Our investigation confirms the reliability of optic nerve ultrasound as a non-invasive method to detect elevated ICP in intracranial hemorrhage patients. ONSD measurements proved to have a good reproducibility. ONSD changes almost concurrently with CSF pressure variations.

The rapid diagnosis of intracranial hypertension is urgently needed for therapeutic reasons in various clinical settings. This can rarely be achieved without invasive procedures such as intracranial pressure (ICP) monitoring or neuroimaging. The optic nerve is surrounded by cerebrospinal fluid (CSF) and dura mater, which forms the optic nerve sheath (ONS). Because of the connection with the intracranial subarachnoid space, ONS diameter (ONSD) is influenced by CSF pressure variations. Bedside ultrasonographic measurement of ONSD has been proposed as a non-invasive and reliable means to detect raised ICP in neurocritically ill patients. In several studies, it proves to have a good correlation with the direct measurement of ICP and a low interobserver variability. However, no general consensus exists over the upper normal ONSD limit. We performed a review of the literature on the use of the ultrasonography of the optic nerve in the evaluation of patients with suspected intracranial hypertension. The aim of this review is to describe the technique and to assess the validity of this diagnostic method.

Bedside ultrasonographic measurement of optic nerve sheath diameter (ONSD) has been proposed as a method to detect raised intracranial pressure (ICP) in various clinical settings. The aim of our study is to evaluate the use of ultrasonography in the case of intracranial hemorrhage and to assess the validity of the conventional cut-off point of 5 mm. A prospective blind observational study in a 10-bed multivalent intensive care unit was carried out by enrolling 53 adult patients with primary intracerebral hemorrhage (23) or subarachnoid hemorrhage (30), requiring ICP monitoring, sedation, and mechanical ventilation and 53 control patients with no intracranial pathology, requiring sedation and mechanical ventilation. ONSD was measured 3 mm behind the globe by using a 7.5 MHz linear ultrasound probe. Mean binocular ONSD was used for data analysis. Nineteen patients proved to have raised ICP (>20 mm Hg). In this group, ONSD at admission was 6.2+/-0.6 mm, a significantly higher value than in low ICP patients (P<0.01). In the 34 patients with ICP <20 mm Hg, ONSD was 5.0+/-0.5 mm, and it resulted not significantly different from ONSD in the control group (4.9+/-0.4 mm). A receiver operator characteristic curve was constructed and an ONSD threshold of 5.2 mm as a predictor of ICP >20 mm Hg proved to be an attractive combination of sensitivity and specificity (94% and 76%, respectively). In conclusion, our study confirms the utility of optic nerve ultrasound in the early diagnostic evaluation of patients with known or suspected intracranial hemorrhage.

dIVC proved to be a reliable predictor of fluid responsiveness in ICU patients with subarachnoid hemorrhage.