SGEM#283: Can You Be Absolutely Right in Diagnosing a SAH Using a Clinical Decision Instrument?

Date: January 29th, 2020 Reference: Perry et al. Prospective Implementation of the Ottawa Subarachnoid Hemorrhage Rule and 6-Hour Computed Tomography Rule. Stroke 2019 Guest Skeptic: Dr. Rory Spiegel is an EM/CC doctor who splits his time in the Emergency Department and Critical Care department. He also has this amazing #FOAMed blog called EM Nerd. Case: A 48-year-old male presents to your emergency department with a sudden onset headache, which started about one-hour prior to arrival. The headache is severe is quality and the patient does not have a history of similar headaches in the past. It is associated with nausea, vomiting and photophobia.  Background: Headaches are a common complaint presenting to the emergency department.  Subarachnoid hemorrhage represents one of the most serious underlying causes of headaches and we have covered it a number of times on the SGEM: SGEM#48: Thunderstruck – Subarachnoid Hemorrhage SGEM#134: Listen, to what the British Doctors Say about LPs post CT for SAH SGEM#140: CT Scans to Rule Out Subarachnoid Hemorrhages in A Non-Academic Setting SGEM#201: It’s in the Way That You Use It – Ottawa SAH Tool In patients who present neurologically intact making the diagnosis early is key to preventing subsequent more life-threatening bleeding. A number of controversies surround the diagnosis of SAH in the emergency department. Two of the more provocative are the use of the Ottawa SAH Rule and whether a lumbar puncture (LP) is required following a negative CT if the scan is performed within 6-hours of symptom onset. The Ottawa SAH Rule (tool) was covered on SGEM#201. The bottom line from that study was that the clinical decision instrument needed external validation, a meaningful impact analysis performed and patient acceptability of incorporating this rule into a shared decision-making instrument before being widely adopted. We were surprised that in their background/introduction material they did not include the excellent SRMA on this topic by Carpenter et al. AEM 2016. Clinical Question: What is the clinical impact of the Ottawa SAH Rule and the 6-hour CT Rule compared to standard care when implemented in six emergency departments across Canada? Reference: Perry et al. Prospective Implementation of the Ottawa Subarachnoid Hemorrhage Rule and 6-Hour Computed Tomography Rule. Stroke 2019 The senior author on this publication was the legend of emergency medicine, Dr. Ian Stiell from Ottawa. Population: Neurologically intact adult presenting to the ED with a chief complaint of a nontraumatic, acute headache, or syncope associated with a headache. Exclusions: Patients with any of the following: 3 or more previous similar headaches (ie, same intensity/character as their current headache) over a period of >6 months (eg, established migraines) confirmed SAH before arrival at study ED previously investigated with CT and LP for the same headache papilledema new focal neurological deficit previous diagnosis of intracranial aneurysm or SAH known brain neoplasm cerebroventricular shunt headache within 72 hours following a LP headache described as gradual or peak intensity beyond 1 hour. Intervention: Physicians were actively encouraged to use the Ottawa SAH Rule and the 6-hour-CT Ruleto determine when to undergoing diagnostic workups for SAH and when a CT alone with an appropriate workup. Clinicians had the option to override the proposed rules. Comparison: The control phase was standard care. Clinicians were encouraged to not use any clinical decision instrument and make the decision to pursue diagnostic studies based on their own clinical discretion. Outcome: The primary outcome was the clinical impact of the Ottawa SAH Rule and 6-hr CT Rule for making the diagnosis of a SAH compared to usual care. SAH was defined as: Subarachnoid blood on CT Xanthochromia in the cerebrospinal fluid