Tom Roberts, an Emergency Medicine Registrar and collaborator on the SHED study, dives into the critical world of subarachnoid hemorrhage diagnosis. He discusses how non-invasive blood pressure readings can mislead in pre-hospital settings, raising important clinical questions. The conversation also explores the SHED study's findings on CT scan accuracy for SAH detection and the vital role of naloxone in improving outcomes during out-of-hospital cardiac arrests. It's a captivating blend of research insights and practical implications for emergency medicine.
Non-invasive blood pressure readings can often mislead clinicians in critically ill patients, necessitating cautious interpretation and possible invasive monitoring.
The SHED study emphasizes the importance of timely CT imaging for accurately diagnosing subarachnoid hemorrhage, particularly within the first six hours of symptom onset.
Deep dives
Non-Invasive vs. Arterial Blood Pressure Monitoring
The accuracy of non-invasive blood pressure measurements compared to invasive arterial pressure monitoring in critically ill pre-hospital patients is examined, highlighting the limitations of the former. A study involving nearly 2,400 paired measurements from 220 patients found that non-invasive systolic blood pressure readings aligned with invasive measurements only 64% of the time. The study found that non-invasive methods tend to overestimate systolic and mean arterial pressures during hypotensive events and underestimate them during hypertensive episodes. Consequently, the study emphasizes the need for clinicians to interpret non-invasive readings cautiously and consider invasive monitoring when appropriate.
Subarachnoid Hemorrhage (SAH) Diagnostics
The significance of timely imaging in diagnosing subarachnoid hemorrhage (SAH) in patients presenting with acute headache is explored through the SHED study, which involved over 3,600 patients across 88 emergency departments. Results indicated that CT scans performed within six hours of headache onset have a sensitivity of 97% for detecting SAH, while this sensitivity diminishes to 75% beyond 18 hours. The study also revealed that 56% of SAH cases were aneurysmal, underscoring the necessity for rapid diagnosis to prevent serious complications. Post-test probabilities were calculated, showing a low risk of SAH when CTs were negative, assisting clinicians in better communicating risks to patients.
Impact of Early Naloxone in Cardiac Arrests
The potential benefits of administering early naloxone during non-shockable out-of-hospital cardiac arrests are analyzed, indicating improved outcomes when naloxone is given before vascular access. In a review of over 1,800 cases, patients who received naloxone early had significantly higher rates of return of spontaneous circulation (ROSC) and survival to discharge. While these findings suggest a promising role for naloxone in opioid-induced cardiac arrest, the study's retrospective nature raises concerns about selection bias and unmeasured confounders. The authors advocate for further prospective studies to fully validate naloxone's efficacy in resuscitation guidelines.
Clinical Implications and Considerations
The discussions throughout the episode bring to light important clinical considerations regarding blood pressure monitoring, SAH diagnostics, and the use of naloxone in cardiac arrest scenarios. In the context of blood pressure, practitioners must navigate the balance between relying on potentially flawed non-invasive readings and the invasiveness of arterial monitoring. The findings on SAH highlight the critical timeline for effective imaging and the challenges presented in ongoing headache cases. Finally, the emerging evidence surrounding early naloxone administration prompts a reassessment of established protocols, suggesting that evolving knowledge could reshape emergency care practices.
Welcome back to October's Papers of the Month. We've been really spoilt with three fantastic papers to discuss this month!
First up we take a look at the accuracy of non-invasive blood pressure readings in critically unwell patients in the prehospital environment and see how they could falsely reassure in both hypotension and hypertension.
Next up we take a look at the superb SHED study, which looks to evaluate the accuracy of a plain CT head in identifying subarachnoid haemorrhage at different time frames. Currently NICE recommend an LP after a negative scan if the scan was performed more than 6 hours from onset. But what does this significant dataset show and importantly how likely are you to 'miss' an aneurysmal subarachnoid haemorrhage if scanned within the first 24 hours and not following up with an LP?
Lastly we look at a paper that highlight the potential benefit of naloxone in out of hospital cardiac arrest in opioid overdose. This delves into priorities in resuscitation, the fundamentals and some possible unexpected physiological effects from naloxone.
Once again we’d love to hear any thoughts or feedback either on the website or via X @TheResusRoom!
Simon & Rob
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