INTERSTITIAL GLYCEROL AS A MARKER FOR MEMBRANE PHOSPHOLIPID DEGRADATION IN THE ACUTELY INJURED HUMAN BRAIN

Objective-Brain interstitial glycerol was studied as a potential marke r for membrane phospholipid degradation in acute human brain injury. M ethods-Glycerol was measured in microdialysis samples from the frontal lobe cortex in four patients in the neurointensive care unit, during the acute phase after severe aneurysmal subarachnoid haemorrhage. Micr odialysis probes were inserted in conjunction with a ventriculostomy u sed for routine intracranial pressure monitoring. Clinical events invo lving hypoxia/ischaemia were diagnosed by neurological signs, neuroima ging (CT and PET), and neurochemical changes of the dialysate-for exam ple, lactate/pyruvate ratios and hypoxanthine concentrations. Results- Altogether 1554 chemical analyses on 518 microdialysis samples were pe rformed. Clinical events involving secondary hypoxia/ischaemia were ge nerally associated with pronounced increases (up to 15-fold) of the di alysate glycerol concentration. In a patient with a stable condition a nd no signs of secondary hypoxia/ischaemia the glycerol concentration remained low. Simultaneous determination of glycerol in arterial plasm a samples showed that the changes in brain interstitial glycerol could not be attributed to systemic changes and an injured blood brain barr ier. Conclusions-This study suggests that membrane phospholipid degrad ation occurs in human cerebral ischaemia. Interstitial glycerol harves ted by microdialysis seems to be a promising tool for monitoring of me mbrane lipolysis in acute brain injury. The marker may be useful for s tudies on cell membrane injury mechanisms mediated by for example, Ca disturbances, excitatory amino acids, and reactive oxygen species; and in the evaluation of new neuroprotective therapeutic strategies.