IntroductionThe optimal blood glucose target following severe traumatic brain injury (TBI) must be defined. Cerebral microdialysis was used to investigate the influence of arterial blood and brain glucose on cerebral glucose, lactate, pyruvate, glutamate, and calculated indices of downstream metabolism.MethodsIn twenty TBI patients, microdialysis catheters inserted in the edematous frontal lobe were dialyzed at 1 μl/min, collecting samples at 60 minute intervals. Occult metabolic alterations were determined by calculating the lactate- pyruvate (L/P), lactate- glucose (L/Glc), and lactate- glutamate (L/Glu) ratios.ResultsBrain glucose was influenced by arterial blood glucose. Elevated L/P and L/Glc were significantly reduced at brain glucose above 1 mM, reaching lowest values at blood and brain glucose levels between 6-9 mM (P < 0.001). Lowest cerebral glutamate was measured at brain glucose 3-5 mM with a significant increase at brain glucose below 3 mM and above 6 mM. While L/Glu was significantly increased at low brain glucose levels, it was significantly decreased at brain glucose above 5 mM (P < 0.001). Insulin administration increased brain glutamate at low brain glucose, but prevented increase in L/Glu.ConclusionsArterial blood glucose levels appear to be optimal at 6-9 mM. While low brain glucose levels below 1 mM are detrimental, elevated brain glucose are to be targeted despite increased brain glutamate at brain glucose >5 mM. Pathogenity of elevated glutamate appears to be relativized by L/Glu and suggests to exclude insulin- induced brain injury.

Symptomatic tracheal stenosis is a rare but significant complication of long-term tracheal intubation and mechanical ventilation. Airway management for tracheal resection in severe tracheal stenosis, especially sequential stenoses, requires multidisciplinary planning. A valuable method of airway management is the insertion of a small-bore, cuffed tracheal tube (Tritubeâ, Ventinova Medical B.V., Eindhoven, The Netherlands) in combination with flow-controlled ventilation. In this case, a patient with tracheal stenosis following prolonged ventilation required resection of the stenosed tissue. A Tritube was placed via a J-tipped guidewire inserted through the working channel of a bronchoscope. Bronchoscopic cuff visualisation along the tube in severe stenosis is impossible because of the outer diameter of the tracheal tube. In this case, we therefore estimated the position of the tube tip based on the distance from the vocal cords to the carina measured on pre-operative computed tomography imaging. During completion of the dorsal tracheal anastomosis, cross field ventilation using a conventional tracheal tube had to be started due to impeded ventilation caused by the Tritube protruding distal to the carina. In severe sequential tracheal stenosis, a small-bore tracheal tube can safely be placed by guidance with a J-tipped guidewire. However, it is important to plan a backup method of ventilation, such as cross field ventilation, prior to commencing a critical procedure.

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