THE NATURE OF CIRCULATORY COLLAPSE INDUCED BY SODIUM NITRITE 1

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Abstract
NaNO2, in an amt. which produced no symptoms and only slight if any changes in the circulation in the horizontal position, caused circulatory collapse in the immobile upright position. Tachycardia, fall in the systolic pressure, small arterial pulse pressure and pulse volume, fall in the venous pressure in the foot, arteriolar constriction with a moderate or pronounced decrease in the "actual" blood flow but with only a small decrease in the "maximal" blood flow in the hands preceded the symptoms of collapse. Pronounced manifestations of circulatory collapse appeared when the maximal blood flow through the hands reached a level of 20-40% of the normal value. Simultaneously, there was a fall in the venous pressure, usually reaching a level below that of the right auricle. Further decrease in blood flow resulted in vasovagal syncope. The electrocardiogram revealed but minor changes. Changes in the autonomic nervous system appeared as secondary manifestations to the primary action of nitrite on the peripheral vascular system. The simultaneous over-activity of the sympathetic and parasympathetic autonomic nervous systems arose first through peripheral vascular reflexes and subsequently through medullary ischemia.

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