Bedside monitoring of cerebral energy metabolism using intracerebral microdialysis during neuro intensive care

Abstract: In clinical situations with raised intracranial pressure (ICP) and impending insufficient cerebral blood flow (ischaemia), bedside information about energy metabolism in the brain would be helpful. Microdialysis is a technique that makes it possible to monitor the interstitial concentrations of various compounds in an organ. Intracerebral microdialysis with bedside analysis of metabolites related to energy metabolism might therefore be a valuable tool to elucidate important aspects on biochemical events during neuro intensive care and ultimately a tool for supervision of the neurologically critically ill patient. In order to estimate the consequences for cerebral energy metabolism during a controlled reduction of cerebral perfusion pressure as in the “Lund concept”, we have used clinical intracerebral microdialysis with multiple catheters as a routine in patients with severe head injuries. Baseline levels for different metabolites under physiological conditions are provided. Changes of cerebral energy metabolism in different parts of the brain during an intractable increase of ICP are described. Treatment according to the “Lund concept” does not interfere with cerebral energy metabolism. A ”biochemical penumbra zone” with increased vulnerability to secondary insults surrounds focal traumatic lesions. Transient hyperglycaemia (<15 mmol/L) does not affect cerebral energy metabolism if oxygen delivery is sufficient. Intracerebral microdialysis with bedside biochemical analyses can be performed as a routine procedure during neuro intensive care. The technique is useful both for analysing groups of patients and for supervision of the individual patient in the neuro intensive care.