Ottawa Rules for Subarachnoid Hemmorhage (SAH)
Background
- Headache is a common reason for ER visits
- 1-3% of headaches are SAH
- Misdiagnosis of SAH can be fatal
- Lumbar puncture can be a painful/time-consuming procedure
- Goal is to design a decision rule to help guide the clinician
Design
- Multi-center study at ten Canadian emergency departments.
- 2131 adults with a headache peaking within 1 hour and no neurologic deficits
- Non-traumatic headaches only; GCS of 15 required
- SAH defined as: 1. CT evidence of SAH; 2. Xanthochromia in CSF; or 3. RBCs in the final tube of CSF, WITH positive angiography findings.
Results
132 (6.2%) had SAH
Decision rule including any:
- age 40 years or older
- neck pain or stiffness
- witnessed LOC
- onset during exertion
Had 98.5% sensitivity (95% CI, 94.6%-99.6%) and 27.5% specificity (95% CI, 25.6%-29.5%)
Adding “thunder-clap” headache and “limited neck flexion on examination” (inability to touch chin to chest or raise the head 8cm off the bed if supine) resulted in 100% (95% CI, 97.2%-100%) sensitivity.
The rule was then evaluated using a bootstrap analysis on old cohort data to validate the rule.
Conclusion/Limitations
- Exciting new rule for SAH that needs to be validated in a new, independent cohort
- The rule may not decrease the rate of investigation (CT, LP, or both)
- It may decrease the amount of SAH that are missed on first visit to the ER
- Limited by narrow criteria for inclusion in the rule/not meant for other causes of headache
- See the JAMA editorial with the article for a nice discussion of the difficulties with decision making rules.
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The rule:
The Ottawa SAH Rule
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For alert patients older than 15 y with new severe nontraumatic headache reaching maximum intensity within 1 h
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Not for patients with new neurologic deficits, previous aneurysms, SAH, brain tumors, or history of recurrent headaches (≥3 episodes over the course of ≥6 mo)
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Investigate if ≥1 high-risk variables present:
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Age ≥40 y
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Neck pain or stiffness
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Witnessed loss of consciousness
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Onset during exertion
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Thunderclap headache (instantly peaking pain)
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Limited neck flexion on examination
References
Clinical Decision Rules to Rule Out Subarachnoid Hemorrhage for Acute Headache
Jeffrey J. Perry, MD, MSc1; Ian G. Stiell, MD, MSc1; Marco L. A. Sivilotti, MD, MSc5,6; Michael J. Bullard, MD11; Corinne M. Hohl, MD, MHSc7; Jane Sutherland, MEd4; Marcel Émond, MD, MSc8; Andrew Worster, MD9; Jacques S. Lee, MD, MSc10; Duncan Mackey, MD11; Merril Pauls, MD12; Howard Lesiuk, MD3; Cheryl Symington, RN, ENCC1; George A. Wells, PhD2
[+-] Author Affiliations JAMA. 2013;310(12):1248-1255. doi:10.1001/jama.2013.278018.
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