.