Intracranial pressure management

Intracranial pressure management

Intracranial pressure management

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🧠 The Pressure Cooker Cranium

  • Monro-Kellie Doctrine: The cranium is a fixed-volume box containing brain, blood, and CSF. An increase in one component requires a compensatory decrease in another to maintain normal intracranial pressure (ICP).
  • Normal ICP: <15 mmHg.
  • Cerebral Perfusion Pressure (CPP): $CPP = MAP - ICP$.
    • Goal: >60 mmHg to prevent ischemia.

Monro-Kellie doctrine: ICP compensation for expanding mass

Cushing's Triad: A late sign of severely ↑ICP indicating impending brainstem herniation.

  • Hypertension (with wide pulse pressure)
  • Bradycardia
  • Irregular respirations

🧠 Pathophysiology - When Pressure Goes Rogue

Based on the Monro-Kellie doctrine: the skull is a fixed vault (Brain, Blood, CSF). An increase in one volume requires a compensatory decrease in another to maintain normal pressure.

  • Cerebral Perfusion Pressure (CPP) is the key driver of blood flow: $CPP = MAP - ICP$.
  • Goal CPP is >60 mmHg.
  • When ICP rises, CPP falls, leading to cerebral ischemia. This triggers a dangerous feedback loop, further increasing ICP and risking herniation.

Cushing's Triad: A late, ominous sign of brainstem compression.

  • Hypertension (widened pulse pressure)
  • Bradycardia
  • Irregular respirations

🧠 Clinical Manifestations - The Brain's Distress Signals

  • Early Signs: Headache (worse in AM), nausea/vomiting, papilledema, altered mental status (lethargy, confusion).
  • Late Signs (Herniation):
    • Cushing's Triad:
      • Hypertension (↑ systolic BP, widening pulse pressure)
      • Bradycardia (↓ HR)
      • Irregular respirations (e.g., Cheyne-Stokes)
    • Pupillary Changes: Ipsilateral, fixed, and dilated pupil (CN III compression).
    • Posturing: Decorticate (flexor) → Decerebrate (extensor).

⭐ Cushing's triad is a LATE and ominous sign of severely ↑ ICP, often indicating impending brainstem herniation.

Intracranial Pressure (ICP) and Cushing's Triad

🕵️ Diagnosis - Spotting the Squeeze

  • Initial Imaging: Non-contrast CT head is the first-line test.
    • Look for: midline shift, effacement of sulci/cisterns, ventricular compression.
  • ICP Monitoring (Gold Standard): Intraventricular catheter (EVD).
    • Allows both monitoring & therapeutic CSF drainage.
  • Calculate CPP: $CPP = MAP - ICP$.
    • Goal CPP: 50-70 mmHg.

⭐ Cushing's triad (hypertension, bradycardia, irregular respirations) is a LATE and ominous sign of severely ↑ICP, indicating impending brainstem herniation.

CT scan showing signs of elevated intracranial pressure

📉 Management - Bringing Down the Pressure

A tiered approach is used to manage elevated ICP, starting with the least invasive measures.

  • Initial Steps (Tier 1):
    • Elevate head of bed to 30° (promotes venous outflow).
    • Sedation & analgesia (↓ metabolic demand).
  • Medical Management (Tier 2):
    • Hyperosmolar therapy: Mannitol or hypertonic saline (3%).
    • Hyperventilation (Temporary): Target PaCO₂ 30-35 mmHg to cause vasoconstriction.
  • Refractory ICP (Tier 3):
    • CSF Drainage: Via External Ventricular Drain (EVD).
    • Barbiturate Coma: ↓ cerebral metabolic rate.
    • Decompressive Craniectomy: Last resort.

⭐ Hyperventilation is a rapid but temporary bridge to definitive treatment. Prolonged use risks ischemia from excessive vasoconstriction.

Tiered approach to intracranial pressure management

💥 Complications - The Brain's Breaking Point

Brain Herniation Syndromes Diagram

  • Subfalcine: Cingulate gyrus under falx → ACA compression.
  • Transtentorial (Uncal): Uncus through tentorial notch → CN III palsy (blown pupil), contralateral hemiparesis (Kernohan's notch), coma.
  • Tonsillar: Cerebellar tonsils through foramen magnum → brainstem compression → cardiorespiratory arrest.

⭐ Uncal herniation: Ipsilateral fixed, dilated pupil (CN III palsy) often precedes contralateral hemiparesis.

⚡ Biggest Takeaways

  • Cushing's triad (hypertension, bradycardia, irregular respirations) signals impending herniation.
  • Maintain CPP > 60 mmHg (CPP = MAP - ICP) and keep ICP < 20 mmHg.
  • Initial management includes head elevation (30°), sedation, and analgesia.
  • Use hyperosmolar therapy (mannitol, hypertonic saline) to draw fluid from the brain.
  • Hyperventilation (target pCO₂ 30-35 mmHg) causes transient vasoconstriction, lowering ICP.
  • An EVD is the gold standard for both ICP monitoring and therapeutic CSF drainage.

Practice Questions: Intracranial pressure management

Test your understanding with these related questions

A 67-year-old man presents to the emergency department for a headache. The patient states his symptoms started thirty minutes ago. He states he experienced a sudden and severe headache while painting his house, causing him to fall off the ladder and hit his head. He has also experienced two episodes of vomiting and difficulty walking since the fall. The patient has a past medical history of hypertension, obesity, and atrial fibrillation. His current medications include lisinopril, rivaroxaban, atorvastatin, and metformin. His temperature is 99.5°F (37.5°C), blood pressure is 150/105 mmHg, pulse is 90/min, respirations are 15/min, and oxygen saturation is 98% on room air. On physical exam, the patient localizes his headache to the back of his head. Cardiac exam reveals a normal rate and rhythm. Pulmonary exam reveals minor bibasilar crackles. Neurological exam is notable for minor weakness of the muscles of facial expression. Examination of cranial nerve three reveals a notable nystagmus. Heel to shin exam is abnormal bilaterally. The patient's gait is notably ataxic. A non-contrast CT scan of the head is currently pending. Which of the following is the most likely diagnosis?

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Flashcards: Intracranial pressure management

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One treatment for refractory Idiopathic intracranial hypertension is _____ shunt placement to reroute CSF from the ventricles

TAP TO REVEAL ANSWER

One treatment for refractory Idiopathic intracranial hypertension is _____ shunt placement to reroute CSF from the ventricles

ventriculoperitoneal (VP)

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