CT measurements of optic nerve sheath diameter to evaluate the outcome of acute carbon monoxide poisoning

Abstract Background Thousands of people die each year from carbon monoxide poisoning. There are no clear indicators for evaluating the outcome of carbon monoxide poisoning. We aimed to evaluate the relationship between optic nerve sheath diameter (ONSD) and ONSD/ transverse eyeball diameter ((ETD)) measured by CT and the outcome of acute carbon monoxide poisoning. Methods We retrospectively analyzed all acute carbon monoxide poisoning patients who had received CT November 2017 to July 2020. All patients underwent cranial CT examination on the day of admission, the ONSD at 3 mm behind the eyeball on CT was measured and the ONSD/ETD ratio was calculated by ETD. According to the CPC score, the patients were divided into two groups: good outcome group and poor outcome group. ROC curve was used to evaluate the diagnostic value of each index in outcome. Logistic regression analysis was used to screen the related factors affecting the outcome of patients. Results We identified 146 patients who received cranial CT as the first clinical evaluation after acute carbon monoxide poisoning, which including 108 patients with good outcome and 38 patients with poor outcome. Compared with the good outcome group, there were significant differences in ONSD, ONSO/ETD, Lactic acid, CPK, NSE, PSS and APACHEII scores between the poor outcome group and the poor outcome group. An ONSD model for predicting poor outcome was established, and the corresponding ROC curve was drawn. The area under the ROC curve (AUC) was 0.925, the best prediction probability out-off value was 0.3585, the sensitivity was 89.5%, and the specificity was 94.4%. The same method obtains the prediction model of ONSD/ETD, the AUC is 0.916, the out-off value of the best prediction probability is 0.3547, the sensitivity is 89.5%, and the specificity is 92.6%. Conclusion ONSD and ONSD/ETD are significantly related to the outcome of patients with acute carbon monoxide poisoning. The outcome is poor when ONSD > 5.68 mm or ONSD/ETD > 0.24. Measuring the diameter of optic nerve sheath by CT may be a simple and rapid method to evaluate the clinical outcome of patients with carbon monoxide poisoning.