Extracellular amino acid changes in patients during reversible cerebral ischaemia.

This study investigated the changes in extracellular chemistry during reversible human cerebral ischaemia. Delayed analysis was performed on samples taken from a subgroup of patients during aneurysm surgery previously reported. Frozen microdialysis samples from 14 patients who had all undergone temporary clipping of the ipsilateral internal carotid artery (ICA) were analysed for another 15 amino acids with HPLC and for glycerol with CMA-600.

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

Objective: 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.

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

Subjects: 16 patients monitored during complex aneurysm surgery.

Clinical cerebral microdialysis--determining the true extracellular concentration.

Current monitoring of the cerebral extracellular chemistry of neurosurgical patients using microdialysis does not provide the true extracellular concentration because full equilibration across the membrane is not achieved. By varying the flow rate and extrapolating to zero flow, the relative recovery i.e.

Effects of variation in cerebral haemodynamics during aneurysm surgery on brain tissue oxygen and metabolism.

Objectives: This study explores the sensitivities of multiparameter tissue gas sensors and microdialysis to variations in blood pressure, CSF drainage and to well-defined periods of ischaemia accompanying aneurysm surgery, and their predictive value for infarction.

Methods: A Neurotrend sensor [brain tissue partial pressure of oxygen (PBO2), carbon dioxide (PBCO2), brain pH (pHB) and temperature] and microdialysis catheter were inserted into the appropriate vascular territory prior to craniotomy.

Results: Baseline data showed a clear correlation between PBO2 and mean arterial pressure (MAP) below a threshold of 80 mmHg.