Optimal timing to measure optic nerve sheath diameter as a prognostic predictor in post-cardiac arrest patients treated with targeted temperature management

Abstract

Aim

We evaluated the optimal timing of optic nerve sheath diameter (ONSD) measurement to predict neurologic outcome in post-cardiac arrest patients treated with target temperature management (TTM).

Methods

This was a prospective single-centre observational study from April 2018 to March 2019. Good outcome was defined as the Glasgow-Pittsburgh cerebral performance categories (CPC) 1 or 2, and poor outcome as a CPC between 3 and 5. ONSD was measured initially after return of spontaneous circulation (ROSC) (ONSD_initial), at 24 h (ONSD₂₄), 48 h (ONSD₄₈), and 72 h (ONSD₇₂) using ultrasonography. The receiver operating characteristic (ROC) curves and DeLong method were used to compare the values for predicting neurologic outcomes.

Results

Out of the 36 patients enrolled, 18 had a good outcome. ONSD₂₄, ONSD₄₈, and ONSD₇₂ were higher in the poor outcome group. The area under ROC curve of ONSD₂₄ was 0.91 (95% confidence interval 0.77–0.98) in predicting poor neurologic outcomes. With a cut off value of 4.90 mm, ONSD₂₄ had a sensitivity of 83.3% and a specificity of 94.4% in predicting poor neurologic outcomes.

Conclusion

Our findings demonstrate ONSD₂₄ as a valuable tool to predict the neurologic outcome in post-cardiac arrest patients treated with TTM. Therefore, we recommend performing ONSD measurement using ultrasonography at 24 h after ROSC, rather than immediately after ROSC, to predict neurologic outcome in post-cardiac arrest patients treated with TTM.

Introduction

Ischemia-reperfusion cerebral injury after cardiac arrest (CA) significantly contributes to mortality and may reduce the quality of life in many survivors.1, 2, 3 Brain oedema and loss of pressure reactivity are among the most serious complications following ischaemia-reperfusion cerebral injury, and are associated with poor neurologic outcome and death.4, 5, 6 Brain oedema and increased intracranial blood volume from loss of pressure reactivity can result in a harmful increase in intracranial pressure (ICP). Previous studies have shown that a higher ICP follows global cerebral ischaemia after return of spontaneous circulation (ROSC); severe blood-brain barrier (BBB) disruption began at 24 h after ROSC in the poor neurologic outcome group treated with target temperature management (TTM). In these previous studies, a higher ICP was strongly associated with and was apparently predictive of a poor outcome.7, 8

However, measuring ICP directly in CA patients is difficult and invasive; therefore, this has limited the number of studies using the direct measurement technique.⁹ Instead, previous studies have applied indirect methods such as the measurement of the optic nerve sheath diameter (ONSD). Some studies have examined the relationship between ONSD and ICP in patients with non-traumatic causes of elevated ICP. Good sensitivity has been reported for ONSD measurements in cases of idiopathic intracranial hypertension.¹⁰ Another study reported that ONSD demonstrated the best agreement to assess ICP non-invasively in patients with hypoxic brain injury after cardiac arrest and that it may help in detecting or ruling out of ICP.¹¹ Conversely, another study reported that ONSD after ROSC was not correlated with neurological outcome at 6 months in patients who underwent TTM.¹² A study that performed a meta-analysis to evaluate the diagnostic performance of ONSD in predicting neurologic outcome in post-cardiac arrest patients reported that one of the significant sources of sensitivity heterogeneity was the time of ONSD measurement after ROSC.¹³

However, to the best of our knowledge, no study has assessed the optimal timing for ONSD measurements for predicting neurologic outcomes. Therefore, in this study, we evaluated the optimal timing for ONSD measurement to predict neurologic outcomes in post-CA patients treated with TTM.