Rosen & Barkin's 5-Minute Emergency Medicine Consult (764 page)

427.41 Ventricular fibrillation

BASICS

• 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
    

• 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

• 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
    

• Timing of shunt placement
  
• Reason for shunt
  
• Recent instrumentation/revision
  

• Altered mental status
  
• Focal neurologic deficit
  
• Fever
  
• Erythema or tender shunt
  

• 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
      

• 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
    

• 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
  

• 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 H
    ₂
    O implies distal shunt obstruction
    
  • Also used to evaluate CNS infection
    

• 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

• 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°
  

• Signs of impending herniation:
  
  • Rapid-sequence intubation and controlled ventilation to Pco
    ₂
    ∼35 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 H
    ₂
    O
    
• 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)
  

• 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 patient’s supine position
    
  • Correct volume depletion
    
• Shunt infection:
  
  • Systemic antibiotics:
    
    • Vancomycin
      plus
      cefotaxime or gentamicin if gram-negative suspected
      

• 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