Effect of Pitressin in Circulatory Collapse Induced by Sodium Nitrite.

Pitressin is frequently used in the treatment of circulatory collapse. Evaluation of its usefulness has been hindered by the difficulty of interpreting symptoms and of obtaining circulatory measurements in critically ill patients. Previous studies on normal subjects in the upright position (1) (2) have demonstrated that sodium nitrite produces a type of collapse, often ending in syncope, which is similar in its circulatory manifestations to certain types of clinical shock. The symptoms of this collapse are accompanied by a fall in arterial pressure and by a decrease in pulse pressure. There is an increase in arteriolar tone, but a decrease in venous tone. The blood flow in the hand, as indicated by plethysmographic studies, shows no marked changes during the early stage of collapse because of compensatory changes; later, however, there is a progressive fall in blood flow, which frequently drops to zero as syncope develops. The syncope is the result of progressive cerebral anoxia which develops when the venous return to the heart and the cardiac output are decreased because of the blood pooled in the veins of the dependent portions of the body. This type of collapse, which could be produced under controlled conditions, was ideal for study of the action of pitressin. Similar studies on the effect of epinephrin have previously been reported (3).