Background and Goal of Study: The incidence of postoperative sore throat is quoted as 17.5% with LMA1. Clinical evidence has failed to show a consistent link between LMA cuff pressures (CP) and sore throat1,2. However, LMA manufacturers state that CP should remain <60cmH2O. Does cuff over inflation contribute to sore throat?
Materials and Methods: LMA CP was measured in theatre and patients scored sore throat on a visual analogue scale in recovery (fig.1). Exclusion criteria were: ENT surgery, <18 years old or dementia. Fannin Integral single use LMA was used in all patients. A questionnaire was completed by anaesthetists in our department, investigating their knowledge of recommended CP and if it was routinely measured.
Results and Discussion: 89 patients were studied. Operation duration was 15–285mins. Median CP was 120cmH20. 14.6% patients had CP <60cmH20. Incidence of sore throat was 15.4% in this group vs. 40.8% in patients with CP > 60cmH20 (fig.2). No sore throat was observed when CP <48cmH2O (n=10). LMAs inserted by consultants resulted in 22.7% vs. 41.8% sore throat with trainees. One anaesthetist was aware of maximum recommended CP and none routinely measured CP (n=33). A positive correlation was shown between CP and sore throat. No link was found between duration of LMA in situ and sore throat. Trainees were almost twice as likely to cause sore throat than consultants. Knowledge of CP recommendations were poor.
Conclusion(s): Increasing LMA CP contributes to sore throat. Maximum recommended CP is largely unknown by anaesthetists and CP is not monitored. We suggest that CP should be routinely measured and reduced to <60cmH20 in accordance with manufacture recommendations.
1 Steele et al. Ambulatory Anaesthesia and Perioperative Analgesia Manual. McGraw-Hill. 2005; p488.
2 Reiger et al. Intracuff pressures do not predict laryngopharyngeal discomfort after use of the LMA. Anaesthesiology. 1997; 87(1): 63-7.