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Correspondence

Can't intubate, can't ventilate: rescue airway using a size 2½ laryngeal mask airway in a morbidly obese female patient

Lomax, Suzi La; Loveland, Robinb; Rangasami, Jairajb

Author Information
European Journal of Anaesthesiology: December 2009 - Volume 26 - Issue 12 - p 1090-1091
doi: 10.1097/EJA.0b013e32832a2273

Editor,

With the incidence of obesity increasing in the UK, difficult mask ventilation with increasing BMI is well documented. The laryngeal mask airway (LMA) is an established adjunct for use when difficulty is encountered with mask ventilation. We describe a case of a morbidly obese female patient which deteriorated into a can't intubate, can't ventilate (CICV) scenario and how the situation was salvaged using a paediatric-sized LMA when other recognized techniques had failed. This is the first documented case of a paediatric-sized LMA being used as a rescue technique in an adult CICV scenario.

Case report

A 51-year-old female patient, known to be a Lehane and Cormack grade 4 laryngoscopy, presented for elective revision of a left total elbow replacement. At 110 kg, she had a BMI of 50. Apart from juvenile arthritis, her past medical history was unremarkable and she denied symptoms of obstructive sleep apnoea. Examination revealed a morbidly obese female patient with mouth opening of two fingers due to temporomandibular joint involvement and a Mallampati grade 4 view. She had a receding mandible and limited neck extension. The cricothyroid membrane was not palpable. Other examination and investigations were normal. For the original operation 2 years previously, the anaesthetist had abandoned an awake fibre-optic intubation (FOI) due to the patient being unable to tolerate it. Anaesthesia was achieved at that time using a gas induction, with mask ventilation made possible using a two-person technique. Intubation was ultimately performed fibre optically using a size 3 LMA. Extubation and the postoperative period had been uneventful. Over the intervening 2 years, the patient had gained 20 kg. A combined regional and general anaesthesia approach was planned. However, after her previous experience, despite counselling, the patient refused to undergo an awake FOI. Therefore, the initial plan was to induce anaesthesia while maintaining spontaneous ventilation and to perform an oral FOI using a Berman airway (Vital Signs, Littlehampton, UK). The back-up plan was to wake the patient up. The patient consented, and risks including hypoxic brain injury and death were discussed. Two anaesthetists with experience in difficult airway management were present, and an ear, nose and throat (ENT) surgeon was immediately available. The patient was positioned using a ‘ramping’ technique and the airway topicalized using 4% lidocaine. After preoxygenation, anaesthesia was induced using increments of propofol followed by a maintenance of sevoflurane in oxygen to maintain spontaneous ventilation. Oral FOI via the Berman airway failed due to supraglottic tissue folds obstructing the view, despite repositioning and resizing of the Berman airway. During this time, the airway had become increasingly obstructed despite maximum jaw thrust and a two-person mask technique. Despite success at the previous anaesthetic, oropharyngeal, nasopharyngeal airways and a size 3 LMA failed to improve the now impending CICV situation. A size 2½ classic LMA was inserted in an attempt to provide better positioning in the airway with the shorter tube length and smaller mask. Immediately on insertion, there was resolution of the clinical signs of obstruction. Anaesthesia was maintained using sevoflurane, and the size 2½ LMA was used as a conduit for a fibre optically placed Aintree intubating catheter (AIC) (Cook, Letchworth, UK), before removal of the LMA and railroading of a size 6.5 Fastrach endotracheal tube (Intavent Orthofix, Maidenhead, UK). An axillary brachial plexus block was performed and the 2½ h operation proceeded uneventfully. Prior to extubation, the AIC was reinserted and the patient extubated in the upright position fully awake. The postoperative period prior to discharge was uncomplicated.

Discussion

This is the first case in the literature in which a size 2½ LMA has been used, not only as a rescue technique but also as a conduit for intubation in the difficult adult airway. The reason for failing to establish a patent airway with the size 3 LMA in the same patient in whom previous use had been successful is unclear. Reasons often cited for difficulty with LMA insertion and airway obstruction, apart from light anaesthesia and laryngospasm, lay in a failure to negotiate the back of the tongue, epiglottic downfolding and overinsertion or underinsertion. The size 2½ LMA itself is shorter at 12.5 cm versus 19 cm with an internal diameter of 8.4 mm versus 10 mm. However, the likely reason was the size of the mask itself. It is credible that, in a morbidly obese female patient, the loss of upper airway tone, in combination with increased supraglottic folds of tissue, may result in a decreased space for the mask, thus causing potential folding of the size 3 tip onto itself and epiglottic downfolding. Alternatively, the underinsertion of the larger size 3 cuff may have in fact resulted in the LMA tip impinging on the arytenoids causing them to infold or for the tip itself to collide with the laryngeal inlet causing complete obstruction. The only major change on examination was the patient's weight gain with potential changes in the supraglottic tissues which may have been more suited to the smaller mask size of the size 2½ LMA. However, on searching the literature, there are no data looking at pharyngeal architecture in patients with increased BMIs and how this impinges on LMA size. Indeed, the manufacturers advocate a size 6 LMA for patients over 100 kg and a size 2½ for patients of 20–30 kg. With the increased numbers of morbidly obese patients presenting for surgery and documented difficulty with mask ventilation, this is an area requiring further study.

Owing to the previous difficulties, an appropriate plan for this patient would have been to perform an awake FOI. It is unclear from the records as to why the procedure was not previously tolerated by the patient but highlights the importance of appropriate sedation, good topicalization, and skilled endoscopy. A number of different sedation techniques and drugs are used individually or in combination. The merits of propofol versus remifentanil have been previously discussed [1]. Although propofol has the benefit of amnesia, particularly of importance in patients requiring repeated procedures, remifentanil has been shown to generate better intubating conditions, is more ‘forgiving’ of inadequate topicalization, and advocates argue that amnesia is less of an issue if the procedure is done well with no patient distress. The learning curve for nasal FOI has been quoted as 18 to achieve intubation in less than 60 s, but the number required to maintain those skills is unclear [2]. Indeed, awake FOI failure rates have been previously quoted as 1.5%, and anaesthetists in the UK in comparison with other countries do not perform many awake FOIs, resulting in a rarely practised skill which is then used in difficult patients [3].

The merits of an inhalational versus intravenous induction to maintain spontaneous ventilation have been previously discussed in the literature, and the target-controlled infusion (TCI) of propofol may have given more control and perhaps averted the CICV scenario. However, it is likely that problems with upper airway obstruction would still have remained an issue in trying to achieve a deep enough plane of anaesthesia for airway manipulation even in the presence of airway topicalization. In addition, difficulties lay in deciding the appropriate weight for TCI pump programming.

Case reports of intubation using an AIC loaded on a fibre-optic scope and using a classic LMA in difficult intubations have been reported in the literature [4,5]. Indeed, there are two case series published regarding the use of the AIC via the classic LMA in adults, but none using a paediatric-sized LMA in this group [6,7]. This is the first case in the literature.

Finally, this case highlights several ethical issues and the importance of communication between the anaesthetist and the patient after the difficult situation of a previously failed awake FOI and the importance of informed consent.

We have described the successful rescue of a morbidly obese patient in a CICV scenario using a recognized technique yet in an unconventional way by using a paediatric-sized LMA in a morbidly obese adult. This case reiterates the difficulty of mask ventilation, a need for alternative techniques for airway patency, and further work required to ascertain the appropriate size of LMA in this group of patients when difficulty arises.

References

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2 Smith J, Jackson A, Hurdley J, et al. Learning curves for fibreoptic nasotracheal intubation when using the endoscopic video camera. Anaesthesia 1997; 52:101–106.
3 Heidegger T, Gerig H, Ulrich B, et al. Structure and process quality illustrated by fibreoptic intubation: analysis of 1612 cases. Anaesthesia 2003; 58:734–739.
4 Zura A, Doyle D, Orlandi M. Use of the Aintree intubation catheter in a patient with an unexpected difficult airway. Can J Anesth 2005; 52:646–649.
5 Avitsian R, Doyle D, Helfand R, et al. Sucessful reintubation after cervical spine exposure using an Aintree intubation catheter and a laryngeal mask airway. J Clin Anesth 2006; 18:224–225.
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7 Higgs A, Clark E, Premraj K. Low-skill fibreoptic intubation: use of the Aintree Catheter with the classic LMA. Anaesthesia 2005; 60:915–920.
© 2009 European Society of Anaesthesiology