REBEL Cast Ep 59: AIRWAYS-2 – Supraglottic vs Tracheal Intubation in OHCA

Background:There is a lack of high quality RCTs  investigating optimal airway management in patients with out-of-hospital cardiac arrest (OHCA).  The majority of evidence comes from observational studies and expert opinion. The observational trials have consistently favored basic airway management (i.e. BVM) over tracheal intubation [3]. Supraglottic airway(SGA) devices offer an alternative advanced airway management technique to endotracheal intubation (ETI) during OHCA. SGA devices may offer an advantage over ETI as they are simpler and faster to place.  Additionally, proficiency  with SGAs requires less training and ongoing practice. Although there have been several recent studies published on airway management in OHCA, this post/podcast will focus on the recently published AIRWAYS-2 trial.

REBEL Cast Episode 59 – AIRWAYS-2 – Supraglottic vs Tracheal Intubation in OHCA?

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What They Did: This was a multicenter, cluster*randomized clinical trial of paramedics from 4 ambulance services in England. The objective of the study was to determine whether a supraglottic airway device (SGA) is superior to tracheal intubation (TI) as the initial advanced airway management strategy in adults with non-traumatic OHCA

• *Interestingly, randomizing patients at the point of OHCA was considered impractical, therefore, paramedics were randomized to use 1 of 2 advanced airway management strategies for the eligible patients that they treated
  • SGA = Second-generation supraglottic airway device with a soft non-inflatable cuff (i-gel; intersurgical)
  • TI = Direct laryngoscopy as video laryngoscopy not used by paramedics in England

Outcomes:

• Primary: modified Rankin Scale (mRS) score at hospital discharge or 30 days after OHCA (whichever occurred sooner). mRS dichotomized into good outcome (score 0 – 3) vs poor outcome (score 4 – 6)
• Secondary:
  • Initial ventilation success (visible chest rise)
  • Regurgitation (stomach contents visible in the mouth or nose)
  • Aspiration (stomach contents visible below the vocal cords or inside a correctly placed tracheal tube or airway channel)
  • Unintended loss of a previously established airway
  • Sequence of airway interventions delivered
  • Return of spontaneous circulation (ROSC)
  • Airway management in place when ROSC achieved or resuscitation discontinued
  • Chest compression fraction (in a subset of patients)
  • Time to death

Inclusion:

• Age ≥18 years
• Non-traumatic OHCA
• Treated by a participating paramedic who was either the 1^stor 2nd paramedic to arrive at the scene
• Resuscitation was commenced or continued by emergency medical services personnel

Exclusion:

• Prisoners
• Previously recruited to the trial
• Resuscitation deemed inappropriate
• Advanced airway in place prior to arrival of participating paramedic
• Known to be enrolled in another prehospital RCT
• Patients mouth opens <2cm

Results:

• 9,296 patients enrolled into trial
  • SGA Group = 4886
  • TI Group = 4410
• Good mRS Score (0 – 3) at Hospital DC or 30 days:
  • SGA = 6.4%
  • TI = 6.8%
  • Adjusted RD -0.6%; 95% CI -1.6% – 0.4%
• Successful Initial Ventilation:
  • SGA: 87.4%
  • TI = 79.0%
  • Adjusted RD 8.3%; 95% CI 6.3% – 10.2%
• No statistical difference in aspiration or regurgitation
• 7576 (81%) of patient received advanced airway management
  • Good Neuro Outcome:
    • SGA = 3.9%
    • TI = 2.6%
    • Adjusted OR 1.57; 95% CI 1.18 – 2.07
  • 1,707 of patients received no advanced airway management
    • Survival
      • TI but No Advanced Airway Management = 25.2%
      • SGA but No Advanced Airway Management = 23.9%
    • Survival with Good Neuro Outcome
      • TI but No Advanced Airway Management = 21.6%
      • SGA but No Advanced Airway Management = 20.5%

Strengths:

• Asks a clinically important question that has not previously been adequately answered
• Largest RCT on airway management in OHCA
• Paramedics could not be blinded to their allocation which could cause risk of bias in recruitment by paramedics based on patient’s perceived likely outcome. Therefore eligible patients treated by a participating paramedic were automatically enrolled in the study
• Because OHCA requires immediate treatment, randomizing patients at the point of OHCA was considered impractical, therefore, paramedics were randomized to use 1 of 2 advanced airway management strategies for the eligible patients that they treated
• A standard approach to airway management (from basic to advanced techniques) was agreed on by the participating ambulance services
• Assessors who collected the modified Rankin Scale score were blinded to treatment group
• Used previous retrospective data to determine the power calculation of requiring 9070 patients to detect a difference of 8 vs 10% at a significance level of 5% with 90% power after allowing clustering
• Patient characteristics and cardiac arrest details were balanced between groups

Limitations:

• Automatic enrollment may have caused patients to not be treated according to the study protocol if paramedics could not recall the protocol details
• The ventilation and tracheal intubation success rate (≈70%) in this study was lower than previous other observational trials, which may be due to practitioners with lesser training and experience in this study
• Imbalance in the number of patients in the 2 groups, due to unequal distribution of a small number of paramedics who recruited considerably more patients than the average
• There was a significant crossover differential between groups (i.e. tracheal intubation arm (≈20% cross over) vs the SGA group (≈3%))
• Other elements of care (i.e. initial basic airway management, subsequent on-scene and in-hospital care, such as TTM and access to angiography) followed established guidelines and between group differences could have influenced the findings of this study
• Participating paramedics were volunteers, and their airway skills may not be representative of those who chose not to participate in the study
• The findings are applicable to use for the particular supraglottic airway device in countries with similar EMS provisions to England where paramedics treat most patients with OHCA

Discussion:

• The trial protocol specified 2 attempts using the allocated strategy before proceeding to the alternative, however paramedics had discretion to deviate from the trial protocol on clinical grounds
• Emergency call to 1^stparamedic arrival was 7 – 8 minutes (This is fast)
• Presenting Rhythm was Asystole in ≈54% of patients
• CPR prior to paramedic arrival in ≈63% of patients
• Compression fraction in a small sample of patients was rather good between groups (SGA 86% vs TI 83%) and not statistically different
• Patients with a short duration of cardiac arrest and who receive bystander resuscitation defibrillation or both are considerably more likely to survive and are less likely to require advanced airway management. This creates a problem of confounding by indication which is an important limitation of large observational studies that show an association between advanced airway management and poor outcomes in OHCA (i.e. patients who have quick cardiac arrest with ROSC will obviously have better survival with neurologic outcomes than patients with more prolonged cardiac arrest that may require more advanced airway management).
  • This is extremely evident when you look at the ROSC/survival outcomes in the patients not managed by any advanced airway interventions
• The use of advanced airway management was greater among paramedics in the supraglottic airway device group (85%) compared with those in the tracheal intubation group (78%), which could result in confounding by indication as well.
• Paramedics received additional training in their allocated advanced airway management intervention immediately after randomization. This can be seen as both a strength and a weakness. Great for provider proficiency, but additional training may lower generalizability to other prehospital systems
• The use of supraglottic airway devices as the first advanced airway technique in OHCA was associated with better outcomes, however the between group differences were less than the pre-specified clinically important difference and less than the minimally important difference of ≈3% reported in other studies.Therefore this is a hypothesis generating conclusion.
• A paper by Jabre P et al [2] comparing BVM vs TI for airway management during OHCA in >2000 patients in France and Belgium. The primary outcome was favorable neurological outcome at 28 days. There was essentially no difference in this outcome between groups (4.3% vs 4.2%; 95% CI -7.7% – 0.3%).
• Among patient with OHCA, it appears the key to airway management seems to be choosing a strategy that doesn’t get in the way of the things that matter most to achieve better survival with good neurologic outcomes (i.e. high quality CPR).

Author Conclusion: “Among patients with out-of-hospital cardiac arrest, randomization to a strategy of advanced airway management with a supraglottic airway device compared with tracheal intubation did not result in a favorable functional outcome at 30 days.”

Clinical Take Home Point: In patients with OHCA, there was no difference in survival with good neurologic outcome regardless of supraglottic airway or tracheal intubation, however the supraglottic airway is easier to place, more likely to be successful, not more likely to lead to more regurgitation/aspiration, and allows for more focus on high quality CPR and should be used as the primary advanced airway technique in OHCA.

Guest Expert

Ashley Liebig, RN, BSN, CCRN
Clinical Supervisor
STAR Flight
Austin, TX
Twitter: ashleyliebig

• The use of advanced airway management was greater among paramedics in the SGA group (85%) vs the use of tracheal intubation (78%). Also there was more crossover in the tracheal intubation arm (≈20%) vs the SGA arm (≈3%). Does this surprise you and what are your thoughts on this?
  • Ashley’s Response: There is a risk affiliated with tracheal intubation.  In the PART trial [4], there was a 2.7min difference from arrival to airway intervention, meaning SGA was an easier go to with less risk vs endotracheal intubation.
• There was no statistical or clinical difference in survival with neuro intact outcomes regardless of whether a SGA was used or ETI was performed. The use of SGA as the 1^stadvanced airway technique in OHCA was associated with better outcomes, however the between group differences were less than the pre-specified clinically important difference.  So maybe some signal that SGA is superior but hypothesis generating at best.  Do you think this should make us rethink which advanced airway device we should be using as our go to?
  • Ashley’s Response: Evidence interpretation is challenging because prehospital environments are dynamic.  If you have a large number of providers who are experienced in airway management, maybe endotracheal intubation is the way to go. But if providers only get one intubation every six months, or there are limited people available to assist with the resuscitation, then maybe SGA is the way to go.  This is going to be situation and service dependent.  Also we should caution translating care from one international profession to another.  There are a number of differences around the world from training, to education, to equipment available.  We have to consider these things when we draw conclusions from studies like this.

• Another paper by Jabre et al [2] in France and Belgium looked at BVM vs Tracheal intubation and also found no difference in survival with good neurologic outcome. The gap I see here is none of the papers compared BVM vs SGA.  In the pre-hospital setting which of these two devices do you think we should be using and why?
  • Ashley’s Response: Ashley agrees that SGA 100% over BVM in prehospital setting is the way to go. BVM has known risks of air in the belly, requires 4 hands to get a good seal and good simultaneous ventilation. SGA manages airway better than BVM with fewer hands required and less potential risks such as insufflating the stomach.
• So it appears that among patients with OHCA, the key to airway management seems to be choosing a strategy that doesn’t get in the way of the things that matter most to achieve better survival with good neurologic outcomes (i.e. high quality CPR and early defibrillation). Do you think this would be SGA in most services?
  • Ashley’s Response: Again this is dependent on the amount of training and maintenance of skills in any particular prehospital service. Maintaining airway skills requires cadaver labs, OR visits, and simulation training combined.  This may not be realistic in many services and we have to take a good look at what we can do in terms of training for our providers in making this decision.

Infographics From Study Authors:

References:

1. Benger JR et al. Effect of a Strategy of a Supraglottic Airway Device vs Tracheal Intubation During Out-of-Hospital Cardiac Arrest on Functional Outcome: The AIRWAYS-2 Randomized Clinical Trial. JAMA 2018. [Epub Ahead of Print]
2. Jabre P et al. Effect of Bag-Mask Ventilation vs Endotracheal Intubation During Cardioplmonary Resuscitation on Neurological Outcome after Out-of-Hospital Cardiorespiratory Arrest: A Randomized Clinical Trial. JAMA 2018 [Epub Ahead of Print]
3. Monsieurs KG et al. ERC Guidelines 2015 Writing Group. European Resuscitation council guidelines for Resuscitation 2015: Section 1: Executive Summary. Resuscitation 2015. PMID: 26477410
4. Wang HE et al. Effect of a Strategy of Initial Laryngeal Tube Insertion vs Endotracheal Intubation on 72-Hour Survival in Adults with Out-of-Hospital Cardiac Arrest: A Randomized Clinical Trial. JAMA 2018. PMID: 30167699

For More Thoughts on This Topic Checkout:

• The Resus Room Podcast: AIRWAYS-2 Featuring Lead Author Professor Jonathan Benger
• EM Lit of Note: The Great Prehospital Airway Debate
• EM Nerd: The Case of the Needless Imperative
• Emlyn’s: OOHCA and Airway Management – Do We Need a Tube?
• The Bottom Line: AIRWAYS-2
• First10EM: Airway Management in Cardiac Arrest Part 1 – AIRWAYS 2 (Benger 2018)

Post Peer Reviewed By: Anand Swaminathan, MD (Twitter: @EMSwami)