Basics
Description
- Ventricular peritoneal (VP) shunts are usually placed for hydrocephalus:
- Conduit between CSF and peritoneal cavity (or right atrium)
- Obstruction: Shunt malfunction impairs drainage of CSF:
- Increases intracranial pressure (ICP)
- Rate of increase in ICP determines severity
- 30 " 40% mechanical malfunction rate in 1st year
- Overdrainage syndrome:
- Upright posture increases CSF outflow
- Decreases ICP
- Produces postural headache and nausea (as after lumbar puncture)
- Infection:
- Shunt is a foreign body
- Staphylococcus epidermidis and other Staphylococcus species in 75% of infections
- Gram-negative organisms also implicated
- Multidrug-resistant Staphylococcus aureus (MRSA) has been reported
- Most occur soon after placement
- Shunt removal usually required
- Slit ventricle syndrome:
- Prolonged overdrainage causes decreased ventricular size
- Intermittent increases in ICP occur owing to proximal obstruction
- Complications more common in children, especially neonates
- If cranial sutures are open, CSF may accumulate without much ICP increase
- Produces relatively nonspecific signs and symptoms:
- Drowsy
- Headache
- Nausea and Vomiting
Etiology
- Shunt may be needed to treat increased ICP due to:
- Congenital malformations
- Idiopathic intracranial hypertension (pseudotumor cerebri)
- Post CVA
- Tumor or other mass lesions
- Post head trauma
- Subarachnoid hemorrhage
- Scarring at base of brain after bacterial meningitis
Diagnosis
Signs and Symptoms
- Shunt obstruction:
- Headache, nausea
- Malaise, general weakness, irritability
- Decreased level of consciousness (LOC)
- Increased head size or bulging fontanelle
- Seizures: New-onset or increased frequency
- Autonomic instability
- Decreased upward gaze
- Apnea
- Papilledema " rare
- Overdrainage syndrome:
- Headache, focal neurologic signs, malaise, seizures, coma
- Signs and symptoms often postural
- Rapid overdrainage may cause upward shift of the brainstem, leading to signs and symptoms of herniation: Apnea, bradycardia, decreased LOC
- Shunt infections:
- Fever (may be absent)
- Meningeal signs
- Local signs of infection (erythema, swelling, tenderness)
- Peritonitis (can cause retrograde CSF infection)
- Infections usually occur soon after shunt placement (about 80% ≤6 mo)
- Slit ventricle syndrome:
- Episodic headache
- Alternating periods of normal behavior and lethargy
- Headache, nausea, and vomiting
History
- Timing of shunt placement
- Reason for shunt
- Recent instrumentation/revision
Physical Exam
- Altered mental status
- Focal neurologic deficit
- Fever
- Erythema or tender shunt
Essential Workup
- Suspected shunt malfunction:
- Manipulation of the pumping chamber:
- Chamber should compress easily and refill within 3 sec
- Failure to compress easily implies distal obstruction
- Failure to fill implies proximal obstruction
- Up to 40% of malfunctioning shunts compress/fill normally
- Head CT
- Shunt series:
- Radiographs of skull, chest, abdomen
- Aids in diagnosis of disconnection, malposition, or kinking of shunt components
- Suspected infection:
- Aspiration of CSF from shunt reservoir (in consultation with neurosurgeon):
- May be performed using sterile technique and 23G butterfly needle
- Slowly aspirate 5 " 10 mL CSF for the studies noted in the next section
Diagnosis Tests & Interpretation
Lab
- Electrolytes, renal function, and glucose
- Anticonvulsant levels
- CBC
- Suspected infection:
- Analysis of CSF from the shunt reservoir:
- Send for culture, cell count, Gram stain, glucose, and protein levels
- CSF analysis may have normal early result, especially with prior antibiotic treatment
- Blood cultures
Imaging
- Head CT: To compare ventricular size and evaluate catheter position:
- Enlarged ventricles: Shunt malfunction
- Smaller ventricles: Overdrainage
- Most useful when compared with previous scan
- Diagnose subdural hematoma
- US: Used in children with open fontanelle to evaluate position of shunt tip and assess ventricular size
Diagnostic Procedures/Surgery
- If symptoms of shunt malfunction are present but CT scan is not diagnostic, shunt tap is the next test:
- Shunt manometry: High pressure >20 cm H2O implies distal shunt obstruction
- Also used to evaluate CNS infection
Differential Diagnosis
- Seizure disorder (idiopathic, toxic, metabolic)
- Infections:
- CNS infection not related to the shunt
- Systemic infections
- Metabolic abnormalities:
- Hypoglycemia
- Hyponatremia
- Hypoxia
- Intoxication/poisoning
- Head trauma
Treatment
Pre-Hospital
- Patients with shunt malfunction are at risk for apnea and respiratory arrest
- Oxygen should be applied with close monitoring of respiratory status
- When increased ICP is suspected, transport patient with head elevated to 30 °
Initial Stabilization/Therapy
- Signs of impending herniation:
- Rapid-sequence intubation and controlled ventilation to Pco2 ’ Ό35 mm Hg
- Consider pretreatment with lidocaine (pediatric: Plus atropine)
- Thiopental or etomidate for induction
- Succinylcholine may increase ICP a few mm Hg, although this may not be clinically significant
- Use only pretreatment dose of nondepolarizing agent if depolarizing agent chosen
- Nondepolarizing agent (rocuronium) may be preferable
- Forced pumping of shunt chamber:
- Flush the device with 1 mL of saline solution to remove distal obstruction
- Allow slow drainage of CSF from the reservoir to achieve pressure <20 cm H2O
- IV mannitol to lower ICP
- Ventricular puncture and CSF drainage is a procedure of last resort if less invasive procedures unsuccessful and neurosurgeon unavailable
- Status epilepticus: Treated with benzodiazepines (lorazepam)
Ed Treatment/Procedures
- Early neurosurgeon consultation
- Shunt malfunction:
- Elevate head of bed to 30 °
- Medical management with diuretics (mannitol, furosemide) may be appropriate in certain mild cases
- Overdrainage syndrome:
- Maintain patients supine position
- Correct volume depletion
- Shunt infection:
- Systemic antibiotics:
- Vancomycinpluscefotaxime or gentamicin if gram-negative suspected
Medication
- Adult and pediatric doses:
- Atropine: 0.02 mg/kg IV (min. 0.1 mg)
- Cefotaxime: 1 " 2 g (peds: 50 mg/kg) IV/IM q8 " 12h
- Furosemide: 1 mg/kg IV
- Gentamicin: 2 " 5 mg/kg IV
- Lidocaine: 1 mg/kg IV
- Mannitol: 1 g/kg IV
- Rocuronium: 1 mg/kg IV
- Succinylcholine: 1.5 mg/kg IV
- Vancomycin: 15 mg/kg loading dose IV
- Vecuronium: 0.08-0.1 mg/kg IV
Follow-Up
Disposition
Admission Criteria
Patients with shunt complications usually require neurosurgical consultation and admission. An ICU or other monitored setting is often needed.
Discharge Criteria
When shunt malfunction is ruled out, disposition depends on alternate diagnosis and patient condition.
Pearls and Pitfalls
- Avoid "tunnel vision " in a patient with a shunt and consider other causes for the presentation
- Severe constipation may cause increased intra-abdominal pressure and decrease drainage resulting in increased ICP:
- Treatment of constipation may ameliorate the apparent "shunt malfunction "
Additional Reading
- Barnes NP, Jones SJ, Hayward RD, et al. Ventriculoperitoneal shunt block: What are the best predictive clinical indicators? Arch Dis Child. 2002;87:198 " 201.
- Madsen MA. Emergency department management of ventriculoperitoneal cerebrospinal fluid shunts. Ann Emerg Med. 1986;15:1330 " 1343.
- Mart nez-Lage JF, Martos-Tello JM, Ros-de-San Pedro J, et al. Severe constipation: An under-appreciated cause of VP shunt malfunction: A case-based update. Childs Nerv Syst. 2008;24:431 " 435.
- Moza K, McMenomey SO, Delashaw JB Jr. Indications for cerebrospinal fluid drainage and avoidance of complications. Otolaryngol Clin North Am. 2005;38:577 " 582.
- Stein SC, Guo W. Have we made progress in preventing shunt failure? A critical analysis. J Neurosurg Pediatr. 2008;1(1):40 " 47.
Codes
ICD9
- V45.2 Presence of cerebrospinal fluid drainage device
- 996.63 Infection and inflammatory reaction due to nervous system device, implant, and graft
- 996.75 Other complications due to nervous system device, implant, and graft
- 331.4 Obstructive hydrocephalus
ICD10
- T85.09XA Other mechanical complication of ventricular intracranial (communicating) shunt, initial encounter
- T85.79XA Infect/inflm reaction due to oth int prosth dev/grft, init
- Z98.2 Presence of cerebrospinal fluid drainage device
- G91.9 Hydrocephalus, unspecified
SNOMED
- 257354000 ventriculoperitoneal shunt device (physical object)
- 230808006 Brain ventricular shunt obstruction (disorder)
- 432616009 Infection of ventriculoperitoneal shunt (disorder)
- 230745008 Hydrocephalus (disorder)
- 431468008 Slit ventricle syndrome (disorder)