Yawning during iv anesthetic induction is an
occasional clinical occurrence without known
untoward effects. During iv induction, the
typical sequence of clinical endpoints consists
of loss of response to verbal command, followed
by loss of eyelash reflex, occasional
yawning, then apnea. We experienced an
unusual complication of yawning in a patient
during anesthetic induction.
A 31-yr-old, 52-kg man with a recent history
of head injury secondary to a motor vehicle
accident was referred to our hospital. He had
progressive proptosis and reduced vision
(diagnosed as post-traumatic bilateral
carotico-cavernous fistulae) for which
endovascular embolization of the fistulae was
scheduled. On examination the patient was
conscious, cooperative, and breathing
spontaneously though a tracheostomy tube which
had remained in situ since his last
hospitalization. He had a residual left
hemiparesis and both eyes were covered because
of bleeding from episcleral vessels and exposure
keratitis. He was able to communicate in
writing, and routine laboratory investigations
were within normal limits. In the neuroradiology
suite standard monitoring was applied and the
anesthesia circuit was connected to the
tracheostomy tube with the patient spontaneously
breathing 100%O2. General anesthesia was induced
with fentanyl 2 pg.kg iv and propofol 2 mg-kg
iv. We could not elicit standard clinical
endpoints such as loss of response to verbal
command and eyelash reflex, although the patient
was observed to yawn during induction.
Pancuronium 8 mg iv was administered, and
anesthesia was maintained with 50% N» in 02
and 1% isoflurane while the patient's lungs were
mechanically ventilated.
To our surprise, the patient's mouth
remained in a locked open position, and several
attempts to close his mouth passively were
unsuccessful. Immediately, fluoroscopic
examination of the patient's head and neck was
undertaken which revealed anterior dislocation
of both temperomandibular joints (TMJ). A closed
reduction of mandible was performed under
fluoroscopic guidance and both TMJs were
strapped with an elastic bandage. Thereafter,
anesthesia and the embolization procedure were
uneventful, and the patient made a good
recovery. Later questioning revealed that the
patient had experienced two previous episodes of
jaw dislocation within the past two years,
information which had not been disclosed during
the preanaesthetic evaluation.
Although TMJ dislocation is not uncommon, a
search of the anesthetic literature revealed
very few reports' in relation to the
perioperative setting. The majority of TMJ
disclocations were related to a jaw thrust
maneuver during mask ventilation, placement of
an oral airway or nasogastric tube, or in
association with direct laryngoscopy. This is
the first report of TMJ dislocation occurring
during anesthetic induction with yawning as an
isolated precipitating factor.
The TMJ represents the articulation of the
condybid process of the mandible with the
glenoid fossa of the temporal bone. It is unique
amongst synovial joints since it can be
dislocated without external force.5 On mouth
opening, the condyloid process moves forward and
is usually limited by the articular tubercle
(eminentia articularis). Laxity of supporting
ligaments will allow the condyle to move
anteriorly past its normal position. This
results in dislocation that may be self-reducing
or require manipulation for reduction. This may
occur when the jaw is forcibly opened during
general anesthesia, or rarely, spontaneously
while yawning, as occurred in our patient. A
more subtle degree of dislocation might have
gone unnoticed in a patient whose airway was
managed with an existing tracheostomy. Failure
to promptly reduce a dislocated mandible could
later result in severe pain, parotiditis, spasm
of external pterygoid muscles, and ankylosis of
the TMJ secondary to joint hematoma and
subsequent intra-articular adhesion
formation.
To conclude, yawning during induction of
anesthesia may prompt TMJ dislocation in the
patient with pre-existing TMJ laxity. Early
diagnosis of TMJ dislocation and prompt
reduction are important in view of potential
complications.
References
1 Sosis M, Lazar S. Jaw dislocation during
general anaesthesia. Can J Anaesth 1987; 34:
407-8.
2 Gambling DR, Ross FL. Temporomandibular
joint subluxation on induction of anesthesia.
Anesth Analg 1988;67:91-2.
3 Rastogi NK, Vakharia N, Hung OR.
Perioperative anterior dislocation of the
temporomandibular joint. Anesth Analg 1997; 84:
924-6.
4 Rattan T' Arora S. Prolonged
temporomandibular joint dislocation in an
unconscious patient after airway manipulation.
Anesth Analg 2006; 102: 1294.
5 Aiello G, Metcalf I. Anaesthetic
implications of temporomandibular joint disease.
Can J Anaesth 1992; 39: 610-6.
