Algorithm Allows Paramedics to Predict Brain Damage Risk After Cardiac Arrest

Out-of-hospital cardiac arrest carries a high risk of death, with survival rates below 10%. Even when the heart is restarted, clinicians often face uncertainty about the extent of brain injury. Researchers have now shown that a widely used hospital-based risk score can be applied in the field, allowing paramedics to assess brain injury risk earlier and guide immediate treatment decisions.

In a new collaborative study, researchers at King’s College London (London, UK) evaluated whether the MIRACLE2 score, originally designed for hospital use, could be adapted for pre-hospital assessment following cardiac arrest. The MIRACLE2 score was developed to predict neurological outcomes 30 days after out-of-hospital cardiac arrest. Until now, it has only been used once patients reach the hospital.

In the RAPID-MIRACLE trial, researchers tested whether the score could be calculated immediately after return of spontaneous circulation in the pre-hospital setting. Patients were followed from paramedic care through to hospital treatment across multiple London sites, providing real-world evidence of the tool’s performance outside hospital environments.

Two versions of the score were evaluated. One version included a blood test, while the other relied solely on clinical data. Although the blood test version showed high accuracy, it proved impractical in emergency settings due to time constraints and technical challenges. The findings, published in European Heart Journal – Acute Cardiovascular Care, show that the simplified version, known as Pre-MIRACLE2, achieved nearly identical accuracy without requiring blood testing.

Applying the MIRACLE2 score in the pre-hospital setting could significantly improve early decision-making in emergency care. By identifying patients at higher risk of severe brain injury, paramedics may be able to prioritize direct transfer to specialist cardiac centers rather than local emergency departments. This approach could ensure faster access to advanced treatments and improve patient outcomes, while also helping healthcare systems allocate resources more effectively.

To support clinical use, the MIRACLE2 mobile application has been updated to include the validated pre-hospital model. The app allows paramedics and clinicians to quickly calculate risk scores using patient data such as age, heart rhythm, and other clinical indicators. The research team is now working with emergency medical services to explore how the tool can be integrated into routine practice and assess its impact on patient care pathways.

“While MIRACLE² has supported early in-hospital risk stratification following out-of-hospital cardiac arrest, RAPID-MIRACLE extends this work into the pre-hospital setting, enabling paramedics to assess risk earlier in a patient’s care pathway,” said Dr. Nilesh Pareek, senior author of the study. “By validating the model in the field, we have taken an important step towards integrating earlier risk assessment into routine emergency care.”

Related Links:
King’s College London