**4. Factors determining prognosis in subarachnoid hemorrhage**

The prognosis after SAH may vary from severe disability to death, depending on the complications usually seen in the first 2 weeks associated with the severity of bleeding.

Common causes of this deterioration include neurological events such as hydrocephalus, seizures, ischemia, and systemic conditions, such as fever and infections, respiratory failure, and electrolyte abnormalities. The level of consciousness is considered the most important early predictor of outcome. For these reasons, patients presenting with a GCS score of less than 13 have traditionally been defined as having poor-grade SAH (classified as grade 4 and 5 according to the Hunt and Hess or the WFNS grading scales 5 or more recently as VASOGRADE-Red 6). Brain injury refers to the acute consequences of SAH-associated sudden increase of intracranial pressure (ICP), which can cause decreased cerebral perfusion and transient global cerebral ischemia. The global cerebral ischemia can result in transient loss of consciousness or progressive intracranial hypertension [2, 38–41].
