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Subarachnoid Hemorrhage Overview and Management

Aug 28, 2024

Subarachnoid Hemorrhage Overview

Definition

  • Subarachnoid hemorrhage (SAH): Hemorrhage of cerebral vessels (primarily from the Circle of Willis) into the subarachnoid space.
  • Can also involve intraventricular hemorrhage if vessels rupture into the ventricles.

Causes

Traumatic SAH (Most Common)

  • Blunt force trauma: E.g., hit on the head.
  • Penetrating trauma: E.g., stab wound.

Non-Traumatic SAH (Less Common)

  • Aneurysmal:
    • Saccular (Berry) Aneurysm: Asymmetric ballooning of the vessel.
    • Giant Saccular Aneurysm: >2.5 cm.
    • Fusiform Aneurysm: Symmetrical dilation of vessels.
    • Pseudoaneurysm: Vessel dissection that resembles an aneurysm.
    • Mycotic Aneurysm: Infected aneurysm.

Risk Factors for Aneurysm Formation

  • Hypertension: Increases stress on vessel walls.
  • Sympathomimetics: Drugs like cocaine and methamphetamine increase sympathetic activity.
  • Smoking and Alcohol: Contributes to vessel wall stress.
  • Oral Contraceptives/Pregnancy: Hormonal influences on vascular integrity.
  • Connective Tissue Disorders:
    • Marfan Syndrome: Deficiency in fibrillin.
    • Ehlers-Danlos Syndrome: Deficiency in collagen.
    • Polycystic Kidney Disease: Defect in polycystin proteins.
  • Fibromuscular Dysplasia: Abnormal growth of smooth muscle in vessels.

Triggers for Aneurysm Rupture

  • Acute rise in blood pressure.
  • Painful stimuli or anger can also trigger rupture.

Locations of Aneurysms within the Circle of Willis

  1. Anterior Communicating Artery: ~30% of saccular aneurysms.
  2. Posterior Communicating Artery: ~25%.
  3. Middle Cerebral Artery (MCA) bifurcation: ~20%.
  4. Internal Carotid Artery (ICA) terminus: ~7.5%.
  5. Basilar Tip: ~7%.
  6. Anterior Cerebral Artery: ~4%.
  7. Posterior Inferior Cerebellar Artery (PICA): ~3.5%.

Clinical Features of SAH

  • Thunderclap headache: Sudden onset, often described as the worst headache ever.
  • Meningeal signs: Photophobia, neck stiffness, positive Kernig's and Brudzinski's signs.
  • Increased intracranial pressure (ICP): Symptoms include nausea, vomiting, cranial nerve deficits, and Cushing's triad (hypertension, bradycardia, irregular respirations).
  • Focal neurological deficits: Possible stroke-like symptoms depending on the affected vessel.

Diagnosis

  1. Non-contrast CT scan: Initial test to identify SAH.
    • Look for blood in the sulci and cisterns.
    • Assess for intraventricular hemorrhage (IVH) and hydrocephalus.
  2. Modified Fischer Score: Helps assess the risk of vasospasm and delayed cerebral ischemia.
  3. CT Angiogram (CTA): To identify the ruptured aneurysm.
  4. Digital Subtraction Angiogram: Gold standard for visualizing blood vessels.
  5. Lumbar Puncture: Can confirm SAH if CT is inconclusive (look for xanthochromia).

Treatment

Initial Care

  • Airway, Breathing, Circulation (ABCs): Secure airway due to potential ICP increase.
  • Ventilation: Options include Continuous Mechanical Ventilation (CMV) or Adaptive Support Ventilation (ASV).

Blood Pressure Control

  • Target systolic BP <160 mmHg to prevent rebleeding.
  • Medications: Nicardipine, Labetalol, Hydralazine, Enalapril.

External Ventricular Drain (EVD)

  • Indicated in high Hunt-Hess score, presence of IVH, or hydrocephalus to monitor and reduce ICP.

Aneurysm Management

  • Coiling or Clipping within 24 hours to prevent rebleeding.
  • Choice depends on various factors: age of the patient, neck size of the aneurysm, hemodynamic stability, and aneurysm location.

Complications Management

  1. Rebleeding: High mortality (70%); stabilize with antifibrinolytics (Aminocaproic acid, TXA) and replace fibrinogen.
  2. Vasospasm: Delayed cerebral ischemia may occur around days 4-14.
    • Monitor with daily Transcranial Dopplers (TCDs) for blood flow velocity and Lindegaard ratio.
    • Treatment: Nimodipine, induced hypertension, intra-arterial dilators.
  3. Seizures: Treat with antiepileptic medications.
  4. Pyrexia: Manage with cooling measures and medications that prevent shivering.
  5. Cerebral Salt Wasting: Treat with Florinef (Fludrocortisone) and sodium/water replacement.
  6. Stress Cardiomyopathy: Address hypotension with vasopressors.
  7. Neurogenic Pulmonary Edema: Manage hypoxia with increased PEEP and oxygenation.

Conclusion

  • Understand pathophysiology, risk factors, clinical features, and management strategies for subarachnoid hemorrhage to improve patient outcomes.

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