An MRI study to examine the relationship between blood pressure and cerebral blood flow in patients with subarachnoidal hemorrhage and suspect or verified vasospasm.

Subarachnoidal hemorrhage (SAH) is a type of stroke with high mortality rates and often requires care at the intensive care unit. Cerebral blood flow (CBF) needs to be ensured so that the brain receives optimal nourishment, and this is largely controlled by regulating blood pressure (BP) using medications that affect the heart and blood vessels. Approximately 3-7 days after SAH onset, vasospasm (SAH-V) can occur. Treatment usually includes maintaining blood pressure (BP) above a certain threshold to achieve adequate cerebral blood flow (CBF). An important component of raising BP is increasing vascular resistance using vasoconstrictive medications, which paradoxically can decrease CBF.

The study objective is to investigate the correlation between BP changes and their impact on CBF in patients with suspect or verified SAH-V using MRI.

To achieve this purpose, the investigators plan to examine the relationship between BP and CBF in patients with SAH-V who require neuro-intensive care. To measure CBF, two techniquis will be used: phase-contrast MRI and arterial spin labeling.

Flow measurement with MRI:

1. Baseline images will be acquired at baseline blood pressure.
2. Mean arterial pressure (MAP) will be increased using norepinephrine. New images will be acquired when MAP is increased by approximately 20-30% from the baseline.

All BP levels will be maintained within clinically acceptable ranges. All data will be recorded in the patient's medical record, and MRI images will be processed at a later stage.

Inclusion Criteria:

• Coiled or clipped aneurysm
• Suspected or confirmed vasospasm

Exclusion Criteria:

• BMI >30
• Pregnancy
• Pacemaker or other MRI contraindications
• Severe congestive heart failure (NYHA III-IV) or cardiac arrhythmia.
• Severe respiratory failure or FiO2 >0.6
• Severe kidney failure