What is the mortality rate for a patient with subarachnoid hemorrhage (SAH)?

Subarachnoid Hemorrhage Mortality

The 30-day mortality rate for subarachnoid hemorrhage is 45% in population-based studies, with the majority of deaths occurring in the first days after the initial bleed. 1, 2

Overall Mortality Statistics

• In-hospital mortality ranges from 33% to 39% depending on hospital volume and patient characteristics 1, 2
• Approximately 12% of patients die before receiving any medical attention, underscoring the catastrophic nature of the initial hemorrhage 2
• The overall case fatality rate approaches 50% when pre-hospital deaths are included 2
• Modern studies suggest mortality may be declining slightly compared to historical rates, though SAH remains highly lethal 1

Primary Causes of Death

The mortality from SAH can be attributed to four roughly equal contributors:

• Direct effects of the initial hemorrhage: 19-23% of deaths 2
• Rebleeding: 22-23% of deaths, with a devastating 70% case fatality rate for patients who experience rebleeding 1, 2, 3
• Delayed cerebral ischemia/vasospasm: 23% of deaths 4
• Medical (non-neurologic) complications: 23% of deaths, with pulmonary complications being the most common cause 4

Critical Time-Dependent Mortality Risk

The risk of ultra-early rebleeding within the first 24 hours is approximately 15%, considerably higher than previously recognized 2, 3:

• 70% of ultra-early rebleeds occur within 2 hours of the initial SAH 1, 2, 3
• Rebleeding risk is maximal at 4% on day one, then continues at 1-2% per day over the subsequent 4 weeks 1, 2, 3
• This ultra-early rebleeding window represents the most critical and treatable cause of preventable mortality 1

Hospital Volume Impact on Mortality

Treatment at high-volume centers significantly reduces mortality:

• Low-volume hospitals (<10 SAH patients annually): 39-49% mortality 1, 2
• High-volume hospitals (>35 patients annually): 27-32% mortality 1, 2
• This represents a 16-22% absolute mortality reduction at high-volume centers 1, 2
• High-volume centers demonstrate greater use of endovascular services and multidisciplinary neurointensive care 1

Key Prognostic Factors Determining Mortality

Clinical grade on admission is the single most important predictor of outcome 1, 2:

• Worse neurological status (higher Hunt-Hess grade) strongly predicts mortality 1, 2
• Age, with younger patients having better outcomes but still elevated standardized mortality ratios of 2.1-3.7 for those aged 50-65 years 5
• Medical comorbidities including hypertension, atrial fibrillation, heart failure, coronary disease, and renal disease 1
• Time to treatment, with delays increasing rebleeding risk 1

Long-Term Mortality Beyond Acute Phase

For patients surviving the initial 3 months, excess mortality persists 5:

• 12.9% cumulative mortality within 5 years 5
• 23.6% cumulative mortality within 10 years 5
• 35.4% cumulative mortality within 15 years 5
• Standardized mortality ratio of 1.61 for all-cause death compared to general population 5

Common Pitfalls in Understanding SAH Mortality

Do not underestimate the contribution of medical complications - they account for 23% of deaths, equal to rebleeding or vasospasm individually, with pulmonary edema being the most lethal 4. Cardiac arrhythmias occur in 30% of patients but rarely cause death directly 4.

Do not assume modern mortality rates are substantially improved - despite advances in neurocritical care and endovascular techniques, 30-day mortality remains 40-45% in most contemporary series 1, 2, 6. Only about 30% of patients recover sufficiently to return to independent living 7.

Recognize that only 29-34% of all SAH patients admitted to hospitals actually receive definitive aneurysm treatment, suggesting many die or are deemed too poor grade for intervention 1.