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Air humidification might help to prevent irritation and damage to the vocal cords during intermittent positive pressure ventilation using a laryngeal mask airway

Joaquín Fabregat, MD^* and Cristina De Arce, MD

^* Hospital Rosell, Cartagena;
Hospital Virgen del, Toro, Mahon, Spain, E-mail: kinoyo{at}hotmail.com

To the Editor:

We read with interest the recent correspondence by Hemmerling et al.¹ We agree that a small dose of a non-depolarizing neuromuscular blocking drug may improve intermittent positive pressure ventilation (IPPV) with a laryngeal mask airway (LMA). We titrate non-depolarizing NMBDs (e.g., rocuronium 0.5 X ED₉₅ ) whenever patients "fight" against mechanical ventilation, or when patients emit snoring or other high-pitched sounds during IPPV with an LMA, even when patients are already partially paralyzed (Figure).

View larger version (22K): [in this window] [in a new window]   FIGURE An electromyographic tracing at the adductor pollicis muscle is shown for a 155-minute general anesthetic for achilles tendon surgery managed with a laryngeal mask airway. Whenever high-pitched snoring sounds occurred during surgery, the first twitch response was > 50% of control, and the train-of-four ratio was less than 0.25. Despite adequate surgical relaxation, phonation occurred intermittently. Small doses of rocuronium 5 to 10 mg iv resolved the stridor and facilitated smooth intermittent positive pressure ventilation. Arrows show where stridor (S) occurred, and where neuromuscular blocking drug (NMBD) muscle relaxant was administered.

We therefore suggest that the inspired gases should be humidified and warmed routinely with heat and moisture exchangers. The use of low-flow or minimal-flow anesthesia and heat and moisture exchangers may potentially reduce irritation or trauma to the vocal cords with the LMA,^3–5 and avoid unnecessary use of neuromuscular blocking drugs.

Footnotes

Accepted for publication October 17, 2005.

References

1 Hemmerling TM, Michaud G, Deschamps S, Trager G. ‘Patients who sing need to be relaxed’--neuromuscular blockade as a solution for air-leaking during intermittent positive pressure ventilation using LMA (Letter). Can J Anesth 2005; 52: 549.[Free Full Text]

2 Figueredo E, Vivar-Diago M, Munoz-Blanco F. Laryngo-pharyngeal complaints after use of the laryngeal mask airway. Can J Anesth 1999; 46: 220–5.[Abstract/Free Full Text]

3 Mollhoff T, Burgard G, Prien T. Low-flow and minimal-flow anaesthesia using the laryngeal mask airway. Eur J Anaesthesiol 1996; 13: 456–62.[Medline]

4 Honemann CW, Hahnenkamp K, Mollhoff T, Baum JA. Minimal-flow anaesthesia with controlled ventilation: comparison between laryngeal mask airway and endotracheal tube. Eur J Anaesthesiol 2001; 18: 458–66.[Medline]

5 Hemmerling TM, Beaulieu P, Jacobi KE, Babin D, Schmidt J. Neuromuscular blockade does not change the incidence or severity of pharyngolaryngeal discomfort after LMA anesthesia. Can J Anesth 2004; 51: 728–32.[Abstract/Free Full Text]

This article has been cited by other articles:

				D.-K. Kim, K.-Y. Rhee, W.-K. Kwon, T.-Y. Kim, and J.-E. Kang A heated humidifier does not reduce laryngo- pharyngeal complaints after brief laryngeal mask anesthesia: [L'utilisation d'un humidificateur chauffant ne reduit pas les douleurs laryngo-pharyngees lors d'une anesthesie breve avec un masque larynge] Can J Anesth, February 1, 2007; 54(2): 134 - 140. [Abstract] [Full Text] [PDF]

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