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The principal complications of subarachnoid haemorrhage are:

  • death - 50% in first 30 days, many before reaching hospital
  • decreased level of consciousness - sudden causes include rebleeding, epilepsy, and ischaemia; a gradual onset suggests ischaemia, hydrocephalus and metabolic dysfunction
  • rebleed - in the absence of intervention, 10% rebleed within hours, 30% within 4 weeks, and 50% within 6 months. Apnoea occurs in 30% of all cases. Assisted ventilation restores spontaneous respiration in most cases. Emergency clipping is advised.
  • cerebral ischaemia - usually insidious and multifocal or diffuse. The level of consciousness falls in 75% of cases, with focal neurological signs in 50%. Cerebral perfusion must be increased by expanding plasma volume and/or inducing hypertension with dopamine or dobutamine. Transluminal angioplasty is rarely performed because of the associated risks.
  • acute hydrocephalus - in 15-20% of cases, usually within the first few days. Gradual obtundation is suggestive. Spontaneous improvement within 24 hours occurs in 50% of cases in the absence of massive intraventricular haemorrhage. An external ventricular catheter may be beneficial but at the cost of an increased risk of rebleeding. Lumbar puncture may obviate the need for a shunt if the obstruction lies in the subarachnoid space rather than the ventricular system.
  • rarely, myocardial infarction, pulmonary oedema, and gastric haemorrhage.

Last reviewed 01/2018