• A S Sarrafzadeh, K L Kiening, T A Callsen, and A W Unterberg.
• Department of Neurosurgery, Charité Virchow Medical Center, Humboldt University of Berlin, Germany. asita.sarrafzadeh@charite.de
• Br J Neurosurg. 2003 Aug 1; 17 (4): 340-6.

AbstractThe objective was to measure metabolic changes monitored by bedside microdialysis during impending and manifest hypoxia in traumatic brain injury. In 41 patients, a PtiO2-catheter (Licox; 1/min) was placed into non-lesioned frontal white matter together with a microdialysis catheter (CMA, hourly). Data were analysed for identification of episodes of impending (PtiO2 < 10 - 15 mmHg > 5 min) and manifest cerebral hypoxia (PtiO2 < 10 mmHg, > 5 min). In 69% of patients hypoxic episodes occurred, most frequently associated with hyperventilation (p < 0.001). During impending hypoxia, glutamate was increased (p = 0.03), while the energy metabolites remained stable. Manifest hypoxia was reflected by significant increases of glutamate (p = 0.007) and lactate (p = 0.044), but normal lactate-pyruvate ratios. We conclude that hyperventilation had a potential adverse effect on cerebral metabolism and was most frequently associated with cerebral hypoxia. A PtiO2 < 10 mmHg can induce metabolic changes with increase of glutamate and lactate. The presence of anaerobic cerebral metabolism probably depends on duration and severity of the hypoxic episode.

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