H(2) gas improves functional outcome after cardiac arrest to an extent comparable to therapeutic hypothermia in a rat model.
Hayashida K, Sano M, Kamimura N, Yokota T, Suzuki M, Maekawa Y, Kawamura A, Abe T, Ohta S, Fukuda K, Hori S. · 2012.
Study at a glance
Preclinical
Rats after ventricular-fibrillation cardiac arrest and resuscitation.
2% H₂ with 98% O₂ from the start of resuscitation, with or without therapeutic hypothermia. · 2% H₂ and 98% O₂ for two hours after return of spontaneous circulation.
Gas and temperature intervention through two hours after resuscitation with survival and functional follow-up.
H₂ inhalation was reported to improve survival and neurological scores comparably to hypothermia and to favor selected cardiac, inflammatory and oxidative measures.
Animal resuscitation model using 98% oxygen; findings do not establish a clinical cardiac-arrest protocol.
What kind of evidence is this?
Preclinical
Randomized controlled rat cardiac-arrest study
Critical care and ischemia-reperfusion
Inhaled H₂
Positive preclinical signal.
Animal survival, functional, cardiac and biomarker outcomes.
Methods
Rats after ventricular-fibrillation cardiac arrest and resuscitation.
Four intervention groups; animal totals and survival denominators were checked in the full article.
Gas and temperature intervention through two hours after resuscitation with survival and functional follow-up.
2% H₂ with 98% O₂ from the start of resuscitation, with or without therapeutic hypothermia.
Inhaled molecular H₂ with oxygen.
2% H₂ and 98% O₂ for two hours after return of spontaneous circulation.
Absolute gas flow was not reported separately here.
98% O₂ was co-delivered.
Normothermic and hypothermia groups ventilated with 2% N₂/98% O₂.
Outcomes and reported result
Survival, neurological deficit, cardiac function, inflammation and oxidative tissue markers.
H₂ inhalation was reported to improve survival and neurological scores comparably to hypothermia and to favor selected cardiac, inflammatory and oxidative measures.
The full article was checked for methods, intervention details, outcomes, positive and null findings, funding and conflicts. This record does not imply medical efficacy.
A reported association, difference or mechanism is not automatically a clinical benefit.
Limitations and applicability
Animal resuscitation model using 98% oxygen; findings do not establish a clinical cardiac-arrest protocol.
The reported rat ventricular-fibrillation arrest model only.
SYRCLE animal-study tool — preliminary
Some concerns
Random assignment and active comparators were used, but concealment, blinded assessment and multiplicity handling were incompletely reported.
Sequence generation checked where reported · Allocation concealment generally unclear · Personnel blinding generally unclear · Outcome-assessor blinding generally unclear · No prospectively registered analysis plan identified
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
Sources and record status
PMID: 23316300 · DOI: 10.1161/jaha.112.003459
A free full article is available through PubMed Central.
Official PubMed Central full article and PubMed bibliographic record; source identity, methods, intervention, results, funding and conflicts checked 10 August 2026.
10 August 2026
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