The Influence of Age on Bispectral Index Associated With Propofol-induced Sedation
Status:
Completed
Trial end date:
2013-11-01
Target enrollment:
Participant gender:
Summary
The bispectral index (BIS) is commonly used in anesthesia to evaluate the depth of sedation.
Numerous studies in adults have shown good correlation between bispectral index values and
depth of sedation regardless of the hypnotic drug used. Requirements of intravenous and
inhalational hypnotic agents to suppress consciousness decrease with age. A study showed that
the loss of consciousness (LOC) was obtained with lower concentrations of sevoflurane in
elderly than in young adults, but at identical BIS values, so that BIS would predict depth of
sedation better than drug monitoring. This result incited the use of bispectral index
monitoring to overcome the significant pharmacological variability, especially in elderly.
Nevertheless, another research with a comparable methodology during propofol-induced
anaesthesia provided higher BIS values at LOC in elderly compared to younger patients. In
these two trials, LOC was defined differently: either by absence of verbal response
corresponding to loss of eyelash reflex (LOER) or by absence of response to prodding [(OAA/S)
<2)]. Otherwise electromyographic activity (EMG) was not taken in account. As high EMG level
(greater than 50 decibels) could create subtle artifact signal pollution without necessarily
being displayed as artifacts, this would be misinterpreted by the BIS algorithm as EEG
activity and assigned a spuriously increased BIS value.
The main objective of our study was to specifically evaluate BIS values according to age
during propofol-induced sedation. LOC was measured by obtaining an OAA/S score <2 (OAA/S2),
or a deeper sedation criterion: loss of eyelash reflex (LOER). The secondary objective was to
specify the influence of EMG on the displayed BIS values and its age-related modifications.