Brain monitoring devices are used to monitor brain activities of the patients during their conscious and unconscious conditions. Some of the monitors are used to measure the oxygen level and provides accurate, consistent measurements of oxygen in tissue.
Brain monitoring is important in critical clinical scenarios where the extent or evolution of neurologic injury is unknown. Common situations include the comatose state after cardiac arrest, poor grade aneurysmal subarachnoid hemorrhage (aSAH), and severe traumatic brain injury (TBI) et al. The extent of neurologic injury and injury progression are crucial in determining prognosis and guiding intensive care strategies to ameliorate the neurologic injury.
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Brain injury occurs either at the time of a direct insult or subsequently due to changes in the physical and biochemical environment. The ability to measure these changes reliably is of paramount importance in order to tailor the treatment to each individual patient and therefore prevent the onset of secondary brain injury.
Multimodal brain monitoring can be grouped into three categories:
(1)direct signals which are monitored invasively (e.g., intracranial pressure (ICP), tissue oxygenation, microdialysis, parenchymal blood flow, etc.);
(2)variables which may be monitored noninvasively (e.g., transcranial Doppler (TCD) or near infrared spectroscopy (NIRS));
(3)variables describing brain pathophysiology which are not monitored directly but are calculated at the bedside by dedicated computer software. The simplest example is the cerebral perfusion pressure (CPP), which is the difference between the mean arterial blood pressure (MAP) and the ICP , and therefore it is a calculated variable. More sophisticated examples include various indices of vascular reactivity or cerebral autoregulation, brain compensatory reserve, vascular resistances, and brain compartmental compliances.
Optogenetics—Possible Future Monitoring Tool?
Optogenetics is an interesting area of research relatively in its infancy but may have potential clinical applications in brain monitoring. In its simplest permutation, optogenetics involves optically recording changes in membrane potential. Regarding the central nervous system, changes in membrane potential is how action potentials spread down an axon, across a synapse, and activate second order neurons. The ability to see neuronal signal transmission in action implicates that functional circuitry can be characterized. The functional assessment possible through optogenetics is an advantage over current brain monitoring techniques.
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