You probably don’t need a medical degree to know that breathing is important, and that in order to breathe, you need to have an unobstructed airway that connects your lungs to the world. As a result, when you die, one of our first instincts in medicine is to ensure that you have an open airway. However, if your heart is stopped, fiddling around with the airway will do nothing to restart it. Furthermore, it has never been clear whether advanced airway interventions like intubation are any better than simply maneuvers like a jaw thrust in the context of cardiac arrest. Although emergency physicians love intubating, observational data has suggested that advanced airway management might not be a priority in cardiac arrest. (Hasegawa 2013; Benoit 2015) This week we will cover 3 large RCTs addressing the issue. This is part 1.
The rest of the series:
Benger JR, Kirby K, Black S, 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; 320(8):779-791. PMID: 30167701
AIRWAYS 2 is a multicenter, cluster randomized trial.
Patients: Adult patients with non-traumatic out of hospital cardiac arrests, treated by a participating paramedic from 1 of 4 ambulance services in England.
- Exclusions: Resuscitation deemed inappropriate, advanced airway already in place when the paramedic arrived, patient known to be enrolled in another prehospital RCT, or patient’s mouth opened less than 2 cm.
Intervention: Supraglottic airway (SGA) (second generation without an inflatable cuff; i-gel) as the initial advanced airway management plan.
Comparison: Tracheal intubation (direct laryngoscopy, with a bougie recommended) as the initial advanced airway management plan.
- Randomization was done at the level of the paramedic (1523 paramedics were randomized).
- Paramedic discretion in choosing the airway device was allowed.
Outcome: The primary outcome was survival with good neurologic outcome at 30 days or hospital discharge, whichever occurred sooner.
9296 patients were enrolled (out of 26,376 screened).
There was no difference in the primary outcome of neurologically intact survival (6.4% with SGA and 6.8% with ETT; adjusted risk difference −0.6%; 95% CI, −1.6% to 0.4%).
There was significant crossover between the two groups. In the SGA group, 82% actually got a SGA, while 15% did not receive an advanced airway, and 2% were intubated. In the intubation group, 62% were intubated, 22% did not get an advanced airway, and 14% received an SGA. Clearly, the groups are not balanced.
There was no difference in regurgitation or aspiration.
The SGA group was more likely to have successful ventilation after up to 2 attempts (87.4% vs 79.0%)
In the SGA group, there was also a higher rate of loss of a previously established airway (11% vs 5%).
AIRWAYS 2 is a large RCT that looks at a group of patients I care about and an outcome that I (and more importantly patients) care about.
There are a number of shortcomings. Randomizing at the level of the paramedic allows for selection bias. There were some paramedic “super recruiters”, but it isn’t clear why. Although the number of paramedics randomized was equal (696 vs 686), the number of patients recruited to the SGA group was much higher (4886 vs 4410).
This is a unblinded trial and paramedics were allowed to use the alternative technique if they saw fit, resulting in a number of crossovers, and potential selection bias. There were more crossovers in the intubation group.
Crossover is not inherently bad. In fact, constricting the clinician’s’ choice to only a single airway technique would have created a faulty control group. That isn’t how we practice in real life. In real life, we use clinical judgement to choose the right intervention for the right patient.
The crossover between groups reminds us that we should not be dogmatic about applying these results in practice. (Of course, we should never be dogmatic about applying any research results.) If you decided to continue to use tracheal intubation as your first line option based on these results, it is clearly important to be trained in supraglottic airways, as a significant number of patients may not be intubatable in a prehospital setting. On the other hand, if you interpret the results as indicating that supraglottic airways are the better first line option, you have to be aware that there still may be patients who would benefit from a tracheal intubation.
In what will be a recurring theme this week, we have to be careful about extrapolating these results to other environments, where different providers may be present in the prehospital arena, and different equipment or techniques might be used. For intubation in particular, the results of a trial could be significantly influenced by the skill level of the individuals performing the intubations. That being said, the results are pretty consistent with all other research available on this topic, and therefore probably allow us to make general decisions about how to train and equip our EMS crews.
This is a pragmatic trial. It doesn’t provide us with a perfect “clean” scientific answer comparing SGA to intubation, because it allowed for judgement and crossover between the two groups. The pragmatic nature of the trial makes the results a little more “messy”, but I think the two groups probably do a good job of representing real world practice, and therefore suggest that endotracheal intubation is unlikely to be beneficial over supraglottic airway use in the real world.
I have always favoured a LMA first approach to cardiac arrest. That approach is supported by this study. However, I appreciate that there will be cases that will warrant early intubation, and will continue to use clinical judgement in my choice of airway management.
Benger JR, Kirby K, Black S, 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; 320(8):779-791.
Benoit JL, Gerecht RB, Steuerwald MT, McMullan JT. Endotracheal intubation versus supraglottic airway placement in out-of-hospital cardiac arrest: A meta-analysis. Resuscitation. 2015; 93:20-6.
Hasegawa K, Hiraide A, Chang Y, Brown DF. Association of prehospital advanced airway management with neurologic outcome and survival in patients with out-of-hospital cardiac arrest. JAMA. 2013;309(3):257-266.
Jabre P, Penaloza A, Pinero D, et al. Effect of Bag-Mask Ventilation vs Endotracheal Intubation During Cardiopulmonary Resuscitation on Neurological Outcome After Out-of-Hospital Cardiorespiratory Arrest: A Randomized Clinical Trial. JAMA. 2018; 319(8):779-787.
Wang HE, Schmicker RH, Daya MR, 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.