Capillary flow in hemorrhagic shock. II. Hemorrhage in the anesthetized pig.

A deficiency in nutritive capillary blood flow is accepted as the basic pathophysiologic defect in hemorrhagic shock.1-4Therefore, we must understand the microcirculatory flow changes produced by hemorrhage, and the ability of therapeutic modalities to correct flow deficits, if we are to adequately evaluate methods of treatment of hemorrhagic shock. Attempts to study the flow changes in shock have been hindered by the lack of a method of measuring capillary flow. Many investigators have attempted to estimate capillary flow by measuring large vessel flow, usually by operative methods in anesthetized animals. These methods fail to differentiate nutritive flow from flow through arteriovenous pathways. Furthermore, enough sufficient hemodynamic variables are introduced by anesthesia,5-10operative manipulation,8-11and the frequently resultant mild hypothermia5,12and hypovolemia to cast doubt upon the validity of these methods. A new method, the tissue-blood radioactive potassium (42K) uptake ratio comparison technique, determines nutritive