Optic nerve sheath diameter on computed tomography not predictive of neurological status post-cardiac arrest

Objective: Optic nerve sheath diameter (ONSD) measured on a head computed tomography (CT) has been suggested as a potential prognostic factor for poor neurological outcome after cardiac arrest. We performed a single centre retrospective cohort analysis to further investigate this relationship. Methods: All patients >18 years of age admitted to St. Paul's Hospital in Vancouver, Canada who survived a cardiac arrest and had a CT scan of the head within 48 hours were included in the analysis. Results: A total of 72 patients met inclusion criteria for the study; 54 (75.0%) of the patients had a poor neurological outcome, whereas 18 (25.0%) patients were discharged from the hospital with a good outcome. A CT head was obtained for patients in the good outcome group in a mean time of 9.3 hours (SD 10.0) compared to 10.2 hours (SD 11.2) for the poor outcome group (p = 0.75). There was no difference in average ONSD observed between the two outcome groups (6.66mm SD 0.78 v. 6.60mm SD 0.82, p = 0.77). Multiple logistic regression failed to show any association between ONSD and neurological outcome when adjusted for all other covariates (OR 1.32 95% CI 0.40-4.34, p = 0.65). Setting an ONSD threshold of >8mm (OR 2.32, 95% CI 0.14-39.40, p = 0.55) or >7mm (OR 0.28, 95% CI 0.03-2.77, p = 0.28) also failed to show any association on neurological outcome. Conclusion: There was no observed difference in ONSD between those with a good neurological outcome and those with a poor outcome. ONSD was not an independent predictor of poor neurological outcome.