10. Subarachnoid Hemorrhage (SAH)

Etiology / Risk Factors

Secondary to trauma or nontraumatic causes, of which ruptured cerebral aneurysms are the most common cause (~ 80%). Risk factors for aneurysmal subarachnoid hemorrhage include smoking, HTN, cocaine use, and alcohol use as well as conditions such as Marfan syndrome, Ehlers-Danlos syndrome, polycystic kidney disease, which predispose to aneurysm development.

Evaluation

  • Symptoms:
    • Sudden onset severe headache (“worst headache of my life”) which reaches maximal intensity immediately (it is the sudden onset of the headache that is most useful in making the diagnosis rather than severity)
    • Examination can be benign early
    • May be associated with nausea, vomiting, nuchal rigidity, photophobia, loss of consciousness, focal neurologic deficits, seizures
  • Exam:
    • Low-grade fever is common (blood is a pyretic)
    • Full neurologic exam looking for focal deficits, signs of increased ICP, and nuchal rigidity
  • Studies:
    • STAT CBC, BMP, coags, urine tox screen
    • Non-contrast head CT has a very high sensitivity within the first 6 hours but diminishes over time thus a negative CT should always be followed by an LP in patients where there is suspicion for SAH
    • LP may show elevated opening pressure. Compare RBC count in tubes 1 and 4, evaluate for xanthochromia though may be absent early (within 6 to 12 hours)

Management

  • Consult neurology and neurosurgery early. If not available, patient will require transfer to center with neurosurgeons or interventional radiologists to identify and then secure the ruptured aneurysm with either surgical clipping or endovascular coiling
  • Keep SBP < 160 mmHg using nicardipine or labetalol until aneurysm is secured
  • Maintain euvolemia, normothermia, and normoglycemia
  • Nimodipine 60 mg q4 hours (or 30 mg q2h if hypotensive after higher dose) for 21 days to avoid delayed cerebral ischemia from vasospasm
  • Monitor for hyponatremia with goal Na level at least >135 but may higher and require 3% hypertonic saline or sodium chloride tablets to maintain
  • Monitor mental status closely; if patient becomes drowsy, stat head CT and call neurosurgery for possible external ventricular drain to relieve hydrocephalus
  • Start DVT prophylaxis 24 hours after aneurysm has been secured

Feigin et al. Risk factors for subarachnoid hemorrhage: an updated systematic review of epidemiologic studies. Stroke 2005 Dec;36(12) :2773-80

Suarez JI, Tarr RW, Selman WR. Aneurysmal subarachnoid hemorrhage. N Engl J Med 2006;354:387-396

Hernandez, C., & Geocadin, R. (2017). Neurologic Care After Cardiac Arrest. In The Pocket Guide to Neurocritical Care: A concise reference for the evaluation and management of neurologic emergenies (pp. 55-60). Chicago, IL: Neurocritical Care Society.