Laryngeal morbidity after use of the laryngeal mask airway

POST-OPERATIVE hoarseness (PH), sore throat (ST), and vocal cord injuries (VCI) are common complications after general anaesthesia. Methods for maintaining a patent airway during anaesthesia include the endotracheal tube (ETT) and the laryngeal mask airway (LMA). The LMA insertion is a blind technique, is easy to learn, and has a high first-time success rate. However, types of nerve injury, arytenoid dislocation, and epiglottitis have been described in association with the LMA, leading to PH and ST. The trauma causing laryngeal injury by the ETT can occur on several occasions: during induction of anaesthesia as a direct trauma of the tracheal tube, during surgery, or during tracheal extubation. Many factors contribute to laryngeal intubation trauma, and several risk factors have been identified, including gender, weight, smoking, and gastrooesophageal reflux. Technical factors are also important, such as ETT size, type of tube, cuff design, cuff pressure, use of introducer, use of gastric tube, type and duration of surgery, and intubating conditions. In this issue of Acta Anaesthesiologica Scandinavica, Abdi et al. present a study dealing with the problem of laryngeal morbidity, i.e. PH and ST after tracheal intubation vs. insertion of the new LMA (LMA Supremet). The LMA Supremet (LMASUP) with the possibility to suction the stomach could be an interesting alternative to the ETT during laparoscopic procedures. In terms of laryngeal morbidity, the LMA-SUP was associated with a decreased incidence of PH and ST compared with tracheal intubation (in women) after laparoscopic surgery. Moreover, the use of the LMA Supremet was as safe and efficient as the ETT in this special clinical setting, i.e. laparoscopic surgery. The sealing pressure, defined as the highest peak inspiratory pressure with no audible and measured gas leak, reached 30 cmH2O in 95% of the patients. In addition, in all patients in the LMA-SUP group, the drainage of the gastric contents was successful. The authors suggest that this feature associated with the LMA-SUP enhances safety during use of this new device in infertility laparoscopic surgery instead of the tracheal tube. A limitation of the study design might be the fact that only female patients were studied. Thus, the ‘gold standard’ for laparoscopic procedures is still the tracheal tube combined with a gastric tube. However, for women without an increased risk of regurgitation and a sealing pressure o30 cmH2O, it could be an alternative technique for elective pelvic laparoscopy. PH, commonly caused by the injury of the vocal cords during tracheal intubation, was significantly reduced in the LMA-SUP group compared with the ETT group. Therefore, it could be recommended especially for patients who use their voice professionally, such as singers, actors, or teachers. Another limitation is the fact that the laryngeal mask was inserted after administration of the muscle relaxant, which was required for the surgical procedure, and this is not the usual practice. Thus, the incidence of PH could have increased if the insertion of the LMA had been performed without a muscle relaxant. Based on these results, additional research could be conducted to determine the incidence of PH and safety of the LMA-SUP in patients receiving no neuromuscular blocking agent during surgery. If the results are the same, the LMA-SUP can be recommended for patients with a known contraindication to neuromuscular blocking agents as well.