Ultrasonographic measurement of the optic nerve sheath diameter to detect intracranial hypertension: an observational study

Abstract

Objectives To evaluate the ultrasonographic measurement of optic nerve sheath diameter (ONSD) as a predictor of intracranial hypertension as compared to the invasive measurement of intracranial pressure (ICP). Design Cross-sectional observational study. Setting Intensive Care Unit (ICU) of two tertiary university hospitals in Montevideo, Uruguay. Patients We included 56 adult patients, over 18 years of age, who required sedation, mechanical ventilation, and invasive ICP monitoring as a result of a severe acute neurologic injury (traumatic or non-traumatic) and had a Glascow Coma Score (GCS) equal to or less than 8 on admission to the ICU. Interventions Ultrasonographic measurement of ONSD to detect intracranial hypertension. Measurements and main results In our study, a logistic regression model was performed in which it was observed that the variable ONSD is statistically significant with a p value of 0.00803 (< 0.05). This model estimates and predicts the probability that a patient will have an ICP greater than 20 mmHg. From the analysis of the cut-off points, it is observed that a value of 5.7 mm of ONSD maximizes the sensitivity (92.9%) of the method (a greater number of individuals with ICP > 20 mmHg are correctly identified). Conclusions In sedated neurocritical patients, with structural Acute Brain Injury, the ONSD measurement correlates with the invasive measurement of ICP. It was observed that with ONSD values less than 5.7 mm, the probability of being in the presence of ICP above 20 mmHg is very low, while for ONSD values greater than 5.7 mm, said probability clearly increases.

Effect of Neck Rotation With Flexion on Ultrasonographic Optic Nerve Sheath Diameter in Patients Undergoing Elective Craniotomy

“…In literature, it was stated that the head can typically be safely rotated up to 45 degrees away from the body. If more rotation is needed, a roll or pillow placement under the opposite shoulder is recommended [ 14 ]. However, in a recent review on surgical positioning for neurosurgical procedures, it is stated that the head shouldn’t be turned more than 30 degrees to one side, especially when turning it towards the dominant jugular vein [ 1 ].…”

A Novel Method for Prediction of Raised Intracranial Pressure Through Automated ONSD and ETD Ratio Measurement From Ocular Ultrasound

“…By adjusting the acoustic power while using the small parts preset, we achieved a mechanical index below 0.23. 32 The ultrasound machine (SonoSite M-Turbo) uses the linear probe (frequency of 6-13 MHz), which is held longitudinally to the retinal globe to measure the optic nerve diameter at a distance of 3 mm below the optic nerve tip. The proper contact between the linear probe and the patient's eye is provided by applying sufficient gel.…”