EMed

Subarachnoid Haemorrhage (SAH)

High risk patients.

Please have a high index of suspicion in lone acute headaches with if any of the following:

  • Age >40
  • Complaint of neck pain or stiffness
  • Witnessed loss of consciousness
  • Onset with exertion
  • Arrival by ambulance
  • Vomiting at least once
  • DBP >100 mmHg or SBP >160 mmHg

Ottawa SAH rule

The Ottawa SAH rule is 98% sensitive but has low specificity (good at ruling OUT but poor at ruling IN a SAH). If a patient does not have any of the following - you can safely exclude SAH.

  • Neck pain or stiffness
  • Age >40
  • Witnessed loss of consciousness
  • Onset during exertion
  • Thunderclap (peak pain instantly)
  • Limited neck flexion on exam

On the other hand, having the above does not mandate investigation - please get a second opinion from your senior.

Background

Incidence of subarachnoid haemorrhage (SAH) is about 12 per 100,000 population per year.

80% are due to a ruptured aneurysm, 10% perimesencephalic haemorrhages, 10% Other – AVM, cocaine.

  • 50% of these patients die or are permanently disabled as a result of the initial event
  • Another 30% will die if left untreated

The clinical presentation is variable but the "classical" presentation is of acute, severe ("worst ever") headache.

Transient loss of consciousness is common at first presentation.

20% of patients have a seizure.

There are five clinical grades of severity, ranging from :

  • Grade 1 (asymptomatic or minimal headache)
  • Grade 2 is mild to severe headaches, some nuchal rigidity (neck stiffness) and no neurological deficits (other than cranial nerve palsy)
  • Grade 3 is drowsiness, confusion, and mild focal deficit
  • Grade 5 is deep coma

The outcome from SAH is dependent upon the initial classification.

  • 90 - 95% of patients presenting in grades 1 and 2 are well and living independently
  • Patients presenting at Grade 4 or 5, have an 80% - 100% mortality

Re-bleeding occurs in up to 30%, usually within the first 1-2 weeks.

  • Of those who re-bleed, mortality is 50%
  • Re-bleeding is more commonly seen in people with initial low-grade coma levels

Vaso-spasm occurs in about 30% of patients with SAH (usually between 4-14 days).

  • With vaso-spasm, 30% die and 30% have a permanent neurological deficit

Early diagnosis of subarachnoid haemorrhage is important for two reasons.

  • Possible introduction of Nimodipine (reduces the vaso-spasm) = 24% in reduction in relative risk of death or dependency when given following a SAH
  • Surgery. When indicated, early surgery dramatically reduces the chance of a re-bleed and improves prognosis

CT brain (within 24 hrs of onset) should detect over 95% of sub-arachnoid haemorrhages (though less sensitive in people with lower initial coma grades).

Any patient with a suspected SAH and negative CT scan should have a lumbar puncture. This is the definitive test for excluding a subarachnoid haemorrhage.

Pitfalls

  • Do not make the diagnosis of "tension headache" or "migraine" in patients first episode of severe headache
  • Patients with SAH may have a secondary head injury, hypertension ( primary or secondary), ECG changes or a mild pyrexia
  • The pain is not always occipital
  • Eye or temple pain may indicate a middle cerebral artery aneurysm
  • Photophobia or is neither sensitive nor specific
  • Cranial nerve palsies (3rd, 5th or 6th) or visual field defects may be associated findings

ECG changes in SAH

  • Non-specific changes
  • ST & T wave changes may mimic ischaemia (inf leads)
  • Widened QRS
  • Prolonged QT
  • Peaked or deeply inverted T waves
  • ST elevation rare

Risk factors

  • Previous subarachnoid haemorrhage
  • 1st or 2nd degree relative with SAH
  • Female
  • The same risk factors for coronary artery disease apply (smoking, hypertension, lack of exercise and drinking too much)
  • Connective tissue diseases (autosomal dominant polycystic kidney disease, coarctation of the aorta, Marfan's syndrome, Ehlers-Danlos syndrome type IV, neurofibromatosis type I, alpha-1-antitrypsin deficiency)
  • Anticoagulation (Aspirin or Warfarin)

Investigation (CT ± LP)

  • Sudden onset headache
  • Headache with loss of consciousness at onset
  • Worst ever headache
  • Headache with neurological signs
  • Age >40
  • Complaint of neck pain or stiffness
  • Onset with exertion
  • Arrival by ambulance
  • Vomiting at least once
  • DBP >100 mmHg or SBP >160 mmHg

Note

  • CT should be performed at the earliest opportunity [BestBets]
  • Urgent neurosurgical consultation required for proven SAH
  • If CT is negative LP should be delayed until 12 hours post onset of symptoms [BestBets]

Management of ? SAH

  • ABCs, Oxygen
  • Monitoring as appropriate
  • IV access, analgesia (titrated Morphine), and anti-emetic (Metoclopramide)

Other investigations:

  • FBC (haemoglobin <10g/dl reduces CT sensitivity)
  • U&Es (? hyponatraemia)
  • LFTs (plasma bilirubin required for spectrophotometric interpretation)
  • Clotting screen
  • Consider venous COHb

Admit to CDU for observation and further Mx (note exclusion criteria).

Not for CDU

  • GCS <15
  • Focal neurological signs
  • Signs of meningitis
  • Signs of ↑ ICP
  • Petechial or purpuric rash
  • Headache associated with seizures

Lumbar puncture

For further instructions on performing LP procedure please see LP page (to be updated) in procedures section.

  • Sit patient upright on trolley, back flexed away from you
  • Orientate yourself to : The superior iliac crest is the L4 landmark
  • In adults the spinal cord ends at approximately the L1/2 disc space
  • Inject 1% Lignocaine with adrenaline into the skin and subcut. tissue at the marked site. Wait minutes for effect
  • Use sterile gloves and sterilise the area on the back, including up to the iliac crest with antiseptic solution
  • Insert a Whitacre 22-25G pencil point spinal needle through the mark, aiming towards the umbilicus
  • As you insert the needle deeper you will feel the resistance as you pass through the spinal ligaments, following which you will then enter the dura
  • After entering the dura the needle will give as it enters the subarachnoid space
  • Withdraw the stylet from the spinal needle and assess whether CSF drains
  • Measure the opening pressure

LP samples

  • A fluoride/EDTA (yellow) for glucose
  • 2 sample for microbiology (universal container)(labelled 1 & 3)
  • A sample (universal container) for protein (labelled 2)
  • At least one ml (25 drops) for spectrophotometry into the dark brown (light resistant) sample bottle. Please indicate the clinical indication for the test, date/time of onset of symptoms, date/time of LP, CT result if appropriate
  • Contact the on-call biochemist to process this sample promptly
  • Reinsert the stylet prior to removing the needle. The patients are less likely to suffer post lumbar puncture headache as a result (Reference 1)
  • Traumatic tap? - see troubleshooting
  • There is no need for the patient to rest in bed [BestBets]
  • The incidence of post LP headache is reduced by the use of pencil point spinal needles (6.7% for 22G needles, 1.1% for 25G)

Spectrophotometric interpretation of CSF

  • The presence of Bilirubin is strongly supportive of SAH
  • Oxyhaemoglobin on its own is an equivocal finding, arising from both SAH and during the LP

Three options with spectophotometry result:

  • Positive - refer to neurosurgeon
  • Negative - no further investigation required
  • Equivocal - equivocal!

Equivocal results should be discussed with the duty EM consultant and the neurosurgeons(hence the need to take serum LFTs at the time of LP). Consider the patient's total protein and serum bilirubin levels. For example, for a patient with an excellent story, a negative scan and an equivocal result, a CT angiogram is the appropriate next investigation. In contrast, a patient with a limited story, negative scan and equivocal result in the presence of raised total protein or raised serum bilirubin will probably need no further investigations.

A traumatic tap will be positive for oxyhaemoglobin but not bilirubin.

Spectrophotometry in CUH

  • During working hours only Print version
  • CSF sampled >12 hours after event
  • Complete all details on request form
  • Include time onset symptoms
  • Note if differential included meningitis
  • Sterile universal container and labelled with patient’s name, hospital number and date of birth.
  • 1 ml of CSF is required for spectrophotometric analysis (the last sample taken)
  • A separate sample for glucose and protein
  • Spectrophotometric samples must be protected from light.
  • Immediate transport to labs by hand
  • A sample of blood must be taken at the same time for glucose, protein and serum bilirubin measurement
  • Please note : On the weekend, CSF samples should reach the labs before 12 midday. Please also ring and alert the labs that a sample is on the way. CUH sepctrophotometry request form

Management of proven (atraumatic)SAH

  • Give Nimodipine 60 mg orally, four hourly (for the first seven days) [BestBets/Cochrane]
  • Note BNF cautions, including concurrent calcium channel blockers or β-blockers
  • The drug can be given via a NG tube or IV via central line - 1mg per hour initially, increased after two hours to 2 mg per hour providing no serious decrease in blood pressure;
  • For patients with unstable blood pressure or weighing less than 70kg, give 500 micrograms per hour initially or less if necessary. (Cochrane)
  • Volume expansion? - unproven [Cochrane]
  • Maintain euvolaemia
  • Antifibrinolytic agent (Tranexamic acid)? - unproven [Cochrane]

Criteria for admission (at any time)

  • Social circumstances prevent discharge
  • Unstable patient
  • Seizures during admission
  • Signs of meningeal irritation/↑ ICP
  • Focal neurological deficit
  • Abnormal CT scan
  • Abnormal LP

Criteria for admission (after final review)

  • Headache/vomiting persists
  • Pyrexial or unstable patient

Criteria for discharge from CDU

  • Headache much improved
  • Apyrexial
  • No meningism
  • No neurological symptoms/signs
  • Pulse and BP within normal limits
  • CT scan & LP normal
  • Dx and treatment explained to patient
  • Tolerating diet and fluids
  • Social circumstances permit discharge
  • Letter to GP/follow-up arranged

Troubleshooting

  • Failed LP? - consultant/first on call anaesthetist for help
  • Late presentation? The spectrophotometric analysis is sensitive up to two weeks post event
  • Traumatic tap? Await results of spectrophotometry - absence of bilirubin excludes SAH since any blood has not been exposed to the enzymes within the CSF for Hb breakdown

Content by Dr Íomhar O' Sullivan. Last review by Dr Í 22/11/24.