End-tidal Carbon Dioxide + Return of Spontaneous Circulation After Cardiac Arrest (RACA) Score to Predict Outcomes After Out-of-hospital Cardiac Arrest

Cheng-Yi Wu; Tsung-Chien Lu; Pei-I Su; Chu-Lin Tsai; Joyce Tay; Meng-Che Wu; Yi-Hsuan Yen; Eric H Chou; Chih-Hung Wang; Chien-Hua Huang; Wen-Jone Chen

doi:10.5811/westjem.59005

End-tidal Carbon Dioxide + Return of Spontaneous Circulation After Cardiac Arrest (RACA) Score to Predict Outcomes After Out-of-hospital Cardiac Arrest

West J Emerg Med. 2023 Apr 4;24(3):605-614. doi: 10.5811/westjem.59005.

Authors

Cheng-Yi Wu¹, Tsung-Chien Lu^{1

2}, Pei-I Su¹, Chu-Lin Tsai^{1

2}, Joyce Tay¹, Meng-Che Wu¹, Yi-Hsuan Yen^{3

4}, Eric H Chou^{3

4}, Chih-Hung Wang^{1

2}, Chien-Hua Huang^{1

2}, Wen-Jone Chen^{1

2

5

6}

Affiliations

¹ National Taiwan University Hospital, Department of Emergency Medicine, Taipei, Taiwan.
² National Taiwan University, College of Medicine, Department of Emergency Medicine, Taipei, Taiwan.
³ Baylor Scott and White All Saints Medical Center, Department of Emergency Medicine, Fort Worth, TX.
⁴ Baylor University Medical Center, Department of Emergency Medicine, Dallas, TX.
⁵ National Taiwan University Hospital and National Taiwan University College of Medicine, Department of Internal Medicine, Division of Cardiology, Taipei, Taiwan.
⁶ Min-Shen General Hospital, Taoyuan, Taiwan.

Abstract

Introduction: The return of spontaneous circulation after cardiac arrest (RACA) score is a well-validated model for estimating the probability of return of spontaneous circulation (ROSC) in patients with out-of-hospital cardiac arrest (OHCA) by incorporating several variables, including gender, age, arrest aetiology, witness status, arrest location, initial cardiac rhythms, bystander cardiopulmonary resuscitation (CPR), and emergency medical services (EMS) arrival time. The RACA score was initially designed for comparisons between different EMS systems by standardising ROSC rates. End-tidal carbon dioxide (EtCO₂) is a quality indicator of CPR. We aimed to improve the performance of the RACA score by adding minimum EtCO₂ measured during CPR to develop the EtCO₂ + RACA score for OHCA patients transported to an emergency department (ED).

Methods: This was a retrospective analysis using prospectively collected data for OHCA patients resuscitated at an ED during 2015-2020. Adult patients with advanced airways inserted and available EtCO₂ measurements were included. We used the EtCO₂ values recorded in the ED for analysis. The primary outcome was ROSC. In the derivation cohort, we used multivariable logistic regression to develop the model. In the temporally split validation cohort, we assessed the discriminative performance of the EtCO₂ + RACA score by the area under the receiver operating characteristic curve (AUC) and compared it with the RACA score using the DeLong test.

Results: There were 530 and 228 patients in the derivation and validation cohorts, respectively. The median measurements of EtCO₂ were 8.0 times (interquartile range [IQR] 3.0-12.0 times), with the median minimum EtCO₂ of 15.5 millimeters of mercury (mm Hg) (IQR 8.0-26.0 mm Hg). The median RACA score was 36.4% (IQR 28.9-48.0%), and a total of 393 patients (51.8%) achieved ROSC. The EtCO₂ + RACA score was validated with good discriminative performance (AUC, 0.82, 95% CI 0.77-0.88), outperforming the RACA score (AUC, 0.71, 95% CI 0.65-0.78) (DeLong test: P < 0.001).

Conclusion: The EtCO₂ + RACA score may facilitate the decision-making process regarding allocations of medical resources in EDs for OHCA resuscitation.

MeSH terms

Adult
Carbon Dioxide
Cardiopulmonary Resuscitation*
Emergency Medical Services*
Humans
Out-of-Hospital Cardiac Arrest* / therapy
Retrospective Studies
Return of Spontaneous Circulation

Substances

Carbon Dioxide