Early derangements in oxygen and glucose metabolism following head injury: the ischemic penumbra and pathophysiological heterogeneity.
BACKGROUND
Conclusive evidence of cerebral ischemia following head injury has been elusive. We aimed to use (15)O and (18)Fluorodeoxyglucose positron emission tomography (PET) to investigate pathophysiological derangements following head injury.


RESULTS
Eight patients underwent PET within 24 h of injury to map cerebral blood flow (CBF), cerebral oxygen metabolism (CMRO2), oxygen extraction fraction (OEF), and cerebral glucose metabolism (CMRglc). Physiological regions of interest (ROI) were generated for each subject using a range of OEF values from very low (<10), low (10-30), normal range (30-50), high (50-70), and critically high (> or =70%). We applied these ROIs to each subject to generate data that would examine the balance between blood flow and metabolism across the injured brain independent of structural injury.


CONCLUSIONS
Compared to the normal range, brain regions with higher OEF demonstrate a progressive CBF reduction (P < 0.01), CMRO2 increase (P < 0.05), and no change in CMRglc, while regions with lower OEF are associated with reductions in CBF, CMRO2, and CMRglc (P < 0.01). Although all subjects demonstrate a decrease in CBF with increases in OEF > 70%, CMRO2 and CMRglc were generally unchanged. One subject demonstrated a reduction in CBF and small fall in CMRO2 within the high OEF region (>70%), combined with a progressive increase in CMRglc.


CONCLUSIONS
The low CBF and maintained CMRO2 in the high OEF ROIs is consistent with classical cerebral ischemia and the presence of an 'ischemic penumbra' following early head injury, while the metabolic heterogeneity that we observed suggests significant pathophysiological complexity. Other mechanisms of energy failure are clearly important and further study is required to delineate the processes involved.
The Division of Anaesthesia, Addenbrooke's Hospital, University of Cambridge, Box 93, Cambridge, CB2 2QQ, UK.
M Giulia
MG
Abate
Monica
M
Trivedi
Tim D
TD
Fryer
Piotr
P
Smielewski
Doris A
DA
Chatfield
Guy B
GB
Williams
Franklin
F
Aigbirhio
T Adrian
TA
Carpenter
John D
JD
Pickard
David K
DK
Menon
Jonathan P
JP
Coles
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D001930:Brain Injuries / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D020925:Hypoxia-Ischemia, Brain / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D010104:Oxygen Radioisotopes; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D019275:Radiopharmaceuticals; D055815:Young Adult
D001786:Blood Glucose; D010104:Oxygen Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18