Multimodal Sonographic Monitoring of Cerebral Perfusion, Ventricle Seize and Optic Nerve Diameter During Weaning of Cerebrospinal Fluid Drainage Catheters: a Single Centre Observational Trial

Background

Placement of a CSF drainage catheter (external ventricular drainage (EVD) or lumbar drainage (LD)) is a frequent neurosurgical emergency intervention. It is used in case of obstructive hydrocephalus as it can occur after e.g. intracerebral hemorrhage with intraventricular involvement, subarachnoid hemorrhage or traumatic brain injury but also in situations with reduced CSF resorption or increased CSF production (e.g. meningitis, ventriculitis). Furthermore, this technique can be used to monitor intracranial pressure. In all these situations, the EVD/LD can be used to reduce the elevated intracranial pressure during the acute phase. However, because of impairment of the Paccioni granulations by blood and its breakdown products, a continuing hydrocephalus may develop, leading to permanent necessity of CSF drainage. To evaluate the need for a permanent (implanted) drainage system (e.g. ventriculoperitoneal or ventriculoatrial shunt) attempts to clamp the EVD/LD are carried out during the subacute phase. Successful clamping is verified by absent increase of intracranial pressure, absent clinical deterioration and lack of ventricular enlargement on serial CT scans. The latter means that a first CT scan has to be performed before clamping of the drainage catheter (baseline examination) and again 24 hours after clamping of the drainage catheter. This leads to the need for repeated transportations of critically ill patients with possible harm of the patient, high costs, need for more staff and repeated exposure of the patient to radiation. Hence, a simple, repeatable, non-invasive, bedside tool for diagnosis of ventricular enlargement due to clamping of EVD/LD is strongly needed.

Transcranial ultrasound has become a widely used technique mainly for measuring arterial blood flow velocities. More recently, transcranial ultrasound has been also used to assess brain tissue, brain perfusion and ventricular size. The major advantages of ultrasound are its non-invasive character, the possibility for bedside application, low costs and safety (no X-ray exposure). Some studies have tried to use transcranial ultrasound for indirect assessment of intracranial pressure. As target structures for transcranial ultrasound either the lateral ventricles, the third ventricle or the diameter of the optic nerve were used. All studies could demonstrate a correlation between the width of the lateral or third ventricle or the diameter of the optic nerve with intracranial pressure. To the investigators' knowledge, only one study assessed the change of the width of the lateral ventricles during clamping of EVD/LD.

To summarize, a bedside method for assessment of changes of ventricle width/diameter of the optic nerve during clamping of EVD/LD is urgently needed and would facilitate the procedure, higher patient safety and lower costs. By now, there are some promising ultrasound methods (transcranial ultrasound with or without contrast enhancing agent to determine the width of the side and third ventricle, diameter of the optic nerve), which might substitute repeated CT scans but have not been evaluated for monitoring clamping of EVD/LD.

Objective