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2025 PACUPrep BCCCP Preparatory Course Subarachnoid Hemorrhage Foundational Concepts in Aneurysmal Subarachnoid Hemorrhage

Lesson 23, Topic 2

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Foundational Concepts in Aneurysmal Subarachnoid Hemorrhage

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Diagnostic Stratification and Initial Assessment in Aneurysmal Subarachnoid Hemorrhage

Lesson Objective

Apply diagnostic and classification criteria to assess the severity of subarachnoid hemorrhage and guide immediate management.

Learning Points

Use Hunt and Hess and WFNS scales to stratify aSAH severity and predict outcome.
Perform non-contrast CT promptly; interpret Fisher grade for vasospasm risk.
When CT is negative but suspicion remains, use lumbar puncture with xanthochromia analysis.
Evaluate coagulation status and reverse anticoagulation before aneurysm securing.
Integrate GCS, focal deficits, and BP targets into an urgent management algorithm.

1. Clinical Grading Scales

Clinical scales quantify neurologic injury, guide prognosis, and inform triage urgency.

Hunt and Hess Scale (Grades I–V)

Grade I: Asymptomatic or mild headache, nuchal rigidity; mortality ≈5%
Grade II: Moderate–severe headache, no focal deficit; mortality ≈10%
Grade III: Drowsiness, mild focal deficit; mortality ≈30%
Grade IV: Stupor, moderate–severe hemiparesis; mortality ≈50%
Grade V: Deep coma, decerebrate posturing; mortality ≈80%

WFNS Scale (Grades I–V)

(World Federation of Neurological Surgeons)

Grade I: GCS 15, no motor deficit
Grade II: GCS 13–14, no deficit
Grade III: GCS 13–14, with deficit
Grade IV: GCS 7–12, with/without deficit
Grade V: GCS 3–6, with/without deficit

Key Pearls for Clinical Grading +

Hunt and Hess (HH) is most reliable at extremes (I and V); intermediate grades are prone to misclassification.
WFNS integrates GCS for objectivity; preferred when intubation or sedation confounds exam.
Document pre-hospital sedation or seizure activity; re-grade after stabilization if possible.

2. Imaging Modalities

Non-contrast head CT is the first test; CTA and DSA localize aneurysms and guide therapy.

A. Non-Contrast CT (NCCT)

Sensitivity: >98% within 6 hours of symptom onset, >95% within 24 hours, declines thereafter.
Fisher Scale for vasospasm risk:
- Grade 1: No blood detected.
- Grade 2: Thin (<1 mm thick layer) diffuse or localized cisternal blood.
- Grade 3: Thick (>1 mm thick layer) localized or diffuse cisternal blood.
- Grade 4: Intracerebral or intraventricular hemorrhage with or without diffuse cisternal blood.
Pitfalls: Very early or diffuse bleeds, low hematocrit (making blood appear less dense), small perimesencephalic non-aneurysmal hemorrhage.

Key Pearl: NCCT Timing +

A high-quality non-contrast head CT performed within 6 hours of headache onset in an alert patient effectively excludes aneurysmal subarachnoid hemorrhage.

B. CT Angiography (CTA)

Utility: Rapid aneurysm detection, 3D reconstruction for surgical or endovascular planning.
Sensitivity: Approximately 95–98% for aneurysms ≥3 mm; may miss very small or thrombosed lesions.
Risks: Contrast-induced nephropathy (screen for renal dysfunction, ensure hydration), allergic reaction to contrast.
Next step: If CTA is negative or equivocal and suspicion for aSAH remains high (e.g., positive LP), proceed to DSA.

C. Digital Subtraction Angiography (DSA)

Gold standard: Offers the highest spatial resolution for aneurysm detection and characterization. Allows for simultaneous endovascular therapy if an aneurysm is identified.
Risks: Thromboembolism (stroke), vessel injury (dissection, perforation), contrast reaction, radiation exposure.
Timing:
- Good-grade patients (HH I-III, WFNS I-III): Generally immediate DSA to expedite aneurysm repair and reduce rebleeding risk.
- Poor-grade/unstable patients (HH IV-V, WFNS IV-V): Stabilize medically first (airway, breathing, circulation, ICP management if indicated), then proceed with DSA.

Controversy: DSA Timing in Poor-Grade Patients +

The optimal timing of DSA in poor-grade aSAH patients is debated. Early intervention aims to prevent rebleeding, which is a major cause of mortality and morbidity. However, these patients are often hemodynamically unstable and may have elevated intracranial pressure, increasing procedural risks. The decision balances the risk of rebleeding against the risk of neurological deterioration during or after an invasive procedure. A multidisciplinary discussion is often crucial.

3. Lumbar Puncture (LP)

LP confirms SAH when CT is negative and clinical suspicion remains high, typically after 6 hours from symptom onset.

Indications: Non-contrast CT is negative or equivocal, particularly if performed >6 hours after symptom onset, and clinical suspicion for SAH remains high (e.g., “worst headache of life,” nuchal rigidity). Also considered for atypical presentations.
Technique:
- Measure opening pressure (often elevated in SAH).
- Collect cerebrospinal fluid (CSF) in 3-4 serial tubes.
- Send tube 1 and tube 4 (or last tube) for cell count (RBC, WBC) and differential.
- Send a separate CSF sample (typically from tube 2 or 3, protected from light) for xanthochromia assessment (visual inspection and/or spectrophotometry).
Interpretation:
- Xanthochromia: Yellowish discoloration of CSF supernatant due to bilirubin (hemoglobin breakdown product). Appears ≥12 hours after hemorrhage and can persist for approximately 2 weeks. Spectrophotometry is more sensitive than visual inspection.
- Traumatic tap vs. SAH:
  - Traumatic tap: RBC count typically declines significantly from tube 1 to tube 4. Xanthochromia is absent (unless recent prior traumatic tap or hyperbilirubinemia).
  - SAH: Persistently elevated RBC count across tubes. Xanthochromia present (if LP >12h post-ictus).
Pitfall: Performing LP too early (<12 hours after symptom onset) may result in a false negative for xanthochromia, as bilirubin takes time to form. If CT is negative within 6 hours and suspicion is very high, some centers may wait until the 12-hour mark for LP or repeat CT.

4. Laboratory Assessment

Identify coagulopathy and initiate reversal before aneurysm securing to reduce the risk of rebleeding.

Essential Tests:

Complete Blood Count (CBC) with platelet count
Prothrombin Time (PT) / International Normalized Ratio (INR)
Activated Partial Thromboplastin Time (aPTT)
Fibrinogen level
Basic metabolic panel (electrolytes, renal function)
Type and screen (crossmatch if surgery anticipated)

Reversal Strategies for Anticoagulation:

Anticoagulation Reversal Strategies in aSAH
Anticoagulant	Reversal Agent(s)	Notes
Warfarin	Vitamin K (IV) + Four-Factor Prothrombin Complex Concentrate (4F-PCC)	4F-PCC preferred over Fresh Frozen Plasma (FFP) due to faster action, smaller volume. Target INR <1.4.
Dabigatran (Direct Thrombin Inhibitor)	Idarucizumab	Specific monoclonal antibody fragment. Activated charcoal if <2h since ingestion.
Factor Xa Inhibitors (e.g., Rivaroxaban, Apixaban, Edoxaban)	Andexanet Alfa (if available) or 4F-PCC (off-label)	Andexanet alfa is a specific reversal agent. Activated charcoal if <2h since ingestion.
Unfractionated Heparin (UFH)	Protamine Sulfate	Dose depends on timing and amount of last heparin dose.
Low Molecular Weight Heparin (LMWH) (e.g., Enoxaparin)	Protamine Sulfate (partial reversal)	Effectiveness varies; may consider 4F-PCC for severe bleeding.
Antiplatelet Agents (e.g., Aspirin, Clopidogrel)	Platelet transfusion (consider if severe thrombocytopenia or active bleeding pre-procedure)	Routine platelet transfusion for patients on antiplatelets is controversial and not generally recommended unless profound thrombocytopenia or planned urgent surgery. Desmopressin (DDAVP) may be considered.

Timing: Complete reversal of anticoagulation should be achieved prior to aneurysm securing (surgical clipping or endovascular coiling/stenting) whenever feasible to minimize rebleeding risk.

Key Pearl: Coagulopathy Correction +

Emergent correction of any identified coagulopathy is a Class I recommendation (strongest level of evidence) in patients with aSAH to prevent aneurysm rebleeding, a devastating complication associated with high mortality.

5. Neurological Examination and Vital Signs Management

Ongoing neurological assessment and meticulous blood pressure control are critical to guide the urgency of treatment and detect early signs of complications like rebleeding or vasospasm.

Neurologic Examination:

Glasgow Coma Scale (GCS): Assess individual components (Eye, Verbal, Motor) frequently.
Pupillary Examination: Size, symmetry, reactivity to light. Anisocoria or a newly sluggish/fixed dilated pupil can indicate rising intracranial pressure (ICP) or brain herniation.
Cranial Nerves: Particular attention to CN III (oculomotor) palsy (ptosis, “down and out” gaze, dilated pupil) which can occur with posterior communicating artery aneurysms.
Motor Strength: Assess for focal deficits (hemiparesis, monoparesis) or changes from baseline.
Level of Consciousness: Note any drowsiness, confusion, or decline in alertness.
Frequency: Every 1-2 hours initially, or more frequently if the patient is unstable or has a poor grade.

Blood Pressure Targets:

Pre-aneurysm securing: Systolic Blood Pressure (SBP) <160 mmHg is generally recommended. Some guidelines suggest <140 mmHg if feasible without causing cerebral hypoperfusion. The goal is to balance the risk of rebleeding (from high BP) against the risk of ischemia (from low BP). Avoid wide fluctuations.
Post-aneurysm securing: Maintain adequate Cerebral Perfusion Pressure (CPP). CPP = Mean Arterial Pressure (MAP) – Intracranial Pressure (ICP). If ICP is not monitored, target MAP 70–90 mmHg, or higher if vasospasm is suspected/present (permissive hypertension).

Antihypertensive Agents (for pre-secure SBP control):

Common Antihypertensive Agents in aSAH
Agent	Route/Dose	Notes
Nicardipine	IV Infusion	Start 5 mg/h, titrate by 2.5 mg/h every 5-15 min to max 15 mg/h. Easily titratable, cerebral vasodilator (may increase ICP in some cases but generally safe).
Labetalol	IV Bolus or Infusion	Bolus: 10–20 mg IV q10–20 min (max 300 mg). Infusion: 0.5–2 mg/min. Combined alpha- and beta-blocker. Avoid in bradycardia, heart block, asthma.
Esmolol	IV Infusion	Loading dose: 500 mcg/kg over 1 min. Infusion: 50–200 mcg/kg/min (max 300 mcg/kg/min). Short-acting, cardioselective beta-blocker. Useful if tachycardia is also present.
Clevidipine	IV Infusion	Start 1-2 mg/h, double dose q90s initially, then less frequently. Max 16-32 mg/h. Ultrashort-acting calcium channel blocker. Lipid emulsion (monitor triglycerides).

Monitoring: Continuous arterial blood pressure monitoring is ideal for precise titration. Neurological checks and vital signs should be documented frequently, and therapy adjusted promptly in response to changes.

6. Integration and Immediate Management Algorithm

A protocolized, multidisciplinary approach minimizes diagnostic delays, facilitates timely intervention, and expedites aneurysm securing, ultimately improving patient outcomes.

Start: Suspected aSAH (e.g., Thunderclap Headache)

Step 1: Non-Contrast CT Head Immediately

Decision: Is CT Positive for SAH?

If Yes (CT Positive):

Obtain CTA for Aneurysm Localization.

Decision: Is CTA Negative or Equivocal?

If Yes (CTA Negative/Equivocal):

Consider DSA.

If No (CTA Positive):

Proceed to Concurrent Management (SAH Confirmed).

If No (CT Negative):

Decision: High Suspicion & CT >6h or Atypical Presentation?

If Yes (High Suspicion/Atypical):

Perform LP with Xanthochromia Analysis.

Decision: Is LP Positive for SAH?

If Yes (LP Positive):

Obtain CTA/DSA.

If No (LP Negative):

SAH Ruled Out.

If No (Low Suspicion/Typical):

SAH Ruled Out.

CONCURRENTLY (Once SAH Confirmed):

Admit to Neuro ICU / Stroke Unit
Labs & Reverse Coagulopathy
BP Control (SBP <160 mmHg pre-secure)
Serial Neuro Exams & Vital Signs

Consult Neurosurgery/Neurointerventional Radiology

Transfer to Center for Definitive Aneurysm Repair

Figure 1: Initial Diagnostic and Management Algorithm for Suspected Aneurysmal Subarachnoid Hemorrhage. This flowchart outlines key decision points from initial suspicion through diagnostic imaging, laboratory assessment, and concurrent medical management, leading to definitive aneurysm treatment.

Clinical Example:

A 55-year-old woman presents to the emergency department 8 hours after experiencing a sudden, severe “thunderclap” headache. Her initial Glasgow Coma Scale (GCS) is 14 (E4V4M6), and she has nuchal rigidity. A non-contrast head CT is performed and is negative for subarachnoid hemorrhage. Given the persistent high suspicion and timing (>6 hours from onset), you order a lumbar puncture. The CSF analysis reveals persistently elevated red blood cell counts across all tubes and positive xanthochromia on spectrophotometry. Her coagulation panel is normal. You initiate a nicardipine infusion to maintain SBP <160 mmHg, arrange for an urgent CT Angiogram (CTA) to localize a potential aneurysm, and coordinate with the neurointerventional team for likely Digital Subtraction Angiography (DSA) and aneurysm repair.

References

Connolly ES Jr, Rabinstein AA, Carhuapoma JR, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2012;43(6):1711-1737.
Diringer MN, Bleck TP, Claude Hemphill J 3rd, et al; Neurocritical Care Society. Critical care management of patients following aneurysmal subarachnoid hemorrhage: recommendations from the Neurocritical Care Society’s Multidisciplinary Consensus Conference. Neurocrit Care. 2011;15(2):211-240.
Hunt WE, Hess RM. Surgical risk as related to time of intervention in the repair of intracranial aneurysms. J Neurosurg. 1968;28(1):14-20.
Report of World Federation of Neurological Surgeons Committee on a Universal Subarachnoid Hemorrhage Grading Scale. J Neurosurg. 1988;68(6):985-986.
Fisher CM, Kistler JP, Davis JM. Relation of cerebral vasospasm to subarachnoid hemorrhage visualized by computerized tomographic scanning. Neurosurgery. 1980;6(1):1-9.
Perry JJ, Stiell IG, Sivilotti ML, et al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study. BMJ. 2011;343:d4277.
Steiner T, Juvela S, Unterberg A, et al; European Stroke Organization. European Stroke Organization guidelines for the management of intracranial aneurysms and subarachnoid haemorrhage. Cerebrovasc Dis. 2013;35(2):93-112.
Frontera JA, Claassen J, Schmidt JM, et al. Prediction of symptomatic vasospasm after subarachnoid hemorrhage: the modified fisher scale. Neurosurgery. 2006;59(1):21-27.

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