O2 transport during two forms of stagnant hypoxia following acid and base infusions

Cardiac output and mean arterial pressure were decreased in two groups of 16 anesthetized paralyzed dogs ventilated by pump. Pericardial tamponade was used in one group, and hemorrhagic hypotension was used in the other. After a 30-min control period and 30 min of circulatory shock by either method, 0.3N HCl was infused into half the dogs in each group and 1.0N NaHCO3 into the other half so that pH was separated by 0.3-0.4 units. The slope of the line relating O2 uptake to total O2 transport (blood flow X arterial O2 concentration) was used to evaluate how well the tissues extracted O2 relative to O2 supply. During the initial shock period before infusion, the slope of the line relating O2 uptake of left hindlimb skeletal muscle to total O2 transport in the limb was almost twice as great as that for the whole body. Acid infusion increased the slope of the whole-body line but did not alter that for the hindlimb. Base infusion, on the other hand, decreased the slope of the line for the limb during hemorrhagic shock but had no other effect. We concluded that acid either improved the distribution of a limiting blood supply to nonmuscle organ systems, or increased tissue capillary PO2 and O2 diffusion by decreasing hemoglobin O2 affinity (HOA), or both. The effect of an increased HOA with base infusion was noticeable in hindlimb skeletal muscle only when volume depletion by hemorrhage presumably greatly increased the normally short intercapillary diffusion distance in muscle.