Subarachnoid Haemorrhage (SAH)

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Pitfalls
ECG in SAH
Risk factors
Indications for Ix
Management
Exclusion criteria for CDU
Lumbar puncture
Spectrophotometry
Mx of SAH
Admission criteria
Troubleshooting
Patient Info
Links

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Background.

• Incidence of subarachnoid haemorrhage (SAH) is about 12 per 100,000 population per year.
• 70% are due to a ruptured aneurysm.
  • 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 an epileptic fit.
• 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.
• Rebleeding occurs in up to 30%, usually within the first 1-2 weeks.
  • Of the people who rebleed, mortality is 50%.
  • Rebleeding is more commonly seen in people with initial low-grade coma levels.
• Vaso-spasm occurs in about 30% of patients with SAH (usualy 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 (a drug which reduces the vaso-spasm).
    • Nimodipine gives about a 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 rebleed and improves prognosis.
• Modern day CT scanners should detect over 95% of sub-arachnoid haemorrhages (though they are less sensitive in people with lower initial coma grades).
• Any patient with a suspected sub-arachnoid haemorrhage and negative CT scan to undergo lumbar puncture. This is the definitive test for excluding a subarachnoid haemorrhage.

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Pitfalls in interpreting the clinical presentation

• 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 (either 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.

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ECG changes in SAH

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Risk factors

• Previous subarachnoid haemorrhage.
• First or second degree relative with SAH.
• Female sex.
• 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).

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Indications for investigation (CT +/- LP)

• Sudden onset headache.
• Headache with loss of consciousness at time of 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

Management of ? SAH

• ABCs, Oxygen 
• Monitoring as appropriate.
• IV access, analgesia (titrated Morphine), and anti-emetic (Metoclopramide).
• Other investigations:
  • FBC (NB 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 management (NB exclusion criteria below)

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Exclusion criteria for CDU management of ? SAH

 

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Lumbar puncture

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

• Place the patient on their left side with their back on the edge of the bed fully flexed, bringing the knees up to the chin (foetal position) OR sit patient upright on trolley, back flexed away from you.
• It is essential to orientate yourself with the landmarks prior to undertaking an LP. 
  • The superior iliac crest is the L4 landmark. 
  • In adults the spinal cord ends at approximately the L1/2 disc space and therefore the L4/5 intervertebral space (mark it) is a safe site for LP.
• Use sterile gloves and sterilise the area on the back, including up to the iliac crest with antiseptic solution.
• Inject 1% Lignocaine (Lidocaine) into the skin and subcutaneous tissue at the marked site. Let this take effect.
• Insert a Whitacre 22G 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 (if calibration tube supplied with LP set).
• The following samples should be collected:
  • A fluoride/EDTA (yellow) for glucose.
  • A sample for microbiology ( universal container).
  • At least one ml (25 drops) for spectrophotometry. 
  • Protect this specimen from light (a thick brown envelope outside the usual plastic envelope) and send immediately to the laboratory. 
  • Contact the on-call biochemist to process this sample promptly
    • Please note that visual inspection  for the presence of xanthochormia is unreliable
    • Spectrophotometric analysis is not available at CUH - samples are still visually inspected 
  • Please indicate the following on the biochemistry form
    • clinical indication for request
    • result of CT scan
    • time of onset of symptoms/event
    • time of LP
• 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 section
• There is no need for the patient to rest in bed [BestBets]
• The incidence of post LP headache is dramatically reduced by the use of pencil point spinal needles (6.7% for 22G needles, 1.1% for 25G).

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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
• Consider the pre-test probability (the test being CT scan)
• The post test probability for a negative scan has to lie between 0% and 5% (unless the patient is scanned >24 hours after the event)
• CSF sent for analysis will be spun down and spectrophotometrically analysed
• Three options with result:
  • Positive - refer to neurosurgeon.
  • Negative - no further investigation required.
  • Equivocal - equivocal!

Equivocal results should be discussed with the duty emergency department consultant, clinical biochemist of the day 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 invistigation. 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.

Management of proven 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 euvolemia.
• Antifibrinolytic agent (Tranexamic acid)? - unproven [Cochrane].

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Criteria for discharge from CDU

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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.

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Links & References

• 1 Strupp and Brandt. New England Journal of Medicine 1997; 1190.
• Suspected SAH in ED National Neurosurgery Programme December 2011
• Weekly Review Emergency Med Review article 2000
• High risk clinical characteristics for subarachnoid haemorrhage in patients with acute headache: prospective cohort study. Jeffrey J Perry JJ, Stiell et al. BMJ 2010; 341:c5204 (local copy)

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Content by Dr Gavin Lloyd, Dr Íomhar O' Sullivan 09/07/2002. Reviewed by Dr ÍOS 09/07/2003, 02/05/2005, 12/06/2007, 01/10/2007, 20/06/2008. Last revie Dr ÍOS 11/03/12