Journal Watch: Intubation Attempts and OHCA Survival

Reviewed This Month

Fewer Tracheal Intubation Attempts Are Associated With Improved Neurologically Intact Survival Following Out-of-Hospital Cardiac Arrest 

Authors: Murphy DL, Bulger NE, Harrington BM, et al. 

Published in: Resuscitation, 2021 Oct; 167: 289–96 

Literature makes it clear that multiple intubation attempts in non-cardiac arrest situations are associated with adverse events, but the relationship between multiple intubation attempts and patient outcomes for out-of-hospital cardiac arrest (OHCA) patients has not been well studied. The objective of the study we review this month was to explore whether number of intubation attempts was associated with clinical outcomes following OHCA. The authors’ hypothesis was that increasing intubation attempts would be associated with a lower likelihood of survival to discharge with favorable neurologic status. 

Study Parameters

This study was a retrospective observational cohort study. It included nontrauma patients treated by the Seattle Fire Department who experienced OHCA prior to EMS arrival and received one or more intubation attempts. The study period was from January 1, 2015 to June 30, 2019. The exclusion criteria removed patients who were not in cardiac arrest upon EMS arrival from the analysis. Patients who had initial intubation attempts after the first return of spontaneous circulation (ROSC) or received ALS treatment from an outside agency prior to Seattle Fire Department involvement were also excluded. 

The authors indicated that during OHCA resuscitation, Seattle Fire Department paramedics prioritize intubation and IV placement while BLS personnel provide chest compressions and rescue breathing. Direct laryngoscopy is employed for endotracheal intubation as the primary advanced airway. Additional airway adjuncts include the i-gel supraglottic airway device, cricothyroidotomy, and bougie stylet. Video laryngoscopy was not used during this study. Department medics confirm endotracheal tube placement using waveform capnography following completion of intubation. 

In this study an endotracheal intubation attempt was defined as the introduction of a laryngoscope past the teeth and concluded when the laryngoscope was removed from the mouth, regardless of whether a tube was inserted. An attempt was defined as successful if the endotracheal tube placement was confirmed by capnography. The 9-1-1 call time was used as a surrogate for the time of the arrest, and the EMS arrival time was the time the first responding unit arrived at the patient’s side. This time was approximated by the initial defibrillator turn-on time. The time of the endotracheal tube placement or other final airway device was defined as the time of the first ventilation via the advanced airway determined by audio recordings of the provider’s verbalization or production of a capnography waveform by inline EtCO₂. 

The primary outcome of interest for this study was favorable neurologic status defined by Cerebral Performance Category (CPC) score. The CPC score is widely used in research and quality assurance. CPC scores range from 1–5, with 1 indicating good cerebral performance and 5 indicating brain death. The authors of this study defined favorable neurologic status as a CPC score of 1 (mild or no neurologic deficit) or 2 (moderate cerebral disability). Secondary outcomes of interest included ROSC, survival to hospital admission, and survival to hospital discharge. 

The authors used multivariable logistic regression to evaluate the association between their primary and secondary outcomes of interest and the number of intubation attempts. The regression model adjusted for age, sex, OHCA witness status, bystander CPR, initial rhythm, and the time from 9-1-1 call to ALS arrival. 

Results

There were 1205 patients included in this analysis. The median age was 68, and 68% were male. One-third of arrests were bystander-witnessed, and 61% of patients received bystander CPR. Patient age and bystander CPR did not differ as intubation attempts increased. However, males accounted for 65% of those with only one intubation attempt, 70% of those with two intubation attempts, 72% of those with three intubation attempts, and 88% of those with four or more intubation attempts. 

The average time to successful placement of an advanced airway was 6.5 minutes after ALS arrival. Sixty-three percent of patients were successfully intubated on the first attempt, and this rose to 86% by the second attempt. There were 97% of patients whose final advanced airway was endotracheal intubation, with approximately 3% supraglottic devices and less than 1% cricothyrotomy. More than 60% of the OHCAs occurred at the patient’s home or other residence, and 87% were presumed cardiac or of other medical etiologies. The initial arrest rhythm was most often PEA/asystole (76%), followed by VF/VT (21.3%). 

Overall, 44% had documented ROSC, 38% survived to hospital admission, 11% survived to hospital discharge, and 8% had favorable neurologic status at discharge. The proportion of patients with favorable neurologic status at discharge decreased with increasing intubation attempts. There were 11% with CPC scores of 1 or 2 among those with one intubation attempt; 4% with two attempts; 3% with three attempts; and 2% with four or more attempts. 

After adjustment the odds for favorable neurologic status at discharge decreased by 59% for every subsequent intubation attempt (aOR: 0.41; 95% CI: 0.25–0.68). This was similar for the secondary outcomes of interest, with a 34% reduction in the odds of ROSC (aOR: 0.66%; 95% CI: 057–0.75); a 33% reduction in the odds of hospital admission (aOR: 0.67; 95% CI: 0.58–0.78); and a 49% reduction in the odds of hospital discharge (aOR: 0.51; 95% CI: 0.36–0.72) as the number of intubation attempts increased. 

Conclusion

As with all studies, this one has some limitations, most notably using data from only one EMS system that uses endotracheal intubation as its primary means of airway management during resuscitation of OHCA. Nonetheless, this study is an important addition to the literature. The authors note that when put into context with existing literature, these results support training and clinical care strategies to achieve first-attempt intubation success during OHCA resuscitation. 

I hope you have an opportunity to read this manuscript in full. Not only do the authors offer suggestions for successful intubation on the first attempt, but the tables and graphs are helpful in fully understanding the results.   

Antonio R. Fernandez, PhD, NRP, FAHA, is a research scientist at ESO and serves on the board of advisors of the Prehospital Care Research Forum at UCLA.