Chemical monitoring of neurosurgical intensive care patients using intracerebral microdialysis

Abstract

The authors have used intracerebral microdialysis to develop a method for routine monitoring of disturbances in brain energy metabolism in patients in the neurosurgical intensive care unit. Microdialysis was conducted for periods ranging from 2.3 to 8.3 days in four patients (three with severe head injuries and one with severe subarachnoid hemorrhage). Altogether, 4447 chemical analyses from 587 dialysis samples were carried out. Concentrations of the energy-related metabolites lactate, pyruvate, and hypoxanthine were measured, and the lactate:pyruvate ratio was calculated. In addition, the acids glutamate, aspartate, taurine, glutamine, asparagine, and glycine were measured in one patient. The microdialysis data were matched with various clinical events, including intracranial hypertension and therapeutic interventions such as initiation or withdrawal of barbiturates and cerebrospinal fluid drainage. The present study shows that microdialysis can be used for long-term measurement of extracellular fluid (ECF) energy-related metabolites and amino acids in the frontal cortex of neurosurgical patients in a clinical setting. Fluctuations of the measured ECF energy-related substances corresponded to various clinical events presumably involving hypoxia/ischemia. The authors found a 25-fold increase in ECF glutamate, aspartate, and taurine under conditions of energy perturbation, as indicated by high levels of the lactate:pyruvate ratio, lactate, and hypoxanthine. The use of long-term intracerebral microdialysis in patients opens a new field of clinical research, with many possibilities for improving insight into intracranial dynamics in acute cerebral conditions.

Disruptions in the Regulation of Extracellular Glutamate by Neurons and Glia in the Rat Striatum Two Days after Diffuse Brain Injury

“…Clinically, a multitude of studies have detected significant increases in extracellular glutamate levels in the days following injury, with some reports correlating increases in extracellular glutamate with unfavorable outcomes (Bullock et al, 1995Chamoun et al, 2010;Hlatky et al, 2004;Hutchinson et al, 2002;Koura et al, 1998;Persson and Hillered 1992;Reinert et al, 2000;Timofeev et al, 2011;Vespa et al, 1998;Yamamoto et al, 1999). These studies emphasize the significance of glutamate dysregulation in the acute pathophysiology and consequences of TBI.…”

Metabolic Crisis without Brain Ischemia is Common after Traumatic Brain Injury: A Combined Microdialysis and Positron Emission Tomography Study

“…The ratio of lactate to pyruvate has been one of the commonly reported features of microdialysis monitoring since proposed by Hillered (Persson and Hillered, 1992;Valtysson et al, 1998). LPR ratio normally ranges o20 under conditions of uncomplicated metabolism.…”

EBIC-Guidelines for management of severe head injury in adults

“…Clinical studies have shown critically reduced cerebral blood flow [4] following head injury and the presence of ischemia at the tissue level has been further demonstrated in studies where local brain tissue pO2 [20] or jugular oxygen saturation [21] was continuously monitored or microdialysis [17] performed. Although debate exists over the causes of low CBF after head injury, the consequences of secondary ischemic damage are evident, and the adverse influence of further systemic hypoxic and hypotensive insults has been well documented [6,8,14].…”