Why is intravenous (IV) access preferred over intraosseous (IO) access in general clinical practice?

Why IV Access is Preferred Over IO Access

Intravenous (IV) access is preferred over intraosseous (IO) access because IV administration is associated with significantly better patient survival—20 more survivors per 1,000 cardiac arrests—and superior neurological outcomes compared to IO access. 1

Evidence-Based Outcomes Favoring IV Access

The International Consensus on Cardiopulmonary Resuscitation demonstrates clear superiority of IV over IO access across critical outcomes:

• Survival to hospital discharge: IV access results in 20 additional survivors per 1,000 cardiac arrests (adjusted OR 0.71,95% CI 0.63-0.79) 1
• Favorable neurological outcomes: IV access produces 19 more survivors with good neurological function per 1,000 cardiac arrests (adjusted OR 0.60,95% CI 0.52-0.69) 1
• Return of spontaneous circulation (ROSC): IV access achieves 61 more ROSC events per 1,000 cardiac arrests (adjusted OR 0.72,95% CI 0.68-0.76) 1

Clinical Algorithm for Vascular Access Selection

The American Heart Association provides clear guidance on when to use each route:

First-line approach:

• Always attempt peripheral IV access first in all patients requiring vascular access during resuscitation 1, 2
• IV access should be the default choice for drug administration during both out-of-hospital and in-hospital cardiac arrest 1

When to switch to IO access:

• Switch immediately if peripheral IV cannot be obtained within 1-2 attempts 1
• Use IO without delay if patient factors make IV access unlikely to succeed (severe hypovolemia, shock, obesity, IV drug use) 1
• Consider IO as first-line only for severe trauma patients with hemorrhagic shock, patients requiring multiple simultaneous life-saving interventions, or in mass casualty/austere environments 1

Important Caveats About the Evidence

Limitations of current data:

• The certainty of evidence comparing IV to IO is very low due to risk of bias and inconsistency in observational studies 1
• Patients who received IO access may have had worse baseline characteristics that contributed to poorer outcomes, creating confounding bias 1
• Recent meta-analysis of randomized controlled trials found no significant differences between routes for 30-day survival, sustained ROSC, survival to hospital discharge, or favorable neurological outcomes 3

This discrepancy between observational data (favoring IV) and RCT data (showing equivalence) suggests the observational findings may reflect selection bias rather than true route superiority. However, given the potential for better outcomes with IV access and no disadvantage when obtainable, IV remains the preferred first attempt. 1

Practical Advantages of IO Access

Despite outcome data favoring IV, IO access offers procedural advantages in specific scenarios:

• Higher first-attempt success rate: 85% for IO versus 60% for central venous access in patients with difficult peripheral veins 4
• Faster procedure time: IO access takes 2.0 minutes versus 8.0 minutes for central venous catheterization 4
• Reliable in shock states: IO provides access to a noncollapsible venous plexus, enabling drug delivery comparable to peripheral IV at the same doses 5
• No interruption of resuscitation: IO can be established rapidly without stopping chest compressions 5

Common Pitfalls to Avoid

• Do not delay resuscitation: If initial IV attempts fail, switch to IO immediately rather than persisting with multiple IV attempts 1
• Do not assume IO is inferior: When IV access is not feasible, IO provides effective drug delivery and should be used without hesitation 5
• Fluid administration technique: When administering drugs via peripheral IV during resuscitation, follow with a 20-mL bolus of IV fluid and briefly elevate the extremity to facilitate central circulation delivery 5
• Site selection: Tibial and humeral sites are both acceptable for IO insertion, with no evidence favoring one over the other 1, 5