Cerebral Hemodynamic Optimization by Milrinone to Prevent Delayed Cerebral Ischemia

Inclusion Criteria: * patients with severe SAHa (WFNS IV and V,) whose neurological examination is impossible because of coma (Glasgow coma score of 8 or less) or need for sedation at D3 * absence of pre-existing neurological handicap (mRS 0-2) * major patient (≥ 18 years) * affiliation to social security or benefiting through a third person * free patient, without tutorship or curatorship or under judicial protection * obtaining a signed informed consent by a relative (or the person of trust) after clear and fair information about the study. Exclusion Criteria: * patients with non-severe SAHa (WFNS I, II and III) * Occurrence of a major complication (haemorrhagic or ischaemic) documented during the procedure of securing the aneurysm and endangering the short-term vital prognosis * heart failure requiring inotropic administration at the time of randomization * ICHT at the time of randomisation (ICP\> 25 mmHg for at least 20 min) * known severe obstructive heart diseases * flutter patient or atrial fibrillation * hypotension and / or severe hypovolemia with hemodynamic instability * septic shock * acute / chronic renal insufficiency (Cl \<50ml / min) * major hydroelectrolytic disorders (hypokalemia \<3 mmol / L) * known hypersensitivity to milrinone or any of the excipients * early limitation of life-sustaining care * pregnancy, breastfeeding * permanent contraindications to MRI * participation in another clinical interventional study