Oxygen Extraction in Severely Anemic Dogs after Infusion of NaHCO3 or HCl
When anesthetized dogs were made acidemic or alkalemic during very severe hypoxic hypoxia, the slight but significant differences in mixed venous PO2 were not associated with any significant differences in survival time, oxygen delivery, or oxygen uptake (Cain, 1976). Oxygen uptake was apparently dependent only on the total oxygen delivery (QxCaO2). There were at least two reasons for the seemingly independent behavior of oxygen uptake from any Bohr shifts in dissociation curve position. One was the much shorter diffusion distances for O2 as capillary beds were fully utilized. The second was the relative insensitivity of the oxyhemoglobin dissociation curve to Bohr effects at the lower extreme. This last reason would not apply in anemic hypoxia because, at low hematocrits near 10%, mixed venous PO2 and saturation remained in the midrange even though O2 delivery had become limiting to O2 uptake in the whole animal (Cain, 1977). With normal arterial PO2, a shift of the dissociation curve to the right as hemoglobin affinity for O2 is decreased by acid infusion would not bother loading but could increase the PO2 at which O2 was unloaded at the tissues.
KeywordsOxygen Uptake Acid Infusion Dissociation Curve Oxygen Extraction Base Infusion
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