II. Indications: VP Shunt for Hydrocephalus (CSF accumulation)
- Intraventricular Hemorrhage of prematurity
- Spina bifida
- Lisencephaly
- Holoprosencephaly
- Meningitis complication
III. Technique: Shunt position
- VP Shunt proximal catheter tip
- Ventricles
- Reservoir and One-Way Valve
- Located at edge of skull
- Distal tube and proximal tube connect to the one-way valve (which does not allow back flow into brain)
- One way valve should be compressible (unless obstructed)
- VP Shunt course
- Subcutaneously via the right parietal scalp and down neck
- VP Shunt distal tip
- Peritoneum (most common)
- Alternative sites (if limited by prior peritonitis history)
- Pleural space
- Right atrium
- Lumbar region
IV. Complications: Shunt
- Mechanical shunt malfunction (presumed cause until proven otherwise)
- Shunt obstruction (see management below)
- Detached shunt tubing or otherwise broken shunt
- Shunts Fracture most commonly in the distal tubing (esp. near clavicle or lower ribs)
- Cannula dislodged with inadequate drainage
- Shunt failure occurs in 40% within 1 year and in 50% by 2 years after implantation
- Infection
- Complicates 3-10% of shunt procedures
- Accounts for up to 60% of shunt-related mortality
- Very old and very young are at highest infection risk
- Causes
- Typically within 8 weeks of shunt placement, manipulation or revision (accounts for 70% of shunt infections)
- Ascending infection may occur (e.g. peritonitis from Appendicitis)
- Findings of suspected shunt infection
- Meningismus
- Fever without a source
- Persistent Abdominal Pain
- Consult with neurosurgery
- Neurosurgery typically performs shunt tap as described below
- In some cases, neurosurgery will remove the shunt and temporize with external ventricular drain
- Start Antibiotics as soon as shunt tap completed
- In some cases they will recommend starting Antibiotics prior to shunt tap
- Vancomycin is typically used
- Staphylococcus Epidermidis (or other skin flora) causes 75% of shunt infections
- Also cover for abdominal flora (due to distal tubing in Abdomen)
- Complicates 3-10% of shunt procedures
- Intraabdominal complications (especially if distal tip migration)
- Ascites
- Peritonitis
- Ruptured Viscus
- Excessive removal of fluid (less common now with programmable shunts)
- Postural Headache
- Subdural Hematoma (result from tearing of bridging veins)
V. Complications: Shunt obstruction
- Initial symptoms
- Headache
- Lethargy or Somnolence
- Vomiting
- Children with subacute presentation may have behavioral changes, feeding problems, irritability, Headaches
- Later symptoms suggestive of imminent Herniation
- Cranial Nerve palsy
- Unilateral pupilary dilation (Blown Pupil)
- Upward Gaze Paralysis (eye sunsetting)
- Cushing's Triad (Hypertension, Bradycardia, Irregular breathing)
- Altered Mental Status
- Bulging Fontanelle or Bradycardia (infants)
- Findings
- Shunt one-way valve (at lateral skull) is not compressible
- Unrelated findings
- Seizure Disorders are common among children with Hydrocephalus
- Head Trauma
- VP Shunts do not appear to significantly increase complications from minor Head Trauma
VI. Imaging (and other diagnostics)
- CT Head (or MRI Brain)
- Head Ultrasound
- Consider in infants with open Fontanelles
- Shunt Series XRays
- Views include anterior skull, lateral skull, Chest XRay, KUB Xray
- Consider if Trauma to tubing or suspected kinking or tube disruption (e.g. subcutaneous fluid collection)
- Shunts Fracture most commonly in the distal tubing (esp. near clavicle or lower ribs)
- VP Shunt series, however, adds little if CT Head is without acute changes
-
Head Circumference
- Compare measurement to prior Head Circumference measurements (significant increase ay suggest obstruction)
VII. Management: Shunt Malfunction with signs Herniation
- Emergency - involve neurosurgery immediately!
- Mortality shunt obstruction: 1-2%
- Evaluate for symptoms of obstruction (see symptoms above)
- Evaluate for findings of imminent Herniation (see symptoms above)
- Obstruction is proximal in 80% of cases (proximal tip lodges)
- Distal obstructions may also occur in the peritoneum
- Reduce Intracranial Pressure
- See Increased Intracranial Pressure
- Emergent neurosurgery Consultation
- Consider shunt tap if neurosurgery not available (see below)
- Raise head of bed
- Mannitol
- Hypertonic Saline does not appear to be an effective alternative
VIII. Procedure: Shunt Tap
- Indications (only in cases where neurosurgery is not available in an adequate time frame)
- Suspected shunt malfunction with ill appearing patient
- Signs of shunt obstruction with Herniation
- Preparation
- Patient lies supine
- Identify shunt reservoir
- Shunt reservoir sits a few centimeters inferior to entry point in skull
- Palpable firm hub or tube swelling along the shunt course
- Second hub may be palpable in some patients
- Either hub may be accessed
- Mark hub site
- Technique
- Use sterile technique
- Apply antiseptic solution (Betadine or Chlorhexidine) to skin overlying hub
- Drape the skin and wear sterile gloves
- Insert 25 gauge butterfly needle into hub, perpendicular to scalp
- Attach 3-way stopcock and 5 cc syringe
- Allow CSF to freely flow
- Attach manometer (from Lumbar Puncture kit)
- Distal obstruction if CSF flows and opening pressure >15-20 cm H2O
- Proximal obstruction if no CSF flow (not correctable in emergency department)
- Only drain enough fluid until opening pressure <20 cm H2O
- Do not apply back pressure with the syringe (risk of Subdural Hematoma)
- CSF under pressure of obstruction should fill the syringe with force
- Attach manometer (from Lumbar Puncture kit)
- Post-procedure
- Send CSF for Gram Stain and culture
- Anticipate marked clinical improvement after shunt tap
- Use sterile technique
IX. References
- Jhun and Roepke in Herbert (2016) EM:Rap 16(3): 17-8
- Majoewsky (2012) EM:Rap 12(9): 4
- Behar and Claudius in Majoewsky (2013) EM:Rap 13(9): 9