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Three Part Question

In [patients in whom a cervical injury is suspected] is [a McCoy laryngoscope better than a Macintosh laryngoscope] at [improving the view of the laryngeal inlet]?

Clinical Scenario

A 24 year old male is brought to the emergency department after falling whilst sat on the window of a moving car. His only apparent injury is to the head where there is a laceration to the occiput. He is brought in tolerating a guedel airway. He responds to pain with abnormal flexion and opens his eyes to pain, there is no vocal response (GCS 7). You decide to intubate the patient using an RSI technique. As a cervical injury cannot be excluded you attempt intubation in the neutral position with manual C-spine control and the hard collar removed. At laryngoscopy using a size 4 Macintosh blade you are unable to visualise the cords (Grade 3 view) but manage to intubate the patient using a gum elastic bougie. Later, when discussing the case with an anaesthetic colleague they ask why you did not use a McCoy laryngoscope as they claim that these are better when patients are intubated in the neutral position. You wonder is there is any evidence to back this up before you go and buy some more equipment for the emergency department.

Search Strategy

Medline 1966-12/2000 using the OVID interface.
[MCCOY".mp.] AND [exp intubation intratracheal OR exp laryngoscopy OR "laryngoscope".mp]. limit to human and english language and abstracts

Search Outcome

11 papers found of which 2 papers were relevant to the original question.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Uchida T et al, 1997, Canada	50 female patients undergoing elective surgery. Patients were kept in the neutral position by an assistant using inline cervical immobilisationEither a size 3 Macintosh, or size 3 McCoy blade was used	Clinical Trial using within patient controls	% of grade 3 or 4 views at laryngoscopy	76% with Macintosh vs. 16% with McCoy blade (p<0.01)	Only Female patients studied. Elective setting.All patients were first examined using the Macintosh before using the McCoy.The 2 patients scored grade 4 wit the Macintosh did not improve with the McCoy
			Number of patients in whom view improved with McCoy	View was improved in 74% of cases using Cormack score.
Laurent SC et al, 1999, UK	167 elective patients intubated in the neutral c-spine position.Each patient had laryngoscopy performed with both Macintosh and McCoy blades (both size 3 blades)	Clinical trial using within patient controls.Patients were randomised as to which laryngoscope was used first	Cormack view at laryngoscopy	Grade 3 or 4 view in 33% of cases with Macintosh as compared to 5% with McCoy (p<0.001).	Elective setting.Only a size 3 blade used. The authors state that the view may have been improved in some patients by using a size 4 blade.There were no grade 4 views in this study.
			Number of patients who's Cormack score improved	View improved by one or more Cormack grades in 57% of patients using McCoy laryngoscope

Comment(s)

Cormack score is a measure of the view at laryngoscopy. A grade 1 view is the best, 4 the worst. Difficult laryngoscopy has been defined as a Grade 3 or 4 view.

Clinical Bottom Line

The McCoy laryngoscope should be available when RSI is attempted in the patient in whom a cervical spine injury is suspected.

References

1. Uchida T, Hikawa Y, Saito Y et al. The McCoy levering laryngoscope in patients with limited neck extension. Canadian Journal of Anaesthesia 1997;44(6):674-6.
2. Laurent SC, de Melo AE, Alexander-Williams JM. The use of the McCoy laryngoscope in patients with simulated cervical spine injuries. Anaesthesia 1996;51(1):74-5.