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Peter J. Hutchinson, Mark T. O'Connell, Pippa G. Al-Rawi, Lynn B. Maskell, Rupert Kett-White, Arun K. Gupta, Hugh K. Richards, David B. Hutchinson, Peter J. Kirkpatrick, and John D. Pickard

involves implanting a catheter lined with a dialysis membrane into the tissue. 31, 32 This catheter acts as an artificial capillary and is perfused with a physiological solution at ultralow flow rates by using a precision pump. Low-molecular-weight substances (for example, glucose, lactate, pyruvate, and glutamate) diffuse across the membrane into the solution, which is then collected for analysis. There are several variables to be considered when applying microdialysis. These include the length of the microdialysis membrane, the molecular weight capacity of the

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Lennart Persson and Lars Hillered

I ntracerebral microdialysis is a method by which endogenous substances can be retrieved from the extracellular fluid (ECF) of the brain without extraction of water. The method is suitable primarily for measuring changes in the ECF levels of small molecules, including energy-related metabolites (lactate, pyruvate, and purines), amino acids, and other neurotransmitters, and has proved to be useful in experimental neurochemical and neuropharmacological studies on cerebral ischemia and trauma. 3, 6, 28, 30, 42 Changes found in cerebral ischemia and trauma in

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Elisabeth Ronne-Engström, Kristina Giuliana Cesarini, Per Enblad, Göran Hesselager, Niklas Marklund, Pelle Nilsson, Konstantin Salci, Lennart Persson, and Lars Hillered

P atients in the NICU are routinely maintained on continuous physiological monitoring of, for example, blood pressures, ICP, temperature, and blood oxygenation levels. One aim of this practice is to provide indications of ischemia/hypoxia and related metabolic problems that occur in the injured brain. During the past several years methods have been introduced with which to measure the metabolic processes in the brain. One of these is intracerebral microdialysis, a procedure for sampling substances from the brain's interstitial compartment. Microdialysis is

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Lennart Persson, Johann Valtysson, Per Enblad, Per-Erik Wärme, Kristina Cesarini, Anders Lewén, and Lars Hillered

oxygen and lactate, relatively few investigations have been conducted in patients, mainly because of the lack of suitable methods. Intracerebral microdialysis is a new technique by which these mechanisms can be studied in humans. Important chemical substances involved in the development of cerebral ischemia can be retrieved from the extracellular fluid (ECF) of the brain, for example, energy-related substances such as lactate, pyruvate, glucose, and hypoxanthine, and excitatory amino acids such as glutamate and aspartate. Fluctuations in the ECF levels of these

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Andreas W. Unterberg, Oliver W. Sakowitz, Asita S. Sarrafzadeh, Götz Benndorf, and Wolfgang R. Lanksch

. Nowadays, TCD ultrasonography has gained a firm position in the neurovascular laboratory, but there is a common frustration about its ability to prognosticate or confirm the advent of cerebral vasospasm. In a number of studies it was found to be both insufficiently sensitive and specific. 10, 17, 30, 52 Following the pioneering studies of Ungerstedt and Pycock 51 in 1974, cerebral microdialysis was proposed as a diagnostic tool to measure brain metabolism, evolving injury, and insults. Microdialysis allows the sampling of stable low-molecular-weight compounds of the

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Martin Engström, Angelo Polito, Peter Reinstrup, Bertil Romner, Erik Ryding, Urban Ungerstedt, and Carl-Henrik Nordström

brain injuries are characterized by a pronounced regional variability of lesions as disclosed by CT and magnetic resonance imaging or by evaluation of rCBF. 9, 32 Global methods of monitoring (monitoring of intracranial pressure and jugular venous oxygen saturation) usually will not reveal the consequences of secondary adverse events until large parts of the brain are affected. On the other hand, local techniques of monitoring (for example, microdialysis and monitoring of brain tissue PO 2 ) would be expected to provide little or late information if the probes are

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Itzhak Fried, Charles L. Wilson, Nigel T. Maidment, Jerome Engel Jr., Eric Behnke, Tony A. Fields, Katherine A. Macdonald, Jack W. Morrow, and Larry Ackerson

records intracranial EEG readings while at the same time enabling recording of the activity of single neurons and sampling of the extracellular fluid by cerebral microdialysis. We demonstrate the feasibility of using this technique to characterize changes in the neuronal parenchyma of neurosurgical patients during seizures and other behavioral states. Monitoring Technique Patient Population Between January 1993 and March 1998, 42 patients (21 males and 21 females; mean age 33.2 years; range 12–50 years) with pharmacologically intractable seizures underwent implantation

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Roukoz Chamoun, Dima Suki, Shankar P. Gopinath, J. Clay Goodman, and Claudia Robertson

. “Excitotoxicity” is the term used to describe the neurotoxicity induced by glutamate or glutamate receptor agonists. The overactivation of glutamate receptors has been shown to induce an excessive influx of Na + and Ca 2+ , mitochondrial dysfunction, and dendritic morphological changes ultimately leading to cell death by either rapid necrosis or delayed apoptosis. 1 , 4 , 15 In recent years, there has been increased interest in the role of glutamate in neurotrauma. Animal as well as a small number of human studies utilizing microdialysis have documented a marked elevation in

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Jan Hillman, Oscar Åneman, Mikael Persson, Chris Andersson, Charlotte Dabrosin, and Pekka Mellergård

I n recent years microdialysis has become a routine means of studying intrinsic brain biochemistry. 1 , 2 , 17 As previously reported it is now possible to extend the use of this method to explore previously unknown territory in protein chemistry in the human brain. Thus, microdialysis catheters with a high-molecular-weight cutoff can be reliably used for monitoring relevant biochemical markers such as glutamate levels, glycerol levels, lactate/pyruvate ratio, and others while at the same time allowing sampling of proteins and other macromolecules. 5 , 6

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Mette K. Schulz, Lars Peter Wang, Mogens Tange, and Per Bjerre

within this time frame, ischemic neurons will degenerate and cerebral infarction will occur. Monitoring techniques that can assist in the detection of cerebral ischemia at earlier stages, preferably before clinical symptoms occur, may possibly lead to earlier treatment and fewer resulting neurological deficits. Cerebral microdialysis monitoring has been used extensively in basic research and has proved useful in the detection of metabolic perturbations of CNS tissue. 1, 19 During the last few years this technique has been used in clinical settings to monitor