title: On-line monitoring of substrate delivery and brain metabolism in head injury.
abstract: Head injury is associated with complex pathophysiological changes in metabolism. The objective of the study was to investigate these changes by applying on-line bedside monitoring of cerebral metabolism using microdialysis. Following approval by the Local Ethics Committee and consent from the next of kin, a microdialysis catheter was inserted into the frontal cortex of patients with severe head injury. Twenty-one patients were studied for 102.3 +/- 26.9 hours (mean +/- 95% confidence interval; total 89.4 patient monitoring days). The overall cerebral glucose (mean of means) was 1.63 +/- 0.31 mM with periods of undetectable glucose recorded. The cerebral lactate and lactate/pyruvate ratio were 4.69 +/- 0.61 mM and 29.9 +/- 3.73 respectively. Patients who died (n = 4) or who were severely disabled (not proceeding to rehabilitation, n = 5) had a tendency towards lower glucose (1.39 +/- 0.35 mM), higher lactate (5.10 +/- 1.02 mM) and higher lactate/pyruvate ratios (35.5 +/- 7.67) compared to patients with good outcome (home or proceeding to rehabilitation, n = 12, glucose 1.80 +/- 0.49 mM, lactate 4.38 +/- 0.85 mM, lactate/pyruvate ratio 27.9 +/- 4.33). Trends in these metabolic parameters relating to outcome were identifiable. In the majority of patients, cerebral glutamate levels (overall mean of means 9.47 +/- 4.59 microM) were initially high and then declined to stable levels. Patients in whom the glutamate level remained elevated or in whom secondary rises in glutamate were seen had a poor outcome. The application of bedside analysis of microdialysis enables the progress of the patient to be monitored on-line. In addition to establishing trends of improving and deteriorating metabolism, the technique has the potential to monitor the effects of therapeutic manoeuvres on the biochemistry.
authors.affiliation: Academic Department of Neurosurgery, Department of Neuroanaesthesia and Medical Research Council, Centre for Brain Repair, University of Cambridge, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: Hutchinson
authors.forename: P G
authors.initials: PG
authors.lastname: al-Rawi
authors.forename: M T
authors.initials: MT
authors.lastname: O'Connell
authors.forename: A K
authors.initials: AK
authors.lastname: Gupta
authors.forename: L B
authors.initials: LB
authors.lastname: Maskell
authors.forename: D B
authors.initials: DB
authors.lastname: Hutchinson
authors.forename: J D
authors.initials: JD
authors.lastname: Pickard
authors.forename: P J
authors.initials: PJ
authors.lastname: Kirkpatrick
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D001930:Brain Injuries / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology; D002408:Catheters, Indwelling; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000293:injuries / Q000503:physiopathology; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D017551:Microdialysis / Q000295:instrumentation*; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D009862:Online Systems; D011379:Prognosis; D019289:Pyruvic Acid / Q000378:metabolism; D015996:Survival Rate
chemical_list: D001786:Blood Glucose; D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid