Sonographic Optic Nerve Sheath Diameter: A Simple and Rapid Tool to Assess the Neurologic Prognosis After Cardiac Arrest

BACKGROUND AND PURPOSE The early prediction of hypoxic encephalopathy after cardiac arrest is challenging. Measurement of the optic nerve sheath diameter (ONSD) by using sonography is a straightforward, noninvasive technique to detect an increased intracranial pressure, which can even be conducted at the bedside. However, it remains unknown whether or not sonographic ONSD measurement is valuable as a prognostic indicator of hypoxic encephalopathy. METHODS Seventeen patients after cardiac arrest were retrospectively enrolled in this study. ONSD measurements 3 mm behind the papilla were recorded. A Glasgow Outcome Scale score of 4 or above was considered to indicate a favorable prognosis. RESULTS The mean ONSD associated with a favorable prognosis was 5.0 mm (4.4‐6.1 mm). The ONSD associated with a poor prognosis was 6.1 mm (5.4‐7.2 mm). ONSD less than or equal to 5.4 mm was an indicator of a favorable prognosis, with a sensitivity of 83%, specificity of 73%, positive likelihood ratio of 3.1, and negative likelihood ratio of .23. CONCLUSIONS Sonographic ONSD measurement is a simple, rapid technique to assess the neurological prognosis after cardiac arrest.