Prior studies have shown that sentinel bleeds lead to worse outcomes if missed and subsequent aneurysmal subarachnoid hemorrhage (SAH) occurs, but this Kaiser Permanente case-control study suggests this may be a myth.
Why does this matter?
Because current testing thresholds to do LP after negative CT are based on decision analyses that factor in poorer Quality of Life scores for missed sentinel bleeds. Perhaps, future analyses looking at this contemporary data will come to different conclusions regarding when to LP after negative CT for possible SAH.
Sentinel bleeds are bad, right?
This was a case-control study from the Kaiser Permanente (KP) health system that found 450 SAH patients in a 6.5 year period, 46 (10%) of which had a visit for headache or neck pain within 14 days of the date of SAH diagnosis. These 46 are the "cases"; the rest are the "controls." They found no increased risk of death or adverse neurological outcome in the cases vs controls. This was despite the finding that cases had increased risk of delayed vasospasm. In fact, unadjusted results showed cases were protected from adverse outcome, though this did not remain significant after adjustment for confounders. Results were unchanged despite doing multiple sensitivity analyses. They also checked records outside the KP system. The gist is that they found patients presenting with headache within 2 weeks of SAH diagnosis (possible "sentinel bleeds") were no worse off than patients who did not. Of course, this was retrospective, as case-controls must be, so potential bias or confounding could have come into play.
Outcomes following possible undiagnosed aneurysmal subarachnoid hemorrhage: a contemporary analysis. Acad Emerg Med. 2017 Jul 4. doi: 10.1111/acem.13252. [Epub ahead of print]
Peer reviewed by Thomas Davis, MD.