Perishock Pause Intervals and Rearrest after Out-of-Hospital Cardiac Arrest

Background: The loss of pulses after successful return of spontaneous circulation (ROSC) in out-of-hospital cardiac arrest (OHCA) is known as rearrest (RA). The causes of RA are not well understood.

Objectives: To investigate the association between shock pause intervals and RA.

Methods: Data from treated OHCA with ROSC and one or more defibrillation attempts were obtained from one site of the Resuscitation Outcomes Consortium. All analyses were conducted internally. Data available for analysis included cases spanning 2006-2008 and 2010-2011. Defibrillator tracings were used to calculate both components of the perishock pause (PSP) interval: the pre- (preSP) and the postshock pauses (postSP). RA and no-RA shock pauses were compared and independent associations between shock pause intervals, patient characteristics, and RA were assessed with the appropriate statistical tests.

Results: Analysis included 241 shocks from 101 cases. Forty-one cases (41%) had RA. RA vs. no-RA median (interquartile range) shock pauses in seconds were: preSP 13.5 (6.0-18.0) vs. 15.0 (10.9-21.5) (p = 0.121); postSP 6.0 (3.5-8.2) vs. 8.7 (4.5-13.9) (p = 0.053); and PSP 18.0 (12.3-24.0) vs. 24.0 (16.7-30.2) (p = 0.022). Considering all possible shock pause durations, shock pause lengths and various patient characteristics were not associated with RA. If 30 s or shorter, the preSP (odds ratio [OR] 0.90, 955 confidence interval [CI] 0.82-0.98) and postSP (OR 0.89, 95% CI 0.79-0.99) were related to RA.

Conclusion: Shock pause length was inversely associated with RA when shock pause intervals were limited to 30 s or less. Shock pauses and RA were not associated when all durations of shock pauses were considered.