USMLE Prep - Medical Reference Library

Subarachnoid Hemorrhage — Diagnosis & Early Management

System: Neurology • Reviewed: Aug 31, 2025 • Step 1Step 2Step 3

Synopsis:

Thunderclap headache is classic; diagnose with CT head and, if needed, LP or CTA; secure aneurysm early; give nimodipine and prevent complications.

Key Points

  • Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
  • Use system-specific risk tools to guide testing and disposition.
  • Order high-yield tests first; escalate imaging when indicated.
  • Start evidence-based initial therapy and reassess frequently.

Algorithm

  1. Primary survey and vitals; IV access and monitors.
  2. Focused history/physical; identify red flags and likely etiologies.
  3. Order system-appropriate labs and imaging (see Investigations).
  4. Initiate guideline-based empiric therapy (see Pharmacology).
  5. Reassess response; arrange consultation and definitive management.

Clinical Synopsis & Reasoning

For Subarachnoid Hemorrhage Early, frame the differential by acuity and pathophysiology, then align diagnostics to the leading hypotheses. Prioritize stabilization while obtaining high‑yield studies such as CT Head (NC) (Hemorrhage exclusion), Glucose (POC) (Exclude hypoglycemia), MRI Brain (selected) (Ischemia/structural). Incorporate bedside imaging and targeted labs to define severity and identify complications; synthesize results with clinical trajectory to refine the working diagnosis and disposition needs.


Treatment Strategy & Disposition

Initiate disease‑directed therapy alongside supportive care, titrating to objective response. Pharmacologic options commonly include Thrombolytic (eligible), Antiepileptics. Use validated frameworks (e.g., Common Early Orders) to guide escalation and site of care. Address precipitating factors, de‑escalate empiric therapies with data, and arrange follow‑up for monitoring and risk‑factor modification; admit patients with instability, high risk of deterioration, or needs for close monitoring.


Epidemiology / Risk Factors

  • Hypertension, AF, atherosclerosis; prior stroke/TIA

Investigations

TestRole / RationaleTypical FindingsNotes
CT Head (NC)Hemorrhage exclusionAcute bloodFirst-line
Glucose (POC)Exclude hypoglycemiaLowTreat promptly
MRI Brain (selected)Ischemia/structuralDiffusion restriction

Common Early Orders

DomainAction
Blood pressureTitrate IV agents to target as per protocol
Vasospasm preventionNimodipine scheduled dosing
DVT prophylaxisMechanical initially; pharmacologic when safe

Pharmacology

MedicationMechanismOnsetRole in TherapyLimitations
NimodipineDHP CCB (cerebral)HoursPrevents DCI/vasospasmHypotension
Analgesia/antiemeticSymptomaticMinutesComfort; reduce BP surgesSedation/QT
BP control (labetalol/nicardipine)AntihypertensivesMinutesAneurysmal rupture risk reductionHypotension

Prognosis / Complications

  • Outcome tied to time-to-reperfusion; aspiration/DVT risks

Patient Education / Counseling

  • Explain red flags and when to seek emergent care.
  • Reinforce medication adherence and follow-up plan.

Notes

Hyponatremia may reflect SIADH or cerebral salt wasting. Avoid routine seizure prophylaxis unless indicated by cortex involvement or seizures.


References

  1. AHA/ASA Aneurysmal SAH Guideline — Link
  2. Neurocritical Care Society — Link