Studies in clinical shock and hypotension. IV. Variations in reflex vasoconstriction and cardiac stimulation.

Abstract

Hemodynamic studies were performed on 44 patients with nonhemorrhagic shock or hypotension in order to assess the degree of vasoconstriction and cardiac stimulation. In 19 patients, reflex adrenergic discharge was characterized by elevated total peripheral vascular resistance, a high ratio of central blood volume to total blood volume, tachycardia, and clinical signs of skin vasoconstriction. Reduced total blood volume in most of these patients at the time of study could be explained as the result of fever, administration of vasopressor drugs, or prolonged reflex vasoconstriction. Eight patients were hypotensive with low peripheral resistance usually associated with tachycardia and hypovolemia. The fact that all died within several hours suggests that this "irreversible" syndrome was related to local accumulation of acid metabolites with terminal failure of vasoconstriction. In 17 patients, absence of reflex vasoconstriction despite hypotension was manifested by low or normal peripheral resistance, low ratios of central blood volume to total blood volume, warm skin, and normal total blood volume. While tachycardia often was absent in this group, heart rate was more closely related to body temperature than to vasoconstriction. Lack of intense adrenergic discharge in these hypotensive patients could be attributed either to the absence of a hypovolemic stimulus or to impairment of normal sympathetic nervous system pathways. The high incidence of alcoholism, cirrhosis, malignancy, pulmonary emphysema, and diabetes in these patients suggests the possibility that adrenergic insufficiency was a factor in the failure of vasoconstriction in at least some of them. The frequency of hypovolemia in the patients with vasoconstriction stresses the need for recognition and correction of occult depletion of blood volume in shock of diverse etiologies.