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Role of bedside electroencephalogram in intensive care: a critical review

Electroencephalogram (EEG) is an appropriate monitoring tool in intensive care because it is linked to cerebral metabolism, is sensitive to ischaemia/hypoxia, can detect neuronal dysfunction at a reversible stage and is the best method to detect seizure activity. Scientific data have proved utility of continuous EEG monitoring in intensive care [1, 2]. But there is a paucity of data relating to single recordings of EEG especially in general ICUs.

A retrospective chart review of patients who had bedside EEG in a medical–surgical ICU was done. Data were collected with a focus on: indication for requesting EEG, technical difficulties during the study, the report and its influence on subsequent clinical management.

Forty-two charts were reviewed. The indications were: evaluation of persistent comatose state (n = 27), to diagnose/exclude seizure activity and nonconvulsive status epilepsy (n = 12), and as an adjunct to support clinical diagnosis of suspected brain death prior to formal testing (n = 3). Movement artifacts led to technical difficulty in four studies.

EEG confirmed: moderate to severe nonspecific brain dysfunction as the cause for persistent comatose state by the presence of either diffuse slowing with theta/delta activity, absence of cerebral activity, continuous rhythmic and semi rhythmic lateralized/bilateral epileptiform discharges, burst suppression pattern or continuous bilateral slow U-shaped waves; anoxic brain damage by absence of changes in electrical signals following external application of noxious stimuli; and seizure activity by epileptiform discharges. Twelve reports stated that use of sedation interfered with EEG interpretation.

The following clinical decisions were made based on the EEG report in conjunction with clinical findings: initiating withdrawal of life support or 'do-not-resuscitate orders' in patients diagnosed to have hypoxic ischaemic encephalopathy (n = 15); adding/escalating or stopping antiseizure drugs based on the presence/absence of seizure activity (n = 12); and continuing supportive care in comatose patients diagnosed to have metabolic encephalopathy/prolonged sedation effect as the cause for coma (n = 8).

Based on these results it can be concluded that, despite limitations such as motion artifacts and influence of sedation on electrical signals, EEG impacts on clinical decision-making processes in critical care. Hence it is beneficial, and more widespread use would improve its diagnostic potential.

References

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    Hirsch LJ, Kull LL: Am J Electroneurodiagnostic Technol. 2004, 44: 137-158.

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    Newton DEF: Electrophysiological monitoring of general intensive care patients. Intensive Care Med 1999, 25: 350-352. 10.1007/s001340050856

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Ramachandran, R.J., Hargreaves, C. & Sinha, S. Role of bedside electroencephalogram in intensive care: a critical review. Crit Care 11, P336 (2007). https://doi.org/10.1186/cc5496

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Keywords

  • Brain Death
  • Seizure Activity
  • Epileptiform Discharge
  • Burst Suppression
  • General ICUs