3. Subarachnoid Hemorrhage (Aneurysmal SAH)

Quick Recap

Neurology System, Protocol 3/12. Aneurysmal Subarachnoid Hemorrhage (SAH).

1. Definition & Epidemiology

SAH = bleeding into the subarachnoid space (surrounding brain/spinal cord, containing CSF). Most common cause: ruptured intracranial aneurysm. ~10-20% remain cryptogenic after full angiographic workup — many of these have a perimesencephalic pattern (localized around the brainstem, no extension into Sylvian fissures/ventricles/parenchyma), which is more benign and likely venous in origin.

SAH is only ~10% of all cerebrovascular events but affects a younger population and carries 20-30% 30-day mortality plus significant persistent disability from both the initial bleed and delayed ischemia.

Risk factors: hypertension, smoking, heavy alcohol use, polycystic kidney disease, family history of aneurysm/SAH in first-degree relatives.

Should ideally be managed at centers with both neurocritical care AND endovascular/surgical aneurysm expertise.

2. Etiology Table

3. Presentation & Diagnosis

Sudden severe "thunderclap" headache reaching maximum intensity within seconds — the classic presentation; may include transient LOC (syncope) or persistent altered consciousness/coma; meningismus often develops over hours.

Noncontrast head CT: 99% sensitive if performed within 24 hours of symptom onset.

If delayed presentation (headache >24h) OR negative CT despite high suspicion: perform lumbar puncture for RBCs and xanthochromia (yellow discoloration of centrifuged CSF from blood breakdown products) — misdiagnosis/delay places the patient at risk of aneurysmal rebleeding, making this workup step time-sensitive, not optional.

MRI is an option for thunderclap headache with delayed presentation — may reveal subacute subarachnoid bleeding missed by CT.

Confirmed SAH with initially negative angiography: repeat angiography (or CTA) in 1-3 weeks to exclude a missed aneurysm, especially if bleeding is diffuse rather than purely perimesencephalic.

4. Immediate Stabilization (ABCDE)

Airway/Breathing: secure per standard indications for depressed consciousness; watch for neurogenic pulmonary edema (Section 8).

Circulation — BP management PRIOR to definitive aneurysm treatment:

• Keep MAP <110 mmHg and/or SBP <140 mmHg to prevent further bleeding, using short-acting agents (labetalol, nicardipine), analgesics, and sedatives
• BP can be liberalized once the aneurysm is successfully secured (surgical clipping or endovascular coiling) — this pre-vs-post-securing distinction is central and easy to miss if not flagged explicitly
• Antifibrinolytics (tranexamic acid 1g IV q4-6h) may reduce rebleeding risk but have NOT demonstrated improved outcomes — consider only when there will be a significant delay from diagnosis to definitive aneurysm treatment

Disability: Hunt and Hess / WFNS grading (Section 6); urgent ventriculostomy if hydrocephalus with impaired mental status.

Checklist:

5. Rebleeding — The Dominant Early Threat

Rebleeding risk is as high as 20% in the first 24-48 hours and is (along with ventricular arrhythmias) the most common cause of early death. Early treatment of the ruptured aneurysm (surgical clipping via craniotomy OR endovascular coiling) is critical to prevent rebleeding — choice depends on patient age, clinical condition, and aneurysm anatomy/location, determined via neurosurgeon/endovascular specialist discussion.

6. Severity Grading

Hunt and Hess Grading:

WFNS Scale:

Survival is inversely proportional to grade; Grade V patients not improving with initial stabilization (including ventriculostomy if hydrocephalus present) almost invariably do poorly.

Modified Fisher Scale (CT blood grading, predicts VASOSPASM risk):

("Thick" = completely fills at least one cistern/fissure; IVH "present" = blood in both lateral ventricles.) Higher grade = greater vasospasm/delayed ischemic deficit/stroke risk — mandates closer monitoring.

7. Acute Hydrocephalus

Occurs in ~50% of patients from CSF flow obstruction — enlarged lateral ventricles (especially temporal horns) on CT; can impair mental status, requiring urgent ventriculostomy for CSF diversion.

8. Cardiopulmonary Complications (Early Brain Injury Cascade)

Aneurysmal rupture triggers a catecholamine/cytokine surge -> sympathetic hyperactivity -> cardiopulmonary dysfunction:

• ECG changes common; troponin mildly elevated in 20-30%
• ~10% develop stunned myocardium (wall motion abnormalities or globally reduced systolic function), often a Takotsubo pattern (apical akinesis/ballooning) — coronary angiography is usually unrevealing and NOT necessary in most cases; this "stress cardiomyopathy" is reversible, typically resolving in 1-2 weeks; some patients need acute inotropic support
• Pulmonary edema/hypoxemia in 10-20%, with both cardiogenic AND neurogenic origins possible
• Diffuse global cerebral edema ("early brain injury") can occur in the first few days, associated with elevated ICP and neurologic deterioration independent of vasospasm

9. Seizures

Most occur early (at ictus or pre-hospitalization, 5-10%); ~5% in-hospital risk. Despite lack of evidence for benefit, time-limited anticonvulsant prophylaxis is commonly given — either a short perioperative course (e.g., 3 days) or continued to discharge in high-risk patients (parenchymal hematoma, post-admission seizures). Levetiracetam 1000mg BID is a common regimen. Patients with poor/fluctuating responsiveness should get EEG monitoring to exclude subclinical seizures.

10. Hyponatremia

Occurs in ~30%, typically 4-10 days after admission — may reflect SIADH (euvolemic) or cerebral salt wasting (CSW, hypovolemic); distinguishing them is important but often difficult since therapy differs (water restriction for SIADH vs volume replacement for CSW).

CRITICAL RULE: total fluid restriction should NEVER be used for post-SAH hyponatremia, even if SIADH is suspected — hypovolemia elevates cerebral infarction risk in this population specifically, unlike hyponatremia management in other contexts. Since SIADH and CSW often overlap and are hard to distinguish confidently, the safer default is saline replacement (normal or hypertonic) unless hypovolemia can be confidently excluded, with modest oral fluid restriction (1-1.5 L/day) as an adjunct only. Daily serum sodium monitoring for all SAH patients; avoid hypotonic fluids; restrict diuretics (hypovolemia promotes cerebral ischemia).

Central fever is also common, may reflect SIRS, making true infection hard to distinguish/diagnose.

11. Cerebral Vasospasm & Delayed Cerebral Ischemia (DCI)

The major source of secondary disability after SAH. Angiographic vasospasm seen in a majority of SAH patients between days 4-21, peaking days 7-10; more likely with higher modified Fisher grade. Some remain asymptomatic; others develop ischemic neurologic deficits as CBF falls below ischemic thresholds — worsened by hypovolemia, hypotension, and anemia.

Prevention:

• Keep all SAH patients EUVOLEMIC (not hypervolemic) and NORMOTENSIVE (avoid BP-lowering agents once aneurysm secured)
• ALL patients should receive nimodipine 60mg enterally every 4 hours for 21 days — demonstrated efficacy for improving neurologic outcomes (mechanism is neuroprotective, NOT primarily through vasodilation); halve the dose (give every 2 hours) if BP drops after each dose, rather than stopping it entirely
• Prophylactic hypervolemia or prophylactic hypertensive therapy is NOT effective at improving cerebral perfusion or preventing vasospasm deficits — an important distinction from the TREATMENT of established symptomatic vasospasm (Section 12)
• Some centers use transcranial Doppler (TCD) surveillance — rising velocities in basal cerebral vessels suggest narrowing caliber

12. Evaluation and Treatment of Suspected DCI

Any new/worsening neurologic deficit or persistent mentation change after SAH requires prompt evaluation (not assumed to be vasospasm by default):

1. Exclude confounders first: head CT (hydrocephalus, new bleeding, edema), metabolic derangements (hyponatremia, fever, hypoxemia/hypercapnia), seizures
2. If ischemia remains suspected: initiate hemodynamic augmentation ("Triple-H" concept, though modern practice emphasizes induced HYPERTENSION more than hypervolemia/hemodilution) — fluid bolus + vasopressors titrated to raise MAP 10-15% above baseline; hemodilution generally avoided unless polycythemia present
3. Titrate to CLINICAL EFFECT (reversal of deficits), not a fixed BP number — though avoid MAP targets >130-140mmHg to prevent iatrogenic PRES
4. High-dose vasopressors may be needed; IV milrinone as an alternative/adjunct, especially with impaired cardiac function; noninvasive cardiac monitoring helpful for optimization
5. Angiography to confirm vasospasm if DCI suspected — CTA (+/- CT perfusion) as initial screen; conventional angiography allows simultaneous endovascular therapy: intra-arterial vasodilators (verapamil, nimodipine, nicardipine, milrinone) or balloon angioplasty
6. Angioplasty provides more durable vasospasm reversal than vasodilators (which typically only offer transient relief) and can improve neurologic deficits
7. Asymptomatic vasospasm (no neurologic deficit) should generally NOT be treated — continue close monitoring with euvolemia and permissive hypertension instead
8. Once clinical response to induced hypertension is achieved, maintain goal BP for 48-72 hours before cautious, gradual weaning; repeat angiogram improvement can help guide weaning timing in complex cases
9. Watch closely for hemodynamic therapy complications: pulmonary edema, arrhythmias, cardiac injury, worsening cerebral edema, hemorrhagic transformation of an established infarct, hypertensive encephalopathy

13. Consultation Matrix

14. Monitoring Framework

Frequent neuro checks (especially days 4-21 for vasospasm window), daily serum sodium, continuous cardiac monitoring, TCD surveillance if used, repeat imaging for new deficits, ICP monitoring if indicated (ventriculostomy already provides this if placed for hydrocephalus).

15. ICU Bundle Checklist (Daily)

16. Complications

Rebleeding (highest risk first 24-48h), hydrocephalus (~50%), vasospasm/DCI (peak days 7-10, major secondary disability driver), seizures, hyponatremia (SIADH/CSW), stress cardiomyopathy/pulmonary edema, global cerebral edema/early brain injury, PRES from overly aggressive induced hypertension. Prevention: prompt aneurysm securing, BP control pre-securing, nimodipine, euvolemia maintenance, avoiding fluid restriction. Rescue: angioplasty/intra-arterial vasodilators for symptomatic vasospasm, ventriculostomy for hydrocephalus, inotropic support for stress cardiomyopathy.

17. Escalation & De-escalation

Escalate: new/worsening deficit -> confounder workup -> hemodynamic augmentation -> angiography +/- endovascular vasospasm therapy if confirmed and symptomatic.

De-escalate: aneurysm secured, past the vasospasm window (day 21+) without DCI, sodium stable, no hydrocephalus -> liberalize BP fully, wean induced hypertension per the 48-72h maintenance/gradual weaning protocol if it was used, transition to standard ward monitoring.

18. ICU Discharge Criteria

Aneurysm definitively secured, past or safely through the high-risk vasospasm window, sodium stable, hydrocephalus resolved or shunt-managed, no active cardiopulmonary complications, neurologic status stable/at post-injury baseline, rehabilitation planning underway.

19. Documentation & Medicolegal Checklist

20. Key Guidelines

Connolly ES Jr, Rabinstein AA, Carhuapoma JR, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage. Stroke. 2012;43:1711-1737 (AHA/ASA); Diringer MN, Bleck TP, Hemphill CJ, et al. Critical care management of patients following aneurysmal SAH: Neurocritical Care Society multidisciplinary consensus conference recommendations. Neurocrit Care. 2011;15:211-240.

21. Controversies

The classic "Triple-H therapy" (hypervolemia, hypertension, hemodilution) has been substantially revised in modern practice — hypervolemia and hemodilution components are now largely de-emphasized/avoided (euvolemia preferred, hemodilution avoided absent polycythemia) in favor of induced hypertension alone, though the "Triple-H" terminology persists in some references and can be misleading if taken literally. Nimodipine's mechanism of benefit (neuroprotective vs vasodilatory) remains debated despite its consistent efficacy signal. Optimal timing/threshold for angioplasty vs intra-arterial vasodilator-first approach in symptomatic vasospasm varies by institutional endovascular expertise.

22. References

1. Dhar R. Aneurysmal Subarachnoid Hemorrhage. Washington Manual of Critical Care, 4th ed, 2025 (Ch. 56).
2. Connolly ES Jr, Rabinstein AA, Carhuapoma JR, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage. Stroke. 2012;43:1711-1737.
3. Diringer MN, Bleck TP, Hemphill CJ, et al. Critical care management of patients following aneurysmal subarachnoid hemorrhage. Neurocrit Care. 2011;15:211-240.
4. Keyrouz SG, Diringer MN. Clinical review: prevention and therapy of vasospasm in subarachnoid hemorrhage. Crit Care. 2007;11:220.
5. Suarez JI, Tarr RW, Selman WR. Aneurysmal subarachnoid hemorrhage. N Engl J Med. 2006;354:387-396.