Date: March 11th, 2021

Guest Skeptic: Dr. Robert Edmonds is an emergency physician in the US Air Force in Ohio.

DISCLAIMER: THE VIEWS AND OPINIONS OF THIS PODCAST DO NOT REPRESENT THE UNITED STATES GOVERNMENT OR THE US AIR FORCE.

Reference: Post et al. Ultra-early tranexamic acid after subarachnoid haemorrhage (ULTRA): a randomised controlled trial. Lancet 2021

Case: You’re working a busy evening shift in your community emergency department (ED) when a 58 year old female presents with a rapid onset terrible intensity headache.  She has no significant headache history and you are concerned for subarachnoid hemorrhage so you order a head CT which confirms your suspicions.  You page neurosurgery at the bigger ED in town, and while you wait for the page back, you wonder if giving tranexamic acid (TXA) could help improve the patient’s chances for a good outcome given its effects in other bleeding processes.

Background: In the case presented, the woman would qualify using the Ottawa SAH Rule because of the rapid onset of an intense headache and her age. We have discussed the incredible work done by Dr. Jeff Perry and his group in the development of the Ottawa SAH Rule. Jeff was actually on the SGEM as the guest skeptic discussing this clinical decision instrument way back in 2013 (SGEM#48).

The Ottawa SAH Rule is to be applied to alert patients older than 15 years of age with new severe non-traumatic headache reaching maximum intensity within one hour.

It is not meant for patients with new neurologic deficits, previous aneurysms, SAH, brain tumor, or who have a history of recurrent headaches. This is defined as at least three or more episodes over the course of at least six months.

Our SGEM Bottom Line eight years ago was that the Ottawa SAH “Tool” was not ready for prime time to rule out low risk patients from investigations.

Fast forward to 2018 and the validation of the Ottawa SAH Rule by Dr. Perry and his group. The results of this prospective observational study were that the clinical decision instrument was 100% sensitive (missed no SAH patients) and 13.6% specific.

The guest skeptic for SGEM#201 was Dr. Chris Carpenter, who literally wrote the book on diagnostic accuracy of clinical decision instruments in the ED with Dr. Jesse Pines. The SGEM bottom line from the episode was that the Ottawa SAH Rule needs external validation, a meaningful impact analysis performed, and patient acceptability of incorporating this rule into a shared decision-making instrument before being widely adopted.

Dr. Perry did publish a prospective implementation of the Ottawa SAH Rule (Stroke 2019). This article was covered on the SGEM with EM Nerd Dr. Rory Spiegel. The results demonstrated that the Ottawa SAH Rule is highly sensitive (100%) but has very poor specificity (13%). It is unclear how it performs against unstructured clinical judgement or in non-urban tertiary care teaching hospitals (SGEM#283).

Another issue the case brings up is whether a CT scan is good enough to rule out a SAH. The debate has historically been about whether or not you need to also get a lumbar puncture on these patients after a non-contrast CT head.