LIMB BLOOD FLOW AND VASCULAR RESISTANCE CHANGES IN DOGS DURING HEMORRHAGIC HYPOTENSION AND SHOCK

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Abstract
Changes in rate of blood flow through limbs of anesthetized dogs were detd. by an adaptation of the Wright-Phelps technique during the course of prolonged sustained post-hemorrhagic hypotension, reinfusion, and post-reinfusional circulatory failure. Alterations in the ratio of pressure/flow were detd. and their significance as criteria of changes in peripheral resistance were discussed. Immediately after bleeding, the blood flow decreases abruptly and the pressure/flow relationship is altered very little. Subsequently, blood flow decreases somewhat more and the pressure/flow ratios increase greatly. While periodic reversals occur the main trend appears to be in the direction of increased resistance to flow. Following reinfusion, blood flow exceeds control rates for a short while, but soon it decreases progressively while arterial pressure remains high or even rises. The tendency toward increased resistance continues during subsequent decline of blood pressure. Supplementary studies of vol. changes of a limb during the entire cour seof the expts. reveal vol. increases ranging from 2 to 6.1 ml./l00 g. The results give no evidence that circulatory changes in the limbs of dogs differ from those observed in clinical shock, or that reduction in resistance in the limbs or loss of circulating fluid into limbs plays a significant part in the circulatory failure which follows reinfusion of blood into animals exposed to prolonged periods of hypotension.