Teleflex | LMA - Better by Design

Authors

Publication

Br J Anaesth 2005; 95 (3): 420-423.

Summary

• A case of lingual nerve injury associated with the use of the LMA ProSeal™ supraglottic airway device was reported
• Although the LMA ProSeal™ and LMA Classic™ supraglottic airway devices may occasionally result in cranial nerve injuries, these most often occur when the devices are incorrectly used
• Cranial nerve injuries during the use of LMA devices can be avoided by minimising cuff volume and by using a correctly sized device

Case report:

• A case of lingual nerve injury associated with the use of the LMA ProSeal™ supraglottic airway device was reported
  • The injury occurred in a 74 kg male patient aged 61 years (American Society of Anesthesiologists physical status 2) during elective shoulder replacement surgery
• The injury was characterised by a 2 cm area of numbness (to both touch and taste) on the left side of the tip of the tongue in the immediate post-operative period, which was confirmed upon examination
  • No other cranial nerves were affected and no other sequelae were apparent  
  • The numbness began to improve from 8 days post-surgery and had completely resolved by 15 days post-surgery
• The LMA ProSeal™ was successfully inserted on the first attempt and the size of the device (size 5), the cuff volume (inflated with 20 ml of air) and the fixation technique (as per the manufacturer’s instructions) were considered appropriate
• The position of the device was considered correct
  • The mid-portion of the bite block was situated inside the oral cavity (with no evidence that the tongue was trapped between the bite block and the teeth)
  • There was no air leakage from the drain tube at an oropharyngeal leak pressure of 25 cm H₂O
  • A size 14 Fr gastric tube was successfully inserted via the drain tube on the first attempt
• Approximately every 30 minutes air was withdrawn from the cuff, minimising any increases in intracuff volume due to the diffusion of nitrous oxide (which was used with sevoflurane to maintain anaesthesia)

Findings:

• A review of the available literature identified 22 other cases of cranial nerve injury (lingual [n=5], hypoglossal [n=6] and recurrent laryngeal [n=11]) during the use of LMA devices, including five cases of lingual nerve injury
  • Twenty of the cases occurred in patients in whom the LMA Classic™ was inserted and two of the cases occurred in patients in whom the LMA ProSeal™ was inserted
• The most likely cause of the injuries was a pressure neuropraxia caused by the tube (lingual) or the cuff (hypoglossal and recurrent laryngeal)
• The two main factors that likely predisposed LMA recipients to cranial nerve injuries were the use of nitrous oxide and the use of a device that was too small
  • Nitrous oxide rapidly diffuses into the cuff of re-usable laryngeal masks resulting in an increased intracuff pressure
  • Using a device that is too small may increase the likelihood of malposition and lead to over inflation of the cuff in an attempt to improve the effectiveness of the airway seal
• In the case described, the nerve injury may have been caused by multiple factors
  • A non-supine (i.e. semi-beach chair) position
  • Firm attachment of the patient’s head to the operating table
  • Shoulder surgery
  • Use of nitrous oxide
  • A long surgical procedure (the device was in situ for 2.5 hours)

Implications:

• This case report and a review of the literature showed that use of the LMA ProSeal™ and LMA Classic™ supraglottic airway devices may occasionally result in cranial nerve injuries, even when the positioning of the device is correct
• Cranial nerve injuries associated with the LMA Classic™ device most often occurred during incorrect use
• Cranial nerve injuries can be avoided by minimising cuff volume and by using a correctly sized device