What have we actually learned about running codes in the ED?
As the debate for the best airway in out-of-hospital cardiac arrest continues and remains largely inconclusive, what can we learn as emergency physicians running codes and managing the airway in the emergency department?
Minimally interrupted chest compressions of adequate depth and rate and early defibrillation have remained undisputed, core tenants of high-quality CPR, but the pharmacologic and airway management aspects remain under continuous debate. EMS providers are challenged with austere environments, limited personnel, limited equipment and few opportunities to maintain procedural skills, making airway choice in out-of-hospital cardiac arrest (OHCA) a complicated and important decision.
As emergency physicians, we are also then faced with a secondary decision of what, if anything, to do with the prehospital airway upon arrival to the ED. How does endotracheal intubation (ETI) compare with supraglotic airways (SGAs) and bag-valved masks (BVM’s)?
Airway in OHCA: The original evidence base
ETI > SGA
Endotracheal intubation (ETI) has been the gold standard for airway management in cardiac arrest for most EMS agencies. It definitively secures the airway, reduces the risk of aspiration from gastric insufflation and provides direct ventilation and oxygenation to the lungs. A 2015 meta-analysis with 75k total patients in 10 observational studies shows patients with OHCA are more likely to obtain ROSC and survive neurologically intact when they are intubated, as opposed to getting a supraglottic airway (SGA).[1]
A 2012 swine study showed supraglottic airways (SGA) reduces cerebral blood flow by compressing the carotid arteries. [2] While those results haven’t been duplicated in humans, it may have dissuaded some medical directors from recommending them as a first-line intervention.
BVM ≥ ETI
Despite the popularity of ETI, there are also several major studies supporting basic airway management with BVM only in lieu of intubation, claiming it was superior, equivalent or noninferior to intubation based on patient outcomes in OHCA.[3],[4],[5],[6]
A February 2018 study based in France and Belgium studied 2k patients in cardiac arrest and compared BVM and ETI, performed by an EMS physician and studied the cerebral performance category at 28 days. They found survival to hospital admission was 28.9% in the BVM group and 32.6% in the ETI group. [5] Survival at day 28 was 5.4% and 5.3%, both not statistically different. The unique aspect of this study compared to the other US studies is that the airway was managed by a physician as opposed to EMTs and paramedics yet outcomes were not significantly different between the airway types. There is a significant confounding variable with these studies, however.
Patients who have early ROSC are more likely to have basic airway management and are less likely to be intubated, which may falsely convey that survival is more likely because a BVM was used. This correlation is likely rather a function of other important variables known to increase rates of survival, such as brief down time, witnessed arrest, bystander CPR and early defibrillation.
For instance, if a patient gets resuscitated on scene for 30 minutes prior to ROSC, providers will have more opportunity to intubate the patient. On the other hand, if a patient gets defibrillated and gets ROSC within minutes of EMS arrival, they would be more likely to only have basic airway management (or perhaps none at all if they are protecting their own airway and ventilating on their own).
There have not been many studies comparing BVM to SGAs – BVM requires gentle, consistent positive pressure and a high-quality seal, often requiring at least two providers to work well. SGAs, however, can easily be performed by one provider and have fewer complications associated with gastric inflation compared to BVM’s or just oropharyngeal airways. Perhaps comparing these airway methods, or all three, would be a beneficial next step in the OHCA airway debate. The most recent major studies focused on SGA and ETI.
What’s new?
Two major OHCA airway studies came out last summer, the PART and AIRWAYS-2 trials. Using outcomes of 72-hour survival and ROSC, the PART trial found SGA to be superior to ETI[8] and the AIRWAY-2 trial showed no superiority for either SGA or ETI.[9] Neither specifically looked at oral airways or BVM use. Both articles have been heavily discussed and publicized, many citing the frustration of having a lack of a clear conclusion… should EMS intubate or not.
Other than ROSC, 72-hour survival and neurologic outcome, there are several other “outcomes” and questions worth considering:
What airway is best for patients in cardiac arrest once they’re in the ED?
The decision of what airway to initially place by an EMS provider is a complicated one, as the decision can lead to certain complications, affect compression quality, hands-off time, on-scene time and is performed by providers who rarely intubate when compared to EPs. Once the prehospital airway is placed and the patient transported to the ED, another decision has to be made by the Emergency Physician: Does the airway need to be exchanged, adjusted or should it be left alone?
Instead of basing that decision on whether the airway is “definitive,” i.e. an endotracheal tube in the proper location, the EP should instead base it on if the patient can be reliably ventilated, with adequate EtCO2. While the patient is adequately ventilated with their original airway, be it an oral airway, SGA or ETI, providers can then focus on maximizing other interventions and address the patient’s other H’s & T’s before eventually returning to the airway, if necessary.
While an SGA or oral airway may not definitively secure airways, swapping one out for an endotracheal tube is not always a benign procedure. Swapping the airway device can lead to aspiration, aggravation of cervical spine injuries, esophageal intubation, interruptions in compressions and delayed recognition and management of any other underlying pathology. These are all unnecessary complications if the patient was initially adequately ventilated.
How does avoiding endotracheal intubation in OHCA affect skill maintenance?
If paramedics used only basic airways for OHCA, it could also negatively affect their skill proficiency for other scenarios when intubation is indicated, like when initial basic airways fail in OHCA, cases of facial trauma or burns, etc. In a 2018 study of 57k+ airway procedures, authored by PART trial’s Dr. Wang, they found providers in systems with higher rates of intubation were successful intubating 92% of the time compared to providers who rarely intubated, who had a success rate of 77%.[1]
Whether paramedics should intubate patients in cardiac arrest mainly for skill maintenance elicits a moral question – if it leads to a patient in cardiac arrest dying that would have otherwise lived with an SGA, but saved another in respiratory arrest from asthma, would it be justifiable? While no experience can replace intubating a real patient in a real emergency, there are still ways to maintain providers’ procedural skills in the OR, simulation lab or with manikins, just as an emergency physician would maintain competency in performing a cricothyroidotomy.
If one airway were shown to be clearly superior, which EMS systems should adopt it?
EMS systems vary widely in terms of what level of service is first on scene, how long transport time is, and how often providers have opportunities to use advanced airways and therefore one airway is likely to be the correct answer for every EMS agency. A patient who achieves ROSC with a GCS of 3 an hour away from definitive care may benefit from ETI, whereas a patient with witnessed, sudden cardiac arrest across the street from an emergency room may benefit most from an oral airway and quick transport.
Bottom line
The airway leading to the highest rates of ROSC and best neurological outcome in OHCA remains unclear, but there is still a lot to learn from the research already done.
Don’t fix what isn’t broken – while intubating a patient may address an underlying cause to their cardiac arrest, it should be done judiciously and thoughtfully at the right time during the resuscitation when indicated, rather than immediately upon arrival just because the patient doesn’t have a “definitive airway.” Research on OHCA airway management shouldn’t just teach us about what airway is best for paramedics to use to ventilate patients, but also how the airway affects (and potentially distracts) from other aspects of the resuscitation.
Finally, these studies about prehospital airway placement are also not directly applicable to airway use in the ED, as patient’s show up to our door already being ventilated at some level. The real question is, will the patient benefit from a different airway?
References:
[1] Resuscitation. 2015 Aug;93:20-6. doi:10.1016/j.resuscitation.2015/5/007.Epub 2015 May 23. Meta-Analysis; Review.
[2] Resuscitation. 2012 Aug;83(8):1025-30. doi: 10.1016/j.resuscitation.2012.03.025. Epub 2012 Mar 28.
[3] JAMA. 2013 Jan 16;309(3):257-66. doi: 10.1001/jama.2012.187612.
[4] Acad Emerg Med. 2010 Sep;17(9):926-31. doi: 10.1111/j.1553-2712.2010.00829.x.
[5] JAMA. 2018 Feb 27;319(8):779-787. doi: 10.1001/jama.2018.0156.
[6] Lewis RJ, Gausche-Hill M. Airway Management During Out-of-Hospital Cardiac Arrest. JAMA.2018;319(8):771–772. doi:10.1001/jama.2018.0155
[7] JAMA Intern Med. 2015 Feb;175(2):196-204. doi: 10.1001/jamainternmed.2014.5420.
[8] 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. 2018;320(8):769–778. doi:10.1001/jama.2018.7044
[9] 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 OutcomeThe AIRWAYS-2 Randomized Clinical Trial. JAMA. 2018;320(8):779–791. doi:10.1001/jama.2018.11597
[10] Ann Emerg Med. 2018 May;71(5):597-607.e3. doi: 10.1016/j.annemergmed.2017.12.012. Epub 2018 Jan 17.
1 Comment
If the breaths are getting in, we are not hyperventilating & good CPR is not being interrupted, ANY airway is just fine. And if you can only do VBM ventilation, as long as is good technique, that’s OK too. Let’s stop being dogmatic about things…. shall we?