Chapter 7.3 Neurochemical monitoring in neurointensive care using intracerebral microdialysis

Abstract

Abstract For more than a decade, bedside cerebral microdialysis (C-MD) has been commercially available for biochemical monitoring of brain-injured patients. This has led to defined normal biochemical range values, which are not yet fully validated for clinical use under pathological conditions. We have carefully reviewed the literature regarding the threshold levels proposed for various biochemical markers detected by microdialysis in stroke, brain trauma, subarachnoid hemorrhage and brain death. We also considered studies comparing C-MD data with PET-scan findings. In general, the results obtained by C-MD are in accordance with those obtained with PET-scan in brain-injured patients. However, we found very few papers where the absolute biochemical values in microdialysates were significantly correlated with the clinical outcome, except for long-lasting very low glucose levels that were strongly related to brain death. For a reliable interpretation of C-MD values, the present review shows the importance of taking into account both the implantation site of the probe and the time resolution of the dialysis system. The changes observed through C-MD monitoring after therapeutic approaches such as modifying CPP, hyperglycemia, insulin therapy, hypo-, and hyperthermia for different brain injuries are also considered in this review. However, the interest to treat patients on the basis of dialysate biochemical data has not yet been demonstrated in appropriate multicentric clinical trials.