Extracellular lactate/pyruvate and glutamate changes in patients during per-operative episodes of cerebral ischaemia

Temporary Internal Carotid Artery (ICA) clipping necessary during aneurysm surgery was used as a model to investigate metabolic changes in the human brain during defined episodes of ischaemia.

An observational study using intracerebral monitors: PBO2 (Neurotrend) and microdialysis (CMA, Sweden).

16 patients monitored during complex aneurysm surgery.

Changes in extracellular concentrations of glucose, lactate, and glutamate and lactate/pyruvate ratio (L/P).

Mean age was 55. 10 patients presented with subarachnoid haemorrhage and 6 with mass effect (4 giant). Temporary ICA occlusion was required for dissection (n = 9), intraoperative rupture (n = 5) or aneurysmal thrombectomy (n = 2). The mean total duration was 15 minutes (range 4-52 minutes). No infarcts developed in the monitored regions. Microdialysis was unsuccessful in 3 patients and Neurotrend in 1. Patients were grouped according to the degree and duration of fall in PBO2: minimal brief falls were not associated with microdialysis changes (n = 5). More pronounced falls were associated with increases in L/P (n = 4). Only prolonged occlusions averaging 42 minutes (n = 3) with PBO2 sustained below 1 kPa were associated with rises in glutamate.

Brief temporary ICA occlusion caused an initial increased L/P. Glutamate increases were only seen after occlusion that was prolonged with PBO2 below 1.0 kPa.