The hypoxic response to hypovolemia.
The response of tissue-PO2 to hypovolemic hypotension was determined in the rat brain cortex and liver surface using needle and surface PO2 electrodes. At hypotensive MAP values of 35-40 mm Hg the cerebral cortex is preferentially supplied with blood through sympathico-adrenergic vasoconstriction of the peripheral circulation. This centralization of the blood volume is not sufficient to prevent a significant fall in cerebral PO2 from 34 +/- 18 mm Hg to 24 +/- 16 mm Hg however (n = 27 animals). The decrease in tissue PO2 during hypovolemia is dependent on body temperature and is more pronounced at lower temperatures (32-34 degrees C) than slightly raised temperatures (37.5-39 degrees C). The same degree of hypovolemia gave rise to large anoxic regions on the liver surface which showed signs of irreversible damage after 90 minutes. This was particularly obvious from the values measured after retransfusion of the missing blood with only a mean PO2 of 18 +/- 12 mm Hg compared with 28 +/- 7 mm Hg (n = 29) at the start of the experiment.
D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism; D005260:Female; D000860:Hypoxia / Q000209:etiology* / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D010101:Oxygen Consumption; D051381:Rats; D011919:Rats, Inbred Strains; D012769:Shock / Q000150:complications* / Q000378:metabolism