Use of proseal™ LMA in mallampati class zero

Sir,

We read with a lot of interest the article “Mallampati class zero, yet another cause?” by Indira G.[1] Mallampati class (MPC) zero patients have been discussed in the context of both easy and difficult tracheal intubation.[2,3] Mask ventilation could be difficult in this class of patients due to large overhanging epiglottis.[4] Endotracheal Intubation though easy in most of the cases, may be rendered difficult and traumatic due to attempts to elevate large floppy epiglottis obstructing the glottis. We present a case of MPC zero patient who underwent laparoscopic cholecystectomy with a Proseal™ LMA.

62 year old female, height 155 cm, weight 64 kg, ASA 1, with no history of gastro-oesopageal reflux disease, was posted for elective laparoscopic cholecystectomy. She had undergone appendicectomy two years back under general anaesthesia with no. 7 cuffed endotracheal tube (Cormack Lehan- 1). General examination was unremarkable. Airway examination showed Mallampati class zero.

On the day of surgery, intravenous line was secured with 20 G cannula. Routine monitoring included 5 lead ECG, pulsoximeter, Non –invasive blood pressure, capnograph, gas monitoring. After intravenous sedation with inj. Midazolam 1 mg and inj. Fentanyl 100 μg, anaesthesia was induced with inj. Propofol 120 mg. Gentle mask ventilation was easy. Inj. Vecuronium 6 mg was given and Proseal™ LMA no. 4 was introduced after 2 minutes in a single attempt by a qualified anaesthetist. Cuff was inflated with 20 cc of air (till there was no audible leak on positive pressure ventilation). Peak airway pressure was measured as 22 cm of H₂O and capnograph showed a satisfactory square waveform. LMA cuff pressure was measured and maintained within 60 cm of H₂O. Anaesthesia was maintained with 50% nitrous oxide in oxygen with 1-1.2% isoflurane, inj. Vecuronium 1 mg top- ups as required. Intraoperatively flexible fiberscope no. 6 was passed through the airway tube of Proseal™ and view of epiglottis along with glottis was noted and graded as 3,[5] (grade 3 = larynx and epiglottis tip of anterior surface seen, <50% visual obstruction of epiglottis to larynx) [Figure 1]. Surgical time was 2 hours and was uneventful. Neuromuscular blockade was reversed at the end of surgery and laryngeal mask was removed without deflating the cuff as soon as patient was breathing spontaneously. Cuff CO₂ measured immediately after removal of laryngeal mask attaching the gas analyzer to the pilot balloon was 41%.[6]

Figure 1.

Fibreoptic view through Proseal™ LMA

Mallampati class zero patients have generated enthusiasm regarding their easy intubation according to some authors or difficult mask ventilation and intubation according to the others. MacCoy laryngoscope can be used to lift the large overhanging epiglottis in such cases. Fibreoptic intubation is an alternative method when available.

In the above case, we chose to put a Proseal™ laryngeal mask with controlled ventilation, which is a routine method of anaesthesia for laparoscopic cholecystectomy in our institute for the patients who have no risk factors for regurgitation and aspiration. Laryngeal mask airway has been used successfully in children with MPC zero.[7] Its use, if documented adequately in adult MPC class zero patients, can save possible traumatic intubations. The fibreoptic view of larynx in our patient was grade 3 which indicates acceptable positioning of LMA. Cuff CO₂ value closer to end tidal CO₂ is an indicator of good pharyngeal seal after 2 hours of anaesthesia.

Thus, use of Proseal™ LMA can avoid traumatic intubations in Mallampati class zero adults though we need more such cases to prove its reliability in this class of patients. Experience of handling LMAs and careful selection of cases is mandatory.