Relationship between optic nerve sheath diameter measured by magnetic resonance imaging, intracranial pressure, and neurological outcome in cardiac arrest survivors who underwent targeted temperature management.

Aim: Studies on the prognostic performance of optic nerve sheath diameter (ONSD) in out-of-hospital cardiac arrest survivors (OHCA) have reported conflicting results. We aimed to investigate the usefulness of ONSD measured using magnetic resonance imaging (MRI) to estimate its association with intracranial pressure (ICP) and 6-month neurological outcomes in CA survivors treated with targeted temperature management (TTM).

Method: This retrospective study included 37 CA survivors who underwent TTM from January 2018 to December 2018. ICP was measured by lumbar catheter during TTM on Days 0, 1, 2, and 3. ONSD was measured using MRI on Days 0 and 3. The primary outcome was the correlation between ONSD and ICP associated with neurological outcomes obtained after 6 months.

Results: The median (interquartile range [IQR]) ONSD was not significantly different between the good and poor neurological outcome group on Day 0 (5.2 mm [4.8-5.8] vs 5.2 mm [4.8-5.6]; p = 0.948) and Day 3 (5.0 mm [4.8-5.2] vs 5.5 mm [4.4-5.9]; p = 0.105). ONSD and ICP had excellent correlation on Day 3 (r = 0.90, p < 0.001). ONSD showed excellent correlation with increased ICP (IICP) defined as ICP above 20 mmHg (r = 0.89, p < 0.001). ONSD cut-off of 5.99 mm was used with a sensitivity of 90.0% and specificity of 98.0% to identify IICP.

Conclusion: The ONSD on Days 0 or 3 did not show differences in neurological outcomes in OHCA patients treated with TTM. However, ONSD had an excellent correlation with ICP on Day 3 and with IICP. Further studies are required to confirm our results.