Awareness During Blended Anaesthesia
Condition: Consciousness, Level Depressed; Intraoperative Awareness
MeSH terms: Consciousness Disorders; Intraoperative Awareness
Study type: Observational

Summary: 
      the aim of this study was to estimate the relations between Bispectral Index values and
      explicit or implicit memory or dreams during two different minimal alveolar concentration
      (MAC) of sevoflurane in patients undergoing blended anaesthesia for major abdominal surgery
      and ,in this way, estimate the possibility to reduce, in presence of a deep analgesia, like
      epidural analgesia, the requirement of halogenated volatile anesthetics.
    

Detailed description: 
      The decreased responsiveness to stimulation defines depth of anaesthesia which is a balance
      between effects of anaesthetic drugs and surgical stimulations.

      Awareness is a rare occurrence with an incidence of 0,1-0,2 % , defined as postoperative
      recall of events occurring during general anaesthesia.

      Different stages of awareness should be defined: conscious awareness with explicit recalls
      with pain; conscious awareness with explicit recalls without pain; conscious awareness
      without explicit recall and possible implicit recall; subconscious awareness without explicit
      recall and possible implicit recall; no awareness .

      This memory can be traumatic and may result in developing a chronic posttraumatic stress
      disorder (PTSD) in more than half of subjects .

      Some cases of awareness are caused by inadequate anesthesia and are potentially avoidable
      through the assessment of depth of hypnosis by an intraoperative monitoring , especially when
      muscle relaxants are used.

      The Bispectral Index ( BIS ), one of the devices designed to monitor brain activity, through
      a proprietary algorithm , elaborates EEG and provides an index of hypnotic level.

      Thus, several variables, derived from EEG time and frequency domain, are combined into a
      single index indicating the patient's level of consciousness.

      A range between 40 and 60, during surgery, permits both to prevent awareness and to reduce
      the dose of anesthetic agent administered .

      In this study, during major abdominal surgery, an epidural analgesia was performed to
      suppress afferent noxious stimuli and combined with a general anaesthesia based on
      halogenates.

      Thereby the aim of this study was to estimate the relations between Bispectral Index values
      and explicit or implicit memory or dreams during two different minimal alveolar concentration
      (MAC) of sevoflurane in patients undergoing blended anaesthesia for major abdominal surgery
      and ,in this way, estimate the possibility to reduce, in presence of a deep analgesia, like
      epidural analgesia, the requirement of halogenated volatile anesthetics.
    

Intervention name(s): monitor for depth of hypnosis
Intervention type(s): Device
Intervention description(s): evaluation of depth of hypnosis
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Observational model: Case-Only
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        patients undergoing elective major abdominal surgery
      
Keywords: Cerebral State Index Monitor