Local cerebral metabolic changes, induced by brain retraction and surgery, during craniotomy, monitored by cerebral microdialysis

摘要

Introduction: Brain retractors applied during brain surgery may inducelocal changes in cerebral perfusion.Cerebral microdialysis (MD) is a recentlyavailable tool for monitoring local cerebral metabolism. In the present study,we evaluated whether MD revealed any changes in local metabolism in thebrain area under the retractor and in the vascular territory of surgery.Patients and Methods: With IRB approval, 38 pts scheduled for large frontaltumor resection received peroperative MD. After opening of the dura, the MDcatheter was inserted into the brain cortex and was perfused at 5l/minenabling analysis (for glucose, lactate, pyruvate, glycerol and glutamate) ofthe dialysates every 5 min. A brain retractor was finally applied for the periodof tumor resection above the area of MD catheter insertion.Results: Insertion of brain retractors resulted in a overall decrease in local glucose,most probably due to a decrease in local perfusion. In all patients, weobserved a shortlasting increase in local glucose after removal of the brainretractor. In most (32 pts) of the 38 patients, there was moreover a furthermarked decrease in glucose during the whole period of brain retraction. In allthese pts, we observed an increase in local lactate concentration. In 14 of these32 patients, we observed an increase in lactate/pyruvate ratio. We observedthat 5 of these 14 episodes went along with a large increase in glycerol. In4 of these patients, no neurosurgical peroperative complications wereobserved, except for one patient. In this patient, the ischemic pattern wasobserved 15 min before a major neurosurgical warning sign (extensive brainbulging) occurred. Retrieval of the retractor resulted in an immediate normalizationof all parameters. Only in the last patient, an extensive increase inglutamate was observed. Postoperative outcome was uneventful for allpatients, except for this last one.Conclusion: Use of MD during routine brain retraction revealed the possiblepresence of pronounced local cerebral ischemia under the retractor.Peroperative use of high flow MD, enabling almost on-line metabolic monitoringof brain tissue under the retractor, might become a valuable warningtool during those neurosurgical procedures necessitating extensive brainretraction.