CCCF ePoster library. FAQIHI F. Oct 3, 2017; 198223; 109
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Fahad Faqihi1, Ibrahim Soliman1, Garrett G R J Johnson2, Lawrence M Gillman3, Frederick A. Zeiler2,3,4, Gunavathy Jakaraddi1, Nagesh Jakaraddi1, Ahmed Balshi1, Salem Bawazir1, Abdullah Balhamar1, Mahmood Nasir Nasim1, Abdulrahman Alharthy 1, Dimitrios Karakitsos1,5

1Critical Care and Neurocritcal Care Units, King Saud Medical City, Kingdom of Saudi Arabia; 2Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada; 3Department of Surgery, Rady Faculty of Health Science, University of Manitoba, Winnipeg, MB, Canada; 4Division of Anesthesia, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK; 5Department of Critical Care, Keck Medical School, USC, Los Angeles, CA, USA

Introduction: Ultrasound assessment of optic nerve sheath diameter (ONSD) aids in the diagnosis of elevated intracranial pressure (ICP). Recently, new quality criteria for obtaining acceptable ONSD measurements in critical care settings were proposed as a way to standardize measurements across different sonographers and scans and to improve image quality.
Objectives: We applied the above-mentioned criteria to sonographic ONSD measurements and compared to invasive measurements made by intra-parenchymal ICP monitoring in patients with severe traumatic brain injury (TBI).
Patients and Methods: Forty patients with severe TBI were evaluated clinically and by computed tomography. Each patient had an intra-parenchymal ICP catheter inserted, and the ONSD of both eyes were measured by ultrasound based on the new quality criteria: 1. ONSD measurement should not be made through the lens (even the edge of the lens may not be visible on the image); 2. Sonographic differentiation (contrast) between the nerve proper and the arachnoid (CSF space) must be obvious; 3. The outer border of the arachnoid must be identifiable for actual ONSD measurement; 4. Ideal views of the optic nerve demonstrate the point of its penetration into the globe; 5. Good views offer opportunities for additional information such as tortuosity of the nerve, hypo-echogenicity of the arachnoid, its irregularity due to distention of CSF-containing “cells”; this also allows seeing optic disk area protrusion into the globe and flattening of the posterior globe in chronic ICP elevations that may mimic acute states in ICU; 6. Correct standardized measurements: since the most distensible portion of the sheath is at the 3-4 mm distance from the vitreo-retinal interface, measurements are performed at this level in a direction perpendicular to the axis of the nerve. 7. It is highly recommended to measure ONSD bilaterally and in more than one image frame.
In each patient, mean ONSD was compared to ICP. ICP and ONSD measurements were measured 5 times per patient over 48 hours, for a total of 200 measurements.
Results: Of the 200 measurements, 177 (88%) of measurements were on patients with elevated ICP (>20mm Hg), while the remaining 23 (12%) were not elevated. ONSD measurements were strongly correlated to invasively monitored ICP (r = 0.747, P < 0.0001); Figure 1. The ROC curve results revealed that the optimal cut-off value of ONSD for predicting elevated ICP was 5.93 mm when using the mean of both eyes (area under the ROC curve = 0.880, 95% CI = 0.804 to 0.955); Figure 2. The sensitivity and the specificity of this cut-off value were 85.3% and 82.6%, respectively. ICP, sex, height and weight all correlated with ONSD, however, on linear regression analysis, only ICP (ß = 0.68, p < 0.001), sex (ß = -0.195, p = 0.002) and height (ß = 0.112, p = 0.04) were significant predictors. The overall model fit was R2 = 0.60.
Conclusion: In patients with severe TBI, ONSD measured using new quality criteria is highly correlated to invasively monitored ICP. A larger cut-off value for ONSD is needed when using the above-mentioned criteria in TBI patients, compared to the previous published data using the black stripe method. Further study is needed to determine how these new criteria affect ONSD measurement in other patient populations, and whether they can be used in the future to monitor ONSD as a proxy for ICP trend in brain injured patients.


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