title: Simultaneous recording of tissue PCO2, interstitial pH and potassium activity in the rat cerebral cortex during anoxia and the subsequent recovery period.
abstract: Tissue PCO2 (carbon dioxide tension) (PtCO2), interstitial H+ (H+e) and potassium activities (K+e) were monitored in the cerebral cortex of rats during and after 2-3 min of anoxia. Anoxia was associated with systemic hypotension and caused H+e (extracellular hydrogen ion activity) to increase from pH approximately equal to 7.2 to pH approximately equal to 6.5, K+e to rise from approximately equal to 2.4 up to a maximum of approximately equal to 39 mmol/l, and PtCO2 to increase from approximately equal to 52 to approximately equal to 80 mmHg. Lactate increased from 2 to 5 mmol/kg tissue weight during anoxia and did not fall significantly after re-oxygenation for 10 min. A marked relationship existed between changes in PtCO2 and H+e. After re-oxygenation, K+e (extracellular potassium ion activity) and PtCO2 returned to the pre-anoxic level in a few minutes, whereas H+e took approximately equal to 30 min to recover. H+e recovered in a biphasic manner; a rapid decrease lasting approximately equal to 1 min preceded a much slower phase. We propose that the biphasic normalization of H+e after anoxia mainly reflects an initial and rapid washout of CO2 from brain tissue and a subsequent slow elimination of lactic acid occurring via metabolism and removal by the circulation.
authors.affiliation: Gough-Cooper Department of Neurological Surgery, Institute of Neurology, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Ohno
authors.forename: T P
authors.initials: TP
authors.lastname: Obrenovitch
authors.forename: N
authors.initials: N
authors.lastname: Hartell
authors.forename: S
authors.initials: S
authors.lastname: Barratt
authors.forename: H S
authors.initials: HS
authors.lastname: Bachelard
authors.forename: L
authors.initials: L
authors.lastname: Symon
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism / Q000503:physiopathology*; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000378:metabolism; D002534:Hypoxia, Brain / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism*; D019344:Lactic Acid; D008297:Male; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D007773:Lactates; D002245:Carbon Dioxide; D019344:Lactic Acid; D011188:Potassium