decision rule for subarachnoid hemorrhage?

THOSE CANADIANS ARE AT IT AGAIN:
--study by Ottawa docs, Perry et al. reviewed nicely in an AAEM/Common Sense article (see reference)
--tried to identify a set of clinical characteristics to make a decision rule for those who need SAH workup


BASIC STRUCTURE:
--1,999 patients, 130 diagnosed with SAH
--SAH diagnosis defined by +CT, xanthrochromia, or >5 x 10^6/L RBCs + aneurysm/AVM on cerebral angiography

--included:

• adults (>16 yo)
• chief complaint = headache
• GCS 15
• non-traumatic
• peak intensity of HA within 1 hr

--excluded:

• >2 wks after symptom onset
• prior SAH
• previous CT and/or LP workup
• 3 similar HA's within past six months
• papilledema/focal neuro symptom
• prior hydrocephalus or cerebral neoplasm

RULES THEY CAME UP WITH:
--all have sensitivity 100%, but specificity sucked (28-39%)

--the rules (each set works to help rule-out SAH):

• age >40, neck pain/stiffness, witnessed LOC, DBP > 100mmHg
• arrival by EMS, age>45, vomiting, DBP > 100
• arrival by EMS, age 45-55, neck pain/stiffness, SBP > 160

BOTTOM LINE:
--nice study, helps think about why we do what we do, but isolated population
--the extra H&P details (age, BP, vomiting, neck pain/stiffness, etc.) are not very specific for SAH, but together might be sensitive (reminds me of appendicitis)
--not ready for primetime just yet, but food for thought


Submitted by S. Lee.


Reference(s): AAEM/RSA review, picture