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Does Prehospital Intubation Influence Cardiac Arrest Survival?

The authors of this study analyze which types of outcomes for cardiac arrest are associated with multiple ETI attempts. Photo Ryche Guerrero

Review of: The Association between prehospital endotracheal intubation attempts and survival to hospital discharge among out-of-hospital cardiac arrest patients. Acad Emerg Med. 2010;17:918–925.

This is a retrospective study from the Mecklenburg EMS Agency in Charlotte, N.C., examining the impact prehospital endotracheal intubation (ETI) attempts and return of spontaneous circulation (ROSC) and survival to discharge after out-of-hospital cardiac arrest (OOHCA). The analysis included a two-year period from 2006 to 2008 and analyzed 1,142 cardiac arrests; 299 patients had ROSC, with 118 patients being discharged from the hospital alive. The authors found that individuals with no ETI attempt were 2.33 times more likely to have ROSC compared with individuals with one successful ETI attempt, and individuals with no ETI attempt were 5.46 times more likely to be discharged from the hospital alive compared with one successful ETI attempt. The authors concluded that ETI attempts are associated with negative outcomes in OOHCA.

Medic Marshall: I think Dr. Studnek (a nationally registered paramedic), and the other authors did a fantastic job organizing this paper and clearly showing the negative effects of ETI on ROSC and survival to hospital discharge. Despite the inherent limits of the study—only demonstrating a negative association of ETI for the OOHCA patient, instead of a causal affect—I still think it’s worth taking into consideration. With advancements in non-visualized airways, we ought to consider their value and also the value of the bag-valve mask.

As with any study, there are limitations that should be evaluated. First of all, the authors don’t mention whether the patients that had ROSC prior to EMS arrival “woke-up” and didn’t require advanced airway management. The study reports there were 28 documented cases—but that is only documented. Further, based on the type of study (the retrospective observational study), it becomes difficult to ensure a consistent approach on classifying the main variable—ETI. Each documenting paramedic is responsible for documenting attempts; however, it’s unknown if there’s a consistent definition used among providers. So what does this paper mean? Well, it’s time for me to get on my soapbox here.

Just how many nails does it take to finally seal the coffin and bury this issue? I hate to say it, but I really believe it’s just a matter of time before prehospital intubation (at least for cardiac arrests) is going to go by the wayside. But if intubation goes to the wayside in cardiac arrests, then I can only imagine the next logical step would be to remove the skill altogether from the hands of paramedics. Personally, I think it’s time we start accepting this as reality and start acting in the best interest of our patients—and ETI isn’t in the best interest of the patient. So with that said, I’ll dive back into my fox hole and wait for the shelling that’s about to ensue.

Dr. Wesley: I don’t have much to say after hearing Marshall’s comments, as I’m busy digging my foxhole. The important thing to understand is that this is an “association” study. Nothing in this study indicates that intubation “caused” the death or failure of the patient to survive their cardiac arrest. However, as with the “association” studies with traumatic brain injury patients, we must now examine what’s specifically different about those who were intubated, which may have caused the increase in mortality. With traumatic brain injury, the studies indicate that hypoxia, hypercarbia, bradycardia and excessive ventilation pressures often occur with intubation, and each of those factors are known to negatively affect this specific patient population.

All cardiac arrest patients are hypoxic and rarely hypercarbic. Bradycardia isn’t an issue, as these patients are all pulseless. So what are the other characteristics of cardiac arrest intubation? The first is timing. I found myself wondering the following questions: When during the resuscitation were the patients intubated? What was the form of airway management before they were intubated? How many times was intubation attempted, and what was the failure rate? How long did intubation take, and were chest compressions interrupted during the intubation? None of these questions were addressed, recorded or reported by the authors.

I’m not criticizing the authors for failing to address these questions. I’m only attempting to make sense of the results. Clearly, for this particular service, intubation has a negative effect on cardiac arrest survival. Is this common? I don’t know. But I know I’m going to examine it in my system and then attempt to examine the other characteristics I listed above.

Objectives: The benefit of prehospital endotracheal intubation (ETI) among individuals experiencing out-of-hospital cardiac arrest (OOHCA) hasn’t been fully examined. The objective of this study was to determine if prehospital ETI attempts were associated with return of spontaneous circulation (ROSC) and survival to discharge among individuals experiencing OOHCA.

Methods: This retrospective study included individuals who experienced a medical cardiac arrest between July 2006 and December 2008 and had resuscitation efforts initiated by paramedics from Mecklenburg County, North Carolina. Outcome variables were prehospital ROSC and survival to hospital discharge, while the primary independent variable was the number of prehospital ETI attempts.

Results:?There were 1,142 cardiac arrests included in the analytic data set. Prehospital ROSC occurred in 299 individuals (26.2%). When controlling for initial arrest rhythm and other confounding variables, individuals with no ETI attempted were 2.33 (95% confidence interval [CI] = 1.63 to 3.33) times more likely to have ROSC compared to those with one successful ETI attempt. Of the 299 individuals with prehospital ROSC, 118 (39.5%) were subsequently discharged alive from the hospital. Individuals having no ETI were 5.46 (95% CI = 3.36 to 8.90) times more likely to be discharged from the hospital alive compared to individuals with one successful ETI attempt.

Conclusions: Results from these analyses suggest a negative association between prehospital ETI attempts and survival from OOHCA. In this study, the individuals most likely to have prehospital ROSC and survival to hospital discharge were those who did not have a reported ETI attempt. Further comparative research should assess the potential causes of the demonstrated associations.

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  1. I have a couple of questions. Although abstract states controlliing for initial rhythm and other confounding variables, what were those other variables? Was CPR being performed prior to arrival of EMS? What was the initial presenting rhythm? Shockable or unshockable? Along with Dr. Honeybadger Wesley’s questions (was CPR interrupted – and if so for how long during the intubation attempt I also wondered how long the patient had been in cardiac arrest – as well as what other co-morbidities were present. Finally, I’m sure the study addressed the definition of ‘attempt’ I’m curious as to what that was.

    • Dr. Honey Badger Wesley

      I’m surprised by the number of posts criticizing this study and form their posts I have to assume that none of them have actually read the article. Let me address the various comments.

      1. The authors controlled for those patients that had quick ROSC with AED application. They found that regardless of presenting rhythm those patients who did not respond to one AED application (the usual arrest) that if they got the ET tube they did not do as well as those that were managed with an Advanced Airway or even BVM.

      2. This is not a study of whether or not medics CAN intubate but whether or not the SHOULD intubate.

      This study mirrors what we have found at HealthEast in St. Paul. Pts would get the ET tube are significantly less likely to survive than those the medics go straight to the King.

      I believe there is something inherently harmful with the ET in early cardiac arrest management. It makes it too easy to overinflate the chest with air with significantly inhibits blood return.

      As for the issue of aspiration pneumonia? Aspiration has already occurred from regurgitation and BVM before we ever pass a tube. Early ET use will not reduce that incidence.

  2. There may be 2 distinct questions:

    1. Is an ETT somehow against the interest of the patient- I think this is unlikely?
    2. Is the negative impact due to the need to interrupt CPR for 20-60 seconds for attempts at intubation or if video intubation were carried out during uninterrupted CPR would this produce a different result?

    These questions will only be resolved with double blind study .

    • ETI gives one control of the airway, and without that control, there will be some aspiration pneumonia related deaths. The question is one of which is the greater evil – losing patients to aspiration pneumonia and losing patients to death or level 3 o4 4 neurological deficit. I would really like to see a well-structured trial conducted. I’ll be betting that the improvement in SCA survival will far outweigh the increase in aspiration pneumonia deaths.

      And let’s not forget that devices such as the Combitube and the King airway are alternatives that many services consider to be a ‘last resort’ – or don’t carry at all – because of the cost. I’d also like to see a well-structured study performed on the S.A.L.T. airway, because that preserves the advantages of ETI with minimal-to-no interruption in chest compressions.


      • You raise an excellent point Bob, perhaps alternate airways should be considered a ‘better line of management’ out of hospital. I think paramedics as a profession should be willing to loosen their death grip on individual skills and consider what is in the patients best interest.. We’ve already changed practice with regard to CPR and (arguably) improved survival to discharge, maybe this is one more aspect of that change.

    • Dr. Honey Badger Wesley

      I believe that in the pre-hospital environment the ETT is inherently harmful. Not due to competence but simply that the closed circuit of the ETT makes is too easy to hyperinflate the lungs and increase the intrathoracic pressure thus impeding blood return to the heart.

      Can fiberoptics be used to eliminate the interruptions? Certainly. But frankly, the costs of the devices are too high compared to the available and satisfactory alternatives such as the King LT

  3. could it simply be because the people who require intubation are just sicker than the average bear?

  4. Alot of assumptions are being made, without realistic consideration of facts the real world.

    What CPR guildlines were followed? Had they adopted 2005 acls/CPR in 2006? My experince is that is takes a year or two until protocols change.

    If they were following 2005 guildlines we started with CPR
    Then shock
    Then iv access. Maybe io. If iv this could possibly take several minutes.
    Then drugs.
    Lastly ETI.

    Which is the same order as now.
    If you have not gotten rosc before you go to tube, do you really expect to? I know I don’t. I just want to ensure I did everything I could.

    Frankly I am a little tired of hearing “paramedics can’t tube”
    Have you been to a teaching hospital (read trauma center), and watched first through 3rd year residents? Or a hospital with a 6 bed ER (or less)? It is extremely painful to watch, at times. I’d love to see an honest study comparing paramedics to MDs, or PAs. I suspect that we would be competitive.

    It is time to put up. Students should have 10 tubes in an OR before graduating.
    Some food for thought.

    Time 911 was call to dispatch? Usually about three min.
    Dispatch til response? 1 min
    Time to scene in dream world 3 min.
    Time to scene in real world 10 to 20.
    By the time I get around to

  5. Of course the patients that don’t need intubation will have more ROSCs. To say that ETI caused this is almost insane. Seeing this study mentioned several times I have never seen it stated how many were not intubated for purposes of this study. If someone is stopping CPR or letting the patient become hypoxic they should be dealt with. I have seen more MDs stop CPR or have long intubation attempts than Paramedics. By experience I would believe that more cardiac arrests had successful ROSC and walked out of the hospital than what the study provided that were not intubated. Good CPR and Defibrillation is what saves cardiac arrests. When the patient needs intubation the survival rate drops tremendously.

  6. Studys show that studys are inaccurate. The possibilities are endless as to what events led to each case. How far from the hospital was each case. Down time. And what is the benefit of a combitube or LMAs to Et. As we all have learned the latest study show non stop CPR are vital to a pts chances for survival. The benefit there would be airway control without stopping CPR. Every person that talks about removing ET intubation for Medics in the Field should answer the biggest question of all. If its bad in the field then why is it golden 3 mins later in the ER??? ET is not the problem. Procedure is the issue. And heck. Wait around 5 years and a brand new study will show something totally different.

  7. This study only concluded that ETI was associated with a worse outcome and not the cause. What do we know:

    1. ETI leads to interruptions in vital chest compressions (medium of 45 seconds in 1 study)
    2. The only proven therapies in cardiac arrest resuscitation are defibrillation and quality, minimally interrupted chest compressions
    3. 2 large studies in AZ and WI showed improved survival if airway management was delayed for up to 8 minutes and the patient had chest compression only CPR while on a NRFM.
    4. The best evidence we have suggests we should do all possible to minimize interruptions in chest compressions (this includes airway management).

    My conclusion is that ETI may be harmful and and is of no benefit. The best practice is airway management without interrupting chest compressions (e.g., King airway).

  8. I like using the Combitube. I can have it inserted and secured in under 10 seconds. CPR is not interupted. I like having the skill for endotracheal intubation. Airway control is critical however the blind insertion method is a Bronze standard that is good enough.

    I’m going to state that time is a critical factor in survival. Endotracheal intubation takes longer than most people admit. IO also saves time.

  9. ETI should not take that long. I would be in position ready to place the tube before I would have them stop CPR. And then they would only pause for the length of about 2 or 3 compressions. Once the tube was in I would have them continue compressions while I inflated and secured the tube. Very minimal interuption. If in my head, or have someone else count: 1:1000, to 3 you should have the tube placed, not nessarly secured, and be able to contine CPR. If I couldn’t get it in that time continue BVM. Once we got King airways I would alot of the time just drop a king and roll with it.

    Don’t know how many made it out of the hospital but had several ROSC prior to arriving at ER.

    • Dr. Honey Badger Wesley

      If only everyone to abide by these precepts. Unfortunately, in the heat of battle that is EMS Cardiac Arrest there are few controls for variation.

  10. If ETI is really going to die in the prehopspital setting, you should take a look at Allina´s use of Rescue Pod device during CPR and their results in the Minneapolis St Paul Area before you condemn the technique for ever. Facts need to be examined consistently. Something very interesting is going on that need to be brought up to our attention regarding ROSC, and we need to use a very wide scope to look at the complete facts and try to understand what is really hapening here.

    • Dr. Honey Badger Wesley

      The ITD can be used effectively with the King LT and more importantly it can be depoloyed with the BVM early in the arrest which is where the strongest data exists for its benefit.

  11. Guy’s , some questions from Ireland on intubation.
    How do you feel about Pre-hospital intubation for long transport times?
    Intubation after 3 cycles of CPR with passive oxygen insufflation for VF/VT arrests?
    reduced ventilation rate while intubated – would it help?
    raised intrathoracic pressure inhibits coronary blood flow – so why use resq-pod?
    regular training could improve skill and time?
    comments welcome!
    Please be honest, Im researching this topic in Ireland.

  12. Has anyone studied in-hospital ETI in cardiac arrest? I know I have seen many cardiac arrest patients ventilated 20-50/min by hospital employees, and I have never seen a King placed in the ER as the primary airway in a cardiac arrest. Other rescue airways are generally placed when the staff has been unable to intubate, after numerous attempts and interruptions in chest compressions. Whether a doc or a paramedic, becoming a resuscitiation expert should be the goal, and I have seen my share of both professions who couldn’t run a code if their lives depended on it.

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