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CDHB

Subarachnoid Haemorrhage (SAH)

Causes

• Intracranial aneurysm - 80%.
• "No cause found" - usually associated with systemic hypertension and with negative intracranial angiography - 14%.
• Intracranial arterio-venous malformation. (AVM/angioma) - 5%.
• Haemorrhage from intracranial tumour, coagulation disorder (usually iatrogenic) - 1%.

Mortality

• Mortality from the first bleed of an intracranial aneurysm is approximately 30%.
• Mortality of an early rebleed is at least 40%.
• Mortality of the first and probably subsequent bleeds of an arterio-venous malformation is approximately 10%.
• 5% of ruptured aneurysms rebleed within the first 24 hours and by 14 days a total of 20% have rebled.
• Approximately 30% of patients surviving a ruptured aneurysm, where the aneurysm is not treated surgically, will be alive at the end of 12 months, the deaths occurring from rebleeding.

Specific Investigations

• CT head scan as soon as possible. CT scan within 3 days has a high positive yield for subarachnoid blood and gives added information as to the possible site of the ruptured aneurysm and also ventricular size. If subarachnoid haemorrhage is confirmed on the CT then a CT angiogram (CTA) should immediately follow. It should also be noted that an MRI scan with T2 and FLAIR sequences has as high, if not higher, diagnostic yield for subarachnoid blood and that an MRA can also be performed at the same time.
• If CT or MRI scan is negative for presence of blood and there is no evidence of an intracranial mass lesion, then a diagnostic lumbar puncture should be performed provided there is no contraindication.

  Note: Lumbar puncture is contraindicated if the patient has an impaired conscious level, or has significant lateralizing neurological signs. In such patients CT scan must be obtained as likelihood of intracerebral haematoma is high and a lumbar puncture could prove fatal. See lumbar puncture for a full list of contraindications.

  Remember: There are only three ways to diagnose a subarachnoid haemorrhage: lumbar puncture, cranial imaging (CT or MRI scan) or post mortem.

• Once the diagnosis of subarachnoid haemorrhage has been made the patient may require additional intracranial angiography. Neurosurgical intervention to clip an aneurysm or excise an AVM (craniotomy) or neuro-interventional treatment to coil an aneurysm or embolize an AVM, will then be undertaken as appropriate.

Treatment Guidelines

• Complete bedrest.
• Adequate analgesia (paracetamol, narcotics e.g., morphine 5-7.5 mg IM).
• Intravenous fluids to ensure adequate hydration - with a minimum of 2 L of IV fluids per day assuming that there is also a normal oral intake, and no increased risk of fluid overload.
• The patient should be admitted under the care of a Neurosurgeon or if admitted to another team, a neurosurgical referral is required in all cases.
• Nimodopine (IV or oral) as per Neurosurgery protocol will now usually be commenced to help counteract cerebral ischaemia and any neurological deficit associated with impaired autoregulation/vasospasm from the subarachnoid blood. Dexamethasone may be indicated in "poor grade" patients.
• Prevent vomiting. Antiemetics: ondansetron is the drug of choice with metoclopramide second choice; avoid prochlorperazine and cyclizine, the latter can cause sedation. Avoid straining. Do not prescribe codeine phosphate. Stool softeners if needed.
• Raised blood pressure should only be treated if:
  • The diastolic blood pressure is greater than 100 mm Hg for several hours, in the absence of any evidence of high intracranial pressure. Avoid hypotension or large swings in blood pressure.
  • If the patient was already on anti-hypertensive drugs before the haemorrhage, continue the current therapy. Beware of hypotension which may occur in conjunction with the intravenous nimodipine - such hypotension may seriously impair cerebral blood flow.

Christchurch Hospital Admission Arrangements

• Patients who have sustained a subarachnoid haemorrhage should be admitted under the care of Neurosurgery.

Topic Code: 1510