Dear EMSy friends and emergency colleagues,
Vascular access in the prehospital setting is like searching for the perfect parking spot—everyone wants it, but you often settle for the least bad option. When it comes to cardiac arrest, the situation gets even more "interesting." Between IV and IO, which one should we choose?
Let’s be clear: choosing between intravenous (IV) and intraosseous (IO) access in cardiac arrest isn’t just about personal preference or how skilled we are at finding hidden veins. It’s a decision that can significantly impact patient outcomes. While a few years ago we were navigating this question without much certainty, today we have solid data to guide our choices.
A bit of recent history
In 2020, a retrospective study seemed to suggest that IV access was superior to IO in terms of ROSC and favorable neurological outcomes. However, the study had several methodological limitations:
It was not randomized, meaning that patients who received IO access were likely those in whom IV access was not obtainable, and therefore in worse overall condition.
The IO group included more complex patients, with fewer witnessed arrests and fewer shockable rhythms.
IO placement sites were not specified (and we know that humeral IO has better pharmacokinetics than tibial IO).
In other words: correlation does not imply causation.
2024: A game-changing year
Fast forward to today, and we now have three fresh RCTs that completely reshuffle the deck. Here’s what they found:
VICTOR Trial (Taiwan)
This study took a smart approach: it compared humeral IO vs. IV in the upper extremity, creating a fairer comparison. The result?
Survival rates were nearly identical (10.7% IO vs. 10.3% IV).
But IO had a first-attempt success rate of 94% vs. 58% for IV. Not bad, right?
PARAMEDIC-3 Trial (UK)
The Brits went big: over 6,000 patients enrolled.
30-day survival: 4.5% IO vs. 5.1% IV (not statistically significant).
ROSC advantage for IV (24.6% vs. 21.7%), but we all know ROSC isn’t the outcome that truly matters.
IVIO Trial (Denmark)
The Danes went even further: they randomized IO patients into humeral vs. tibial placement.
Sustained ROSC: 30% IO vs. 29% IV.
And the big surprise? No difference between humeral and tibial IO.
Practical implications: What really changes?
Here are some key takeaways:
✅ First-attempt success matters: If IO gives you 94% success vs. 58% for IV, think twice before insisting on IV just because "we've always done it this way."
✅ Cognitive offloading is key: During cardiac arrest, your brain is already juggling compressions, rhythm analysis, medications, and team coordination. A faster, more reliable procedure makes life easier—why not use it?
✅ Flexibility is a virtue: Every patient is different.
A young athlete with great veins? IV might be the best choice.
An elderly, dehydrated patient with collapsed veins? IO might be the smarter option.
Final thoughts
The real victory of these studies isn’t deciding which method is "better"—it’s proving that both are valid options. This gives us the freedom to choose the best strategy for each situation, based on practical factors rather than personal preferences or outdated traditions.
And remember: next time someone tells you, "But I’ve always done it this way," you can smile and cite not one, not two, but three RCTs proving that both IV and IO are equally valid approaches.
References
📖 Ko YC, et al. JAMA Med. 2024;178(7):731-740. [VICTOR Trial]
📖 Cooper JJ, Perkins GD, et al. N Engl J Med. 2024;389(18):1668-1679. [PARAMEDIC-3 Trial]
📖 Valentin JB, et al. N Engl J Med. 2024;389(18):1680-1691. [IVIO Trial]
📖 Zhang Y, et al. Resuscitation. 2020;149:209-216.