Subarachnoid Haemorrhage

Diagnosing and excluding SAH

Wait at least 12 hours before LP, to allow formation of bilirubin for differentiation of SAH from traumatic tap.1

"Typical" RBC count in SAH seems to be 10,000 to 1,000,000 per mm3, though counts of several million and in the "few hundreds" are reported.2,3

Managing confirmed SAH

Hypertension - avoid treating unless MAP>130mmHg.4

Nimodipine 60mg 4-hrly - orally.

Magnesium - may help, 50% of patients become Mg deplete.

Deterioration may be due to:

  • Delayed cerebral ischaemia - gradual evolution of localising hemispheric signs, reduced conscious level, or both.
  • Rebeleeding - sudden deterioration.
  • Hydrocephalus - deterioration over hours. Downward deviation of eyes with small unreactive pupils may indicate dilatation of proximal aqueduct.


  1. Emergency Medicine Journal 2005; 22: 121-122
  2. Journal of Emergency Medicine 2002; 23: 67-74
  3. American Journal of Neuroradiology 2001; 22: 571-576
  4. Lancet 2007; 369: 306-318