The video laryngoscopes, blind spots and retromolar trigonum injury by the GlideRite(®) rigid stylet.

We report the first case of retromolar trigonum tissue injury in an 80-year-old female, caused by the Rigid GlideScope® Stylet. This complication was discovered during oral surgery.

INTRODUCTION

The GlideScope® video laryngoscope is a relatively new intubating device designed to provide better view of the glottis, without alignment of the oral, pharyngeal and tracheal axes. The aim of this case presentation is to increase awareness for possible serious complications that may arise with increased popularity and usage of video laryngoscopes, and their rigid stylet.

CASE REPORT

A morbidly obese 80-year-old female [weight 102.1 kg, height 157.5 cm, body mass index (BMI) of 41] presented with mouth pain, and multiple carious teeth were scheduled for teeth extraction with an alveoplasty. She had a past medical history of Cerebrovascular accident (CVA), transient ischemic attack (TIA), congestive heart failure (CHF), hypertension, and myocardial infarction (MI). Electrocardiogram (ECG) showed first-degree heart block, prolonged QT interval with anterolateral infarct. Echocardiograph (ECHO) showed an ejection fraction of 45–50%, left atrial enlargement, mild pulmonary hypertension, and trace mitral regurgitation.

Preoperative airway assessment revealed a Mallampati score of IV, three finger breadth mouth opening, slight limitation of neck movement, and loose carious teeth. With this assessment, the patient was predicted to be difficult to intubate. The anesthetic plan included management of the predicted difficult intubation with the GlideScope® with other usual backup planes for difficult intubation.

Anesthesia was induced with fentanyl 150 µg, lidocaine 100 mg, propofol 150 mg and succinylcholine 100 mg.

The GlideScope® blade tip was placed in the vallecula and the vocal cords and epiglottis were seen. A size 7 endotracheal tube (ETT) was mounted in the GlideRite® rigid stylet and then passed into the oral cavity for intubation. The endotracheal tube (ETT appeared to slide into the oropharynx with relative ease and the endotracheal tube was placed into the trachea. The stylet was removed, and positive EtCO2 and equal bilateral breath sounds was confirmed. A successful GlideScope® intubation was assumed.

As the surgeon began the procedure, he noticed that ETT had pierced and entered the tissue of the retromolar trigonum (the same space which holds the lingual nerve), and then proceeded to pass through the oropharyngeal space and re-enter the vocal cords [Figure 1a and b].

Figure 1

(a and b) ETT had pierced into retromolar trigonum tissues and then entered the vocal cords

We decided to remove ETT rather than cutting the tissues to free it, to avoid trauma to lingual nerve. We re-inserted another size 7 ETT with the aid of the GlideScope® camera. Positive EtCO2 and equal bilateral breath sounds was confirmed. Surgery was completed uneventfully; however, the surgeon stated multiple times that the patient's oral mucosa was very fragile and easily torn. The patient was easily extubated and transported to post anesthesia care unit (PACU). Both intubations were performed by the student registered nurse anesthetist (SRNA).

PACU staff was instructed to look for signs of lingual nerve injury (numbness in the tongue, loss of ability to taste, tingling sensation in the tongue, pain, burning, or electric shock sensations in the tongue, speech impairment and drooling).

The PACU stay was uneventful, the patient denied any of the above mentioned symptoms, and was discharged.

DISCUSSION

The GlideScope® and other video laryngoscopes have improved tracheal intubation, especially in patients with difficult airways.[1]

The GlideRite® rigid stylet [Figure 2a and b] was introduced to overcome the difficulties found with intubation with GlideScope® and other similar video laryngoscopes and help reduce patient trauma.[23]

Figure 2

(a and b) The GlideRite® rigid stylet is specifically designed to work with GlideScope® video laryngoscopes

A study by Tukstra et al. showed that the dedicated GlideScope® rigid stylet and the standard malleable ETT stylet are equally effective in facilitating endotracheal intubation.[34] The Flex-It® stylet was no more effective in facilitating endotracheal intubation than the standard malleable ETT stylet.[35]

In our case, the rigid stylet converted the endotracheal tube tip into a sharp knife-like weapon that cut through the patient's oral tissues.

When intubating with video laryngoscope, the operator usually concentrates on the perfect image of the cords. The path of the tube from the mouth opening to the vocal cords is a “blind spot” to the intubating person.

Although lingual nerve injury was reported with other intubation and airway devices, this is the first reported case of near lingual nerve injury by the Rigid GlideScope® Stylet. The incident was accidently discovered during oral surgery and prevented by not cutting and preserving the retromolar tissues.

Injuries to lingual nerve are now frequently reported with upper airway intubation and instrumentation. Lingual nerve injury was even reported with the use of Larangyal Mask Airway (LMA) cuffed oropharyngeal airway, oropharyngeal airway, proseal LMA, and conventional endotracheal intubation. Both unilateral and bilateral injuries have been reported. Potential predisposing factors include the use of nitrous oxide[6-13] using an LMA that was too small[6913-16] and excessive pressure.

We recommend and conclude that injuries from video laryngoscope intubation aids could be avoided by careful attention to the following steps.

The ETT must be passed close to the scope and away from the corners of the mouth. Close attention to the path of ETT, in the screen of the scope picture, from the time of entering the mouth to the time of entering the vocal cord. ETT course must be re-inspected by the video scopes on the way out after intubation.

When using rigid stylet, ETT with softer tips must be used. The parker ETT has a soft malleable tip and may be helpful in these situations. The tip of the conventional ETT, if dipped into warm saline, will turn softer and less traumatic.