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:

  1. Did the study address a clearly focused issue? Yes
  2. Did the authors use an appropriate method to answer their question? Yes
  3. Was the cohort recruited in an acceptable way? Yes
  4. Was the exposure accurately measured to minimize bias? Yes
  5. Was the outcome accurately measured to minimize bias? Yes
  6. Have the authors identified all-important confounding factors? Yes
  7. Was the follow-up of subjects complete enough? Unsure
  8. How precise are the results? Very
  9. Do you believe the results? Yes
  10. Can the results be applied to the local population? Unsure
  11. 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]
    • Survival to discharge to home OR 1.23 [95% CI; 1.02 to 1.48]

1. Retrospective Observational Study: The study’s retrospective observational design could lead to potential biases from unmeasured confounder factors.

2, Upper or Lower: 76% of the IOs which were placed were performed in the lower extremity (98% tibial and 2% femoral). The remaining 24% were all upper (humeral). It would be interesting to know what factors determined the insertion site chosen and if this might affect the outcomes.

3. Loss to Follow-up: There was 17% of patients lost to follow-up. Given the small effect sizes observed in the study, this could have been biased by the results if those patients were systematically different.

4. Subgroup Analysis: Intubated patients with upper extremity IO did worse than intubated patients with lower extremity IO. Is this an outlier or is it possible that doing multiple complex procedures distracts the team from providing meaningful procedures (high-quality CPR and defibrillation) in a timely manner?

Another subgroup difference observed was patients with shorter ischemic time (witnessed arrest and/or bystander CPR) and shockable rhythms had better survival with upper extremity versus lower extremity IO placement. A faster rate of antiarrhythmic, vasopressor and IVF administration may (may not) lead to an improvement in clinical outcomes. This information is hypothesis-generating but would need to be confirmed in a properly designed randomized control trial.

5. Patient-Oriented Outcome: While ROSC and survival are important a more patient-oriented outcome would be survival with good neurologic function. We saw this in the PARAMEDIC2 trial (SGEM#238). Survival of OOHCA was better with epinephrine but not survival with a good outcome.

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We agree with the authors’ conclusion about an association between upper extremity IO placement and survival and the need for better quality studies to confirm this finding. 

SGEM Bottom Line: Upper extremity intraosseous access may/may not be superior in patients with out-of-hospital cardiac arrests.

Case Resolution: You tell the medic she made a good choice in her IO site selection. Although the evidence is still building about the benefits of the upper extremity site it may provide a quicker route for medication and IV fluid administration which may improve the rates of ROSC.

Missy Carter

Clinical Application: IO insertion remains a valuable tool for both in and OOHCAs. The location in which we place the IO may be clinically relevant, but this procedure (like all advanced procedures) should never detract from the core goals of cardiac arrest.

What Do I Tell My Patient? Not applicable.

Keener Kontest: Last week’s winner was Dr. Joseph Reardon who is the Medical Director for Laurens Emergency Department. He knew the three categories of human ribs are true ribs, false ribs, and floating ribs!

Listen to the podcast to hear this week’s keener question. If you think you know the answer, send an email to with “keener” in the subject line. The first correct answer will receive a cool skeptical prize.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.