Effect of Xenon on Brain Injury After Aneurysmal Subarachnoid Hemorrhage

Inclusion Criteria: To be considered eligible to participate in this study, a SAH subject must meet the inclusion criteria listed below: 1. Informed consent obtained from the next of kin or legal representative 2. Aneurysmal subarachnoid hemorrhage visible on CTA or DSA. 3. Deterioration of consciousness to Hunt-Hess 3-5 4. Age of ≥ 18 years 5. Intubated. 6. GCS 3-12 obtained off neuromuscular blocking agents 7. Xenon treatment can be started within 6 hours after onset of SAH symptoms Exclusion Criteria: An aSAH subject may not be enrolled in the trial if he/she meets any one of the exclusion criteria below: 1. Acute or chronic traumatic brain injury 2. Maximum diameter of intracerebral hemorrhage \> 2.5 cm 3. Pneumothorax or pneumomediastinum, 4. Acute lung injury requiring ≥ 60% FIO2 (fraction of inspired oxygen). 5. Systolic arterial pressure \< 80 mmHg or mean arterial pressure \< 60 mmHg for over 30 min period 6. Bilaterally fixed and dilated pupils 7. Positive pregnancy test, known pregnancy, or current breast-feeding 8. Neurological deficiency due to traumatic brain injury or other neurological illness 9. Imminent death or current life-threatening disease 10. Current enrollment in another interventional study 11. The subject is known to have clinically significant laboratory abnormality, medical condition (such as decompensated liver disease or severe chronic obstructive pulmonary disease), or social circumstance that, in the investigator's opinion, makes it inappropriate for the subject to participate in this clinical trial. 12. Presence of implants or foreign bodies which are not known to be MRI safe