Why this topic matters: Subarachnoid haemorrhage (SAH) is bleeding into the space around the brain, often from a ruptured aneurysm. It can present with a sudden “worst-ever” headache, collapse, vomiting, neck stiffness, seizure or focal deficit. Rebleeding, hydrocephalus, vasospasm/delayed cerebral ischaemia, seizures and cardiopulmonary complications can cause rapid deterioration. Treat thunderclap headache as a neurological emergency, document exact onset, stabilise ABCDE, obtain urgent brain imaging and transfer to neurosurgical/stroke expertise.
Learning objectives
- Recognise aneurysmal and non-aneurysmal SAH, including atypical and sentinel presentations.
- Perform an ABCDE and focused neurological examination while protecting cerebral perfusion.
- Describe CT, vascular imaging and lumbar-puncture pathways and their safety precautions.
- Outline early treatment, aneurysm securing, seizure care, hydrocephalus management and vasospasm surveillance.
- Plan nursing care, communication, transfer, rehabilitation and secondary prevention.
Definition and causes
SAH is extravasation of blood into the subarachnoid space. Aneurysmal SAH commonly involves rupture of a saccular intracranial aneurysm; other causes include arteriovenous malformation, head trauma, vascular dissection, coagulopathy and illicit stimulant use. The initial bleed can cause abrupt intracranial pressure rise, loss of consciousness, meningism and secondary brain injury.
After the first event, rebleeding is a major early danger. Blood products can impair cerebrospinal-fluid circulation and cause acute hydrocephalus. Days later, arterial narrowing and delayed cerebral ischaemia may produce new deficits or reduced consciousness. SAH can also trigger neurogenic stunned myocardium, arrhythmia, pulmonary oedema, seizures, electrolyte disturbance and fever.
Safety point: A patient may describe a thunderclap headache as “migraine,” and neurological examination may initially be normal. A sudden maximal-at-onset headache, exertional headache, headache with collapse or new neck stiffness requires urgent assessment and senior review.
Recognition and red flags
| Feature | Possible meaning | Action |
|---|---|---|
| Thunderclap headache | Sudden severe pain reaching maximum intensity within seconds or minutes. | Record exact onset and activate urgent brain-imaging pathway. |
| Vomiting/photophobia/neck stiffness | Meningeal irritation and raised intracranial pressure. | Protect airway, control symptoms and escalate for imaging. |
| Collapse or transient loss of consciousness | Large initial bleed, raised ICP or seizure. | ABCDE, glucose, ECG and urgent specialist care. |
| Focal deficit or seizure | Brain injury, vasospasm, hydrocephalus or rebleed. | Repeat neurological assessment and urgent imaging. |
| Neck/back pain or exertional onset | Vascular trigger or spinal SAH possibility. | Do not reassure; document and investigate. |
| New deterioration after admission | Rebleed, hydrocephalus, delayed cerebral ischaemia, seizure or metabolic cause. | Call stroke/neurosurgery team immediately and repeat ABCDE/imaging. |
Triage and first contact
- Move the patient to a monitored resuscitation area and call senior emergency, neurology/neurosurgery and critical-care support.
- Ask “When did the pain begin?” and distinguish last-known-well from the time of arrival. Record witness information and any sentinel headaches.
- Check anticoagulants, antiplatelets, bleeding disorders, pregnancy, trauma, stimulant use, hypertension and previous aneurysm.
- Keep the patient nil by mouth, reduce stimulation, provide safe analgesia/antiemetic therapy and prevent straining.
- Pre-alert the receiving stroke/neurosurgical centre; do not send an unstable patient away from resuscitation for nonessential tests.
ABCDE and neurological assessment
| Step | Assess | Actions |
|---|---|---|
| A – Airway | GCS, gag/cough, vomiting, secretions and seizure activity. | Position, suction, airway adjuncts and controlled expert intubation if protection fails. |
| B – Breathing | Rate, effort, SpO₂, aspiration, pulmonary oedema and abnormal pattern. | Oxygen for hypoxaemia, ventilatory support when needed and avoid hypoxia/hypercapnia. |
| C – Circulation | Pulse, BP, ECG, perfusion, temperature and arrhythmia. | IV access, careful BP control, treat shock and monitor neurogenic cardiac injury. |
| D – Disability | GCS, pupils, gaze, speech, power, sensation, headache and seizure. | Check glucose, record a baseline neurological score and repeat after every change. |
| E – Exposure | Trauma, rash, meningism, temperature, neck/back tenderness and medication patches. | Prevent hypothermia, identify trauma/coagulopathy and preserve dignity. |
Emergency investigations
| Investigation | Purpose | Clinical point |
|---|---|---|
| Non-contrast CT brain | Detect acute subarachnoid blood, hydrocephalus or other haemorrhage. | Perform urgently; sensitivity is highest early but a negative scan does not end evaluation in a high-risk case. |
| CT angiography | Identify aneurysm, vascular malformation or dissection. | Guides neurosurgical/endovascular planning after initial assessment. |
| Lumbar puncture | Assess CSF for xanthochromia, red cells, pressure and infection when CT is non-diagnostic and suspicion remains. | Do not perform with mass effect, obstructed CSF flow, focal deficit, reduced consciousness, coagulopathy or unsafe airway without specialist guidance. |
| FBC, group/cross-match, coagulation, renal/electrolytes, glucose | Assess anaemia, bleeding risk, organ function and metabolic mimics. | Correct coagulopathy under specialist protocol; do not delay emergency imaging or transfer. |
| ECG/troponin/echo | Detect neurogenic stunned myocardium, arrhythmia and pulmonary oedema. | Cardiac abnormalities may accompany SAH and alter fluid/BP management. |
Immediate medical management
- Admit or transfer to a centre with neurosurgery, neurocritical care and endovascular/coiling or clipping capability.
- Maintain airway, oxygenation, normocapnia, normoglycaemia and normothermia; avoid hypotension and severe hypertension.
- Use prescribed analgesia and antiemetics to prevent agitation, vomiting and Valsalva-related pressure surges.
- Review and reverse anticoagulation or coagulopathy urgently under haematology/neurosurgical guidance.
- Control BP smoothly according to local SAH protocol, avoiding rapid drops that compromise cerebral perfusion.
- Treat seizures promptly; prophylactic antiseizure medicine is a specialist decision based on seizure risk and clinical features.
- Use isotonic fluids carefully to maintain euvolaemia; avoid routine fluid restriction or excessive free water.
Secure the ruptured aneurysm
The source of aneurysmal bleeding should be identified and secured as soon as safely possible, preferably early in the course. Endovascular coiling, surgical clipping or another specialist approach is chosen according to aneurysm anatomy, clinical grade, age, comorbidities and local expertise.
- Maintain a clear treatment clock and communicate imaging, neurological grade, anticoagulants and last-known-well time.
- Prepare for angiography, anaesthesia, blood products and post-procedure ICU care.
- Continue close monitoring because rebleeding risk remains until the aneurysm is secured.
- After treatment, watch for access-site bleeding, new deficit, vasospasm, hydrocephalus and seizure.
Hydrocephalus and raised intracranial pressure
- Suspect hydrocephalus with declining consciousness, worsening headache/vomiting, gaze abnormality, bradycardia with hypertension or new neurological deficit.
- Elevate the head when safe, keep the neck neutral, prevent hypoxia/hypercapnia and call neurosurgery urgently.
- External ventricular drainage may be required for acute symptomatic hydrocephalus; it is a specialist procedure with strict infection and pressure management.
- Avoid unnecessary lumbar puncture, over-sedation, fever, hypotension and excessive fluid shifts.
- Repeat CT promptly when neurological status changes.
Delayed cerebral ischaemia and vasospasm
Delayed cerebral ischaemia can occur days after SAH and may be related to vasospasm or other microcirculatory mechanisms. A new focal deficit, speech change, confusion, reduced consciousness or worsening headache is an emergency—not simply fatigue or “post-ictal” behaviour.
- Perform frequent neurological observations and compare with the patient’s baseline.
- Maintain euvolaemia and avoid prophylactic hypervolaemia; use specialist-directed haemodynamic augmentation if indicated.
- Administer nimodipine or other disease-specific medicines only according to local neurosurgical protocol and BP tolerance.
- Arrange repeat vascular imaging, CT perfusion or transcranial Doppler when available and clinically indicated.
- Escalate immediately for new deficits; treatment may include endovascular therapy or intensive haemodynamic support.
Nursing care and monitoring
- Record GCS, pupils, power, speech, gaze, headache severity, seizure activity and vital signs at prescribed intervals.
- Monitor BP, ECG, oxygenation, fluid balance, sodium, glucose, temperature and urine output.
- Maintain quiet surroundings, head positioning, aspiration precautions and nil-by-mouth status until swallow assessment.
- Give analgesics, antiemetics, nimodipine and antiseizure medicines exactly as prescribed; observe BP and adverse effects.
- Inspect IV, arterial and procedural sites for bleeding; use pressure precautions and document anticoagulant reversal.
- Communicate any neurological change immediately using SBAR and record the exact time of deterioration.
Complications
| Complication | Clues | Emergency response |
|---|---|---|
| Rebleeding | Sudden recurrent headache, vomiting, collapse, new deficit or falling GCS. | ABCDE, urgent CT/CTA and immediate neurosurgical escalation. |
| Hydrocephalus/raised ICP | Reduced consciousness, pupil change, vomiting or bradycardia with hypertension. | Head positioning, airway support, urgent imaging and ventricular drainage review. |
| Delayed cerebral ischaemia | New weakness, aphasia, confusion or reduced level of consciousness days later. | Immediate neurological review, imaging and vasospasm pathway. |
| Seizure | Convulsions, eye deviation or unexplained postictal state. | Seizure protocol, glucose, airway protection and specialist review. |
| Neurogenic cardiac injury | ECG changes, arrhythmia, pulmonary oedema or troponin rise. | Cardiac monitoring, echo and careful fluid/BP management. |
| Hyponatraemia | Confusion, seizures, headache or worsening neurological status. | Check serum/urine studies and correct under specialist protocol; avoid hypotonic fluid. |
Transfer and communication
- Pre-alert a neurosurgical/stroke centre with CT/CTA results, neurological grade, airway status, BP, medication and anticoagulant history.
- Transport with trained staff, portable oxygen, suction, monitor, emergency drugs and a documented deterioration plan.
- Send imaging electronically or on suitable media, laboratory results, medication chart, ECGs and procedure records.
- Explain to family that early aneurysm treatment, ICU monitoring and rehabilitation may be required even when the patient initially appears improved.
Prevention and recovery
- Control hypertension, stop smoking, avoid cocaine/amphetamines and review family history of aneurysm or connective-tissue disease.
- Ensure follow-up imaging and neurosurgical review after coiling/clipping; recurrence and untreated aneurysms require surveillance.
- Assess cognition, mood, fatigue, headache, seizures, mobility, speech and return-to-work needs.
- Educate family about recurrent thunderclap headache, new weakness, seizures, confusion or collapse as emergency warning signs.
Clinical scenarios
Scenario 1 – Thunderclap headache: A previously well adult develops instantaneous severe headache while lifting, vomits and has neck stiffness. Record onset, ABCDE/glucose, urgent CT, senior review and do not discharge after symptom relief without completing the SAH pathway.
Scenario 2 – Deterioration after known SAH: A patient becomes drowsy with a new left-arm weakness five days after admission. Treat as rebleed, hydrocephalus or delayed cerebral ischaemia until proven otherwise; repeat ABCDE, urgent imaging and call neurosurgery.
Scenario 3 – SAH with pulmonary oedema: A patient develops hypoxia, crackles and ECG changes after the bleed. Support oxygenation, monitor ECG, obtain echo and involve critical care; avoid indiscriminate fluid loading.
Common errors to avoid
- Calling thunderclap headache “migraine” without considering SAH.
- Failing to record exact onset or the presence of sentinel headaches.
- Delaying CT, vascular imaging, antibiotics when indicated, transfer or neurosurgical review.
- Performing lumbar puncture despite mass effect, focal deficit, reduced consciousness or coagulopathy.
- Allowing hypotension, hypoxia, hypercapnia, fever or severe hypertension to persist.
- Missing delayed cerebral ischaemia because the patient’s headache is unchanged.
- Failing to repeat neurological observations after analgesia, seizure or BP treatment.
SAH ALERT: S – Sudden maximal headache; A – Airway/ABCDE; H – Head CT and haemorrhage pathway. A – Aneurysm imaging; L – Limit rebleeding risks; E – Evaluate neuro changes; R – Refer/secure aneurysm; T – Track vasospasm, hydrocephalus and seizures.
Revision questions
- What clinical features make a headache suspicious for SAH?
- Why can a normal early neurological examination not exclude SAH?
- What are the roles of CT, CTA and lumbar puncture?
- List immediate ABCDE actions for a suspected SAH patient.
- How do rebleeding, hydrocephalus and delayed cerebral ischaemia present?
- Why must BP, oxygenation, glucose and temperature be controlled carefully?
- What information belongs in a neurosurgical handover?
Key takeaways
- Thunderclap headache is a neurological emergency until SAH is excluded.
- Record onset, stabilise ABCDE and obtain urgent brain and vascular imaging.
- Do not let LP, transport or laboratory delays postpone life-saving specialist care.
- Secure a ruptured aneurysm early and monitor for rebleeding, hydrocephalus, seizures and delayed cerebral ischaemia.
- Every new neurological change after SAH requires immediate reassessment.