Dual microdialysis probe monitoring for patients with traumatic brain injury

Background In vivo microdialysis can be used to examine the focal metabolism by measuring the extracellular concentration of amino acids and other biochemicals in the focal brain tissue in which the probe is placed. We report two patients with traumatic brain injury who underwent placement of dual microdialysis probes. Materials and methods One probe was placed in the penumbra zone and another in a region remote to the injury. Multiple measurements of several biochemical's were made.

Findings In the first case, a 54-year-old man with right acute subdural hematoma and right fronto-temporal contusion was monitored. Quantitative analysis of in vivo microdialysis was performed. While the extracellular concentration of lactate and glycerol were higher in the penumbra zone than in the region remote to the injury, glutamate remained lower in the penumbra zone than in the remote region. In the second case, dual microdialysis probes were placed in a 56-year-old woman with left acute subdural hematoma and left fronto-temporal lobe contusion. Also in this case, the extracellular glutamate remained lower in the penumbra zone than in the remote region.

Conclusions The reason why the extracellular glutamate value remained lower in the penumbra zone than in the remote region is unclear. The position of each microdialysis probe was ensured by CT scan after the operation. It is important to be aware of the limitations of performing microdialysis in brain injured patients with a single probe.