Vascular Access in a Code – IO or IV?

Written by Clay Smith

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From the best evidence available, it looks like giving medications during arrest is best done via intravenous (IV) vs intraosseous (IO) route.

Why does this matter?
An IO is a quick way to get vascular access in a code, faster than an IV and with greater first-attempt success. But does an IV allow for better drug delivery?

IO, IO, so off to work I go…
We covered three articles this week on IO vs IV meds in out-of-hospital cardiac arrest (OHCA). Let’s put it all together. Looking at the best evidence, what should be our first-line vascular access in a code?

No interaction IV or IO epi but wait… – First, we covered the secondary analysis of the PARAMEDIC2 trial, which showed there was no statistically significant interaction between IV and IO administration for 30-day survival, p=0.18 for the interaction of the treatment (epinephrine) and route – IV or IO. However, it’s hard to ignore that there was an association with improved survival at 30 days when epinephrine was given IV, aOR 1.67 (95%CI 1.18 to 2.35), but no association with improved survival when given IO, aOR 0.9 (95%CI 0.4 to 2.05).

IV epi looks better – Next, we covered the large retrospective analysis of the Resuscitation Outcomes Consortium (ROC), with 35,733 patients. This study found a clear association of improved ROSC, 30-day survival, and survival with good neurological outcome when epinephrine was given IV vs IO.

IV antiarrhythmics look better – Finally, we covered the ROC-ALPS reanalysis, in which administration of IV amiodarone or lidocaine was associated with improved survival to discharge but IO administration of these medications was not.

More studies favor IV – I found another two retrospective studies that showed IO access was worse with regard to outcomes – Feinstein et al and Kawano et al. Another showed IO was non-inferior to IV, but I question the validity of determining non-inferiority in a retrospective study and not a clinical trial. Yet another showed lower ROSC but no difference in survival. A RCT found that IO was faster than IV, with higher first-attempt success as well. It did not assess other outcomes.

Meta-analysis favors IV – There are no Cochrane reviews on this topic. However, I found one metaanalysis from Spain that reviewed 5 retrospective studies (four of which are mentioned above) and found that IO access was, “related to poorer outcomes in terms of ROSC and survival at hospital discharge.” The combined studies showed, “ROSC (odds ratio [OR], 0.69; 95% CI, 0.57-0.83; P=.02; I2=65%) and worse survival to discharge (OR, 0.65; 95% CI, 0.51-0.83); P<.01, I2=30%).” Take this with a grain of salt, because I don’t read Spanish very well.

Wrap up – In summary, the preponderance of observational evidence at this point seems to favor administration of medications for arrest IV rather than IO. Here is the caveat. An IO is fast. If IV attempts are not rapidly successful, don’t hesitate to reach for the IO. But if given the choice, go with IV. This advice is concordant with ILCOR. ILCOR says, “If intravenous access is difficult or impossible, consider the IO route.” A RCT is underway in China to answer this question.


  • Feinstein BA, Stubbs BA, Rea T, Kudenchuk PJ. Intraosseous compared to intravenous drug resuscitation in out-of-hospital cardiac arrest. Resuscitation. 2017;117:91–96. doi:10.1016/j.resuscitation.2017.06.014

  • Kawano T, Grunau B, Scheuermeyer FX, et al. Intraosseous Vascular Access Is Associated With Lower Survival and Neurologic Recovery Among Patients With Out-of-Hospital Cardiac Arrest. Ann Emerg Med. 2018;71(5):588–596. doi:10.1016/j.annemergmed.2017.11.015

  • Clemency B, Tanaka K, May P, et al. Intravenous vs. intraosseous access and return of spontaneous circulation during out of hospital cardiac arrest. Am J Emerg Med. 2017;35(2):222–226. doi:10.1016/j.ajem.2016.10.052

  • Mody P, Brown SP, Kudenchuk PJ, et al. Intraosseous versus intravenous access in patients with out-of-hospital cardiac arrest: Insights from the resuscitation outcomes consortium continuous chest compression trial. Resuscitation. 2019;134:69–75. doi:10.1016/j.resuscitation.2018.10.031

  • Reades R, Studnek JR, Vandeventer S, Garrett J. Intraosseous versus intravenous vascular access during out-of-hospital cardiac arrest: a randomized controlled trial. Ann Emerg Med. 2011;58(6):509–516. doi:10.1016/j.annemergmed.2011.07.020

  • Morales-Cané I, Valverde-León MDR, Rodríguez-Borrego MA, López-Soto PJ. Intraosseous access in adults in cardiac arrest: a systematic review and meta-analysis. Vía intraósea en adultos en situación de parada cardiaca: revisión sistemática y metanálisis. Emergencias. 2020;32(1):49–56.


2 thoughts on “Vascular Access in a Code – IO or IV?”


    I’m curious if the IO sites were separate variables, would you see a difference? I would assume a more favorable response, or one more similar to IV’s, would be seen in humeral head or sternal IOs compared to tibial ones. It would also be interesting to look at outcomes compared to time to achieving access.


      I think you are right. Most were tibial. But the sample size was too small to make a comparison. However, to your point, the article – Survival After Intravenous Versus Intraosseous Amiodarone, Lidocaine, or Placebo in Out-of-Hospital Shock-Refractory Cardiac Arrest – said, "the anatomic site of administration (upper versus lower body) could itself play a role in a drug’s effective delivery to the heart during active CPR, independent of whether it is given intravenously or intraosseously. Experimental work has shown drugs that achieve a delayed time-to-peak, and lower peak concentrations in the heart, as well, when given via an intravenous route that reaches the heart via the inferior vena cava rather than the superior vena cava during active CPR. These pharmacokinetic differences were also seen in an animal model of cardiac arrest when epinephrine was given by tibial intraosseous access in comparison with a peripheral intravenous route, but not when comparing humeral intraosseous administration with peripheral intravenous administration. This phenomenon, which is not observed during spontaneous circulation, may be attributable to the presence of venous valves in the region of the superior vena cava as contrasted with their absence in the inferior vena cava. Closure of these valves in response to the high intrathoracic pressures achieved during the compression phase of CPR can minimize regurgitant blood flow that might otherwise oppose venous blood return and drug delivery from upper extremity veins draining to the heart via the superior vena cava during CPR. Such is not the case for lower extremity vessels draining to the heart via the inferior vena cava, where, lacking such valves, venous blood return and drug delivery to the heart can be impeded during CPR. This phenomenon could explain the apparent effectiveness of intraosseous administered drugs observed under normal circulatory conditions, in contrast to cardiac arrest with ongoing CPR. If true, the preferential selection of an upper extremity for drug administration (such as the proximal humerus or sternum when other intravenous access is not feasible) might address the possible limitations associated with a lower extremity site (such as the tibial intraosseous site) observed in this study during active CPR."

What are your thoughts?

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