The purpose of this study is to investigate how dexmedetomidine affects static and dynamic autoregulation, intracranial pressure (ICP) and cerebral oxygenation in aneurysmal subarachnoid haemorrhage (SAH) patients.

Dexmedetomidine is a selective α2-agonist which induces sedation, anxiolysis and analgesia without respiratory depression. These effects, as well as neuroprotective properties in experimental studies would be ideal in neuroanaesthesia and in neurocritical care. Poor grade SAH patients are treated in intensive care units (ICU). These patients are sedated often with propofol. However, to assess the patient's neurology, the propofol sedation must be stopped and the wakening of the patient may take time. Dexmedetomidine would be more advantageous, allowing wakening during the infusion. However, the effects of dexmedetomidine on cerebral autoregulation are unknown in SAH patients.

15 SAH patients requiring sedation, mechanical ventilation and ICP monitoring will be rolled in to the study.

Inclusion Criteria:

• Aneurysmal SAH
• Aneurysm treated with coil(s) or clip(s)
• Age 18-80 years
• Written informed consent from the next of kin

Exclusion Criteria:

• Pregnancy
• Nursing woman
• Sick sinus syndrome
• Carotid stenosis
• Heart rate less than 50 beats / minute
• Mean arterial pressure less than 50 mmHg