Reference: Tanner et al, A retrospective comparison of upper and lower extremity intraosseous access during out-of-hospital cardiac arrest resuscitation. Prehospital Emergency Care. February 2024. Date: April 25, 2024 Guest Skeptic: Missy Carter is a PA working in an ICU in the Tacoma area and an adjunct faculty member with the Tacoma Community College paramedic program. She is also the local director of the difficult airway EMS course at Washington State. Case: EMS arrives with a 58-year-old woman who suffered an out-of-hospital cardiac arrest (OOHCA). When emergency department (ED) staff roll her to remove her clothing her humeral intraosseous (IO) is dislodged. Later the medic asks you if she should bother placing an upper extremity IO or just stick with the tried-and-true tibial plateau. Background: We have looked at getting access in the pre-hospital setting on  SGEM#231. That episode was a study comparing intravenous (IV) vs IO access for OOHCAs. It was a secondary analysis of an observational study which showed an association between decreased favourable neurologic outcomes in the IO group compared to the IV group. Despite that weak evidence, placement of IO in OOHCA has become a routine procedure for many EMS providers. The classic location for IO placement is the tibial plateau. This is because of the ease of finding anatomic landmarks and their location away from other procedures like defibrillation, CPR, and airway management. Some studies have suggested quicker delivery of medications and fluids through the upper extremity IO route compared to the lower extremity route. Clinical Question: Does upper extremity placement of intraosseous access versus lower extremity placement matter in out-of-hospital cardiac arrest? Reference: Tanner et al, A retrospective comparison of upper and lower extremity intraosseous access during out-of-hospital cardiac arrest resuscitation. Prehospital Emergency Care. February 2024. Population: Adults 18 or greater with an OOHCA Excluded: IV access before IO, DNR, interfacility transfers, and EMS-witnessed arrests Intervention: Upper extremity IO placement (100% humeral) Comparison: Lower extremity IO placement (97.8% tibial & 2.3% femoral) Outcome: Primary Outcome: Return of spontaneous circulation (ROSC) Secondary Outcomes: Survival to hospital discharge and survival to discharge home. Authors’ Conclusions: “In this large prehospital dataset, upper extremity IO access was associated with a small increase in the odds of ROSC in comparison to lower extremity IO access. These data support the need for prospective investigation of the ideal IO access site during OHCA resuscitation.” Quality Checklist for Observational Study: Did the study address a clearly focused issue? Yes Did the authors use an appropriate method to answer their question? Yes Was the cohort recruited in an acceptable way? Yes Was the exposure accurately measured to minimize bias? Yes Was the outcome accurately measured to minimize bias? Yes Have the authors identified all-important confounding factors? Yes Was the follow-up of subjects complete enough? Unsure How precise are the results? Very Do you believe the results? Yes Can the results be applied to the local population? Unsure Do the results of this study fit with other available evidence? Yes and No Results: The study population consisted of 155,884 patients, with 76% receiving lower extremity access and 24% upper extremity access. The median age was 65 years, 61% being male, 81% presumed a cardiac etiology and 54% were witnessed arrests. Key Results: Upper extremity IO access was associated with slightly greater odds of achieving ROSC compared to lower extremity IO access. Primary Outcome: Odds Ratio (OR) for ROSC was 1.11 [95% CI: 1.08 to 1.15] Secondary Outcomes: Survival to discharge OR 1.18 [95% CI; 1.00 to 1.39]