A few weeks ago, Dr Harriott gave a talk on out-of-hospital cardiac arrest (OHCA) and pre-hospital airway management. She reviewed some historical context for the current EMS system and airway management. Her literature search suggested that for OHCA, paramedic-operated endotracheal intubation (ETI) was associated with increased mortality and decreased neurologic recovery.[i],[ii] We nodded, pulling on our limited experience, and imagined what a messy an OHCA airway disaster looks like. Inadequate training, uncontrolled setting…It makes sense that outcomes are poorer. Lots of data exist to support this. [iii],[iv] Ole Dr. Basile talked about it on the older, rougher and tougher SI corner.
It made me wonder what we really know about airway management during cardiac arrest? What about in-hospital arrest? In NYC, OHCAs often come in with some kind of advanced airway. But what if they don’t? How long should we bag-valve mask ventilate ? When is the right time to intubate? Is it ok to use a supraglottic airway (SGA)?
So I went digging. Here’s what’s out there..
There are no RCTs on in-hospital cardiac arrest and airway management. There are 3 RCTs on OHCA and prehospital airway management. One was in kids, wasn’t powered effectively, and was flawed.[v] Another compared paramedic ETI vs supraglottic for OHCA.[vi] The final compared physician-operated ETI vs supraglottic airway for OHCA.[vii] It showed improved outcomes for combitube but wasn’t significant. It is unclear if or when combitube patients were intubated after arrival to the ED.
That’s what we’ve got. That, and an orgy of observational data from OHCA registries. The latest big ones have been published in big journals, like JAMA and Resuscitation. Hasegawa et al. compiled a massive cohort of OHCA, something close to 650,000 and found any kind of advanced airway was associated with decreased neurologic outcome. Another by Wang et al compared ETI to SGA for OHCA found that ETI had improved outcomes.
The biggest problem with these giant observation studies is that we have no idea why EMTs chose to place one airway vs another. Moreover, the entire course of pre-hospital airway management was simplified to the airway in place at time of arrival to ED. All the airway failures, missed attempts, trauma, esophageal placements are washed away.
So, are these big observational studies useless? No. They don’t offer much in the way of causality. But going by the numbers, these patients with OHCA and advanced airways may be a sicker group. Think about your practice: you know that the patient who comes in arrested with a combitube did not have a run-of-the-mill prehospital course.
So where does this leave us when confronted with a patient in arrest with airway? Continue BVM? Place a SGA? Go right for ETI? We don’t know. Our practice is based on expert opinion and consensus. Nowadays, we worship at the church of compressions. The 2010 AHA Guidelines sum it up:
“During CPR providers should minimize the number and duration of interruptions in chest compressions, with a goal to limit interruptions to no more than 10 seconds. Interruptions for supraglottic airway placement should not be necessary at all, whereas interruptions for endotracheal intubation can be minimized if the intubating provider is prepared to begin the intubation attempt—ie, insert the laryngoscope blade with the tube ready at hand—as soon as the compressing provider pauses compressions. Compressions should be interrupted only for the time required by the intubating provider to visualize the vocal cords and insert the tube; this is ideally less than 10 seconds. The compressing provider should be prepared to resume chest compressions immediately after the tube is passed through the vocal cords. If the initial intubation attempt is unsuccessful, a second attempt may be reasonable, but early consideration should be given to using a supraglottic airway.“
And then, about a year ago, Scott Weingart posts this: Are Extraglottic Airways Harmful in Cardiac Arrest? Are we creating a blockage of blood flow to the brain?[viii]
How this study of 9 pigs stuffed with human-shaped SGAs caused such a stir, I’ll never know. But it got the attention of the resuscitation world, if only briefly.
So where do we go? What do we do? Best practiceMinimize interruptions; secure the airway quickly. Sounds like the mantra of the supraglottic airway camp, no? Despite a lack of evidence to support them, it makes sense to throw in an LMA.?
In med school, they told us: “half of what we teach you is wrong. We’re just not sure which half…” Accepting dogma in medicine comes with the turf. And, depending on when you come up, you adopt a different set of knowns and unknowns. What we know for sure is always changing. Nowhere is there more conjecture and less-evidence than in ACLS and the management of cardiac arrest and ACLS algorithms.
In short, paradigms shift. Dogmas get verified or tossed. What of contemporary ACLS will stand the test of time and evidence? Flip a coin. 50% of the time, you’ll be right.
Hasegawa K, Hiraide A, Chang Y, Brown DM. 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. doi:10.1001/jama.2012.187612
Gausche M, Lewis RJ, Stratton SJ, Haynes BE, Gunter CS, Goodrich SM, et al.Effect of out-of-hospital pediatric endotracheal intubation on survival and neurological
outcome: a controlled clinical trial. JAMA. 2000;9(283):783–90.
Wang HE, Lave JR, Sirio CA, Yealy DM. Paramedic intubation errors: isolated events or symptoms of larger problems? Health Aff (Millwood). 2006;25(2):501-509
Johnston BD, Seitz SR, Wang HE. Limited opportunities for paramedic student endotracheal intubation training in the operating room. Acad Emerg Med. 2006;13(10):1051-1055
Gausche M, Lewis RJ, Stratton SJ, Haynes BE, GunterCS, Goodrich SM, et al.Effect of out-of-hospital pediatricendotracheal intubation on survival and neurological
outcome: a controlled clinical trial. JAMA. 2000; 9 (283): 783–90.
Goldenberg IF, Campion BC, Siebold CM, McBride JW, Long LA. Esophageal gastric tube airway vs endotracheal tube in prehospital cardiopulmonary arrest. Chest 1986; 90(1):90–6.
Rabitsch W, Schellongowski P, Staudinger T, Hofbauer R, Dufek V, Eder B, et al.Comparison of a conventional tracheal airway with the Combitube in an urban emergency medical services system run by physicians. Resuscitation 2003; 57 (1):27–32.
Hasegawa K, Hiraide A, Chang Y, Brown DM. 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
Wang HE, Szydlo D, Stouffer JA, et al. Endotracheal intubation vs supraglottic airway insertion in out-of-hospital cardiac arrest. Resuscitation. 2012;83(9):1061-1066
Segal N, Yannopoulos D, Mahoney BD, Frascone RJ, Matsuura T, Cowles CG, McKnite SH, Chase DG. Impairment of carotid artery blood flow by supraglottic airway use in a swine model of cardiac arrest. Resuscitation. 2012 Mar 28.
[i] Hasegawa et al, 2013
[ii] Gausche et al, 2000
[iii] Wang et al, 2006
[iv] Johnston et al 2006
[v] Gausche et al., 2006
[vi] Goldernberg et al 1986
[vii] Rabitsch et al, 2003
[viii] Segal et al, 2012
jfreedman
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Totally agreed. I reviewed the literature and came up with something similar during my EMS rotation. Another criticism of these studies, none of them differentiated between LMA’s and the King LT or Combitube. I’ve used both of the latter tubes (on mannequins) and really don’t like them or the idea that you just shove them in. The amount of air you inflate them with is substantial and I could image they would interfere with blood flow.
I dont think this is a problem with LMA’s. They are inflate with small volume of air. Anesthesia uses them all the time and I personally love them (they have saved my butt a couple times).
Good job, Freedman. I believe that in arrest situations, the of scientific evidence (even if not RCTs) points toward the use of the LMA or other advanced airway OTHER THAN ET TUBE during early resuscitation. This is due mainly to the ease/speed of placement so as to minimize interruptions in compressions. Remember, than in cases of hypoperfusion, you do not need to ventilate normally to maintain V/Q matching. If perfusion (Q) is minimal, then ventilation (V) may be small as well without much compromise in oxygen delivery. ET intubation should be reserved for the cases where there is return of spontaneous circulation for some period of time and really should be part of post-arrest management (along with hypothermia, vasopressor support, urgent PCI).