The most important problems with laryngeal mask airway (LMA) use occur during insertion and/or removal. A very rare case of pharyngolaryngeal rupture, pneumomediastinum and widespread subcutaneous emphysema is presented as a complication of LMA use. The patient reviewed the case report and gave written permission for publication.
A 72-year-old man, weight 80 kg, height 178 cm, American Society of Anesthesiologists’ (ASA) physical status 2 (arterial hypertension) was having a cystoscopy under general anaesthesia to investigate the cause of haematuria and urinary retention. After applying standard ASA monitoring, anaesthesia was induced by the intravenous administration of 150 μg fentanyl, 150 mg propofol and 10 mg rocuronium. Facemask ventilation was performed until the conditions for insertion of a LMA were suitable. A size 4 LMA (LMA Classic; LMA North America, San Diego, CA, USA) was easily inserted by an experienced user at the first attempt, using the digital technique.1 Following insertion, the LMA was inflated with 30 ml of air until the airway was sealed. Controlled mechanical ventilation was initiated with a tidal volume of 8 ml kg−1 at 10 breaths per minute (I:E ratio 1 : 2), 4 l min−1 fresh gas flow rate and 20 cmH2O peak airway pressure. To maintain anaesthesia, the inspired agent concentrations were 50% O2 in N2O with 1 to 2% sevoflurane and this was supplemented with a remifentanil infusion (0.05 to 0.1 μg kg−1 min−1). In the first hour of the operation, peak airway pressure progressively increased up to 30 cmH2O and abdominal distension and subcutaneous emphysema developed. The laryngeal mask was deflated, 30 mg of rocuronium was administered and the patient underwent orotracheal intubation. Intraoperative abdominal ultrasonography was performed and free air was seen in the abdominal cavity. The patient was transferred to the ICU with the orotracheal tube in situ at the end of the operation. The patient's haemodynamic and respiratory parameters were stable, and the trachea was extubated after 2 h. A chest radiograph and computerised tomography revealed no pneumothorax, but a widespread pneumomediastinum and pneumoperitoneum were observed, with subcutaneous emphysema extending from the cervical region to the anterior abdominal wall (Fig. 1). There was no leakage of nonionic contrast medium from the oesophagus. A mucosal abrasion of the left posterolateral region of the pharynx was observed on flexible endoscopy. The patient remained stable and, with the subcutaneous emphysema resolving, he was discharged to the ward next day.
A high insertion success rate and a low incidence of complications have resulted in the LMA becoming more popular than other airway management devices. However, although the LMA is designed as a noninvasive means of establishing and maintaining airway patency, it does have some specific complications, which are most commonly encountered while inserting and/or removing the device. Such complications include regurgitation, mucosal damage, sore throat and hoarseness, despite the use of recommended insertion and removal techniques.
In a retrospective study of 2000 patients who had major ear operations and in whom LMAs were inserted, no major life-threatening complications occurred, but laryngospasm (one case), dislocation of arytenoids (two cases), hoarseness (two cases), cough (10 cases) and gastric regurgitation (five cases) was reported.2 In an observational study of 5655 cases, Haden et al.3 reported a 0.9% incidence rate of difficult LMA insertion (45 cases) or laryngospasm (seven cases).
Some of the complications during the use of LMA might be caused by a high pressure within the inflated cuff exerting excessive pressure on the pharyngeal mucosa.4 Filling the cuff of LMA-Classic with a volume of up to 40 ml of air results in approximately 25 to 35 cmH2O pressure on the pharyngeal and hypopharyngeal mucosa, equally distributed among anterior, lateral and posterior locations.5 As the LMA cuff is permeable to N2O and CO2, the cuff pressure progressively increases during prolonged procedures.5 Pharyngeal mucosal perfusion decreases progressively with intracuff pressures over 34 cmH2O, so increased cuff pressure could cause postoperative complications such as sore throat, temporary hoarseness, epiglottic oedema, hypoglossal or lingual nerve paralysis or laryngeal laceration.4–7 However, Keller and Brimacombe7 found that directly measured mucosal pressure rarely exceeded 34 cmH2O and suggested that mucosal ischaemic injury is uncommon with the LMA.
In our case, we used 30 ml of air, and this may have exceeded the volume required by this particular patient. As we did not use cuff manometry during the operation, the intracuff pressure is unknown. In practice, there is a poor correlation between the intracuff pressure and the ‘compression’ pressure exerted on the tissues.7 Due to this poor correlation, simply measuring the intracuff pressure might not be very helpful.
In the current case, there were no risk factors, except possibly increased tissue fragility due to old age. The LMA was inserted successfully, and there were no obvious complications at that time. Our patient's peak airway pressure was 20 cmH2O. We assume that the airway pressure increased as a result of air leaking through the mucosal tear to create the pneumomediastinum and pneumothorax and so we do not believe that the inflation volume/pressure or positive pressure ventilation was responsible for causing the initial tear in the mucosa. Furthermore, the tear cannot be related to tissue perfusion and necrosis because that requires at least several hours to develop. Another possibility is that minor trauma associated with mucosal fragility could have caused the tear. Despite a standard digital insertion technique being used, it is possible that the tear might have been caused by a finger while pushing the fingers down the patient's throat to guide the LMA into place.
In conclusion, we believe that the complication in the present case was due to increased mucosal fragility associated with old age. We suggest that more care is needed when inserting the LMA device in older patients.
Acknowledgements relating to this article
Assistance with the article: we would like to thank the patient for his kindness in giving written informed consent for publication.
Conflict of interests: none.
Financial support and sponsorship: none.
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