Aim of the study: This study aimed to apply a Bayesian probabilistic framework to the Intravenous vs. Intraosseous Vascular Access for Out-of-Hospital Cardiac Arrest (IVIO) trial data to evaluate the likelihood of benefit for each vascular access method while incorporating various prior beliefs.

Methods: The IVIO trial was a randomised trial comparing intraosseous to intravenous access in 1,479 adults with non-traumatic out-of-hospital cardiac arrest. Bayesian analyses were pre-planned in the protocol and conducted using both non-informative and informative priors to calculate posterior probabilities for sustained return of spontaneous circulation, 30-day survival, and 30-day survival with a favourable neurologic outcome.

Results: Using non-informative priors for return of spontaneous circulation, the posterior probabilities that the effect of either vascular access exceeds the hypothesised difference were 1.2% (risk ratio > 1.27, favouring intraosseous access) and < 0.1% (risk ratio < 0.79 [1/1.27], favouring intravenous access). For 30-day survival and survival with a favourable neurologic outcome, the posterior probability that the risk ratio for intraosseous compared to intravenous access is between 0.83 (1/1.2) and 1.2 was 58% and 55%, respectively. For all analyses with informative priors, the results did not provide probabilities strongly favouring either intraosseous or intravenous access.

Conclusions: The probability of a clinically meaningful difference in return of spontaneous circulation between intraosseous and intravenous access for out-of-hospital cardiac arrest was very low, while results for 30-day outcomes were uncertain, with no strong evidence favouring either method.

Trial registration: EU Clinical Trials number: 2022-500744-38-00.

Clinicaltrials: gov number: NCT05205031.

Vallentin MF, Holmberg MJ, Granfeldt A, Klitgaard TL, Mikkelsen S, Folke F, Christensen HC, Povlsen AL, Petersen AH, Winther S, Frilund LW, Meilandt C, Winther KB, Bach A, Dissing TH, Terkelsen CJ, Christensen S, Rasmussen LK, Mortensen LR, Loldrup ML, Elkmann T, Nielsen AG, Runge C, Klæstrup E, Holm JH, Bak M, Nielsen LR, Pedersen M, Kjærgaard-Andersen G, Hansen PM, Brøchner AC, Christensen EF, Nielsen FM, Nissen CG, Bjørn JW, Burholt P, Obling LER, Holle SLD, Russell L, Alstrøm H, Hestad S, Fogtmann TH, Hove Buciek JU, Jakobsen K, Krag M, Sandgaard M, Sindberg B, Andersen LW. Intraosseous vs. intravenous access during out-of-hospital cardiac arrest: a Bayesian secondary analysis of a randomised clinical trial. Resuscitation. 2025 May 17;212:110634. doi: 10.1016/j.resuscitation.2025.110634. Epub ahead of print. PMID: 40348355.