Macintosh blade entrapment during direct laryngoscopy.

Sir,

Accomplishment of successful laryngoscopy depends upon certain key factors, including head positioning, route of blade insertion, direction of applied force and the type of anaesthesia.[1] Failure of adherence to the recommended technique may end up in devastating complications. We report a similar deviation from the advocated standards resulting in Macintosh blade entrapment inside the oral cavity, followed by acute trismus, managed successfully by performing mandibular nerve block.

A 25-year-old male presented to the outpatient department with the chief complaint of hoarseness of voice for the past 3 months. The results of indirect laryngoscopy were inconclusive and hence the attending physician tried for direct laryngoscopy under local anaesthesia and sedation, to precisely locate the origin of symptoms. While doing conventional laryngoscopy, the flange of Macintosh blade got stuck on the under surface of upper incisors and in an attempt to release the laryngoscope, the handle of the scope got disengaged from the Macintosh blade. To solve this problem, anaesthesia team was called to manage the situation.

On examination, the patient was irritable, had masseteric spasm, oxygen saturation (SpO2) of 98%, and the Macintosh blade was seen entrapped in the oral cavity [Figure 1]. The patient was immediately sedated with propofol (60 mg intravenous [IV]), oxygenated through nasal prongs, and the mandibular nerve block (bilateral) was performed using the Gow-Gates approach.[2] The anterior border of the mandibular ramus was palpated by the forefinger via intraoral approach, and the insufflating syringe was aligned along the plane extending from lower borders of the intertragic notch up to corner of the mouth. The needle (25G Quincke spinal needle) penetrated the mucosa at the lateral margin of the pterygomandibular depression, just medial to the tendon of the temporal muscle and advanced to a depth of 2.5 cm. After negative aspiration, 2.2 ml of lignocaine (2%) was injected. As the block ensued, the mouth opening increased, and the entrapped Macintosh blade was easily removed after 10 min. Thereafter, the patient was anaesthetized by rapid sequence induction (propofol 120 mg IV, and rocuronium 40 mg IV), and the airway was inspected for any complications and the underlying cause of the chief complaints. The patient was intubated until the return of adequate breathing efforts. Reversal was uneventful and patient was extubated without any complications.

Figure 1

Macintosh blade lying entrapped inside oral cavity

Direct laryngoscopy remains the mainstay technique for establishing a secure airway. Competence in this technique requires mastery in a wide range of manoeuvres, right from holding a laryngoscope, up to endotracheal intubation. During this procedure, axial force has to be applied on the laryngoscope handle to visualize the epiglottis, while perpendicular force is required for balancing the torque on the laryngoscope.[3] A misdirected force may land up in difficult laryngoscopy and dreaded complications.[456] In our case, the attending physician undertook rotational movement at the level of wrist to lift the mandible, instead of applying a tangential force through the shoulders. This manoeuvre resulted in sinking of flange under the upper incisor and further attempt to release this entrapment resulted in dislodgement of Macintosh blade from the laryngoscope handle.

The other basis for above complication could be acute trismus secondary to pain, muscle spasm or any mechanical obstruction associated with the procedure or the underlying pathology. Heard et al. showed that such patients could be successfully managed by performing mandibular nerve block, having an additional advantage of increase in interincisor gap.[7] Furthermore, if the initiating cause is not primarily pain, but mechanical obstruction, there would be no further increase in mouth opening with induction of general anaesthesia. As the underlying cause was uncertain in our patient, we chose to perform bilateral mandibular nerve blockade in this patient, to relieve the trismus and to preserve the spontaneous respiration.[2] Although waiting for spontaneous resolution of trismus could be an alternative for such cases, associated risk of laryngospasm secondary to mucosal stimulation by Macintosh blade in situ, ruled out that option.

Considering the associated risk of trauma with conscious sedation, direct laryngoscopy should always be performed by a well-trained physician under general anaesthesia even for diagnostic purposes, although fibreoptic laryngoscopy remains the genuine choice in such cases. The role of the mandibular nerve block under conscious sedation may be promising, but needs future randomized trials.