Efficacy of inhaled hydrogen on neurological outcome following brain ischaemia during post-cardiac arrest care (HYBRID II)
Tamura T et al.; HYBRID II Study Group · EClinicalMedicine. 2023;58:101907.
Study at a glance
Human
Comatose adults aged 20–80 after cardiogenic out-of-hospital cardiac arrest
2% H₂ added to supplementary oxygen through mechanical ventilation · 2% H₂ with clinically adjusted inspired O₂ reported in the protocol as 24–50%.
18 hours after admission; outcomes assessed through 90 days
The primary outcome was not statistically significant: CPC 1–2 occurred in 56% with H₂ and 39% with control (p=0.15). Several secondary mRS and survival results favored H₂, but the trial was stopped early and was underpowered.
Stopped early because of pandemic enrollment restrictions, with 73 of 360 planned participants. The prespecified primary endpoint was null; positive secondary findings require cautious interpretation. Taiyo Nippon Sanso funded the trial.
What kind of evidence is this?
Human
Multicenter randomized double-blind placebo-controlled trial
Critical care and ischemia-reperfusion
Other forms
Information not yet classified
Some editorial classification fields are still pending. The source-reported outcomes and result are shown below; Hydrogenology does not infer a positive or negative signal from prose automatically.
Methods
Comatose adults aged 20–80 after cardiogenic out-of-hospital cardiac arrest
73 randomized: H₂ n=39; control n=34
18 hours after admission; outcomes assessed through 90 days
2% H₂ added to supplementary oxygen through mechanical ventilation
H₂ added to ventilator gas with supplemental O₂ — not Brown’s gas.
2% H₂ with clinically adjusted inspired O₂ reported in the protocol as 24–50%.
Supplementary oxygen without H₂ using blinded gas cylinders
Outcomes and reported result
Primary: CPC 1–2 at 90 days. Secondary: modified Rankin scale, survival and safety
The primary outcome was not statistically significant: CPC 1–2 occurred in 56% with H₂ and 39% with control (p=0.15). Several secondary mRS and survival results favored H₂, but the trial was stopped early and was underpowered.
Full methods, outcomes, registration, funding and conflicts checked in the open-access full text; independent appraisal remains incomplete.
A reported association, difference or mechanism is not automatically a clinical benefit.
Limitations and applicability
Stopped early because of pandemic enrollment restrictions, with 73 of 360 planned participants. The prespecified primary endpoint was null; positive secondary findings require cautious interpretation. Taiyo Nippon Sanso funded the trial.
Selected comatose adults after cardiogenic out-of-hospital cardiac arrest receiving intensive post-arrest care.
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
Sources and record status
PMID: 36969346 · DOI: 10.1016/j.eclinm.2023.101907
Open-access full text is available through PMC and the publisher.
Open-access PMC and publisher full texts plus PubMed record.
10 August 2026
Help people check the facts before they buy.
Hydrogenology keeps 665 source-checked records accessible without advertising or product promotion.
Help us correct the recordReport a discrepancy
Send the exact difference between this page and the linked source. The study reference is attached automatically.