Clinical paperThe optic nerve sheath diameter as a useful tool for early prediction of outcome after cardiac arrest: A prospective pilot study☆
Introduction
In resuscitated cardiac arrest (CA) patients, early prognostication within the first days after admission in the intensive care unit (ICU) remains difficult, especially among patients treated with therapeutic hypothermia (TH). Clinical examination, neurological biomarkers, and electrophysiological evaluations can be used, mainly in combination.1, 2, 3 The out-of-hospital cardiac arrest (OHCA) score has also been used to predict outcome.4 According to recent guidelines, a multimodal neuroprognostication approach is recommended, but no specific combination of predictors is sufficiently supported by available evidence.1, 5
In CA as in traumatic brain injury (TBI), anoxic and/or ischemic brain injuries can induce brain edema and increase intracranial pressure (ICP), reducing cerebral perfusion pressure and finally influencing neurological outcome.6, 7, 8, 9, 10 The dural sheath that surrounds the optic nerve can inflate if pressure in the cerebrospinal fluid raised, as it occurs in brain edema or intracranial hypertension.11 As invasive ICP monitoring showed a good correlation with optic nerve sheath diameter (ONSD) measurement, ONSD measurement has been used to detect increased ICP level in TBI.12, 13 Two retrospective studies observed that ONSD measured between 12 and 72 h after CA might be used for assessing neurological outcome.14, 15 The relationship between an early ONSD ultrasonographic measurement and CA outcome has never been prospectively evaluated after adjustment on known predictive factors. The aim of this prospective clinical pilot study was to assess the ability of ONSD ultrasonographic measurement performed within day 1 after CA occurrence to correctly predict in-hospital mortality in post-CA patients treated with TH.
Section snippets
Materials and methods
This prospective observational study was performed in two French ICUs from November 2011 to September 2013. All unconscious (Glasgow Coma Scale ≤6) patients ≥18 years old, admitted in ICU after successful resuscitation from CA, and treated with TH were screened. Exclusion criteria were as follows: unavailable ONSD measurement within 24 h after CA (unavailable investigator, early death, or major hemodynamic instability), CA of traumatic or neurological origin, previous cerebrovascular disease,
Patients’ characteristics
Ninety-four patients were assessed for eligibility and 58 were excluded (Fig. 1). Among the 36 enrolled patients, 19 patients (53%) were discharged alive from hospital, with favorable neurological outcome occurring in 14 patients (39%). Among the 17 patients who died in ICU, 11 patients died from withdrawal or limitation of life-sustaining treatments (WLST) because of severe neurological impairment. Three other patients evolved to brain death, and the three remaining patients died from multiple
Discussion
Our main findings can be summarized as follows: 1/in CA patients successfully resuscitated and treated with TH, a larger ONSD1 is associated with higher in-hospital mortality and worst neurological outcome assessed by the CPC score; 2/ONSD1 measurement is correlated with brain edema as measured by GWR on early brain CT scan, and with NSE on ICU admission and at day 1; 3/interestingly, all three patients who subsequently evolved to brain death had a very high ONSD1 value (≥7.2 mm).
Conclusions
To conclude, our study confirms that ONSD ultrasonographic measurement within the first 24 h after CA is a promising way to evaluate the severity of post-CA brain injuries and outcome in a multimodal neuroprognostication approach. This non-invasive bedside tool is simple, cheap, available for serial measurements, and correlated to brain edema, NSE axonal biomarkers, CPC score and survival. Further multicentre studies are warranted to confirm ours results.
Conflict of interest statement
The authors received no financial support for this work. None of the authors have any financial and non-financial competing interests in relation with this paper.
Acknowledgment
We thank Professor FJ Baud for his critical analysis of the study.
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A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2016.03.006.
- 1
These authors contributed equally to this work and are considered as the 2 first co-authors.