Understanding Survival and Spectrum Bias in Emergency Medicine Trials

Date: November 10, 2024 Reference: Couper et al. The Paramedic 3 Trial: A randomized clinical trial of drug route in out-of-hospital cardiac arrest. October 31, 2024 NEJM Access to the SGEM Podcast episode at this LINK. Guest Skeptic: Missy Carter is a PA currently practicing in critical care after having attended the University of Washington's MEDEX program. An alumnus of Tacoma Community College's paramedic program Missy served as a paramedic for the Bremerton Fire Department for nearly 12 years and has been involved in paramedic education since 2004. Missy has been teaching airway management for over a decade and is the creator of the Prehospital Emergency Airway Course which is taught throughout Washington State. Case: You’re doing a ride along with your local emergency medical service (EMS) crews and responding to an out-of-hospital cardiac arrest (OHCA). After starting cardiopulmonary resuscitation (CPR), you note pulseless electrical activity (PEA) on the monitor.  The paramedic is trying to get intravenous (IV) access to give epinephrine per the protocol. She is struggling to find a good vein and she asks you what you think about going straight to intraosseous (IO) access. Background: OHCA remains one of the most challenging and time-sensitive emergencies faced by prehospital and emergency medicine teams. With a survival rate to discharge often below 10% globally, rapid, effective interventions are needed to improve patient outcomes.  Epinephrine has long been a cornerstone in the management of OHCA. Multiple studies have demonstrated how the administration of epinephrine can improve short-term outcomes, such as return of spontaneous circulation (ROSC). However, the evidence regarding its impact on long-term survival and neurological outcomes is mixed​​. Studies like PARAMEDIC-2 have raised questions about whether epinephrine's benefits in achieving ROSC are offset by potential adverse effects on neurological recovery (SGEM#238).  One critical consideration in prehospital epinephrine administration is the method of vascular access. IV administration has been preferred the preferred route, but securing IV access can be challenging in the field and in patients with compromised vascular systems. Intraosseous (IO) access provides an alternative in challenging clinical scenarios. However, there has been limited research comparing the efficacy of IO versus IV administration of epinephrine in terms of both survival and neurological outcomes in OHCA patients​​. Given these complexities, ongoing research continues to explore the most effective methods of delivering epinephrine to optimize outcomes. Recent randomized trials are now evaluating whether the speed and reliability of IO access provide significant benefits over the traditional IV route. Most EMS providers are choosing the proximal tibial as their go-to IO access. The current evidence has not given a definitive answer as to which type of access is best for OHCAs.  Clinical Question: Should we use an IV first or an IO first approach to deliver epinephrine to adult patients with an OHCA? Reference: Couper et al. The Paramedic 3 Trial: A randomized clinical trial of drug route in out-of-hospital cardiac arrest. October 31, 2024 NEJM Population: Adult patients (≥18 years old) who experienced an OHCA and required vascular access for drug administration during cardiopulmonary resuscitation (CPR).  Intervention: IO first approach Comparison: IV first approach  Outcome:  Primary Outcome: Survival at 30 days Secondary Outcomes: ROSC at any time, sustained ROSC, length of stay (LOS) in hospital, survival at discharge, three and six months, neurologic function measured on the modified Rankin Scale (mRS) at discharge, three and six months, and health-related quality of life (assessed using the EQ-5D-5L questionnaire). Trial: Multi-center, non-masked, randomized trial