Bispectral Index (BIS) Monitoring

OVERVIEW

  • BIS monitor was developed by Aspect Medical Systems
  • BIS = bispectral index
  • other ‘depth of anaesthesia’ monitors exist (e.g. Entropy)

USES

  • used to monitor the depth of sedation or anaesthesia

DESCRIPTION

  • Sensor – consists of disposable, wet gel electrodes
  • Cable
  • Monitoring module – interfaces with anaesthesia machine or monitoring systems

METHOD OF USE

  •  best describe as a monitor of the depth of the hypnotic component of anaesthesia
  • frontoparietal application of electrodes
  • the monitor generates a number
    — 100 = normal cortical activity (maximum alertness)
    — 0 = cortical electrical silence
  • an EMG signal and Signal Quality Index is displayed as well as a single channel EEG

The BIS algorithm

  • EEG data recorded from healthy adults who underwent repeated transitions between consciousness and unconsciousness using different anaesthetic regimens
  • analysis identified those features of EEG recordings that best correlated with clinical depth of sedation/anaesthesia – in essence, the complexity of the EEG reduces with increasing depth of anaesthesia
  • these were fitted to a model by multivariate logistic regression
  • the resulting algorithm generates a bispectral index (BIS)
  • it has been validated on healthy and now other patient populations

COMPLICATIONS

Benefits

  • BIS < 60 results in very low levels of post-op recall
  • shown to lower anaesthetic consumption
  • slightly quicker awaking
  • safe with diathermy and defibrillation

Problems

  • opioids produce changes in depth of consciousness not discernible by BIS
  • BIS is not able to predict movement in response to surgical stimulation
  • BIS values display incredible variability
  • not helpful when using N2O or ketamine
  • cannot use in children under 5

EVIDENCE IN ICU

  • low BIS associated with increasing delirium -> this can increase morbidity and mortality
  • currently no high level evidence to guide use in ICU
  • possible role for patients who are paralysed in the titration of adequate amounts of sedation and analgesia
  • may have an emerging role in out-of-hospital cardiac arrest

CCC Neurocritical Care Series

Journal articles

  • Ball J. How useful is the bispectral index in the management of ICU patients? Minerva Anestesiol. 2002 Apr;68(4):248-51. PMID: 12024092.
  • Bennett C, Voss LJ, Barnard JP, Sleigh JW. Practical use of the raw electroencephalogram waveform during general anesthesia: the art and science.Anesth Analg. 2009 Aug;109(2):539-50. PMID: 19608830
  • Bigham C, Bigham S, Jones C. Does the bispectral index monitor have a role in intensive care? JICS 2012 Oct;13(4):314-319

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the  Clinician Educator Incubator programme, and a CICM First Part Examiner.

He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.

His one great achievement is being the father of three amazing children.

On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

2 Comments

  1. Good afternoon, I have read the instructions for the BIS system in the UCI.
    I work as a neurologist, I am interested in expanding the information regarding the implementation in patients with convulsive status for control and monitoring, who receive deep sedation schemes with the different known antiepileptics.
    I would like to ask you what experience there is in patients with this pathology and the reliability of the system to apply it as an index of response to the proposed treatment in patients.
    Thank you so much

    Fernando González Trujillo

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