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Complete airway obstruction caused by cuff herniation of an overused laryngeal mask airway.

We report an unusual airway problem in an 80-year-old male scheduled to undergo transurethral resection of the prostate. His past medical history included type II diabetes mellitus, hypertension, ischaemic heart disease with stable angina and a permanent pacemaker.

The patient opted for general anaesthesia. Following intravenous induction, a size 4 classic reusable laryngeal mask airway (LMA, Intavent, Orthofix) was sited in his posterior pharynx to facilitate airway maintenance during spontaneous ventilation. Anaesthesia was maintained with sevoflurane in oxygen enriched air, delivered through a circle system.

A few minutes after insertion of the LMA, an audible leak and an abnormal breathing pattern was noted. A diagnosis of either LMA displacement and/or inadequate cuff inflation was made. The cuff was inflated with a further 5 ml of air, however the audible leak increased. The respiratory pattern and capnography revealed complete airway obstruction. A misplacement of the LMA was diagnosed. The LMA was removed with the intention of reinsertion. However a large cuff herniation was noted (Figure 1). A size 5 LMA was inserted without difficulty. This resulted in restoration of a patent airway and a normal respiratory pattern. The operation proceeded uneventfully.

Closer inspection of the LMA revealed numerous hairline cracks in the 15 mm plastic connector as compared to an unused laryngeal mask airway (Figure 2), as well as a yellow discoloration of the shaft. Both these findings suggesting overuse. Theatre records showed that this LMA had been autoclaved 54 times.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Damage to LMAs can occur at any point from manufacture and packaging, to cleaning and autoclaving, as well as during clinical use. LMA cuff weakening is age-related but deterioration is accelerated by over inflation or failure to evacuate all air prior to autoclaving (1). Excessive re-use causes an LMA to be vulnerable to damage and will eventually lead to defects which may cause morbidity or mortality (2).

The LMA is a robust device, but with no clearly defined endpoint for its durability with multiple uses. The manufacturer's recommendation is that an LMA should be reused no more than 40 times, after which the mechanical properties deteriorate significantly, this being related to degradation of the silicone material and loss of integral strength (3). We suggest that there should be compliance with this recommendation and that each LMA should be thoroughly examined by the clinician prior to its use. Examination should include competency of the LMA cuff, a colour check of the shaft and visual inspection of the 15 mm connector. If any abnormalities are found this should signify an end in its safe life and result in the LMA being discarded (4).

A further alternative is to consider the use of disposable laryngeal mask airways, advantages of which include a potential reduction in risk of cross-contamination and prion transfer as well as savings on cost, maintenance, cleaning and sterilisation. Disadvantages of the disposable LMA need to be considered. These include theatre storage capacity, supply line reliability, product shelf life and a number of environmental issues (5).

References

(1.) Bricombe JR. Laryngeal Mask Anaesthesia. Principles and Practice, 2nd ed. London: W B. Saunders Company 2005. p. 566-67.

(2.) McGuire GP Fractured laryngeal mask airway (LMA). Can J Anesth 2000; 47: 716.

(3.) Newnam PT Discarding used laryngeal mask airways--can there still be life after 40? Anaesthesia 1994; 49: 81.

(4.) Boge E, Brandis K. Testing the laryngeal mask. Anaesth Intensive Care 1995; 23: 751-752.

(5.) Cook TM. The classic laryngeal mask airway: a tried and tested airway. What now? Br J Anaesth 2006; 96: 149-152.

N. D. CHRISTELIS

G. K. DOOLAN

Melbourne, Victoria
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Article Details
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Title Annotation:Correspondence
Author:Christelis, N.D.; Doolan, G.K.
Publication:Anaesthesia and Intensive Care
Article Type:Clinical report
Geographic Code:8AUST
Date:Mar 1, 2008
Words:598
Previous Article:Inoprotection review.
Next Article:Use of unapproved medicines in anaesthesia practice in New Zealand.
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