Neuro Pro-Tips with Andy Perron: SAH

Subarachnoid hemorrhage is a high-stakes cause of thunderclap headache, with roughly two-thirds of patients dying or suffering major neurologic disability. Noncontrast head CT is strongest early, but the real bedside challenge is what to do after a negative scan when suspicion remains high.

SAH Diagnosis and Risk Stratification

• High-risk headache features: Sudden crescendo headache, exertional onset, anticoagulant use, heavy smoking, binge drinking, and a first-degree family history of SAH all raise pretest probability and should sharpen your workup.
• Early head CT performance: Noncontrast head CT obtained within 6 hours is highly sensitive for SAH, but the quoted 97% to 100% range matters when you are deciding whether a negative scan is enough.
• All-or-none workup mindset: A useful framing is to decide whether you are truly worried about SAH before ordering tests, because symptom improvement after treatment does not meaningfully lower the chance of a bleed. That bedside stance is worth hearing in the episode.
• CTA versus LP distinction: CTA looks for aneurysm anatomy, while lumbar puncture looks for evidence that an aneurysm has leaked; a negative CTA alone cannot definitively exclude SAH.
• Guideline disagreement after CT: ACEP allows CTA or LP after a negative CT in selected patients, while AHA leans toward LP when suspicion stays high, especially with neurologic deficits or delayed presentation.

Lumbar Puncture and SAH Management

• Traumatic tap reality: About 15% to 20% of lumbar punctures are uninterpretable, so the downstream value of LP depends heavily on procedural quality and how confidently the results can be read.
• Tube four red cells: Less than 500 RBCs in tube 4 strongly argues against SAH, while more than 10,000 is highly concerning for true hemorrhage rather than a traumatic tap.
• Xanthochromia value add: Borderline CSF red cell counts become more useful when paired with xanthochromia, and the chapter gets into how that combination changes confidence after a negative CT.
• Blood pressure target: For confirmed SAH, a systolic blood pressure goal around 160 to 180 mmHg is a reasonable AHA-aligned target while definitive neurosurgical care is being arranged.
• Seizure treatment choices: Routine prophylactic antiseizure therapy is not recommended, and phenytoin or fosphenytoin are best avoided; levetiracetam or valproate are the preferred agents when seizures occur.
• Selective airway planning: Prophylactic intubation is not automatic in SAH; transport time, risk of deterioration, and local resources matter more than a one-size-fits-all rule. We walk through that judgment call in the episode.

References:

1. Perry JJ, Stiell IG, Sivilotti ML, et al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study. BMJ. 2011;343:d4277. Published 2011 Jul 18. PMID: 21768192
2. Hoh BL, et al. 2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage: A Guideline From the American Heart Association/American Stroke Association. Stroke. 2023;54(7):e314-e370. PMID: 37212182
3. Carpenter CR, et al. Spontaneous Subarachnoid Hemorrhage: A Systematic Review and Meta-analysis Describing the Diagnostic Accuracy of History, Physical Examination, Imaging, and Lumbar Puncture With an Exploration of Test Thresholds. Acad Emerg Med. 2016;23(9):963-1003. PMID: 27306497
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5. Perry JJ,  et al. Differentiation between traumatic tap and aneurysmal subarachnoid hemorrhage: prospective cohort study. BMJ. 2015;350:h568. Published 2015 Feb 18. PMID: 25694274
6. Gorchynski J, et al. Interpretation of traumatic lumbar punctures in the setting of possible subarachnoid hemorrhage: who can be safely discharged?. Cal J Emerg Med. 2007;8(1):3-7.PMID: 20440386
7. American College of Emergency Physicians Clinical Policies Subcommittee (Writing Committee) on Acute Headache:, Godwin SA, Cherkas DS, et al. Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department With Acute Headache. Ann Emerg Med. 2019;74(4):e41-e74. PMID: 31543134
8. Connolly ES Jr, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/american Stroke Association. Stroke. 2012;43(6):1711-1737. PMID: 22556195
9. Steiner T, et al. European Stroke Organization guidelines for the management of intracranial aneurysms and subarachnoid haemorrhage. Cerebrovasc Dis. 2013;35(2):93-112. PMID: 23406828
10. Gottlieb M, Morgenstern J. Lumbar Puncture Should Not Be Routinely Performed For Subarachnoid Hemorrhage After A Negative Head Ct. Ann Emerg Med. 2021;77(6):643-645. PMID: 34030777