Subsequent shock delivery and outcomes in out-of-hospital cardiac arrests with initial unshockable rhythm
Authors: Goto Y , Funada A , Maeda T , Goto Y 
Published: May 2021

Abstract

Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Japan Society for the Promotion of Science (Grant-in-Aid for Scientific Research)

Background
The conversion from initial non-shockable to shockable rhythms during cardiopulmonary resuscitation (CPR) by emergency medical service (EMS) providers may be associated with neurologically intact survival after out-of-hospital cardiac arrest (OHCA). However, the prognostic significance of rhythm conversion according to the type of initial nonshockable rhythm is unclear.

Purpose
To determine the association between shock after conversion to shockable rhythm with neurologically intact survival after OHCA and shock delivery time (time from EMS-initiated CPR to first shock delivery) in patients with two types of initial unshockable rhythm.

Methods
We analyzed the records of 90,334 adult patients with witnessed OHCA of cardiac origin who were treated by EMS providers and had an initial unshockable rhythm. Data were obtained from a prospectively recorded Japanese nationwide Utstein-style database for a 5-year period (2013–2017). The primary outcome was 1-month neurologically intact survival, defined as a cerebral performance categories score from 1 to 2. Patients were divided into initial pulseless electrical activity (PEA) (n = 37,977 [42.0%]) and initial asystole (n = 52,357 [58.0%]) groups.

Results
In the initial PEA group, the crude rate of 1-month neurologically intact survival was significantly higher in the subsequently shocked than in the non-shocked patients (4.2% [121/2,896]) vs. 2.4% [857/35,081], p &lt;0.0001). After adjustment for ten prehospital variables, the adjusted odds ratios (aORs) of subsequent shock for 1-month neurologically intact survival compared to no shock delivery were as follows: shock delivery time &lt;10 min, 2.21 (95% confidence interval [CI], 1.77–2.77, p&lt; 0.0001); 10–14 min, 1.43 (0.89–2.28, p = 0.14); and ≥15 min, 0.36 (0.16–0.81; p = 0.013). In the initial asystole group, the crude rate of 1-month neurologically intact survival was significantly higher in the subsequently shocked than in the non-shocked (1.7% [47/2,687] vs. 0.4% [203/49,670], p &lt;0.0001). A multivariate logistic regression model showed that subsequent shock with a shock delivery time &lt;10 min was associated with increased odds of neurologically intact survival compared to no shock delivery (aOR, 5.67; 95% CI, 3.92–8.18; p &lt;0.0001). However, there were no significant differences in neurological outcomes between subsequently shocked and non-shocked patients when the shock delivery time was 10–14 min (p = 0.21) or ≥15 min (p = 0.91).

Conclusions
In patients with witnessed OHCA of cardiac origin and initial nonshockable rhythm, subsequent shock after conversion to shockable rhythm during CPR was associated with increased odds of 1-month neurologically intact survival only when shock was delivered &lt;10 min from EMS-initiated CPR, regardless of the type of initial rhythm. Further, in patients with initial PEA, subsequent shock was associated with decreased odds of neurologically intact survival when shock was delivered ≥15 min from EMS-initiated CPR.