Is cerebral microdialysis a clinical tool?
- PDF / 64,500 Bytes
- 2 Pages / 595.276 x 790.866 pts Page_size
- 27 Downloads / 215 Views
EDITORIAL
Is cerebral microdialysis a clinical tool? Adel Helmy & Peter Hutchinson
Received: 29 November 2012 / Accepted: 5 December 2012 / Published online: 21 December 2012 # Springer-Verlag Wien 2012
Cerebral microdialysis has been utilised in a wide range of contexts for more than 20 years [5]. Nevertheless, despite this longstanding experience and a wealth of literature, it has not taken off as a routine clinical tool in many units. Bossers et al. provide a systematic review of the literature on cerebral microdialysis, specifically in the context of intraoperative monitoring. Their thoughtful and thorough review highlights the poor methodological quality of all current studies in this field when assessed against the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) criteria [6]. This lack of studies that meet the conventional criteria used in evidence-based medicine grading systems reflects the pragmatic difficulties in utilising microdialysis. While proponents of the technique will point to anecdotal evidence for early identification of deranged physiology allowing early institution of treatment, this has been difficult to demonstrate on a population basis in systematic studies. Microdialysis is unique in its ability to dynamically sample the brain extracellular space and provide a direct tissue metric of metabolism [2]. The commonest mediators that are assayed are lactate, pyruvate, glucose, glutamate and glycerol. These small molecules are freely permeable from within the cytosol into the extracellular space where they can cross into the microdialysis catheter. Samples are collected intermittently and assayed at the bedside. The lactate/pyruvate ratio is a surrogate for the cellular redox state. Glucose is a direct measure of substrate delivery to the brain tissue, and glycerol is a marker of cell membrane breakdown. As well as its use in intraoperative monitoring, cerebral microdialysis is also commonly used in the intensive care setting, usually with hourly sampling, as part of multimodality A. Helmy : P. Hutchinson (*) Academic Neurosurgery Unit, Department of Clinical Neurosciences, University of Cambridge, Box 167 Addenbrooks Hospital, Cambridge CB2-2QQ, UK e-mail: [email protected]
monitoring of intubated and ventilated neurosurgical patients: typically in subarachnoid haemorrhage or traumatic brain injury [4]. Relationships between brain chemistry and clinical outcome have been established [3]. The key difference between intraoperative and intensive care use of microdialysis is the time course over which derangements in physiology need to be identified. Surgical manipulations may result in abrupt changes (e.g. over minutes) in tissue physiology as compared with brain swelling following TBI or vasospasm in SAH. Intraoperative monitoring therefore requires modification of the microdialysis methodology with a higher pump flow rate to allow more frequent sampling, as well as rapid or online assay techniques. Microdialysis is a focal monitoring technique, sampling the immediate vicinity of the ca
Data Loading...
