Effectiveness of phentolamine for reversal of circulatory failure (shock)

Pharmacological actions of phentolamine were investigated in 20 patients in advanced stages of acute circulatory failure. The shock was due to cardiac causes in seven, prior hypovolemia in eight, and bacteremia in five patients. Phentolamine increased cardiac output and the velocity of blood flow and reduced peripheral resistance among patients with cardiac causes of shock. This was associated with an increase in oxygen delivery to the tissues and reversal of anoxic metabolism. In patients with bacteremia and in patients with prior hypovolemia, the arterial vasodilator actions of phentolamine predominated. Mean arterial pressure declined disproportionately or cardiac output failed to increase. Although the ultimate benefit of phentolamine in the treatment of patients in shock is not established by this study, its pharmacological effects in patients with cardiogenic shock were sufficiently impressive to warrant more extensive evaluation.