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We will conduct a multi-centre, pragmatic, individually randomised, parallel group, superiority trial with internal pilot and economic evaluation to determine the clinical and cost effectiveness of an intraosseous access first strategy, versus current NHS treatment.

Adult patients who sustain an out-of-hospital cardiac arrest that require vascular access will be randomised in a 1:1 ratio to either an intraosseous first strategy (intervention) or an intravenous first strategy (control) group. The control group reflects current NHS practice. Randomisation will occur at the point that a randomisation envelope (or equivalent) is opened. Participants will be followed-up to six-months following cardiac arrest.

The trial will be conducted across English and Welsh ambulance services.


The primary objective of this trial is to evaluate the clinical effectiveness of intraosseous-first strategy in the treatment of OHCA, measured by our primary outcome of 30-day survival.

Secondary trial objectives of the trial are:

  1. To evaluate the effect of an IO first strategy on neurological function, quality of life and survival at other time-points.
  2. To determine the cost-effectiveness of an IO first strategy.


The primary outcome is survival at 30-days

Secondary outcomes are:

  • Any return of spontaneous circulation (ROSC)
  • Time to ROSC
  • Survived event (sustained ROSC at hospital handover)
  • Survival to hospital discharge, 3 and 6 months
  • Neurological function (measured by modified Rankin Scale (mRS) at discharge, 3, and 6 months)
  • Health related quality of life (measured by EQ-5D-5L at 3 and 6 months)
  • Hospital length of stay
  • Critical care length of stay

The primary health economic Incremental cost per quality-adjusted life year gained from the perspective of the NHS and personal social services.

Inclusion criteria

  1. Out-of-hospital cardiac arrest currently receiving cardiopulmonary resuscitation
  2. Requirement for vascular access to administer cardiac arrest drugs

Exclusion criteria

  1. Children (known or appear to be < 18 years)
  2. Known or apparent pregnancy
  3. Already have vascular access