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Hyperglycemia and Brain Tissue pH after Traumatic Brain Injury

Zygun, David A. M.D., M.Sc; Steiner, Luzius A. M.D., D.E.A.A; Johnston, Andrew J. M.A., F.R.C.A; Hutchinson, Peter J. B.Sc., Ph.D., F.R.C.S.(SN); Al-Rawi, Pippa G. B.Sc; Chatfield, Dot B.Sc. Hons; Kirkpatrick, Peter J. M.S., F.R.C.S.(SN); Menon, David K. M.D., Ph.D; Gupta, Arun K. M.A., F.R.C.A

doi: 10.1227/01.NEU.0000137658.14906.E4
Clinical Studies

OBJECTIVE: Hyperglycemia occurring after head injury is associated with poor neurological outcome. We tested the hypothesis that blood glucose levels are associated with brain tissue pH (pHb) and that the correction of hyperglycemia would result in an improvement in pHb.

METHODS: This is a retrospective analysis of a prospectively collected database. Thirty-four patients in a tertiary care neuroscience critical care unit with major traumatic brain injury underwent pHb monitoring.

RESULTS: A total of 428 glucose measurements were recorded during pHb monitoring. Mean glucose level was 7.1 mmol/L (range, 2.8–21.7 mmol/L) and median (interquartile range) pHb was 7.11 mmol/L (7.00–7.19 mmol/L). To account for the correlated, unbalanced nature of the data, a linear generalized estimating equation model was created. This model predicted that for each 1 mmol/L increase in blood glucose, pHb changed by −0.011 mmol/L (95% confidence interval, −0.016 to −0.005 mmol/L; P < 0.001). This relationship remained significant in a multivariable model that included cerebral perfusion pressure, brain tissue oxygen and carbon dioxide tension, and brain temperature. Twenty-one episodes of significant hyperglycemia (≥11.1 mmol/L) treated with intravenous insulin were identified. Insulin therapy significantly reduced blood glucose concentration from a median (interquartile range) of 11.9 mmol/L (range, 11.4–13.6 mmol/L) to 8.8 mmol/L (range, 7.3–9.6 mmol/L; P < 0.001). Baseline pHb was not significantly different from pHb associated with the subsequent glucose reading of less than 11.1 mmol/L (P = 0.29), but there was a suggestion of improvement if the change in blood glucose was large.

CONCLUSION: Blood glucose is associated with brain tissue acidosis in patients with major head injury. Prospective studies are required to confirm these results and to determine whether treatment of hyperglycemia improves outcome.

Neuroscience Critical Care Unit and Department of Anaesthesia, University of Cambridge, Cambridge, England, and Departments of Critical Care Medicine and Clinical Neuroscience, University of Calgary, Calgary, Alberta, Canada (Zygun)

Department of Anaesthesia, University of Cambridge, and Academic Neurosurgery, Addenbrooke’s Hospital, Cambridge, England (Steiner)

Department of Anaesthesia, University of Cambridge, Cambridge, England (Johnston)

Academic Neurosurgery, Addenbrooke’s Hospital, Cambridge, England (Hutchinson)

Academic Neurosurgery, Addenbrooke’s Hospital, Cambridge, England (Al-Rawi)

Department of Anaesthesia, University of Cambridge, Cambridge, England (Chatfield)

Academic Neurosurgery, Addenbrooke’s Hospital, Cambridge, England (Kirkpatrick)

Neuroscience Critical Care Unit, and Department of Anaesthesia, University of Cambridge, Cambridge, England (Menon)

Neuroscience Critical Care Unit, and Department of Anaesthesia, University of Cambridge, Cambridge, England (Gupta)

Reprint requests: David Zygun, M.D.,Departments of Critical Care Medicine and Clinical Neuroscience, University of Calgary, Calgary Health Region, Room EG23, Foothills Medical Centre, 1403 29th Street NW, Calgary, Alberta, Canada T2N 2T9. Email: david.zygun@calgaryhealthregion.ca

Received, November 4, 2003.

Accepted, March 26, 2004.

Copyright © by the Congress of Neurological Surgeons