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Nasotracheal Intubation, Direct Laryngoscopy and the GlideScope®

Section Editor(s): Saidman, LawrenceJones, Philip M. MD; Turkstra, Timothy P. MD

doi: 10.1213/ane.0b013e31818fa2b7
Letters to the Editor: Letters & Announcements
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Department of Anesthesia and; Perioperative Medicine; London Health Sciences Centre; University Hospital; London, Ontario; Canada; philip.jones@lhsc.on.ca

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In Response:

We agree with Dupanovic that not having to use Magill forceps when using the GlideScope® for nasotracheal intubation may have accounted for some of the improvement seen in time to intubation, ease of intubation, and the lower incidence of moderate to severe sore throat.1 Indeed, we stated as much in the original manuscript: …“ Magill forceps were not used when using the GlideScope®—reducing the amount of time necessary for insertion of the Magill forceps, manipulation of the nasotracheal tube tip, and removal of the Magill forceps.”2

However, we do not agree that it would be helpful to separately analyze time to intubation in the subset of direct laryngoscopy patients in whom the Magill forceps were not used. Using Magill forceps was optional in the trial protocol, and hence the forceps were only used if the operator deemed them necessary to successfully complete the intubation. Direct laryngoscopy for nasotracheal intubation is inextricably linked with the usage of Magill forceps in a certain proportion of cases.3,4 Analyzing only the subset of those patients in whom Magill forceps usage was not necessary would only be reasonable if that subset could be reliably predicted ahead of time. Since this is not possible, it is necessary to analyze all patients in the groups to which they were randomized. In addition, subgroup analysis is rarely warranted and is prone to false conclusions.5 Because of the randomized trial design, any observed differences between the groups can be attributed solely to the intervention: it just so happens that one intervention (direct laryngoscopy) often requires the use an adjunct (Magill forceps) in order for it to be successful, and the other does not.

Philip M. Jones, MD

Timothy P. Turkstra, MD

Department of Anesthesia and

Perioperative Medicine

London Health Sciences Centre

University Hospital

London, Ontario

Canada

philip.jones@lhsc.on.ca

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REFERENCES

1. Dupanovic M. Nasotracheal intubation, direct laryngoscopy and the GlideScope®. Anesth Analg 2009;108:674
2. Jones PM, Armstrong KP, Armstrong PM, Cherry RA, Harle CC, Hoogstra J, Turkstra TP. A comparison of GlideScope videolaryngoscopy to direct laryngoscopy for nasotracheal intubation. Anesth Analg 2008;107:144–8
3. Hirabayashi Y. GlideScope videolaryngoscope facilitates nasotracheal intubation. Can J Anaesth 2006;53:1163–4
4. Lee JH, Kim CH, Bahk JH, Park KS. The influence of endotracheal tube tip design on nasal trauma during nasotracheal intubation: magill-tip versus murphy-tip. Anesth Analg 2005;101:1226–9
5. Oxman AD, Guyatt GH. A consumer’s guide to subgroup analyses. Ann Intern Med 1992;116:78–84
© 2009 International Anesthesia Research Society