title: Minimizing pre- and post-defibrillation pauses increases the likelihood of return of spontaneous circulation (ROSC).
abstract: BACKGROUND
  The three-phase model of ventricular fibrillation (VF) arrest suggests a period of compressions to "prime" the heart prior to defibrillation attempts. In addition, post-shock compressions may increase the likelihood of return of spontaneous circulation (ROSC). The optimal intervals for shock delivery following cessation of compressions (pre-shock interval) and resumption of compressions following a shock (post-shock interval) remain unclear.
  
  
  OBJECTIVE
  To define optimal pre- and post-defibrillation compression pauses for out-of-hospital cardiac arrest (OOHCA).
  
  
  METHODS
  All patients suffering OOHCA from VF were identified over a 1-month period. Defibrillator data were abstracted and analyzed using the combination of ECG, impedance, and audio recording. Receiver-operator curve (ROC) analysis was used to define the optimal pre- and post-shock compression intervals. Multiple logistic regression analysis was used to quantify the relationship between these intervals and ROSC. Covariates included cumulative number of defibrillation attempts, intubation status, and administration of epinephrine in the immediate pre-shock compression cycle. Cluster adjustment was performed due to the possibility of multiple defibrillation attempts for each patient.
  
  
  RESULTS
  A total of 36 patients with 96 defibrillation attempts were included. The ROC analysis identified an optimal pre-shock interval of <3s and an optimal post-shock interval of <6s. Increased likelihood of ROSC was observed with a pre-shock interval <3s (adjusted OR 6.7, 95% CI 2.0-22.3, p=0.002) and a post-shock interval of <6s (adjusted OR 10.7, 95% CI 2.8-41.4, p=0.001). Likelihood of ROSC was substantially increased with the optimization of both pre- and post-shock intervals (adjusted OR 13.1, 95% CI 3.4-49.9, p<0.001).
  
  
  CONCLUSIONS
  Decreasing pre- and post-shock compression intervals increases the likelihood of ROSC in OOHCA from VF.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of California at San Diego, San Diego, CA 92103-8676, USA.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Sell
authors.forename: Renee
authors.initials: R
authors.lastname: Sarno
authors.forename: Brenna
authors.initials: B
authors.lastname: Lawrence
authors.forename: Edward M
authors.initials: EM
authors.lastname: Castillo
authors.forename: Roger
authors.initials: R
authors.lastname: Fisher
authors.forename: Criss
authors.initials: C
authors.lastname: Brainard
authors.forename: James V
authors.initials: JV
authors.lastname: Dunford
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Davis
mesh_terms: D000328:Adult; D000368:Aged; D016887:Cardiopulmonary Resuscitation / Q000379:methods / Q000401:mortality; D015331:Cohort Studies; D016208:Databases, Factual; D047548:Defibrillators; D004554:Electric Countershock / Q000379:methods* / Q000401:mortality; D004562:Electrocardiography; D004632:Emergency Medical Services / Q000379:methods*; D005260:Female; D006323:Heart Arrest / Q000209:etiology / Q000401:mortality / Q000517:prevention & control*; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D020127:Recovery of Function; D018570:Risk Assessment; D015996:Survival Rate; D013997:Time Factors; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000150:complications / Q000401:mortality / Q000628:therapy*