Template:TBI pathophysiology

TBI Pathophysiology

• vasoconstriction
  • HTN, Hypocarbia, alkalosis
• No good way to measure cerebral blood flow
  • Use CPP as surrogate
    • CPP is amount of pressure needed to perfuse the brain
    • CPP=MAP-ICP
      • When ICP elevates, CPP decreases
      • Normal ICP
        • 15 in adults
        • <10 to 15 in children
        • 1.5 to 6.0 in infants
• Autoregulation allows the body to control the cerebral blood flow
  • Autoregulatory mechanism is damaged in most TBI patients
• Cushing Reflex- more common in children than adults
  • Hypertension
  • Bradycardia
  • Respiratory Irregularity

Primary injury

• contusions
  • bruises to brain parenchyma
• Hematomas
  • Epidural
  • Subdural
  • Intraparenchymal
  • Intraventricular
  • Subarachnoid
• Diffuse Axonal Injury
• Direct Cellular Damage
  • neurons
  • axons
• tearing and shearing of tissues

Secondary injury

Brain swelling causes increased ICP which compresses the tissue causing ischemia with direct compression of the vasculature causing brain tissue herniation and brain death

• Leads to expansion of the original injury
• Calcium and ion shifts
• Mitochondrial damage
• Production of free radicals
• Enzyme activity that lead to apoptosis