Vascular access in out-of-hospital cardiac arrest with non-shockable rhythms—a retrospective observational study of the intravenous versus intraosseous approach: the VANISH study

Introduction Early vascular access is a key component of advanced life support in out-of-hospital cardiac arrest (OHCA), particularly in patients with non-shockable rhythms, in whom early adrenaline administration is recommended. However, the comparative clinical impact of intravenous (IV) versus intraosseous (IO) access in this setting remains uncertain. This study aimed to compare IV and IO vascular access in patients with OHCA and non-shockable rhythms and to evaluate their association with time to first adrenaline administration and return of spontaneous circulation (ROSC). Methods We conducted a retrospective observational study including patients with OHCA and a non-shockable initial rhythm attended by Emergency Medical Service 061 La Rioja between January 1, 2022, and December 31, 2024, using data from the Out-of-Hospital Spanish Cardiac Arrest Registry (OHSCAR). Patients in whom cardiopulmonary resuscitation was initiated were eligible. Demographic, temporal, and clinical variables were analyzed. Vascular access was classified as IV or IO. Associations between vascular access route, time to first adrenaline administration, and ROSC status were explored using the chi-square test or Fisher’s exact test, as appropriate. Results A total of 185 patients were included. IV access was established in 72.4% of cases ( N = 134), whereas IO access was used in 27.6% ( N = 51). Any ROSC was achieved in 33.5% of patients ( N = 62), and sustained ROSC to hospital arrival was observed in 23.2% ( N = 43). Initial rhythm was significantly associated with ROSC status ( p = 0.003). Vascular access route was also significantly associated with ROSC status ( p = 0.036). Sustained ROSC to hospital arrival was observed in 24.6% of patients with IV access and 19.6% of those with IO access. Earlier adrenaline administration was more frequently observed in the IV group. Discussion In this retrospective observational cohort of patients with OHCA and non-shockable rhythms, IV access was associated with a higher proportion of sustained ROSC at hospital arrival compared with IO access. However, this association should be interpreted with caution, as the study design precludes causal inference and residual confounding is likely. In particular, patients receiving IO access may have represented more complex cases, such as those with difficult vascular access or longer resuscitation times.