Paramedic Out-of-Hospital Cardiac Arrest Case Volume as a Predictor of Return of Spontaneous Circulation

Introduction—Many factors contribute to the survival of out-of-hospital cardiac arrest (OHCA). These factors include the quality of resuscitation efforts, which in turn may be a function of OHCA case volume. However, few studies have investigated the OHCA case volume-survival relationship. Consequently, we sought to develop a model describing the likelihood of return of spontaneous circulation (ROSC) as a function of paramedic cumulative OHCA experience.

Hypothesis—The likelihood of ROSC increases with greater paramedic OHCA experience.

Methods—The authors conducted a statewide retrospective study of cardiac arrest using the North Carolina Prehospital Care Reporting System (PREMIS). Adult patients suffering a witnessed, nontraumatic cardiac arrest between January 2012 and June 2014 were included. Using logistic regression, an adjusted odds ratio was calculated for the influence of the preceding five-year paramedic OHCA case volume on ROSC while controlling for the potentially confounding variables identified a priori as patient age, gender and non-Caucasian race; shockable presenting rhythm; layperson/first responder CPR; and EMS response time.

Results—Of the 6,405 patients meeting inclusion criteria, 3,155 (49.3%) experienced ROSC. ROSC was more likely among patients treated by paramedics with ≥15 OHCA experiences during the preceding five years (OR 1.21, p<0.01). ROSC was also more likely among patients with shockable initial rhythms (OR 2.35, p<0.01) and who received layperson/first responder CPR (OR 1.77, p<0.01). Increasing patient age (OR 0.996, p=0.02), male gender (OR 0.742, p<0.01) and increasing EMS response time (OR 0.954, p<0.01) were associated with a decreased likelihood of ROSC. Non-Caucasian race was not an independent predictor of ROSC.

Conclusion—The study found a paramedic five-year OHCA case volume of ≥15 is significantly associated with ROSC. Further study is needed to determine the specific actions of these more experienced paramedics that are responsible for the increased likelihood of ROSC, as well as the influence of case volume on the longer-term outcome measures of survival to hospital discharge and neurological function.