Time Factor in Reversibility of Myocardial Metabolic Changes in Hemorrhagic Shock. ∗

Summary

1. The abnormal changes that occur in the % extraction of pyruvate and lactate by the heart in shock are returned to normal if a blood transfusion is given within 1 to 1 1/4 hours of onset of shock. If the shock period is prolonged to 3 or more hours, the changes are irreversible to transfusion. 2. The % extraction of O₂ by the heart, which is markedly elevated in hemorrhagic shock, is returned to normal after an infusion of blood given following 1 to 1 1/4 hours of shock. In contrast, if transfusion is given after more prolonged shock, the myocardial % extraction of O₂ is depressed to abnormally low levels. It is suggested that this may be a reflection of depleted or abnormal myocardial enzyme systems after prolonged shock. 3. These findings support other biochemical, physiological, and pathological observations which point to irreversible myocardial damage as an important factor in the irreversibility of prolonged shock.