Date: November 24th, 2017

Reference: Andersen et al. Association Between Tracheal Intubation During Adult In-Hospital Cardiac Arrest and Survival. JAMA 2017

Guest Skeptic: Dr. Bob Edmonds is an Emergency Physician in the US Air Force.  He is currently deployed, practicing emergency medicine in an undisclosed location.

DISCLAIMER: The views and opinions of this podcast do not represent the United States Government or the US Air Force.

Case: You are working a regular shift in the emergency department when you hear a code blue called. You are the first physician to respond and you begin to resuscitate the patient. Your respiratory therapist is adequately ventilating the patient with a bag valve mask, and they ask you if they should prepare to intubate at the pulse and rhythm check.

Background: We have talked about out-of-hospital cardiac arrests (OHCA) many times on the SGEM.

  • SGEM#64: Classic EM Papers (OPALS Study)
  • SGEM#136: CPR – Man or Machine?
  • SGEM#143: Call Me Maybe for Bystander CPR
  • SGEM#152: Movin’ on Up – Higher Floors, Lower Survival for OHCA
  • SGEM#162: Not Stayin’ Alive More Often with Amiodarone or Lidocaine in OHCA
  • SGEM#189: Bring Me To Life in OHCA

This time, as the case identifies, we are going to be talking about in-hospital cardiac arrests (IHCA) today.

The American Heart Association (AHA) reports that were 209,000 IHCA arrests in 2016. The survival rate for adults to hospital discharge is 24.8%.

The  survival rate for IHCA has almost doubled from the year 2000 when it was only 13.7%. From a patient oriented outcome perspective, more than 80% of adults with IHCA who do survive end up having a favorable neurologic outcome at discharge. This is defined as a Cerebral Performance Category (CPC) score of 1 or 2.

There are five steps in the AHA IHCA Chain of Survival:


Sudden IHCA is a high stakes emergency with a high mortality rate. The decision to intubate is difficult to make and varies widely between clinicians. Due to the nature of intubation in cardiac arrest, it is difficult to study, and the studies that do exist are largely observational.

Until this paper, there were no studies of IHCA arrest intubation and survival.

Clinical Question: Does tracheal intubation during adult in-hospital cardiac arrest affect survival?

Reference: Andersen et al. Association Between Tracheal Intubation During Adult In-Hospital Cardiac Arrest and Survival. JAMA 2017

  • Population: Adult patients 18 years of age and older with an index cardiac arrest for which they received chest compressions.
    • Cardiac Arrest: Pulselessness requiring chest compressions and/or defibrillation, with a hospital wide or unit based emergency response.
    • Exclusions: Having a do-not resuscitate (DNR) order, already having an advanced airway in place (tracheal tube, tracheostomy, laryngeal mask airway, or other invasive airways but not including oropharyngeal or nasopharyngeal airways), or patients missing data (except for race).
  • Exposure: Tracheal intubation-including tracheal tube or a tracheostomy tube during the cardiac arrest.
    • Unsuccessful intubation attempts were not logged as intubations in the registry.
  • Comparison: Patients who did not receive tracheal intubation
  • Outcome:
    • Primary Outcome: Survival to hospital discharge.
    • Secondary Outcomes: return of spontaneous circulation and favorable neurologic outcome at hospital discharge (CPC score of 1 or 2).

Authors’ Conclusions: “Among adult patients with in-hospital cardiac arrest, initiation of tracheal intubation within any given minute during the first 15 minutes of resuscitation, compared with no intubation during that minute, was associated with decreased survival to hospital discharge.  Although the study design does not eliminate the potential for confounding by indication, these findings do not support early tracheal intubation for adult in-hospital cardiac arrest.”

checklistQuality Checklist for Observational Study:

  1. Did the study address a clearly focused issue? Yes
  2. Did the authors use an appropriate method to answer their question? Yes
  3. Was the cohort recruited in an acceptable way? Yes
  4. Was the exposure accurately measured to minimize bias? Unsure
  5. Was the outcome accurately measured to minimize bias? Yes
  6. Have the authors identified all-important confounding factors? Unsure
  7. Was the follow up of subjects complete enough? Yes
  8. How precise is the estimate of risk? Precise with a tight 95% confidence interval
  9. Do you believe the results? Yes
  10. Can the results be applied to the local population? Yes
  11. Do the results of this study fit with other available evidence? Yes

Key Results: The cohort included 108,079 adult patients from 668 US hospitals. Forty-two percent were female, the median age was 69 years and overall survival to hospital discharge was 22.4%.

Primary Outcome: Less survival associated with intubation (16.3%) compared to without intubation (19.4%).

  • Primary Outcome: Survival to hospital discharge was observed to be lower in patients who were intubated vs. those who were not intubated (RR of 0.84, P<0.001).
    • Note: The overall cohort included 108,079 patients and the survival was 22.4%, but both the intubation and “not intubated” groups had survival less than this number.  This is due to their matching process which will be discussed in the Talk Nerdy to Me section. 
  • Secondary Outcomes (Intubated vs. Not Intubated): Less ROSC and less discharge home with good neurologic function in the intubated patients
    • ROSC: 8% vs. 59.3% (RR = 0.97; 95% CI, 0.96-0.99; P < .001)
    • Favorable Neurologic Outcome at Discharge: 6% vs. 13.6% (RR = 0.78; 95% CI, 0.75-0.81; P < .001)

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  1. Study Design – Given the observation cohort study design we can only conclude an inverse association between intubation and the survival to hospital discharge not causation.
  2. Decision to Intubate – The key to the entire study was the decision to intubate or not. It is difficult to ascertain what factors lead some physicians to intubate patients in cardiac arrest-for some doctors, all patients in arrest get intubated.  Others decide to intubate more selectively for a myriad of reasons.  The decision making for this intervention is unable to be derived from this study due to its retrospective nature.
  3. Propensity-Match Cohort – This has been referred to by my friend Dr. Mark Ebell as statistical jujitsu. Others have called it statistical gymnastics. Regardless of the term you use, it is impossible to account for all potential confounders. To their credit the authors’ put this limitation right in their conclusions.
    • The authors used an interesting technique to match cases-patients who were intubated were then matched with cases that at that time in resuscitation were not intubated. The authors specifically state that for these matched “not intubated” patients, many of them (68%) were later intubated. This has the potential to introduce bias as these cases for matching were sometimes “intubated” vs. “at risk of being intubated later”, rather than “intubated” vs. “never intubated.”
  4. Respiratory Insufficiency – A major argument that intubation is needed in sudden cardiac arrest patients is that they suffered from respiratory insufficiency prior to arrest. In the authors’ subgroup analysis, pre-existing respiratory insufficiency showed no association with survival, while the patients without pre-existing respiratory insufficiency showed lower likelihood of survival if they were intubated. However, since the comparison was “intubated at time x” versus “at risk of being intubated at time x,” this argument is muddied, since essentially you have a group of 43,314 patients who were intubated versus a group that’s a combination of 32% patients that were never intubated and 68% patients who were intubated at some time later than the first group.
  5. Exclusions: One-quarter (34,731) of all eligible IHCA patients who met all inclusion criteria were excluded. This was due to missing data. They did a sensitivity analysis to account for missing data. However, with such a small effect size for the primary outcome after propensity score matching (3%) I am still skeptical of the results.
    • 75 Missing data on intubation
    • 9,358 Missing data on timing of intubation
    • 784 Missing data on survival
    • 25,514 Missing data on covariates

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We generally agree that the findings show an association that does not support early tracheal intubation for adult IHCA patients.

SGEM Bottom Line: We should continue to use our clinical judgment and be selective with who we intubate during a cardiac arrest.

Case Resolution: You tell your respiratory therapist not to intubate and to continue to use the bag valve mask.  At your pulse check, the patient is in ventricular fibrillation, you defibrillate them with 200J, and resume CPR.  At the next pulse check the patient has return of spontaneous circulation and is transferred to the intensive care unit.  

Dr. Robert Edmonds

Dr. Robert Edmonds

Clinical Application: Given the data, it appears reasonable to continue to be selective with intubation in sudden cardiac arrest. This data is not strong enough to have an impact on my care. There may be some patients, especially those with respiratory insufficiency, that would derive benefit from intubation during their arrest.

A randomized control trial is needed to answer the question “to intubate or not to intubate in the adult IHCA patient”. This observational cohort study suggest equipoise and could be used to request ethics approval for a randomized control trial.

What do I tell my patient? My patient is currently, actively dying so I don’t tell them anything. If my staff asks while coding the patient, I will tell the  m that unless the patient becomes difficult to ventilate with the bag valve mask, we will hold off on intubation for now.

Keener Kontest: Last weeks’ winner was Jadran Dychioco a FNP student from Valencia, California. They knew haloperidol was discovered by Paul Janssen who ended up having a pharmaceutical company named after him (Janssen Pharmaceutica).

Listen to the SGEM podcast on iTunes to hear this weeks’ keener question. If you know the answer, then send an email to TheSGEM@gmail.com with “keener” in the subject line. The first correct answer will receive a cool skeptical prize.

FOAM logoOther FOAMed:

  • The Bottom Line: Association Between Tracheal Intubation During In-Hospital Cardiac Arrest and Survival
  • St. Emlyn’s: Cardiac Arrest – To Intubate or Not?
  • CORE EM: The Role of Intubation in In-Hospital Cardiac Arrest
  • REBEL EM: In-Hospital Cardiac Arrest: The First 15 Minutes

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.

SkiBEEM 2018