Impact of arterial blood homeostasis on cerebral metabolism and incidence of secondary ischemia – Reliability of neurochemical monitoring in patients with severe subarachnoid hemorrhage. A preliminary report

Background. The present analysis of patients with aneurismal subarachnoid hemorrhage addresses the question of how far systemically administered energy substrates or medication during intensive care management can significantly influence cerebral metabolism and must therefore be considered when interpreting the results of cerebral microdialysis. Methods. An intracerebral microdialysis catheter was implanted in 13 patients with aneurysmal subarachnoid hemorrhage after aneurysmatic clipping. The extracellular concentrations of glucose, lactate, glutamate and glycerol were determined by bed-side analysis together with systemic parameters (blood glucose, insulin and noradrenalin administration). To test our setup in patients with severe aneurysmal subarachnoid hemorrhage typical symptoms, the incidence of secondary cerebral ischemia and cerebral vasospasm, were analyzed in relationship to the course of the measured parameters by cerebral microdialysis. Results. The glucose levels in the microdialysate showed a tendency to be dependent on the systemic glucose concentration, as long as cerebral ischemia was not present. Furthermore there were 7 cases of temporary hypoglycemia mainly in patients with cerebral ischemia (n = 5). Administration of noradrenalin and insulin had no influence on the measured systemic and local metabolic parameters or insulin therapy. The same applies to the administration of glucose or fat during the nutritional therapy. Conclusion. The hypothesis that the glucose level in brain tissue is influenced by the serum glucose levels is valid as long as cerebral ischemia is not present. Systemic administration of energy carriers during parenteral nutrition as well as noradrenalin and insulin does not lead to a relevant effect on the results of cerebral microdialysis. Anestezjologia i Ratownictwo 2011; 5: 290-299.