Use of bispectral electroencephalogram monitoring to assess neurologic status in unsedated, critically ill patients

ObjectiveTo test whether spectral indices derived from the electroencephalogram (EEG), and especially the bispectral index (BIS), can be used as measures of neurologic status in unsedated, critically ill patients. DesignProspective, observational study. SettingMedical intensive care unit (ICU) of a university-affiliated teaching hospital. PatientsThirty-one awake, unsedated critically ill adults were assessed in 108 separate sessions. Measurements and Main Results In each session, severity of illness was assessed by the Acute Physiology and Chronic Health Evaluation (APACHE III). The APACHE III Acute Physiology Score was used to quantify the degree of physiologic derangement. Neurologic function was assessed using the APACHE III Neurologic Score, the Glasgow Coma Scale, the Reaction Level Scale, and the Modified Ramsay Sedation Scale. All indices were plotted against various spectral parameters of the EEG, including BIS, an empirical index of EEG activity that is scaled from 0 to 100. BIS was significantly (p < .05) correlated with neurologic score regardless of scoring system used and was more strongly correlated than any other EEG spectral parameter. Better neurologic function was associated with higher values of BIS. In multivariate analysis, the combination of BIS and relative power in the theta band of the EEG accounted for 38% of the variability in the Glasgow Coma Scale. ConclusionsBIS provides a reliable index of neurologic status in awake, unsedated, critically ill patients. Further research is needed to determine whether the effects of neurologic status and pharmacologic sedation upon EEG are additive, whether BIS can be used to assess pharmacologic sedation in the critically ill patient population, and whether such objective measures of neurologic status have prognostic value.

[1]  Paul F. White,et al.  Electroencephalogram Bispectral Analysis Predicts the Depth of Midazolam‐induced Sedation , 1996, Anesthesiology.

[2]  G. Schackert,et al.  Electroencephalogram silence ratio for early outcome prognosis in severe head trauma , 2000, Critical care medicine.

[3]  M. Ramsay,et al.  Controlled Sedation with Alphaxalone-Alphadolone , 1974, British medical journal.

[4]  Y. Archibald,et al.  The Electroencephalogram in Sepsis‐Associated Encephalopathy , 1992, Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society.

[5]  S L Shafer,et al.  A comparison of spectral edge, delta power, and bispectral index as EEG measures of alfentanil, propofol, and midazolam drug effect , 1997, Clinical pharmacology and therapeutics.

[6]  G. Fraser,et al.  Assessing sedation during intensive care unit mechanical ventilation with the Bispectral Index and the Sedation-Agitation Scale. , 1999, Critical care medicine.

[7]  P. Sebel,et al.  Recovery of Consciousness after Thiopental or Propofol: Bispectral Index and the Isolated Forearm Technique , 1997, Anesthesiology.

[8]  B. Jennett,et al.  Assessment of coma and impaired consciousness. A practical scale. , 1974, Lancet.

[9]  T. Clemmer,et al.  Descriptive analysis of critical care units in the United States , 1992, Critical care medicine.

[10]  T. Bleck,et al.  Neurologic complications of critical medical illnesses , 1993, Critical care medicine.

[11]  T. Sakai,et al.  The effect of ketamine on clinical endpoints of hypnosis and EEG variables during propofol infusion , 1999, Acta anaesthesiologica Scandinavica.

[12]  P Manberg,et al.  Bispectral Analysis Measures Sedation and Memory Effects of Propofol, Midazolam, Isoflurane, and Alfentanil in Healthy Volunteers , 1997, Anesthesiology.

[13]  B. Shapiro.  Bispectral Index: better information for sedation in the intensive care unit? , 1999, Critical care medicine.

[14]  J. van Egmond,et al.  Evaluation of the electroencephalographic bispectral index during fentanyl-midazolam anaesthesia for cardiac surgery. Does it predict haemodynamic responses during endotracheal intubation and sternotomy? , 1999, European journal of anaesthesiology.

[15]  M. Struys,et al.  Use of continuous bispectral EEG monitoring to assess depth of sedation in ICU patients , 1998, Intensive Care Medicine.

[16]  J. Dasta,et al.  Patterns of prescribing and administering drugs for agitation and pain in patients in a surgical intensive care unit , 1994, Critical care medicine.

[17]  J. Hansen-Flaschen,et al.  Use of sedating drugs and neuromuscular blocking agents in patients requiring mechanical ventilation for respiratory failure. A national survey. , 1991, JAMA.

[18]  C. Bolton,et al.  Prediction of outcome in patients with anoxic coma: a clinical and electrophysiologic study. , 1996, Critical care medicine.

[19]  O. Markand.  Electroencephalography in Diffuse Encephalopathies , 1984, Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society.

[20]  J. Jakobsson,et al.  Nitrous oxide does not alter bispectral index: study with nitrous oxide as sole agent and as an adjunct to i.v. anaesthesia. , 1999, British journal of anaesthesia.

[21]  J. Sleigh,et al.  The bispectral index: a measure of depth of sleep? , 1999, Anesthesia and analgesia.

[22]  W. Knaus,et al.  The APACHE III prognostic system. Risk prediction of hospital mortality for critically ill hospitalized adults. , 1991, Chest.

[23]  J. Starmark,et al.  The Reaction Level Scale (RLS85). Manual and guidelines. , 1988, Acta neurochirurgica.

[24]  D. C. Davies,et al.  Pathophysiology of septic encephalopathy: A review , 2000, Critical care medicine.