Ottawa Subarachnoid Hemorrhage (SAH) Rule
For alert patients with non-traumatic headache reaching maximum intensity within 1 hour: check high-risk features.
Calculator
How it works
The Ottawa SAH Rule identifies non-traumatic headache patients in whom SAH was very unlikely when all criteria were absent in derivation studies.
Limits
Applies only to defined inclusion (e.g., GCS 15, onset <1 week); excludes trauma, prior SAH, recurrent headaches, papilledema, focal deficits, anticoagulation, etc.—see original rule.
Educational tool only—not for diagnosis or treatment decisions.