THE COLLAPSE PRODUCED BY VENOUS CONGESTION OF THE EXTREMITIES OR BY VENESECTION FOLLOWING CERTAIN HYPOTENSIVE AGENTS 1

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Abstract
The prior admn. of NaNCO2, the dihydrogenated alkaloids of ergot, hexamethonium, and to a lesser extent tetraethylammonium, to normotensive or hypertensive patients resulted in a state of increased susceptibility to the development of hypotension and collapse when the limbs were congested with venous tourniquets. Veratrum viride and Na amytal did not produce this effect. Measurement of the volume of blood trapped in the limbs (dye method) and the increase in volume of the calf (plethysmograph) indicated that the hypotension and collapse was not due to pooling of excessive amts. of blood in the congested limbs but to failure of compensatory vasoconstriction in areas other than the congested extremeties following moderate blood loss. This was demonstrated by the observation that after the admn. of the above drugs hypotension frequently with collapse occured during venesections of only 250 to 525 cc. of blood. After these drugs loss of as little as 2-4% of the total blood volume frequently resulted in perceptible decrements of arterial pressure. Such observations illustrate the extreme sensitivity of the homeostatic vasoconstrictor mechanisms in the normal (untreated) individual. Patients who had previously undergone lumbodorsal or transthoracic sympathectomy were more resistant to hypotension during the post-drug congestion period than were non-sympathectomized-subjects. This resistance probably was related to the well known return of independent vascular tone in sympathectomized areas.