In this episode of the St Emlyn's podcast, Iain Beardsell is joined by Dan Horner, a consultant in Emergency Medicine and Neurocritical Care, and Tom Roberts, an Emergency Medicine Registrar and clinical lecturer, to discuss their recently published SHED study on subarachnoid haemorrhage in the Emergency Department (ED). This landmark study, published in the Emergency Medicine Journal, explores the safety of CT scans in diagnosing subarachnoid haemorrhage up to 24 hours after headache onset and evaluates the role of further investigations like a lumbar puncture.

The study examines acute severe headache presentations in the ED and the diagnostic approach to ruling out subarachnoid haemorrhage, a critical and often feared diagnosis among emergency physicians. Conducted through the Trainee Emergency Research Network (TURN), the study included over 3,600 patients from 88 UK EDs with acute severe headaches reaching maximum intensity within one hour and no focal neurology. Data collection included CT scans, lumbar puncture results, and 28-day follow-up to identify missed cases of subarachnoid hemorrhage.

Key findings from the study revealed a 6.5% prevalence of subarachnoid haemorrhage, with a significant number presenting within six hours of headache onset. The sensitivity of CT scans remained high beyond the traditional six-hour window, suggesting that CT alone could safely rule out subarachnoid haemorrhage up to 18 hours in many cases, potentially reducing the need for lumbar puncture. The risk of missing an aneurysmal subarachnoid haemorrhage after a negative CT was found to be extremely low, around 1 in 1,000.

These findings challenge the routine use of lumbar puncture in patients presenting beyond six hours if the CT scan is negative, potentially changing ED practice and reducing unnecessary invasive procedures. The discussion also emphasized the importance of shared decision-making and recognizing that diagnostic testing is about managing probabilities, not certainties. For clinicians, the episode highlights the need to expedite CT scans for patients with acute severe headaches, especially those presenting within 10 minutes of onset, as they are more likely to have significant pathology. Emergency physicians are encouraged to own the decision-making process for ruling out serious causes of headaches and not defer solely to 'specialists'.

The SHED study supports extending the diagnostic window for CT scans in ruling out subarachnoid hemorrhage up to 18 hours, reducing the need for lumbar puncture in many cases. This data empowers emergency clinicians to make informed decisions, manage patient expectations, and streamline ED processes. 

For more information, listeners are encouraged to read the SHED Study in the Emergency Medicine Journal and explore the related blog post on the St Emlyn’s website. Emergency clinicians are also invited to connect with TERN to get involved in future research opportunities. 

This episode provides valuable insights for clinicians in managing acute severe headaches, emphasizing a more nuanced approach to subarachnoid hemorrhage diagnosis and the importance of clinical decision-making in the ED.