A ventriculoperitoneal (VP) shunt treats hydrocephalus by diverting excess cerebrospinal fluid (CSF) from the brain’s ventricles to the abdominal cavity for absorption. The entire system, including a catheter, valve, and tubing, is typically placed completely beneath the skin. When a VP shunt is “externalized,” the tubing is temporarily disconnected from the internal system and rerouted to exit the body. This allows CSF to drain into a sterile collection system outside the patient, creating a temporary External Ventricular Drain (EVD) system.
Why Temporary External Drainage is Necessary
The primary reason for externalizing a VP shunt is to address complications, most frequently infection within the existing shunt system. Shunt infection, known as ventriculitis, requires diversion of the internal drainage pathway to prevent bacteria from spreading. Rerouting the CSF flow to an external system allows medical teams to manage the infection while administering targeted antibiotics.
Externalization allows for continuous testing of the cerebrospinal fluid to track infection clearance before a new shunt is placed. This temporary drainage also provides a direct way to monitor and manage intracranial pressure (ICP). Adjusting the external drainage height allows precise control over the amount of CSF drained, stabilizing pressure within the patient’s head. This stabilization is necessary when a permanent shunt malfunctions or when the patient is too unstable for new internal shunt surgery.
Understanding the Shunt Components
The externalized system (EVD) consists of interconnected parts that manage CSF flow outside the body. The system begins with the proximal catheter, which remains surgically positioned within a brain ventricle. This catheter is the conduit for CSF leaving the brain and is secured at the scalp exit site with sutures and a sterile dressing.
Connected to the catheter is sterile tubing that leads to the collection system. This drainage apparatus typically includes a drip chamber, a pressure monitoring transducer, and a stopcock manifold to control the fluid path. The drip chamber’s height relative to the patient’s head determines the pressure threshold at which CSF drains into the final collection bag. The final part is the closed collection bag or reservoir, which safely holds the drained cerebrospinal fluid and protects it from contamination.
Daily Management and Care Protocols
Maintaining sterility around the external exit site is the highest priority due to the direct pathway into the brain’s fluid space. The skin entry site must be meticulously cleaned and dressed using sterile technique, often involving an antimicrobial solution and a dressing. The dressing and surrounding area must be constantly monitored for signs of redness, swelling, warmth, or discharge, which indicate a severe infection risk.
Caregivers must monitor the volume and characteristics of the drained CSF, typically checking and recording output hourly. The volume drained must strictly adhere to the neurosurgeon’s prescribed limit, as improper drainage can lead to complications like over- or under-drainage. The CSF should be clear and colorless; any changes, such as cloudiness, pus, or significant blood, must be immediately reported as these signal infection or hemorrhage.
Accurate positioning is necessary because the external system relies on gravity to regulate drainage. The patient’s head and the drip chamber must be precisely leveled, with the zero point aligned with an anatomical landmark like the tragus of the ear. If the patient moves, the system must be promptly re-leveled to maintain correct pressure and prevent dangerous fluctuations in ICP.
Monitoring Neurological Status
Any rapid neurological decline requires immediate attention. Symptoms such as a sudden worsening headache, new vomiting, lethargy, or a change in consciousness can indicate a severe malfunction or rising intracranial pressure.
Moving to a Permanent Internal Shunt
Externalization is intended to be temporary, and the goal is to safely transition the patient back to a fully internalized VP shunt. Readiness for permanent placement is determined by the resolution of the underlying issue, typically the complete clearance of infection. Medical teams monitor serial CSF cultures and blood markers to confirm the infection has been successfully treated.
Once the patient is stable and infection-free, surgery is scheduled to convert the external drain back to a permanent system. This involves removing the externalized portion and implanting a new, sterile shunt beneath the skin, with the distal end placed into the peritoneal cavity. In some cases, the neurosurgeon may utilize the existing skull entry site for the new shunt catheter.