Point-of-care ultrasound of optic nerve sheath diameter in suspected hypertensive emergency*

Hypertensive emergencies are acute, life-threatening conditions resulting from
markedly increased blood pressure, characterized by acute, ongoing target-organ
damage. They require fast diagnosis and management. Organ damage includes
hypertensive retinopathy grade 3 and/or 4, which is associated with other acute
hypertension-mediated organ damage. Clinical assessment of patients presenting
with possible hypertensive emergency includes therefore imaging of both fundi,
typically fundoscopy by an ophthalmologist in the case of vision loss/symptoms
or if no other apparent organ damage is present that already requires rapid
blood pressure lowering medication.

Measurement of the optic nerve sheath diameter (ONSD) by point-of-care
ultrasonography (POCUS) is performed by internal medicine doctors to support
the evaluation of above-mentioned patients. Measurement of ONSD is based on the
fact that the subarachnoid space around the optic nerve is in continuity with
the intracranial subarachnoid space. (5) Hence, any raised ICP will be
transmitted to the optic nerve subarachnoid space. From earlier studies we know
that ONSD correlates with elevated ICP in patients with suspected intracranial
hypertension. The cut-off value of the ONSD to diagnose an ICP > 20mmgHg varies
in literature between 4.80 and 5.86. Furthermore, ONSD correlates well with
different stages of papilledema in a case-control study of patients with
papilledema, and changes in ONSD are noticeable even in very early papilledema.
Hypertensive retinopathy consists of focal and diffuse arteriolar narrowing,
with retinal hemorrhage (grade 3), and papilledema (grade 4). In the context of
patients presenting with hypertension Roque et al. found a significant
correlation with systolic and diastolic blood pressure, however they did not
investigate the correlation of ONSD with clinical endpoints that have
therapeutic consequences, like hypertensive retinopathy or hypertensive
encephalopathy that require immediate and fast decrease in blood pressure. The
diagnostic characteristics of the ONSD in the context of patients presenting
with a suspected hypertensive emergency are unknown.

The aim of this study is to assess if ultrasonography of the ONSD can be used
to safely rule out papilledema and to evaluate if ONSD measurement can replace
funduscopy in the assessment of certain patients with suspected hypertensive
emergency.

This is a prospective observational multi-centre clinical study.

There is a minimal burden The ultrasound of the optic nerve is already standard
care in some centers. This examination is non-invasive, non-damaging and takes
a few minutes. This is performed during the patient's emergency room visit.
This visit will not be prolonged because of the ultrasound examination.
The fundus examination, which is not covered by regular care in only a small
number of patients, has very minimal risks, since eye drops (mydriatics) are
given. This is only done for patients who are already admitted to hospital, the
length of their stay will not be extended.