To Determine Diagnosis
- CT head:
- Detects the presence of subarachnoid blood
- Highly sensitive on day 1 (>95%) but reduced thereafter (50% on day 5)
- MRI an alternative though not readily available at most centres
- LP:
- Detects presence of xanthochromia
- Should be performed >12 hours after symptom onset if CT non-diagnostic
To Assess Severity / Prognosis
- Graded using clinical severity scale:
- World Federation of Neurosurgeons (WFNS)
- Prognosis on Admission of Aneurysmal Subarachnoid Hemorrhage (PAASH)
- Hunt & Hess
To Determine Aetiology
- CTA: assesses vascular anatomy
- Digital subtraction cerebral angiography (DSA):
- Remains the gold standard
- Allows intervention
- MRI: mostly used for detection of AVM
- Screen for vasculitis and amyloidosis
To Assess for Complications
- To assess for cardiac dysfunction:
- ECG - peaked T waves, ST depression, prolonged QT, arrhythmias
- Echo - neurogenic cardiomyopathy, regional wall motion abnormalities
- Troponin
- Pro-BNP
- To assess for metabolic dysfunction:
- Plasma and urinary sodium / osmolality
- Urine output monitoring
- To assess for respiratory dysfunction:
- CXR - pulmonary oedema
- ABG