Blood Biomarker Improves Early Brain Injury Prognosis After Cardiac Arrest

After a cardiac arrest, many patients remain unconscious for days, leaving doctors and families facing uncertainty about whether meaningful recovery is possible. Current tools to assess brain damage, including neurological exams and imaging, often provide limited or delayed answers. This makes decisions about continuing or withdrawing intensive care extremely difficult. Now, new research shows that a blood-based biomarker can give a far more reliable and earlier picture of brain injury and long-term outcome after cardiac arrest.

In the study led by Lund University (Lund, Sweden) as part of a large international collaboration across Europe, researchers focused on identifying blood biomarkers that reflect the extent of brain damage in patients admitted unconscious to intensive care after out-of-hospital cardiac arrest. The prospective multicenter study included 819 adult patients treated at 24 hospitals in Europe. Blood samples were collected at 0, 24, 48, and 72 hours after hospital admission.

Four biomarkers linked to brain injury were analyzed and compared using a standardized clinical testing approach. The goal was to determine which marker most accurately predicts survival and neurological recovery. Researchers found that two biomarkers commonly used in clinical practice, neuron-specific enolase and S-100 protein, had clear limitations in predicting outcomes after cardiac arrest.

By contrast, neurofilament light (NFL) correctly identified 92% of patient outcomes at six months. Another biomarker, GFAP, also outperformed those currently used in routine care. NFL stood out for its ability to distinguish between severe and mild brain damage as early as 24 hours after cardiac arrest. NFL’s stability in blood and early predictive power make it a strong candidate for improving prognostic accuracy in intensive care.

While the biomarker cannot be used alone to decide whether to stop life-sustaining treatment, it provides critical information when combined with imaging and brain activity tests. Researchers believe this approach could lead to more consistent and reliable decision-making worldwide. The findings, published in The Lancet Respiratory Medicine, could influence future clinical guidelines and improve communication with families during the most critical phase of care after cardiac arrest.

“All those admitted to intensive care after cardiac arrest are unconscious and there is always uncertainty about how long this care is to continue,” said Professor Niklas Nielsen, who led the study. “If the blood test shows that the chances are not exhausted it’s reasonable to continue intensive care. But if it’s clear there are no conditions for survival with a functional status associated with a good life, transition to a palliative phase could be considered.”

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