title: Effect of graded hyperventilation on cerebral metabolism in a cisterna magna blood injection model of subarachnoid hemorrhage in rats.
abstract: In subarachnoid hemorrhage (SAH) with cerebrovascular instability, hyperventilation may induce a risk of inducing or aggravating cerebral ischemia. We measured cerebral blood flow (CBF) and cerebral metabolic rates of oxygen (CMRO2), glucose (CMRglc), and lactate (CMRlac) at different PaCO2 levels after experimental SAH in rats (injection of 0.07 mL of autologous blood into the cisterna magna). Four groups of Sprague-Dawley male rats were studied at predetermined PaCO2 levels: group A: normocapnia (5.01-5.66 kPa [38.0-42.0 mm Hg]); group B: slight hyperventilation (4.34-5.00 kPa [32.5-37.5 mm Hg]); group C: moderate hyperventilation (3.67-4.33 kPa [27.5-32.4 mm Hg]); group D: profound hyperventilation (3.00-3.66 kPa [22.5-27.4 mm Hg]). Each of the four groups included eight rats with SAH and eight sham-operated controls. CBF was determined by the intracarotid Xe method; CMRo2, CMRglc, and CMRlac were obtained by cerebral arteriovenous differences. In both SAH rats and controls, hyperventilation decreased CBF in proportion to the decrement in PaCO2 without affecting either CMRO2, CMRglc, or CMRlac. In groups C and D, CBF decreased by 20%-35%, but CMRs were maintained by a compensatory increase in oxygen extraction fraction (OEF). The results show that even profound hyperventilation in this model of SAH is associated with an adequate increase in OEF so that CMRs of oxygen, glucose, and lactate remain similar to levels observed in normocapnic conditions.
authors.affiliation: Department of Neurosurgery, Neuroscience Center, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Ma
authors.forename: Rikke
authors.initials: R
authors.lastname: Bay-Hansen
authors.forename: John
authors.initials: J
authors.lastname: Hauerberg
authors.forename: Gitte Moos
authors.initials: GM
authors.lastname: Knudsen
authors.forename: Niels Vidiendal
authors.initials: NV
authors.lastname: Olsen
authors.forename: Marianne
authors.initials: M
authors.lastname: Juhler
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001923:Brain Chemistry / Q000502:physiology*; D002245:Carbon Dioxide / Q000494:pharmacology; D002560:Cerebrovascular Circulation; D002946:Cisterna Magna / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial; D013345:Subarachnoid Hemorrhage / Q000628:therapy*; D014980:Xenon Radioisotopes
chemical_list: D014980:Xenon Radioisotopes; D002245:Carbon Dioxide