title: Incidence and mechanisms of cerebral ischemia in early clinical head injury.
abstract: Antemortem demonstration of ischemia has proved elusive in head injury because regional CBF reductions may represent hypoperfusion appropriately coupled to hypometabolism. Fifteen patients underwent positron emission tomography within 24 hours of head injury to map cerebral blood flow (CBF), cerebral oxygen metabolism (CMRO2), and oxygen extraction fraction (OEF). We estimated the volume of ischemic brain (IBV) and used the standard deviation of the OEF distribution to estimate the efficiency of coupling between CBF and CMRO2. The IBV in patients was significantly higher than controls (67 +/- 69 vs. 2 +/- 3 mL; P < 0.01). The coexistence of relative ischemia and hyperemia in some patients implies mismatching of perfusion to oxygen use. Whereas the saturation of jugular bulb blood (SjO2) correlated with the IBV (r = 0.8, P < 0.01), SjO2 values of 50% were only achieved at an IBV of 170 +/- 63 mL (mean +/- 95% CI), which equates to 13 +/- 5% of the brain. Increases in IBV correlated with a poor Glasgow Outcome Score 6 months after injury (rho = -0.6, P < 0.05). These results suggest significant ischemia within the first day after head injury. The ischemic burden represented by this "traumatic penumbra" is poorly detected by bedside clinical monitors and has significant associations with outcome.
authors.affiliation: The Division of Anaesthesia, and The Wolfson Brain Imaging Centre, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Coles
authors.forename: Tim D
authors.initials: TD
authors.lastname: Fryer
authors.forename: Piotr
authors.initials: P
authors.lastname: Smielewski
authors.forename: Doris A
authors.initials: DA
authors.lastname: Chatfield
authors.forename: Luzius A
authors.initials: LA
authors.lastname: Steiner
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Johnston
authors.forename: Stephen P M J
authors.initials: SP
authors.lastname: Downey
authors.forename: Guy B
authors.initials: GB
authors.lastname: Williams
authors.forename: Franklin
authors.initials: F
authors.lastname: Aigbirhio
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hutchinson
authors.forename: Kenneth
authors.initials: K
authors.lastname: Rice
authors.forename: T Adrian
authors.initials: TA
authors.lastname: Carpenter
authors.forename: John C
authors.initials: JC
authors.lastname: Clark
authors.forename: John D
authors.initials: JD
authors.lastname: Pickard
authors.forename: David K
authors.initials: DK
authors.lastname: Menon
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism; D002545:Brain Ischemia / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D006259:Craniocerebral Trauma / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D012039:Regional Blood Flow; D014055:Tomography, Emission-Computed
chemical_list: D010100:Oxygen