Subarachnoid Haemorrhage

Objectives

To guide the investigation and management of patients presenting to medical facilities with suspected sub-arachnoid haemorrhage.

Scope

This guideline covers the initial investigation and management of spontaneous (aneurysmal) subarachnoid haemorrhage (aSAH). The guideline focuses on general management; it does not detail advanced interventions and managements carried out by specialists.

Investigation and management of intracranial haemorrhage secondary to trauma is covered in the CGO on head injury.

Long term follow up and management will take place outside of the operational setting and as such is not included in this guideline.

Audience

This guideline is intended for the use of registered healthcare professionals fulfilling a general role in a forward medical location or in an Emergency Department on deployed operations.

Initial Assessment & Management

Patients who present with headache should be carefully assessed as per the Headache & Migraine CGO.

Take a careful history to establish the rate of onset and peak intensity of the headache. Clearly document the time of symptom onset.

Subarachnoid haemorrhage (SAH) typically presents as a sudden, severe headache that peaks within 1 to 5 minutes (thunderclap headache) and lasts more than an hour; concurrent features often include vomiting, photophobia, and non-focal neurological signs.

Examination findings may include:

  • altered consciousness/confusion
  • meningism (e.g. neck stiffness, muscle aches, photophobia)
  • ocular changes (e.g. intraocular haemorrhages)
  • focal findings (e.g. unilateral loss of motor function, loss of visual field, aphasia

However, be aware that a patient with subarachnoid haemorrhage MAY EXAMINE NORMALLY – beware of the warning or "sentinal bleed” with full recovery.

Patients with suspected SAH require urgent evacuation for CT imaging. If the option is available then consider bypassing forward medical facilities in favour of direct evacuation to a facility with neurosurgical capability.

Avoid delay: the risk of further bleeding is highest within 24 hours of the onset of symptoms.

If the patient is, or becomes unwell with reduced level of consciousness, use a systematic approach to minimise secondary brain injury by managing airway, respiration and circulation in accordance with standard guidance. Request urgent evacuation with enhanced pre-hospital emergency care support if available.

Pending/during evacuation, give analgesia and anti-emetics. Many patients struggle to tolerate adequate oral fluids so also ensure adequate hydration with IV crystalloid.

Advanced Assessment & Management

Non-contrast CT head is the key investigation for suspected SAH. Diagnostic accuracy of CT Head is highest within 6 hours of symptom onset, and where possible the investigation should take place within this time frame.

Early imaging is crucial - sensitivity of modern non-contrast CT approaches 100% in the first 6 hours following symptom onset but drops below 90% after 24 hours and below 50% after 7 days.
Patients with suspected SAH who have a normal CT more than 6 hours after symptom onset would normally require a lumbar puncture to check for xanthochromia. There is no current capability to test for xanthochromia in the deployed setting, but consider whether these investigations might be possible via other routes such as partner/host nation facilities.

If CT shows blood in the sub-arachnoid space:

  • perform CT angiography if possible, to identify the source of bleeding and guide specialist management
  • seek urgent neurosurgical review for specialist advice for ongoing management 

Medical Management

If angiography shows aneurysmal SAH and within 4 days of symptom onset,  (or following specialist advice if angiography is not possible), start Nimodipine 60mg every 4 hours. This should ideally be continued for 21 days (unless stopped on specialist advice).

Target systolic blood pressure 120-160 mmHg with beta blockers (bisoprolol 5mg OD, titrate up to 20mg OD). If not administering nimodipine then other calcium channel blockers could also be used to optimise blood pressure (amlodipine 5mg OD, titrate up to 10mg OD).

Prolonged Casualty Care

If the patient cannot be evacuated to allow imaging to confirm the diagnosis:

Give analgesia and anti-emetics.

Many patients struggle to tolerate adequate oral fluids so ensure adequate hydration with IV crystalloid if needed (up to 3 litres per day depending on oral intake)

Avoid any physical exertion and start stool-softening laxatives to avoid any straining that may precipitate further harm.

If available within 4 days of onset of suspected/confirmed subarachnoid haemorrhage, start Nimodipine 60mg every 4 hours. This should ideally be continued until the diagnosis is excluded or otherwise for 21 days (unless stopped on specialist advice).

Target systolic blood pressure 120-160 mmHg with beta blockers (bisoprolol 5mg OD, titrate up to 20mg OD). If not administering nimodipine then other calcium channel blockers could also be used to optimise blood pressure (amlodipine 5mg OD, titrate up to 10mg OD).

If the patient experiences seizures or requires airway/ventilatory support due to reduced level of consciousness then use a systematic approach and follow standard procedures as per CGOs including guidelines for seizures and airway management.

Paediatric Considerations

Spontaneous subarachnoid haemorrhage is rare in children. Carefully consider alternative diagnoses for headache, including space occupying lesions and infection. Seek reach back to a senior clinician with experience of treating acutely unwell children for advice on appropriate management.

Last reviewed: 13/10/2026

Next review date: 13/10/2027