Unit 1: Ventriculoperitoneal Shunts Flashcards
Implanted cerebrospinal fluid (CSF) shunt system
diverts excess CSF from the brain to another part of the body
What is the most common type of implanted CSF shunt system?
Ventriculoperitoneal shunt (VPS)
Indications for CSF shunting
- signs and symptoms of clinical deterioration due to an increase in CSF volume within the brain, often leading to increased ICP
- conditions that result in obstruction of CSF circulation and/or absorption
What happens if there is overproduction or obstruction of CSF flow and/or impaired absorption?
Leads to:
- ventricular dilation (ventricles in the brain)
- hydrocephalus
- increased ICP
Normal ICP Range
0-15 mmHg
Hydrocephalus
active and progressive dilation of the ventricular system in the brain
- noncommunicating or communicating
- occurs when CSF production exceeds the absorption rate
How can Hydrocephalus Develop?
can result from:
- CSF overproduction
- Obstruction of CSF circulation
- Decreased CSF reabsorption
Noncommunicating Hydrocephalus
“obstructive” hydrocephalus
- the flow of CSF between the ventricles is obstructed or blocked
- brain tumor common cause
Communicating Hydrocephalus
occurs when there is a defect in the sites of absorption of CSF
-CSF can still flow between the ventricles
-due to subarachnoid hemorrhage (SAH), infection (meningitis), or gradual dysfunction due to aging
>debris from blood breakdown in SAH, or exudate associated with meningitis can obstruct the arachnoid villi and prevent them from absorbing CSF normally
Normal Pressure Hydrocephalus (NPH)
cerebral ventricular dilation seen on brain imaging and normal CSF pressure on lumbar puncture
- Triad: Gait disturbance, cognitive impairment, and urinary incontinence
- idiopathic or develop as a complication of SAH, head trauma, infection, or a tumor
Peritoneal Cavity
most common extracranial site for distal shunt catheter termination in ventricular shunting
- easy to access
- provides most reliable absorption of the diverted CSF
4 Basic Components of the Ventriculoperitoneal shunt Systems
- the proximal catheter
- reservoir
- one-way valve
- distal valve
VPS: 4 Components and their roles
- The proximal catheter: drains CSF from the ventricle
- Reservoir: provides support to the proximal catheter, which can prevent kinking as it curves exciting the skull; access to obtain CSF samples for ICP monitoring
- One-Way Valve: controls CSF flow into the distal catheter
- Distal Catheter: tunneled subcutaneously; terminates into the peritoneal cavity via separate incision; shunted CSF is then absorbed by the peritoneal cavity
CSF Shunt Valves
functions as a flow-resistance mechanism
- engineered to control ICP over a range of postural positions and pressures
- can be fixed or programmable (adjustable) pressure settings
CSF Fixed Shunt Valves
not programmable
- have opening and closing pressures set by the manufacturer
- fewer complications
- if rate needs to be adjusted, the patient will need another surgical procedure
CSF Programmable Shunt Valves
opening and closing pressures can be adjusted without the need for surgical procedure
- uses magnetic tools
- more expensive
- fewer surgeries
- settings must be checked and confirmed following an MRI
Siphoning of CSF
posture related “suction” effect on CSF flow dynamics through the shunt system
- caused by increased hydrostatic pressure with patient in an upright position
- siphoning can cause rapid over-drainage of CSF from the brain
- over drainage can cause collapse of the ventricles and tear blood vessels
Goal of Cerebral Ventricular Shunting
regulate the flow of CSF in order to control the volume of CSF; ventricular dilation, and ICP
What happens in CSF Overdrainage
result in the cerebral ventricles shrinking or collapsing, causing the meninges to pull away from the inner surface of the skull
-causes slit-ventricle syndrome; slit-ventricle syndrome can cause severe but intermittent headaches that are relieved only by lying down
What happens in CSF Underdrainage
cerebral ventricles enlarge in conjunction with S/S of hydrocephalus
-valve needs to be revised or externally adjusted
Ventriculoperitoneal Shunt (VPS) Complications
- shunt malfunction (from obstruction)
- infection
- abscess
- pseudocyst
- subdural hematoma (SDH)
- peritonitis
- bowel perforation
- pain
- seizures
- intracranial hemorrhage
- abdominal injury (ascites, peritonitis, abdominal perforations)
Complications: Shunt Malfunction
- obstructions causing shunt malfunction are due to CSF protein or debris buildup
- can become obstructed at any time
- obstruction leads to increased ICP; headache, vomiting, lethargy, irritability, and confusion
- malfunction if the catheter disconnects, migrates, or fractures
Complications: Infection
when shunt is colonized by skin flora
-skin infection can lead to abscess formation or shunt occlusion
Complications: Abscess
abdominal abscesses can occur from shunt contamination or from the shunt migrating into the bowel
-if complains of abdominal pain, must be assessed for formation of an abdominal abscess
