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Level 2 of 6Must-remember

Headache and subarachnoid haemorrhage

Assess, manage and stay safe — enough on its own

The card — assess, manage, caution

Assessment— look, ask, measure

  • The one question that decides everything: ask "from feeling completely normal, how long did it take to reach the worst it ever got?" and record the answer as a number of seconds or minutes with a clock time, because the CT window, the lumbar puncture timing and any decision to reassure are all measured from that moment.
  • Thunderclap headache is defined by speed, not severity: a severe headache reaching maximum intensity almost instantaneously — Davidson's specifies a peak within 60 seconds, elsewhere describes peaking within 5 minutes and lasting over an hour, and CMDT describes maximal severe intensity within seconds or a few minutes; the wider definition is the safer working threshold.
  • Why you must take it seriously: CMDT 2026 puts the estimated prevalence of subarachnoid haemorrhage (SAH) among patients presenting with thunderclap headache at 43%, whereas fewer than 1% of outpatients with non-acute headache have a serious underlying cause.
  • History to ask for: the exact activity at onset (straining, lifting, coughing, defaecation or sexual activity — 5–12% of subarachnoid haemorrhages are precipitated by sexual intercourse), repeated forceful vomiting, loss of consciousness at onset sought from any witness, neck pain and stiffness, photophobia, seizure and fever.
  • Ask specifically about a sentinel bleed: up to half of patients with aneurysmal SAH describe a milder but similarly abrupt headache in the preceding days to three weeks — that patient is announcing that the aneurysm is about to rupture definitively.
  • Risk factors: female sex, increasing age, a first-degree relative with SAH or a known aneurysm, adult polycystic kidney disease, Marfan syndrome, Ehlers–Danlos syndrome and coarctation of the aorta (these structural disorders together under 5% of cases), plus smoking, hypertension, heavy alcohol, cocaine and amfetamines.
  • Examination may be entirely normal — the most dangerous presentation precisely because it is the most reassuring, so a normal examination never overrides the history.
  • Conscious level is the single most important observation: record the Glasgow Coma Scale, using the paediatric GCS under 5 years, because it is the basis of every grading system and of every subsequent comparison.
  • Cardinal signs to look for: meningism (a developing sign that may take hours to appear, so early absence means nothing), subhyaloid pre-retinal haemorrhage on fundoscopy (close to specific for SAH), papilloedema, a third nerve palsy with a dilated unreactive pupil (a posterior communicating artery aneurysm until proven otherwise), focal deficits, and hypertension with bradycardia.
  • Vital signs and bedside tests: pulse, blood pressure, respiratory pattern, temperature (fever is common after SAH and usually non-infective), oxygen saturation with a target of 94–98%, a 12-lead ECG, and a capillary blood glucose in anyone with altered consciousness.
  • Grade the severity with WFNS: grade I is GCS 15 with no major focal deficit; grade II GCS 13–14 with no deficit; grade III GCS 13–14 with aphasia and/or hemiparesis; grade IV GCS 7–12; grade V GCS 3–6 — grades I–II are where lives are saved.
  • Danger signs of deterioration: a fall of two or more points on the GCS, new pupillary asymmetry, abrupt worsening of headache, hypertension with bradycardia and irregular respiration (Cushing's response), progressive drowsiness without new focal signs (acute hydrocephalus), and hypoxia with frothy sputum (neurogenic pulmonary oedema).
  • SNOOP red flags in any headache: Systemic (fever, weight loss, cancer, immunosuppression, pregnancy or puerperium); Neurological (focal deficit, seizure, confusion, reduced conscious level, papilloedema); Onset sudden; Older — new headache after age 50; Pattern change, Positional, Precipitated by Valsalva, Papilloedema, Pregnancy.
  • Migraine is the trap: migraine builds over 20–60 minutes, often with aura evolving over 5–20 minutes, is unilateral and throbbing for 4–72 hours and is stereotyped against previous attacks, whereas SAH is a blow — character and speed discriminate, not intensity, and a migraineur can bleed.
  • The imaging clock: non-contrast CT is most sensitive within the first 6 hours of onset and misses fewer than 10% of subarachnoid haemorrhages when performed early, but a negative CT more than 6 hours after onset does not exclude SAH and is an indication to proceed to lumbar puncture or angiography.Not available at your setup — CT scan.
  • Mimics to consider: bacterial meningitis (fever, antibiotics must not await imaging), cervicocephalic dissection (neck or face pain, Horner syndrome), cerebral venous sinus thrombosis, reversible cerebral vasoconstriction syndrome (recurrent thunderclap headaches), intracerebral haemorrhage, pituitary apoplexy (visual disturbance), hypertensive emergency or PRES, spontaneous intracranial hypotension (worse standing, relieved lying flat), acute angle-closure glaucoma (red painful eye, haloes) and giant cell arteritis over 50 with scalp tenderness and jaw claudication.

Management— do this, in order

  • Airway first: an unprotected airway (GCS 8 or below, or inability to protect against vomit) requires intubation, and the pressor response to laryngoscopy must be blunted because a surge in blood pressure can rupture an unsecured aneurysm.Doctor / NurseNot available at your setup — Endotracheal intubation kit.
  • Intubation drugs: pre-oxygenate, give fentanyl 1–2 microgram/kg IV about 3 minutes before laryngoscopy, induce with propofol 1–2 mg/kg IV (or ketamine 1–2 mg/kg IV if haemodynamically unstable), and paralyse with suxamethonium 1–1.5 mg/kg IV or rocuronium 1 mg/kg IV; target oxygen saturation 94–98%.Doctor / NurseNot available at your setup — Endotracheal intubation kit.
  • Position and environment: nurse head-up at 30 degrees with the head midline (neck flexion or rotation obstructs jugular drainage and raises intracranial pressure), in a quiet, darkened room, on absolute bed rest.
  • Fluids: give isotonic fluid — 0.9% sodium chloride — to maintain euvolaemia; hypotonic fluids including 5% glucose must be avoided because they worsen cerebral oedema and aggravate hyponatraemia.Doctor / Nurse
  • Analgesia, because uncontrolled pain drives hypertension and hypertension ruptures aneurysms: paracetamol 1 g IV or orally 6-hourly (maximum 4 g/24 h; 15 mg/kg per dose and maximum 3 g/day if under 50 kg), paediatric 15 mg/kg per dose orally or IV 6-hourly to a maximum of 60 mg/kg/day.Doctor / Nurse
  • Stronger analgesia: morphine 2 mg IV every 5 minutes, typically 2–10 mg in total, monitoring respiratory rate and GCS; paediatric morphine 0.1 mg/kg IV titrated in 0.05 mg/kg increments; codeine 30–60 mg orally 6-hourly as an adult adjunct only and avoided in children.Doctor / Nurse
  • Antiemesis, because every retch spikes intracranial and arterial pressure: ondansetron 4–8 mg IV over 2–5 minutes 8-hourly (paediatric 0.15 mg/kg IV, maximum 4 mg per dose, 8-hourly) is preferred because it does not sedate; metoclopramide 10 mg IV 8-hourly is an adult alternative avoided under 20 years because of dystonic reactions; prochlorperazine 12.5 mg IM is a further option.Doctor / Nurse
  • Nimodipine — the only drug shown to improve neurological outcome after aneurysmal SAH: 60 mg orally or by nasogastric tube every 4 hours for 21 days in adults, started as soon as SAH is confirmed; Davidson's reduces immediate management to resuscitate, nimodipine 60 mg, refer to neurosurgeons.
  • If nimodipine drops the pressure: check the blood pressure before each dose, and if systolic pressure falls below 100 mmHg (or mean arterial pressure below 70 mmHg) give a fluid bolus and split the dose to 30 mg every 2 hours rather than abandoning the drug; there is no established paediatric dose.
  • Blood pressure before the aneurysm is secured: treat pain, vomiting, a full bladder and fear first, then keep systolic pressure below approximately 160 mmHg without reducing mean arterial pressure by more than about 25% from the presenting value in the first hour.
  • Antihypertensive choice: labetalol 10 mg IV over 1–2 minutes repeated every 10 minutes (usual cumulative maximum 200 mg), avoided in asthma, marked bradycardia and decompensated heart failure; or hydralazine 5 mg IV slowly, repeated after 20 minutes.Doctor / Nurse
  • Reverse anticoagulation immediately: for warfarin give vitamin K (phytomenadione) 5–10 mg by slow IV injection with prothrombin complex concentrate (preferred) or fresh frozen plasma 15 mL/kg (about 4 units in a 70 kg adult), then recheck the INR targeting below 1.3; paediatric vitamin K is 250 microgram/kg IV slowly to a maximum of 10 mg plus PCC or FFP 15 mL/kg.Doctor / NurseNot available at your setup — Coagulation (PT/INR), Blood & blood products.
  • Direct oral anticoagulants: establish drug, dose and exact time of the last dose; idarucizumab reverses dabigatran and andexanet alfa the factor Xa inhibitors, with prothrombin complex concentrate the usual alternative — fresh frozen plasma does not reliably reverse these drugs; stop antiplatelet agents but transfuse platelets only for a count below 100 x 10^9/L.Not available at your setup — Coagulation (PT/INR), Blood & blood products.
  • Seizures are treated as status epilepticus: lorazepam 4 mg IV (paediatric 0.1 mg/kg IV, maximum 4 mg) repeated once after 10 minutes, or diazepam 10 mg IV slowly (paediatric 0.25 mg/kg IV, or 0.5 mg/kg rectally to a maximum of 10 mg); if seizures persist load with levetiracetam 40–60 mg/kg IV (maximum 4.5 g) over 10 minutes or phenytoin 20 mg/kg IV at no more than 50 mg/minute (paediatric over 20 minutes) with cardiac monitoring.Doctor / Nurse
  • The supportive bundle: absolute bed rest head-up 30 degrees in a quiet darkened room, pain and vomiting fully controlled, a stool softener such as lactulose 15 mL orally twice daily because straining raises transmural pressure across the aneurysm, isotonic fluid only with no fluid restriction, mechanical thromboprophylaxis only until the aneurysm is secured, treatment of fever, normoglycaemia, and frequent serial neurological observations.
  • Get the CT and then the CSF: non-contrast CT first; if it is negative and the history remains convincing, perform a lumbar puncture more than 12 hours after headache onset (counted from the headache, not from arrival) to look for xanthochromia, protecting the sample from light and delivering it promptly for centrifugation.Not available at your setup — CT scan.
  • Definitive treatment: occlusion of the aneurysm by endovascular coiling or surgical clipping, ideally within 72 hours; where CT is unavailable, treat the convincing history as SAH — resuscitate, give nimodipine, control pain and pressure, avoid NSAIDs and hypotonic fluid, and arrange transfer.Not available at your setup — CT scan. Where CT is unavailable, treat the convincing history as SAH and arrange transfer.
  • If the conscious level falls, repeat the CT: rebleeding, expanding haematoma and acute hydrocephalus are distinguished radiologically, not clinically, and acute hydrocephalus is treated with external ventricular drainage which frequently reverses the deficit entirely.Not available at your setup — CT scan.

Caution— what harms

  • Never give NSAIDs or aspirin — including ibuprofen, diclofenac and ketorolac — to a patient with suspected or confirmed intracranial haemorrhage: they inhibit platelet function and can convert a survivable bleed into a fatal one, and this is the commonest drug error in this condition because an NSAID is the reflex prescription for severe headache.
  • Never give hypotonic fluid, including 5% glucose, and never fluid-restrict a hyponatraemic SAH patient — hypovolaemia is more dangerous than mild hyponatraemia.
  • Never use sublingual nifedipine: the uncontrolled fall in pressure causes cerebral infarction; and nifedipine and amlodipine are not substitutes for nimodipine, which is the only dihydropyridine with the specific benefit.
  • Do not inject the oral nimodipine preparation — it must not be drawn up and given intravenously.
  • Deep T-wave inversion, ST deviation, QT prolongation, U waves and a modestly raised troponin after a thunderclap headache are the brain, not the heart: treating this as an acute coronary syndrome with antiplatelet agents, anticoagulation or thrombolysis is a lethal error.Not available at your setup — Cardiac troponin.
  • A normal examination is not reassurance — the patient with SAH and a normal examination is the one whose outcome can still be changed, and neck stiffness is a developing sign whose early absence means nothing.
  • A negative CT more than 6 hours after onset does not exclude SAH: a normal CT at 10 hours is an indication to examine the CSF, not a discharge document.Not available at your setup — CT scan.
  • Do not perform a lumbar puncture before excluding contraindications: a formally reported CT showing no mass lesion, no hydrocephalus and no midline shift, GCS 15, no focal deficit, no papilloedema, platelets above 50 x 10^9/L, INR below 1.5, no therapeutic anticoagulation and no infection over the puncture site — and never in acute hydrocephalus.Not available at your setup — CT scan, Coagulation (PT/INR).
  • Do not tap too early: a lumbar puncture performed before 12 hours from headache onset is uninterpretable because bilirubin has not yet had time to form; a patient presenting at hour three with a normal CT must be observed until hour twelve.
  • A traumatic tap does not produce xanthochromia, so a bloody tap does not invalidate the test — the answer is still in the sample, and xanthochromia means SAH irrespective of whether the tap was bloody.
  • Do not give routine antiseizure prophylaxis to a patient who has not fitted: benefit is unproven and phenytoin is associated with worse cognitive outcome.
  • Do not transfuse platelets routinely after stopping antiplatelet agents — the evidence points to harm; transfuse only for a count below 100 x 10^9/L.Not available at your setup — Blood & blood products.
  • Do not diurese neurogenic pulmonary oedema aggressively: treat with oxygen, upright posture and ventilatory support, because aggressive diuresis produces the hypovolaemia that precipitates cerebral ischaemia.Not available at your setup — Mechanical ventilator.
  • Do not skip serial neurological observation: deterioration is the trigger for repeat imaging, and progressive drowsiness without new focal signs is acute hydrocephalus until the scan says otherwise.Not available at your setup — CT scan.
  • Do not accept the diagnosis you were handed: new headache after 50 needs imaging and inflammatory markers for giant cell arteritis (start prednisolone 60 mg daily immediately on suspicion because blindness is preventable), older patients present with confusion, a fall, collapse or drowsiness rather than headache, and in any infant or young child with unexplained intracranial blood abusive head trauma must be actively considered.

Refer / escalate

Refer immediately to neurosurgery once SAH is confirmed — Davidson's reduces immediate management to resuscitate, nimodipine 60 mg, refer — and escalate or transfer urgently for any reduced or falling conscious level, GCS 8 or below, new pupillary asymmetry, focal deficit, seizure, hypertension with bradycardia, a thunderclap history with no CT available, or the need for external ventricular drainage or aneurysm securing within 72 hours.

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