Journal of Applied Physiology, Vol 62, Issue 2 658-667, Copyright © 1987 by American Physiological Society
Seizure-associated pulmonary edema and cerebral oxygenation in the rat
N. R. Kreisman, R. A. Hodin, B. L. Brizzee, M. Rosenthal, T. J. Sick, R. Busto and M. D. Ginsberg
Cerebral partial pressure of O2 (PO2), relative changes in the ratio of
reduced/oxidized cytochrome aa3, blood flow, and the arteriovenous
difference in O2 content were measured during seizures with and without
pulmonary edema. Seizures were induced with bicuculline (0.2-1.2 mg/kg iv)
in rats anesthetized with 70% N2O and paralyzed with curare. Briefer
seizures were accompanied by increased cerebral PO2 and increased oxidation
of cytochrome aa3. Lung water content and arterial O2 partial pressure
(PaO2) remained normal. Longer duration seizures were also accompanied
initially by increases in cerebral oxygenation. Within minutes, however,
PaO2 fell from a mean of 118 to 51 mmHg, and lung water content increased
from 76.2 to 83.6%. Cerebral PO2 fell but most often rose back to or above
control levels, while cytochrome aa3 became markedly reduced.
Simultaneously, cerebral blood flow increased more than 300% above
preseizure values and O2 delivery increased more than O2 consumption. The
reductive shift of cytochrome aa3 was greater than that produced by
lowering PaO2 to equivalent values in seizure-free rats. The reductive
shift of cytochrome aa3, despite increased O2 delivery, may be indicative
of derangements in cerebral O2 diffusion or energy metabolism.
