Inclusion Criteria:  aSAH of all severities Aneurysm treated by either surgical clipping or endovascular coiling Age between 18 - 80 years Proven CVS Cerebral hypoperfusion and neurological deficit despite treatment (oral nimodipine, induced hypertension, hypervolaemia, central venous pressure > 6 mmHg) A negative pregnancy test in women Signed informed consent from the next of kin and an independent physician  Exclusion Criteria:  Unsecured aneurysm Cerebral infarction on imaging in the downstream brain parenchyma of spastic vessel Cerebral herniation Intracranial pressure > 25 mmHg Pregnancy Mean arterial pressure ≤ 90 mmHg despite catecholamines