Effect of respiratory alkalosis on survival in hemorrhagic shock.

The effect of respiratory alkalosis on survival in hemorrhagic shock was studied in pentobarbital-anesthetized dogs. Since cell membranes are relatively poorly permeable to bicarbonate ion, production of alkalosis by hyperventilation may influence intracellular pH more than by bicarbonate infusion. Hyperventilation was produced by increasing tidal volume in one group of dogs. Spontaneously breathing dogs served as controls. Another control group in which ventilation was maintained with a respirator to produce normal blood gas values was also studied. Shock was produced by arterial bleeding at a fixed rate to maintain blood pressure at 50 mm Hg for 90 min, then at 30 mm Hg for 45 min. The blood was then reinfused. In the hyperventilation group 7 of 9 animals survived 480 min with a blood pressure greater than 75 mm Hg, while none of 8 in the control group and none of 7 in which ventilation was maintained at the normal level survived with these criteria. Arterial pH was higher in tlie hyperventilation than the other groups, while differences in Pao2 were not significant throughout most of the experiment. Hyperventilation improved survival and hemorrhagic shock, probably related to the changes in pH. ADDITIONAL