3 DISCUSSION
Cysts on the tongue are one of the major diseases that cause upper
airway obstruction in pediatric patients.2 The origin
of the cysts varies including those derived from the thyroglossal or
lingual ducts, those derived from the cystic degeneration of the lingual
thyroid, retention cysts arising from the mucous glands at the base of
the tongue, and cysts generated from remnant cells during the embryonic
stage.3 In the present report, the cyst was a
thyroglossal duct cyst as revealed by the histopathological diagnosis
after the surgery, and the common sites are shown in Figure
3.4
The first concern of this case is a difficult airway management.
Kumanomido et al.2 described that the necessity of
tracheostomy, subglottic space, presence/absence of a tracheal shift,
mandibular size, and necessity of fiberscope-guided intubation should be
assessed when evaluating the difficulty of tracheal intubation according
to the cyst size. The possibility of tracheostomy was excluded in our
patient because the cyst was near the dorsum of the tongue, anterior to
the typical site of origin, and snoring was the only daily symptom
reported. Furthermore, the patient aged only 5 years; therefore,
fiberscope-guided intubation while conscious was not considered to be
feasible. Moreover, preoperative computed tomography images revealed no
subglottic space or tracheal deviation, and the patient did not present
with micrognathia. Therefore, slow induction with sevoflurane was
performed as usual, with the preparation for emergency airway
maintenance. A route was secured prior to the induction to prepare for
the difficult airway that was expected after the induction of
anesthesia. After the onset of anesthesia, mask ventilation temporarily
was difficult due to the effects of the tongue mass and glossoptosis;
however, mask ventilation was sufficiently performed with the use of
muscle relaxants and an oral airway. Mask ventilation would have still
been difficult if the cyst would have been localized near the base of
the tongue.
For tracheal intubation, McGRATH was used in our patient and its utility
has been reported in pediatric patients.4, 5, 6 Airway
scope with pediatric Intlock blades are useful in pediatric patients
with difficult airways.7 However, in our patient,
McGRATH was used for intubation because the blade of the McGRATH was
thin and had good operability. Although the tongue could not be
completely excluded using McGRATH, the Cormack–Lehane view was Grade 2,
and intubation could be performed in the first attempt without any
issues.
The second concern of this case is airway obstruction associated with
tongue swelling after surgery. In our case, intraoperative findings
included no fistulous tract connected to the cyst, no resection of the
hyoid bone, and no tongue swelling at the end of the surgery. Therefore,
the patient was extubated in the operating room; however, as a
precaution, the patient’s respiratory condition was observed under
sedation with Dexmedetomidine in the ICU. In Japan, Dexmedetomidine for
the sedation of non-intubated pediatric patients is being used since
2018. Without intubation, respiratory depression is a major issue,
particularly in pediatric sedation; Dexmedetomidine does not have a less
respiratory depressant effect and is also used for postoperative
sedation in pediatric patients.8 In our patient, we
were concerned about respiratory depression by sedation, but it was
necessary to keep the patient on bed rest to avoid tongue swelling after
surgery. Therefore, Dexmedetomidine was used. In addition,
Dexmedetomidine has analgesic effects; the analgesic effects, to some
degree, seem to have contributed to the patient being on bed rest.