Association Between Duration of CPR and Outcome

Synopsis Provided By

Deborah C. Silverstein, BS, DVM

https://www.bmj.com/content/bmj/384/bmj-2023-076019.full.pdf

Synopsis

How long should you continue CPR efforts before the chance of a good outcome is minuscule? Okuno et al.’s recent multicenter cohort study sought to find out by utilizing a cardiac arrest registry in the United States to investigate survival to discharge in almost 350,000 adult human patients who received in-hospital cardiopulmonary resuscitation (CPR) from 2000-2021.¹ The investigators found that the probability of survival and a favorable functional outcome following the first return of spontaneous circulation (ROSC) decreased with each minute of CPR (Okuno 2024).

This study exemplifies the usefulness of data registries for analyzing large cohorts of patients who suffered from in-hospital cardiac arrest. The investigators retrospectively looked at the duration of CPR, from the start of chest compressions to first ROSC, and the probability of a good functional outcome. A previous study from Denmark found that for half of human patients who experience in-hospital cardiac arrest, resuscitative efforts are terminated without ROSC.² In addition, previous research utilizing the American Heart Association Get With The Guidelines -Resuscitation registry found that longer resuscitation efforts before termination of CPR were associated with an increased chance of survival to hospital discharge.³

Subsequently, it is difficult for clinicians to decide how long to perform CPR when ROSC is not achieved, so this study attempted to help guide clinicians with this critical decision. The investigators found that after a median of 7 minutes of CPR (interquartile range 3-13), 233,551 out of 348,996 patients (66.9%) achieved ROSC; however, 115,445 (33.1%) of the patients did not achieve ROSC after a median of 20 minutes of CPR (interquartile range 14-30). Only 78,799 (22.6%) of patients survived to hospital discharge, and the likelihood of survival and a favorable functional outcome among patients pending ROSC at one minute’s duration of CPR was 22.0% and 15.1%, respectively. These probabilities decreased over time and were <1% chance of survival at 39 minutes and <1% for favorable functional outcome after 32 minutes of CPR. However, it is possible that continued CPR efforts after 32 minutes could have resulted in a good functional outcome in the 3500 patients that were represented by the “<1%” of this large study cohort. Factors that led to higher estimates of the time-dependent probabilities of survival and functional outcome included <60 years old, witnessed arrest, and initial shockable rhythm.

This study required that all patients were 18 years of age or older. The median age was 67 (56-77) years old and 58.4% were men. A nonshockable rhythm (asystole or pulseless electrical activity) was present in 76.7% of patients.

Okubo M et al, BMJ 2024.

Figure 1: Probability of outcome (survival to discharge or favorable functional outcome at
discharge) decreases with duration of CPR (Open Access article permits distribution)

† Interval in whole minutes between the start of chest compression and the first return of spontaneous circulation or termination of resuscitation

What about small animals? There is a dearth of research looking at the duration of CPR and survival to discharge, and veterinary ROSC rates are lower than reported in human medicine, especially in dogs. The 2024 RECOVER guidelines do not have termination of resuscitation guidelines at this time, However, the RECOVER Registry database was recently used to investigate the optimal duration of CPR in small animals. Sustained ROSC and survival to discharge decreased with every additional minute of CPR, and resuscitation efforts for less than or equal to 10 minutes were associated with higher odds of ROSC and sustained ROSC (pending publication in JVECC).

In conclusion, the optimal duration of CPR efforts in small animals is unknown. Still, in both human and small animal medicine, the evidence suggests that the longer CPR is performed without ROSC, the less likely it is to result in a successful outcome. It is always challenging to determine the appropriate time for termination of CPR efforts, but it is assumed the odds of ROSC is 0% when CPR is terminated. The cause of CPA and comorbidities, as well as the quality of CPR, likely play an important role in studies of this kind. Further research will allow for more individualized recommendations regarding the optimal duration of CPR in dogs and cats.

References

1. Okubo M, Komukai S, Andersen LW, Berg RA, et al on behalf of the American Heart Association’s Get With The Guidelines—Resuscitation Investigators. Duration of cardiopulmonary resuscitation and outcomes for adults with in-hospital cardiac arrest: retrospective cohort study. BMJ 2024;384:e076019 http://dx.doi.org/10.1136/ bmj-2023-076019
2. Andersen LW, Holmberg MJ, Løfgren B, Kirkegaard H, Granfeldt A. Adult in-hospital cardiac arrest in Denmark. Resuscitation 2019;140:31-6. https://doi.org/10.1016/j.resuscitation.2019.04.046
3. Goldberger ZD, Chan PS, Berg RA, et al. American Heart Association Get With The Guidelines—Resuscitation (formerly National Registry of Cardiopulmonary Resuscitation) Investigators. Duration of resuscitation efforts and survival after in-hospital cardiac arrest: an observational study. Lancet 2012;380:1473-81. https://doi.org/10.1016/S0140-6736(12)60862-9

Additional evidence from RECOVER regarding the duration of CPR and outcome in a 2021 presentation by Dr. Boller can be found here: https://www.facebook.com/watch/live/?ref=watch_permalink&v=4208992489123353