Please note: this guideline has exceeded its review date and is currently under review by specialists. Exercise caution in the use of the clinical guideline.

Management of Suspected Subarachnoid Haemorrhage (SAH)

(Also see SIGN 107)


A patient presenting with headache that reaches its maximum severity instantaneously or over a few minutes should be assessed for possible SAH, unless a history of similar recurrent stereotyped events indicates an alternative diagnosis (e.g. coital headache, cough headache, severe migraine).

Assessment / monitoring

Use the flow diagram below to systematically assess the patient for SAH. CT scanning should ideally be done before proceeding to lumbar puncture (LP).

Differential diagnoses to consider in the case of a negative CT result include:

  • Sagittal sinus thrombosis
  • Pituitary apoplexy
  • Intracranial hypertension
  • Malignant hypertension
  • Carotid or vertebral dissection
  • Ischaemic stroke
  • Migraine / cluster headache
  • CNS infection

Most alternative diagnoses which require immediate management can be excluded by history, routine examination, CT and LP. However, some patients may require additional tests such as a CT venogram for patients with suspected Sagittal sinus thrombosis.

Further assessment and monitoring in patients with confirmed SAH:

  • Airway, Breathing and Circulation optimised
  • Monitor (2 hourly) vitals (BP, pulse), GCS
  • Urinary input / output
  • FBC, U&Es (including magnesium), glucose, coagulation screen, Group and Hold
  • Pregnancy screen

Sampling requirements for the Biochemical Investigation of SAH (CSF Xanthochromia):

  1. Spectrophotometric analysis of CSF for xanthochromia is useful in the diagnosis of SAH particularly when CT is not conclusive.
  2. It is recommended that CSF is not sampled until at least 12 hours after a suspected event.
  3. The CSF sample should be centrifuged within 15 minutes of sampling. Phone the laboratory to ensure a technician is available before taking the CSF sample.
  4. The CSF sample for xanthochromia analysis should always be the last fraction to be taken and the volume of sample must be a minimum of 1ml.
  5. Record on the request form:
    • the clinical indication for the request
    • the time of headache onset
    • the time of LP
    • if the differential diagnosis includes meningitis.
  6. Protect the CSF sample from light by placing it in a brown paper envelope.
  7. Analysis is done between 9am-5pm weekdays, and Saturday and Sunday mornings. The result will be phoned to the ward.

General management

Consider Medical ward / ICU / HDU / Neurosurgical ward (after discussion with the neurosurgeon) depending on the patient's condition.

Drug therapy / treatment options

  • TED supportive stockings
  • Isotonic fluids e.g.: sodium chloride 0.9% IV 3 litres over 24 hours (do not restrict fluid if hyponatraemia develops).
  • Ensure adequate analgesia e.g.: paracetamol +/- dihydrocodeine 50mg IM or dihydrocodeine 30mg orally every four to six hours. (Avoid other opiates, NSAIDs.)
  • Nimodipine 60mg orally or via NG tube every 4 hours for 21 days. Once tablet is crushed for NG administration it is extremely light sensitive so must be administered immediately.
  • Phenytoin if necessary for seizures (see Guideline for Phenytoin Dose Calculations)


Content last reviewed: November 2019

Page last updated: September 2022