Evaluation of six videolaryngoscopes in 720 patients with a simulated difficult airway: a multicentre randomized controlled trial

Kleine-Brueggeney. BJA 2016; 116(5):670-9. doi: 10.1093/bja/aew058

Clinical Question

In patients having elective surgery and with a simulated difficult airway (using a cervical collar), does the choice of videolaryngoscope affect the first attempt intubation success rate?

Design

Multicentre randomised controlled trial

Computer generated randomisation using sealed opaque envelopes

Block randomisation of 10 and separated for each anaesthetist

6 different videolaryngoscopes were evaluated

Intention to treat analysis

Sample size calculation: 107 patients per device were required to give an α level of 0.05 and a power 80%. This was based on an intubation success rate of 0.9 as the clinically acceptable lower limit for a device that is designed for management of difficult airways

Setting

3 university hospitals in Switzerland

December 2012 – January 2015

Population

Inclusion: Patients undergoing elective surgery requiring tracheal intubation; ASA I-III

Exclusion: risk of aspiration and known or predicted difficult airway (BMI >35 kg m −2 , Mallampati >III, thyromental distance <6 cm, interincisor distance <3.5 cm, known difficult mask ventilation/ laryngoscopy, and planned or previous history of awake tracheal intubation)

, Mallampati >III, thyromental distance <6 cm, interincisor distance <3.5 cm, known difficult mask ventilation/ laryngoscopy, and planned or previous history of awake tracheal intubation) 720 patients (120 in each group)

Baseline characterstics: sex; age; BMI; mallampati score; thymomental distance; mouth opening with and without collar were similar in all groups

Intervention

6 different videolaryngoscopes were evaluated three unchannelled Reusable C-MAC TM D-blade and stylet GlideScope TM blade 3 with glidescope stylet McGrath TM with MAC blade 3 and stylet three channelled Airtraq TM size 2 in women and 3 in men A.P. Advance TM difficult airway blade KingVision TM with blade 3

Airway managed by one of twelve consultant anaesthetists

Cervical collar was used to simulate a difficult airway. This was adjusted to permit a minimal mouth opening of 18mm. The head was was taped to the trolley to inhibit neck movement

Successful intubation was defined as placement of the tube in the trachea within 180 s, confirmed by end-tidal carbon dioxide

Two intubation attempts with the randomised videolaryngoscope were allowed. The study was terminated once tracheal intubation was achieved, after two unsuccessful attempts, or when airway injury, bronchospasm, technical failure of the videolaryngoscope, or a reduction of oxygen saturation below 90% occurred

Control

Each videolaryngoscope was compared with the other five

Outcome

Primary outcome: first-attempt intubation success rate > 90% for C-MAC and McGrath 95% CI > 0.9 only for McGrath McGrath : 117 patients (98%) CI 92-99 C-MAC : 114 patients (95%) CI 89-98 KingVision : 104 patients (87%) CI 79-92 GlideScope : 102 patients (85%) CI 77-90 Airtraq : 102 patients (85%) CI 77-90 A.P. Advance : 44 patients (37%) CI 28-46

Secondary outcome: subjective grade of handling of videolaryngoscope – combined excellent and good ratings: insertion of the device into the oropharynx McGrath (94%) > CMAC (91%) > Glidescope (79%) > Airtraq (73%) > KingVision (67%) > A.P Advance (58%) quality of view McGrath (93%) + Glidescope (93%) + Airtraq (93%) > CMAC (92%) > KingVision (91%) > A.P Advance (73%) ease of tube insertion Airtraq (82%) > McGrath (78%) > KingVision (73%) CMAC (69%) > Glidescope (64%) > A.P Advance (52%) median time to view vocal cords (in seconds) CMAC (17) > McGrath (18) > Glidescope (19) > Airtraq (20) > KingVision (26) > A.P Advance (30) median time to advance tube (in seconds) Airtraq (27) > KingVision (31) > McGrath (33) > CMAC (36) > Glidescope (40) > A.P Advance (50) median intubation time of successful attempt (in seconds) Airtraq (47) > McGrath (53) > CMAC (56) > KingVision (59) > Glidescope (60) > A.P Advance (93)

Adverse events: no statistically significant differences between the videolaryngoscopes for side-effects such as hoarseness (11–18%), sore throat (10–19%), dysphagia (2–8%), or postoperative nausea and vomiting (9–14%)

Authors’ Conclusions

This trial revealed differences in the performance of six videolaryngoscopes in 720 patients with restricted neck movement and limited mouth opening. In this setting, first-attempt success rates were 85–98%, except for the A.P. Advance difficult airway blade. Highest success and lowest tissue trauma rates were achieved by the McGrath and C-MAC D-blade, highlighting the importance of the videolaryngoscope blade design

Strengths

Study was registered at clinicaltrials.gov (identifier NCT01692535)

To ensure that each anaesthetist intubated 10 times with each videolaryngoscope, block randomisation was separated for each anaesthetist participating in this study

Induction and neuromuscular blocking agent (rocuronium 0.6mg/kg) choice was standardised

Adequate neuromuscular block in readiness for tracheal intubation was controlled by loss if 1Hz muscle twitching (TOF Watch TM )

) All participating consultant anaesthetists were considered airway management experts and trained with all videolaryngoscopes on both manikins and patients until they, as airway specialists, felt competent with each device

This is a well constructed trial bound by the limitations of airway equipment research: blinding and subjectivity are hard to improve

Weaknesses

A standard Macintosh laryngoscope would have been a useful control . The authors provide reasons for this

We did not include a standard Macintosh laryngoscope with direct laryngoscopy because it is known that in patients with difficult airways videolaryngoscopes are superior regarding intubation success rates, glottic view, and rates of difficult intubation

The C-MAC videolaryngoscope macintosh blade would have been a useful comparator

The performance ability for each anaesthetists with the range of videolaryngoscopes was based on self-assessment for competency

Exclusion of patients with predicted difficult airways (including anyone obese) may limit external validity / generalisability

Applying a collar for simulation is not the same as all difficult airways that may present to anaesthetists

The Bottom Line

The trial primary hypothesis, first attempt intubation success rate > 90%, was accepted only for the McGrath. The A.P Advance performed well below the other comparators. Whilst the internal validity of the trial is limited by subjectivity and the operator being unblinded, it provides a useful overview of variation in performance and handling of the scopes

External Links

Metadata

Summary author: Steve Mathieu

Summary date: 30th May 2016

Peer-review editor: Duncan Chambler