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Vasoconstriction due to over-activity of the sympathetic nervous system is an "important component" of shock, according to Ashley E. Thomson, MD, assistant professor of medicine at the University of Manitoba (Canada).
Thomson told the Hahnemann Symposium on Shock and Hypotension, held March 18-21 in Philadelphia, that adrenergic blocking through administration of phenoxybenzamine hydrochloride to patients suffering shock, "appears to provide a rapid estimate of the adequacy of circulating blood volume."
Except for shock of cardiogenic origin, expanding intravascular volume is the first consideration in management of shock cases, he said. Instances arise, however, in which seemingly adequate blood volume replacement and attempts to alleviate the precipitating cause do not assure survival. In such patients the clinical signs of shock—pallor, sweating, tachycardia, low pulse pressure, and slow capillary filling—persist or worsen. "These signs are also the signs of vasoconstriction or of sympathetic nervous system over-activity," Thomson said.
It has long been
Adrenergic Blocking Agents May Provide Rapid Estimate of Blood Volume Adequacy. JAMA. 1964;187(13):32-33. doi:10.1001/jama.1964.03060260080044