Functional consequences of altered blood oxygen affinity

The effect of an acute left shift in the oxygen dissociation curve (ODC) was examined in several animal models. When combined with hemorrhagic shock, a left shift of the ODC produced diminished shock tolerance with evidence of increased sympathetic outflow and increased mortality. Perfusion of the isolated canine brain with low P50 blood produced major electroencephalographic abnormalities and a sharp decrease in cerebral oxygen consumption. Exchange transfusion of normal rats with low P50 blood resulted in a major increase in coronary and cerebral flow. The data suggest that an acute left shift of the ODC is capable of disturbing oxygen delivery significantly, particularly to the brain and probably to the heart. Normal animals appear to compensate for an acute increase in oxygen affinity by increasing blood flow to these organs. When oxygen affinity is increased in combination with a fixed rate of blood flow, hypoxia results.