Relationship Between Bispectral Index (BIS) and Spectral Entropy (SpEn) During Desflurane Anaesthesia
Condition: Intraoperative Awareness
MeSH terms: Intraoperative Awareness
Study type: Observational

Summary: 
      The aim of this study was to estimate the relationship between BIS and Spectral Entropy
      values and any explicit or implicit memory or dreams recall during desflurane anaesthesia.
    

Detailed description: 
      During the last decade, an increasing number of monitor systems were developed designed to
      assess the depth of anesthesia.

      Awareness is a rare occurrence of explicit recalls during anaesthesia with an incidence of
      0,18% and the use of cerebral monitoring prevents about 50% of these events.

      Different stages of awareness should be defined and implicit memorization is subconscious
      awareness without explicit recall and possible implicit recall with an incidence greater than
      awareness.

      To assess implicit recalls, a large number of test can be used, for example the "word stem
      completation test" and the "free recall association test". These result easy to use and
      reliable in detect implicit memory.

      Bispectral Index (BIS) and Spectral Entropy (SpEn) has been proposed, in recent years, as
      electroencephalographic monitors of anaesthesia depth.

      The bispectral index is a monitor of anaesthetic depth approved by the Food and Drug
      Administration in the USA. The BIS monitor reports a dimensionless number between 0 (complete
      EEG inactivity) and 100 (awake state); BIS values from 40 to 60 are thought to be suitable
      for general anaesthesia. Spectral Entropy acquires the electroencephalograph (EEG) and
      frontal electromyography (FEMG) signals which are processed into three parameters: State
      Entropy (SE), Response Entropy (RE) and Burst Suppression Ratio (BSR).

      SE is computed over the EEG dominant part of the spectrum (0.8-32 Hz), and therefore
      primarily should reflect the cortical state of the patient and results useful to assess
      hypnotic effects of drugs .

      RE is computed over a frequency range from 0.8 to47 Hz. It includes both the EEG-dominant and
      EMG-dominant part of the spectrum . The SE and RE values below 60 correlate with a low
      probability of consciousness. Also Bispectral Index provides BRS, an evaluation of burst
      suppression in which cerebral activity results suppressed.

      BIS and Spectral Entropy are intended to decrease the risk of intraoperative awareness and to
      enable the anesthetist to reduce risk of the under- and overdosing of anesthetic agents and
      to ensure faster and more predictable wake-up and extubation.

      Previous studies result contrasting in the correlation between these devices with lack in
      evaluation of implicit memory.

      The aim of this study was to estimate the relationship between BIS and Spectral Entropy
      values and any explicit or implicit memory or dreams recall during desflurane anaesthesia.
    

Intervention name(s): BIS and Spectral Entropy
Intervention type(s): Device
Intervention description(s): The aim of the study was investigated the effectiveness of Spectral Entropy and BIS in avoiding awareness
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        female patients, aged 30-60 years , scheduled for minor elective surgery lasts between 1
        and 3 hours were enrolled.
      
Keywords: awareness