Elevated intracranial pressure

Background

• Monroe-Kellie hypothesis: The total volume of the intracranial space is constant, and comprises 3 main complements, namely the brain tissue (80%), blood (10% or 150mL) and CSF (10% or 150mL). An increase in the volume of any one of the components must necessarily be accompanied by a reduction in that of the other two in order to maintain the fixed total intracranial volume.
• CSF is created at a rate of 20mL/hr or 500mL/day.
• Neuronal injury occurs secondary to vascular compromise to brain cells either by a reduction in cerebral blood flow or direct ischemia. This is an emergency and requires emergent intervention if sustained > 5-10 minutes

Clinical Features

• Headache (from increased pressure on heavily innervated meninges)
• Characteristically worse in the morning
• Nausea/vomiting
  • Vomiting due to increased ICP typically occurs in the morning
• CN palsies
  • CN 6 palsy (false localizing sign)
• Papilloedema (bilaterally blurred optic disc margins)

Differential Diagnosis

Increased ICP is due to an increase in any one of the 3 components of the intracranial space

1. Increased brain tissue
   • Neoplasms
   • Cerebral abscess
2. Increased CSF volume
   • Decreased reabsorption
     • Obstructive hydrocephalus
     • Non-obstructive/communicating hydrocephalus
3. Increased blood volume
   • Intracranial haemorrhage
   • Cerebral venous sinus thrombosis
   • Failed cerebral autoregulation (causing increases CBF or CBV)

Neuro ICU Management

• Ensure data accurate
  • Observe for accurate waveforms in arterial and ICP monitors
    • EVD zeroed at ear, changes with coughing/positioning
    • Arterial line zeroed at ear (for accurate CPP measurement; although typically level at heart reasonably accurate
• Assess ABC (as increased ICP often causes decline in mental status)
  • If need to intubate - ensure measures to avoid coughing/bucking (increases ICP)
    • Lidocaine 1% 1ml/kg 1x IV bolus as premedication

Goals

• Keep CPP 60-110mmHg
  • If <110 utilize pressors (levophed [preferred] or neosynephrine)
  • Levophed: start at 4 mcg/min; maximum 20 mcg/min.
  • Phenylephrine: start at 0.4 mcg/kg/min; maximum 9 mcg/kg/min.
• Keep ICP < 20mmHg (nonsustained temporary elevateions ~<5 minutes ok

Take Stepwise approach to treatment

1st (conservative)

• Elevate Head of bed to 30-45 deg and keep head midline
  • May "sandbag" head of those in c-collar to promote venous drainage(c-collar can restrict venous outlfow)
• Control agitation/pain
  • Narcotics, benzodiazepines, sedative hypnotics
    • Favor short acting medications to allow neuro exam checks
    • Versed, Fentanyl and propofol are often appropriate.
• Maintain normocapnia (pCO2 35-40)
• Maintain normothermia
  • Treat shivering
    • Bair hugger (warms skin temperature)
    • APAP 650 q6prn for temp >38.5°F
• Maintain euvolemia
• Maintain euglycemia

2nd (Intervention-short term)

• Hyperventilate to pCO2 30-35mmHg
  • This is short term as patient will equilibrate; is only meant as a temporizing measure. Attempt to wean to normocapnia as soon as able. Further do not overventilate past 25mmHg as may exacerbate damage via cerbral hypoxia (CO2 is primarily involved in autoregulation of cerebral vasculature).
• Hypertonic fluids
  • Mannitol 20% 1-1.5g/kg rapid IV bolus (no need for central line) OR
  • 23% Na 30mL over 15 minutes (Needs central line)
• Consult Neurosurgery (urgent) for possible evacuation or ventricular drainage
  • This is especially relevant for mass lesions causing mass effect, hydrocephalus and intracranial bleeds

3rd (Intervention- long term)

• Hypertonic fluid maintenance
  • Iatrogenic hypernatremia. Use 3% NaCl to maintain na >145 with q6hr serum Na cks.
    • 3%NS at 1mL/kg/hr appropriate (typically start at 50mL/hr).
    • May continue to push Na > 145, then >150 then >155 prn to manage ICP
      • Eventually osmotic pressures will equilibrate over days. requiring higher Na values (rationale behind pushing Na slowly upward as needed rather than pushing hypernatremia to maximum).
  • Iatrogenic hyperosmolar maintenance
    • Mannitol 20% 0.5g/kg q4hrs with seurm Osm checks q6hrs. (Target osm of 300-320 mOsm/L)

4th (Intervention - Refractory elevation)

• Pentobarbital coma
  • loading dose: 5-20mg/kg bolus then 4mg;kg/hr titrated to burst supression on EEG.
• Induced hypothermia (32-34°F)
  • Cooling System (ie. Arctic Sunt, Stryker Medi-Therm)
    • Must perform surveillance cultures (routine blood culture, UA, CXR) every 48 hours since artificially supressing fever.
  • Shivering protocol
    • Vecuronium or Pancuronium
• Paralytics
  • Risk of ICU myopathy/neuropathy with long term use.

See Also

• Head Trauma (Main)
• Glasgow Coma Scale (GCS)