Does
yawning represent a transient arousal-shift
during intravenous induction of general
anesthesia?
Kasuya Y, Murakami T, Oshima T, Dohi S.
Department of Anesthesiology
and Pain Medicine, Gifu University Graduate
School of Medicine, Japan.
Abtsract : Although yawning occurs
frequently during the IV induction of general
anesthesia, the significance of this
response remains unknown. In this study, we
induced 30 surgical patients with 4 mg/kg
thiopental IV, and 30 patients with 2 mg/kg
propofol IV. Thereafter, the occurrence of
yawning was continuously assessed, as the only
clinical end-point, for 1 min. The
electroencephalographic bispectral index was
monitored throughout the observation period. The
criterion for an arousal response was a
transient increase during a continuing decrease
in the bispectral index value. On the basis of
this criterion, the sensitivity and specificity
of the yawning response as an arousal sign were
77% and 80%, respectively. If a patient
exhibited a yawning response, the chance of
arousal was 84% (positive predictive value).
With no yawning response, the chance of
nonarousal was 71% (negative predictive value).
According to simple logistic regression, the
yawning response was predictive of a transient
arousal-shift with an odds ratio of 13.5 (95%
confidence interval: 3.8-48; P < 0.001). The
occurrence of a yawning response during IV
induction may be a clinical indicator of a
transient arousal-shift during progressive loss
of consciousness.
One of the most frequently encountered
clinical situations during which yawning occurs
is the IV induction of general anesthesia (1). A
typical yawn is characterized by a single large
inspiration with simultaneous mouth opening and
stretching of the trunk (2Ð 4). Yawning can
also be accompanied by changes in autonomic
function, such as lacrimation and penile
erection (5Ð7). Furthermore, yawning has
been established as a phenomenon that subserves
arousal (8). Although a transient arousal-shift
during the yawning behavior has been
demonstrated in awake humans as measured by skin
conductance (9), sympathetic nerve activity
(10), and behavior (11), we thought it important
to know whether this phenomenon also applies to
humans during IV induction, a clinical situation
in which relevant information is still lacking.
We hypothesized that a yawning response during
IV induction is associated with a transient
arousalshift during continuing loss of
consciousness in humans. To examine this
hypothesis, we recorded the
electroencephalographic (EEG) bispectral index
(BIS) during IV induction achieved using a
single bolus induction dose of thiopental or
propofol.
Discussion
The principle finding in this study was that,
in humans, a yawning response was related to a
transient increase during the continuing
decrease in the BIS value seen after IV
administration of thiopental or propofol. This
phenomenon, observed using BIS monitoring, may
reflect a transient arousal-shift during the
progressive loss of consciousness caused by IV
induction. We therefore focus the following
discussion on the arousal-shift that seems to be
related to the yawning response. In our study,
the yawning response elicited during IV
induction had positive and negative predictive
values of 84% and 71%, respectively, for
predicting a transient increase in the BIS
value, with the sensitivity and specificity
being 77% and 80%. Moreover, simple logistic
regression indicated that the odds ratio of the
yawning response as a prediction of a transient
increase in the BIS value was 13.5 (95%
confidence interval: 3.8Ð48; P 0.001). These
statistical values are all consistent with our
hypothesis that the yawning response might
represent a transient arousal-shift during
continuing loss of consciousness and on the
assumption that the BIS monitor is capable of
detecting rapid changes in arousal or
consciousness or whatever it actually measures.
On the BIS record, a transient increase during a
continuing decrease was consistently observed
15Ð20 seconds after the occurrence of a
yawning response. However, because the BIS value
that actually correlates with a given event is
the value recorded after a 20-second delay to
compensate for the time delay in calculating the
BIS value (1), the underlying phenomenon may
occur either before or during the yawning
response. This arousal effect may be of
considerable significance because the data were
obtained under general anesthesia. A few years
ago, Sato-Suzuki et al. (12) recorded the
electrocorticogram to evaluate arousal responses
during yawning in anesthetized rats. During both
spontaneous yawning and yawning responses evoked
by chemical stimulation of the paraventricular
nucleus, electrocorticogram arousal (represented
by lower voltage and faster rhythms) occurred
before the actual yawning behavior. However,
Concu et al. (8) demonstrated that EEG arousal
and yawning appeared concomitantly in cats. When
taken together with these findings in animal
experiments (8,12), the present data suggest
that yawning-induced EEG arousal does not result
from the stretching of the trunk. Although the
BIS monitor is capable of rejecting the
electromyographic artifacts, we cannot exclude
the possibility that the transient increase in
the BIS value may incorporate electromyographic
activity which could have increased because of
muscle activity during opening of the mouth.
Further studies using a multichannel EEG with
electrodes over the mandible are needed to solve
this problem. Although the BIS monitor involves
this limitation, this study is the first to
indicate an arousal-shift associated with
yawning during induction of general anesthesia
in humans
Kasuya Y,
Murakami T, Oshima T, Dohi S. Does yawning
represent a transient arousal-shift during
intravenous induction of general anesthesia?
Anesth Analg 2005;101(2):382-3
Morton
HJV Yawning during thiopentone induction Br.
J. Anaesth 1962;34:133-134
Oshima
T et al. Inhibitory effects of landiolol and
nicardipine on thiopental-induced yawning in
humans J Anesth 2010
