458

Abstract

Introduction: Increased intracranial pressure (ICP) leads to morbidity and mortality in patients with brain injury (stroke, head trauma, encephalopathy) and is an important cause of long-term neuro-cognitive deficit and death. While invasive monitoring techniques remain the diagnostic gold standard, potential bleeding and other complications pose a relevant risk and make them dangerous to apply routinely. Clinical deterioration can be an early indicator of increasing ICP, but is limited in its ability to accurately detect elevated intracranial pressures in this patient population due to fluctuations in mental status, sedation, other life-threatening injuries, and paralysis as part of the acute stabilization process. Measurement of ICP is critical during this early time period in order to optimize hemodynamics and prevent further brain injury. Optic ultrasound (OUS) is a non-invasive technique that can be used to measure the optic nerve sheath dimension providing valuable ICP monitoring data for physicians as they treat critically ill patients. Methods: In a prospective convenience sample study, 115 adult patients at risk for increased ICP (stroke, head trauma, encephalopathy) were enrolled at a tertiary care center. Patients with suspected ocular globe trauma were excluded from the study. OUS using a 7.5 MHz linear array transducer was performed on the first and second day of arrival to the emergency department (ED) or intensive care unit (ICU). Ocular ultrasound is performed non-invasively through placement of sterile conductive ultrasound gel on the eyelids with the eyes closed. Minimal pressure is applied on the eyelid with the ultrasound transducer touching the gel that has been placed on the eyelid (no direct contact with eye surface). The patient’s head position was not changed and was performed bedside with portable ultrasound machines. Due to fluid content in the eyeball and surrounding tissue, ocular structures are well visualized. The optic nerve sheath diameter (ONSD) was examined. A longitudinal and a transverse measurement were taken on both the left and right eye of each patient. Data analysis includes paired t-tests and Chi-Square to compare means and proportions as appropriate. Regression analysis assesses ONSD and patient outcomes relationships using -SAS v.9.3 statistical software. Results: There was no significant difference for measurements of lateral versus transverse measurements of each eye: right p=0.903 and left p=0.467. There was no significant difference for measurements of left versus right eye, for the longitudinal p=0.270 and transverse p=0.163, respectively. The median ONSD for those that died versus those that did not die was 0.60 (IQR 0.55, 0.67) and 0.55 (IQR 0.51, 0.61), respectively p= 0.005. For every 0.1 cm increase in ONSD, the odds of death increased 2.68 fold 95% CI (1.30, 5.51). Conclusions: ONSD measurements can be taken in either eye, in either orientation, with no significant difference in accuracy. Increased ONSD measurements were correlated with worsened short term outcomes (death). We expect that increased ONSD measurements will be correlated with worsened outcomes (Modified Rankin Scale analysis will be done at 6 months). OUS may be used as a screening tool to identify patients at risk for increased ICP. OUS will enable the treating physician to utilize a reliable non-invasive monitoring technique, and will improve patient care.