Surgical Intensive Care, University Hospital Zürich, Rämistrasse 100, 8091 Zürich, Switzerland.
Crit Care. 2010;14(1):R13. doi: 10.1186/cc8869. Epub 2010 Feb 8.
The 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.
In twenty TBI patients, microdialysis catheters inserted in the edematous frontal lobe were dialyzed at 1 microl/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.
Brain 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.
Arterial 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.
严重创伤性脑损伤（TBI）后必须确定最佳血糖目标。本研究采用脑微透析技术研究动脉血血糖和脑葡萄糖对脑葡萄糖、乳酸、丙酮酸、谷氨酸和下游代谢物计算指数的影响。
在 20 例 TBI 患者中，将插入水肿额区的微透析导管以 1 微升/分钟的速度透析，每 60 分钟采集一次样本。通过计算乳酸-丙酮酸（L/P）、乳酸-葡萄糖（L/Glc）和乳酸-谷氨酸（L/Glu）比值来确定隐匿性代谢改变。
脑葡萄糖受动脉血糖影响。脑葡萄糖高于 1mM 时，L/P 和 L/Glc 显著降低，在血糖和脑葡萄糖水平在 6-9mM 之间时达到最低值（P<0.001）。脑葡萄糖 3-5mM 时脑谷氨酸最低，脑葡萄糖低于 3mM 和高于 6mM 时显著增加。L/Glu 在低脑葡萄糖水平显著增加，但在脑葡萄糖高于 5mM 时显著降低（P<0.001）。低脑葡萄糖时胰岛素可增加脑谷氨酸，但可防止 L/Glu 增加。
动脉血糖水平在 6-9mM 时似乎最佳。虽然低于 1mM 的低脑葡萄糖水平有害，但应将升高的脑葡萄糖作为目标，尽管脑葡萄糖>5mM 时脑谷氨酸增加。谷氨酸升高的致病性似乎通过 L/Glu 得到缓和，并提示排除胰岛素诱导的脑损伤。
