Intracerebral microdialysis in severe brain trauma: the importance of catheter location.
OBJECTIVE
Intracerebral microdialysis has attracted increasing interest as a monitoring technique during neurological/neurosurgical intensive care. The purpose of this study was to compare cerebral energy metabolism, an indicator of secondary excitotoxic injury and cell membrane degradation close to focal traumatic lesions ("penumbra zones") and in remote and apparently intact brain regions of the ipsilateral and contralateral hemispheres.


METHODS
The study included 22 consecutive patients with a mean age 44 +/- 17 years and an estimated postresuscitation Glasgow Coma Scale motor score less than 5. Altogether 40 microdialysis catheters with radiopaque tips were inserted. Two catheters could not be localized on postoperative computerized tomography (CT) scans and were excluded from the analysis. The perfusates were analyzed at the patient's bedside for levels of glucose, pyruvate, lactate, glutamate, and glycerol with the aid of a CMA 600 Analyzer. The positions of eight (22%) of the 36 catheters were reclassified after a review of findings on CT scans. Except for pyruvate the values of all biochemical variables and the lactate/pyruvate (L/P) ratio were significantly different in the penumbra zone when compared with mean values found in "normal" tissue ipsilateral to the parenchymal damage and in contralateral normal tissue (p < 0.001). In the penumbra zone a slow normalization of the L/P ratio and levels of glutamate and glycerol were observed. In normal tissue these parameters remained within normal limits.


CONCLUSIONS
Data obtained from intracerebral microdialysis can be correctly interpreted only if the locations of the catheters as they relate to focal brain lesions are visualized. A "biochemical penumbra zone" surrounds focal traumatic brain lesions. It remains to be proven whether therapeutic interventions can protect the penumbra zone from permanent damage.
Engström
Martin
M
Department of Anesthesia and Intensive Care, Lund University Hospital, Sweden.
Polito
Angelo
A
Reinstrup
Peter
P
Romner
Bertil
B
Ryding
Erik
E
Ungerstedt
Urban
U
Nordström
Carl-Henrik
CH
D000328:Adult; D000368:Aged; D001930:Brain Injuries / Q000175:diagnosis*; D002408:Catheters, Indwelling; D002648:Child; D005260:Female; D005947:Glucose; D006801:Humans; D019344:Lactic Acid / Q000032:analysis; D008297:Male; D017551:Microdialysis / Q000379:methods*; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D019289:Pyruvic Acid / Q000032:analysis
D019344:Lactic Acid; D019289:Pyruvic Acid; D005947:Glucose