Subarachnoid Haemorrhage (SAH)

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 the people 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 (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

Risk factors

• Previous subarachnoid haemorrhage
• 1^st or 2^nd 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)

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 and therefore the L4/5 intervertebral space (mark it) is a safe site for LP
• Inject 1-2% Lignocaine with adrenaline into the skin and subcutaneous tissue at the marked site. Let this take 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 (if calibration tube supplied with LP set)

The following samples should be collected:

• A fluoride/EDTA (yellow) for glucose
• 2 sample for microbiology (universal container)(labelled 1 and 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)

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 euvolaemia
• Antifibrinolytic agent (Tranexamic acid)? - unproven [Cochrane]

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

Links & References