This was a randomized, single-center trial. On the basis of standard-of-care, patients in the treatment group inhaled H2-O2 (66% hydrogen; 33% oxygen) at 3 L/min via nasal cannula by using the Hydrogen/Oxygen Generator (model AMS-H-03, Shanghai Asclepius Meditech Co., Ltd., China) during a 7-day stay in the intensive care unit. Patients in the control group received standard-of-care (consisting of oxygen therapy) alone. This study intends to apply Hydrogen/Oxygen Generator in clinical patients with aneurysmal subarachnoid hemorrhage (aSAH), exploring the role of hydrogen-oxygen mixed gas inhalation therapy in early brain injury, and the prevention of cerebral vasospasm and delayed cerebral ischemia, finally providing a scientific basis for hydrogen treatment of aSAH.

Inclusion Criteria:

1. Age ≥ 18 years
2. Signed informed consent
3. Must be admitted within 72 hours after aneurysm rupture

Exclusion Criteria:

1. physical disability caused by any reason before the onset of the disease
2. dementia or mental illness before the onset of the disease
3. more than 72 hours after aneurysm rupture admitted to hospital for treatment
4. do not cooperate with the treatment