Foulds

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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

Clinical Question

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

Design

  • 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.

Setting

  • Operating Theatres, Single centre, Scotland
  • Dates of data collection not stated

Population

  • 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%

Intervention

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

Control

  • 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

Outcome

  • 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%

Authors’ Conclusions

  • 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.

Strengths

  • Clinically important question
  • Appropriate design to compare techniques
  • Randomisation via random number sequence
  • Powered prospectively
  • Similar baseline characteristics

Weaknesses

  • 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

The Bottom Line

  • 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.

External Links

Metadata

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

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