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Correspondence

The intubating laryngeal mask airway (ILMA): disadvantage of being a blind technique

DIMITRIOU, V.; VOYAGIS, G. S.

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European Journal of Anaesthesiology: June 1999 - Volume 16 - Issue 6 - p 418-419

Sir:

Several recent studies have supported the use of the intubating laryngeal mask airway (ILMA), both as a ventilatory device and as blind intubation guide [1-5], but there is only limited data concerning the possibility of accidental oesophageal intubation (OESI). However, several studies demonstrate that the oesophageal inlet may be included in the bowl of the standard laryngeal mask airway (LMA) in 9% of patients [6,7]. In a recent paper the ILMA position was graded fibrescopically and OESI was reported in three of 100 patients [3]. In a limited series reporting the use of ILMA in patients with difficult airways, OESI was reported in one of 30 patients [5]. However, in two other published series (n = 150 [2], n = 100 [4]), the lack of evidence for OESI prevents confirmation of this.

We would like to report in our experience the incidence of OESI through the ILMA. After institutional approval and patient consent, we studied 100 patients ASA I or II presenting for elective surgery. Patients were excluded if they were at risk of regurgitation - aspiration. Two senior anaesthetists experienced in the placement of LMA, studied 50 patients each. After induction of anaesthesia with fentanyl 1 mg kg−1 and propofol 2.5-3.0 mg kg−1, neuromuscular block was achieved with cisatracurium 0.15 μg kg−1. The patients' lungs were ventilated for 3 min with 100% oxygen supplemented with sevoflurane 2% and then an ILMA of the size appropriate to patient weight was introduced according to the manufacturer's guidelines [2]. Successful placement was judged by chest wall movement and capnography as well as by the ability to deliver a tidal volume of 7 mL kg−1 without a leak, at an airway pressure 20 cm H2O. Blind tracheal intubation (TI) was attempted through the ILMA using a silicone tracheal tube (TT) 7.0-8.0 mm. If the first intubation attempt failed, a sequence of adjusting manouevres was performed according the inventor's guidelines [2]. Successful TI was determined by capnography. The ILMA was inserted successfully at the first attempt in all patients. The overall success rate for TI was 91% (45 of 50, 90% and 46 of 50, 92% for each investigator, respectively) − 48% on the first attempt, 20% on the second attempt while 23% required 3-5 attempts. Oesophageal intubation occurred in eight patients (8%) during the first attempt at intubation (5 of 50, 10% and 3 of 50, 6% for each investigator, respectively). However, it was noticed that five of the above eight patients were finally intubated successfully by applying the optimized airway manoeuvre (after withdrawal of the TT from the metal tube of the ILMA, the ILMA was guided with the handle while squeezing the reservoir bag with the expiratory valve of the circuit closed, until an optimal airway was obtained and afterwards a reinsertion of the TT was attempted) [2]. Comparison of our data with that previously published [3,5] revealed that there is no significant difference in the incidence of OESI. Thereafter, difference in percentages result from random chance fluctuations. It should be noted that these three percentages (8%, 3% [3], 3.3% [5]) are statistically homogeneous and consequently it might be presumed that the real incidence of OESI is 5.2% i.e. 12/230.

In summary, we consider that the ILMA, being a 'blind on blind' technique (i.e. both the ILMA and TT are inserted without direct vision of the larynx), runs the risk for accidental OESI, because the oesophageal inlet may be included in the bowl of the ILMA. This event is not necessarily associated either with the inability to ventilate the patient's lungs through the ILMA or with final failure to achieve a successful TI through the ILMA. Thereafter, capnography and/or any other oesophageal detector device should be always available whenever a blind TI through the ILMA is performed.

V. DIMITRIOU

G. S. VOYAGIS

Department of Anaesthesiology, Gennimatas and Sotiria Hospitals, Athens, Greece

References

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© 1999 European Society of Anaesthesiology