Foulds

A randomised cross-over trial comparing the McGrath® series 5 videolaryngoscope with the Macintosh laryngoscope in patients with cervical spine immobilisation

Foulds, L.T et al. Anaesthesia 2016. 71, 437-442. doi:10.1111/anae.13384

In patients with cervical immobilisation, does the Mcgrath® videolaryngoscope compared to the Macintosh laryngoscope provide a better view of the larynx?

Prospective, randomised controlled cross-over study
Randomisation by random number sequence.
Consecutive patients
Powered for equivalence: 50 patients required to determine that the primary outcome would be the same or better in 90% of patients (with 2-sided 95% C.I. of ±8%)
Procedure performed by 2 anaesthetists who were experienced in the use of both the McGrath and Macintosh laryngoscopes.

Inclusion criteria:
- Adult patients presenting for elective operative procedures requiring tracheal intubation.
- Without suspected C-spine pathology
Exclusion criteria:
- Hiatus hernia, symptomatic reflux, pharyngeal pathology, requiring alternative laryngoscopic procedure or raised intra-cranial pressure.
50 patients randomised. 1 patients had procedure cancelled post randomisation
Comparing baseline characteristics and airway parameters of group intubated with McGrath vs. Macintosh laryngoscope – no significant differences
- BMI: 27.4 vs. 29.2
- Mallampati 3/4: 25% vs. 24%
- Mouth-opening <3cm: 4% vs. 0%
- Reduced neck movement: 12.5% vs. 0%

Laryngoscopy with Macintosh blade, followed by laryngoscopy and intubation with McGrath videolaryngosope

Laryngoscopy with McGrath videolaryngoscope, followed by laryngoscopy and intubation with Macintosh blade

In both intervention and control groups

Patients paralysed with muscle relaxant and immobilised with C-spine collar
Initial laryngoscopy to assess view only
For Macintosh laryngoscopy size 4 blade used
For McGrath laryngoscopy, series 5 videolaryngoscope used, with blade set at middle length, and use of stylet pre-formed with 60 degree bend 4cm from the tip
In between each laryngoscopy, the patient was re-oxygenated

Primary outcome: View obtained (Cormack and Lehane grade)
- Cormack and Lehane grade better (92%) or the same (8%) in the McGrath® group versus the Macintosh group (p < 0.01)
- Comparing McGrath® vs. Macintosh group
  - 92% vs. 6% had a Grade 1 view
  - 0% vs. 57% had a Grade 3/4 view
Secondary outcomes: comparing McGrath vs. Macintosh group
- Time to intubation – no significant difference
  - 45 seconds vs. 60 seconds, p = 0.125
- Rate of successful intubation – significantly higher in McGrath group
  - 100% vs. 72%, p=0.017
  - Fragility index: 2 patients
- Complications – No significant difference
  - Minor trauma to lips/pharynx: 10% vs. 20%
  - Desaturation <92%: 0% vs. 4%

In patients with a simulated difficult airway, via cervical immobilisation, the McGrath® videolaryngoscope provided significantly improved laryngeal views when compared with the Macintosh laryngoscope.
Furthermore, the use of the McGrath® videolaryngoscope provided increased tracheal intubation success rates.

Single centre
Only two anaesthetists, both experienced in McGrath® videolaryngoscopy
Didn’t reach target recruitment for power calculation.
Immobilised patients in reality often anaesthetised as an emergency using manual in-line stabilisation rather than electively in theatres with the presence of a cervical collar.
Non-blinded
Lack of standard anaesthesia/muscle relaxant
Subjective primary outcome

In this study, in patients immobilised with a semi-rigid cervical collar, the grade of laryngoscopic view and rate of successful intubations was greater when using a McGrath® series 5 videolaryngoscope when compared with a Macintosh blade, in the hands of two anaesthetists experienced in both techniques.

Summary author: Joe Schrieber
Summary date: 28/10/2016
Peer-review editor: David Slessor