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Does Prehospital Intubation Influence Cardiac Arrest Survival?

Posted on 21 September 2011

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.

Abstract
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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