Hemorrhagic hypotension and the lung: in vitro respiration.

We examined the O2 consumption and respiratory quotient of lung slices from rats whose mean blood pressure was decreased to approximately 40 mm Hg for 1 hour by hemorrhage and from control rats that were handled in the same manner but were not bled. The in vitro O2 consumption of lung slices from the hypotensive rats was lower than the O2 consumption of slices from control rats; exogenous glucose did not alter these differences. In the absence of exogenous glucose, the (mean +/- SE) respiratory quotient of lungs from control rats was 0.75 +/- 0.01; from hypotensive rats 0.78 +/- 0.01 (P less than 0.05). Glucose increased the respiratory quotient of lung slices from control rats to 0.95 +/- 001 but increased the respiratory quotient of slices from hypotensive rats to only 0.86 +/- 0.01. We concluded that hemorrhagic hypotension decreases lung O2 consumption and alters substrate metabolism by the lung.