In my last post, I gave my thoughts on the excellent PART trial which compared King LT vs Endotracheal Intubation (ETI) as the initial strategy in advanced airway management (AAM) of cardiac arrest. It found a 72-hour survival advantage with the King LT.
The second of the blockbuster prehospital airway trials published in the August 28, 2018 issue of JAMA is similar to PART but looking instead at ETI vs the iGel supraglottic airway. Dr. Jonathan Benger is the lead author of the AIRWAYS-2 paper. This was a very large prospective, randomized controlled trial of adult out-of-hospital cardiac arrest patients treated by 4 UK ambulance service collectively covering 21 million citizens (40% of England’s total population). It randomized over 1,523 paramedics who volunteered to participate in the trial to either ETI or iGel groups. Once randomized, each paramedic was to use their assigned method as their initial approach to AAM in cardiac arrest. This is unlike the PART study in which each EMS agency would switch back and forth between devices in blocks of 3-5 month each. These paramedics treated 9,296 patients with 4,886 (52.6%) patients in the iGel group and 4,410 (47.4%) in the ETI group. There was no video laryngoscopy used in this study.
The primary outcome of this study was modified Rankin Score (mRS) at 30 days post arrest. An mRS of 0 to 3 is typically considered neurologically favorable while 4-6 is considered bad (6 is death). The headline result here is that there was no difference in neurologically intact survival between iGel (6.4%) and ETI (6.8%).
As with the PART study, there were patients in both groups who, for whatever reason, did not have any AAM attempted. This was an intention-to-treat analysis which means that these patients, who had no AAM attempted, were analyzed in the group they were assigned to. There were more patients in the ETI group who had no AAM attempted, 908 (22.2%) compared with 638 (14.1%) in the iGel group. We would generally assume that patients without AAM attempted might be more likely to survive (perhaps because they regained consciousness prior to AAM attempts). If this were the case, and these patients were removed, we might see a benefit in the iGel group. There is support for this. In their as-treated analysis in which they analyzed only those patients who had an AAM attempt, there were better outcomes with the iGel (3.9%) compared with ETI (2.6%).
There appears to be a hesitation among paramedics to proceed with intubation. While there is no data presented on why, there was a larger proportion of protocol violations in the ETI group than in the SGA group. Specifically, 18.6% of all patients treated by a paramedic assigned to the ETI first group actually received an iGel first while only 2.9% of patients treated by an iGel assigned paramedic received an ETI first. For context, both ETI and iGel were available to all paramedics in the system. In the FOAMfrat podcast, Dr. Benger seems to think the reason may have been paramedics felt they were more likely to be successful with iGel rather than ETI.
After combing through the data tables and supplements, I can’t actually figure out what the intubation success rates are. The manuscript says “the supraglottic airway device treatment strategy was significantly more successful in achieving ventilation after up to 2 attempts (87.4% vs 79.0% with tracheal intubation; adjusted OR 1.92 [95%CI 1.66 to 2.22])”. The problem is I can’t, for the life of me, figure out where these numbers come from. We can’t directly compare ETI success rates with the PART trial because AIRWAYS2 doesn’t report first pass success in any way.
This paper does report on a very small number of patients (66 out of over 9,000) for whom compression data was available. There was no difference between the compression fraction with SGA of 86% vs 83% with ETI.
What about aspiration?
The PART trial showed no difference in aspiration pneumonitis with King vs ETI. AIRWAYS indirectly reported on this. They report on aspiration and regurgitation. Overall, there was no difference in either between iGel and ETI. However, they very nicely report on regurgitation before and during/after the AAM attempt. There was more regurgitation in the ETI groupbeforeAAM (21.1% vs 17.4%) but more regurgitation during/after AAM in the SGA group (18% vs 12.0%). Aspiration rates were smaller in size but similar in direction. While it is doubtful this made any difference in outcome, it does suggest that ETI may, in fact, be associated with less regurgitation and, presumably, aspiration, than SGA.
Finally, there were more than twice the number of unintended device displacement with the iGel (10.4%) compared to ETI (5.0%). No data is available to describe why this occurs, but my system’s experience suggests the iGel isn’t secured very well, despite the strap. For what it’s worth, we didn’t see this with the King LT when we were using it.
So, to sum up my thoughts on AIRWAYS2:
Another outstanding trial. This represents a huge amount of work. Over 9,000 patients were treated. They have a very nice website if you’re interested (http://www.airways-2.bristol.ac.uk).
I like this randomization strategy better than PART. I worried that paramedics switching from method to method when infrequently used would decrease competence with complex skills like DL. Certainly, the success rates in that study seem to validate my concern. Randomizing by paramedic eliminates this challenge.
I find this paper more applicable to my system’s practice. We use the iGel, too. Success rates are likely closer to that of our system. Given the lack of overall difference in survival and lower presumed ETI success rates, we will continue with our ETI first strategy in our system. I don’t, however, lightly take this step. I’ll continue thinking about this. We may end up with an iGet first approach followed by ETI after ROSC.
I would like to see a secondary analysis that eliminated those patients with no AAM attempt within the median amount of time for an SGA attempt. This would help compare patients who still needed AAM after initial unsuccessful resuscitative efforts.