Scar contracture of anterior tonsillar pillar leading to difficult intubation.

Unanticipated difficult intubations on the operation table have often tested all the anesthetists' intubation skill. The understanding of the causative factor and accordingly using the correct instrument from the difficult intubation kit requires experience and thorough knowledge on the part of the anesthetist. We describe a case of difficult intubation due to scar contracture of anterior tonsillar pillar formed after a previous surgery.

INTRODUCTION

A thorough pre-operative assessment of a patient scheduled for surgery helps foresee a difficult airway. However, an unanticipated difficult airway is occasionally encountered by every Anesthesiologist. Airway impairment can be above the larynx, supraglottic, glottic, subglottic or tracheobronchial.[1] Adequate equipment, anesthetists’ skills and expert help at hand go a long way in tackling such crisis situations. We discuss a case of a lady who was posted for submandibular surgery in whom intubation was difficult due to a rare cause.

CASE REPORT

A 52-year-old woman American Society of Anesthesiologists Grade 2 presented with swelling in right submandibular region. She was diagnosed to have submandibular sialadenitis and posted for surgery. She was a known hypertensive on regular treatment. She had been operated for tonsils at the age of 7 years. She had also undergone a cesarean section and an appendicectomy under spinal anesthesia, both of which were uneventful. Her physical examination was unremarkable with adequate mouth opening and thyromental distance and Mallampati Class II. She had a body mass index of 31.34. Computed tomography scan of neck showed the nasopharynx, oropharynx and oral cavity, hypopharynx and the larynx normal with no mass. The subglottic airway and the post cricoid esophagus did not show any apparent abnormality.

The pre-operative medication given was midazolam 1 mg IV. General anesthesia was induced with propofol 3 mg/kg and fentanyl 1 mg/kg IV. After mask ventilation was found to be satisfactory, atracurium 0.5 mg/kg was administered. After 3 min, direct laryngoscopy was performed with McCoy blade, which is used on a regular basis. Mouth opening was found to be adequate. The laryngoscope was inserted along the right border of the tongue; however, the tongue could not be displaced horizontally. The tip of the epiglottis was visualized, but could not be elevated away from the posterior pharyngeal wall. Direct laryngoscopy was repeated again with similar findings. A band was noticed to extend from the right anterior tonsillar pillar to the tongue [Figure 1]. External laryngeal manipulation did not result in any change in the visual field [Figure 2]. Blind passage of bougie was attempted twice with insertion of endotracheal tube over it. However, each time the endotraceal tube was placed in the esophagus. A size 4 proseal laryngeal mask airway (LMA) was inserted and the rest of the anesthesia was uneventful. At the end of the surgery, the patient was extubated and the post-operative course was uneventful.

Figure 1

Direct laryngoscopic view. Arrow showing the scar contracture of the anterior tonsillar pillar

Figure 2

Direct laryngoscopic view. An artery forceps placed on the contracture tissue between the anterior tonsillar pillar and the tongue

DISCUSSION

Unanticipated difficult airways loom like the sword of Damocles over the heads of anesthetists. On the operation table, a difficult airway can present as the inability to give positive pressure ventilation with a mask or difficult endotracheal intubation. Inability to maintain oxygenation can lead to brain damage and even death.[1] A thorough history and physical examination is essential before taking up any patient for anesthesia induction. Various tests and scores have been devised to predict difficult intubation. Mallampati classification, thyromental distance, extent of mouth opening, dentition and range of neck movements are some of the parameters used to predict difficult airway.

For direct laryngoscopy, “sniff” position with wide mouth opening is ideal for laryngoscope insertion. A crowded oropharynx with decreased pharyngeal width, high Mallampati score and decreased retro lingual space restricts insertion of the laryngoscope blade.

Displacement of the tongue to the left with elevation of the epiglottis by laryngoscope blade provides laryngeal view, which has been graded by Cormack and Lehane (CL).[2]

The most useful modification is sub-classification of Grade 3 of CL view.[3]

Grade 3a: When the epiglottis can be lifted from the posterior pharyngeal wall

Grade 3b: When the epiglottis cannot be lifted from the posterior pharyngeal wall.

Various techniques have been devised to improve the laryngoscopic view and help in intubation. External laryngeal manipulation by an assistant can alter the laryngeal view. McCoy's laryngoscopic blade helps in elevating the epiglottis to reveal the laryngeal inlet. Further a gumelastic bougie can be carefully inserted into the larynx over which the endotracheal tube can be placed. However, this introducer technique doesn’t work well in Grade 3b situation.

In our case, the operating surgeon who was an Otolaryngologist diagnosed the band to be scar contracture of the anterior tonsillar pillar. This had developed as a result of previous tonsillectomy. The contracture restricted the displacement of the tongue and further insertion of the laryngoscope. Hence, CL view Grade 3b could only be obtained. The role of tonsillar pillars has been widely studied in obstructive sleep apnea patients.[4] The muscles of anterior tonsillar pillar are known to contain more elastin and collagen than other muscles in the oropharynx.[5] Scarring and loss of elasticity is known to occur when the pillars are compromised during surgery leading to collapse of the soft palate against the posterior pharyngeal wall. Nasopharyngeal stenosis is a known complication due to resection of posterior tonsillar pillar during tonsillectomy.[6] However, scar contracture of anterior tonsillar pillar has not been widely reported in the literature.

LMA is increasingly being used in scenarios of difficult intubation.[7] The proseal LMA is proven to produce a better seal than classical LMA. Further, it provides some protection from aspiration of gastric contents. In our patient as there was no oral trauma, proseal LMA was safely used and an ideal seal was obtained. Fiberoptic intubation is another modality widely used in anticipated difficult intubation.[8]

CONCLUSION

During induction of anesthesia maintaining oxygenation is the prime aim of the Anesthetist. In case of difficult intubation skilled help and equipment should be readily available. Fiber-optic bronchoscopy and intubation has become a mainstay for difficult intubations especially when anticipated beforehand. Trauma to the airway due to blind attempts should be prevented as far as possible and other devices besides endotracheal tubes should be judiciously considered. Scar contracture of anterior tonsillar pillar should be considered especially with a history of previous tonsillectomy.