Traumatic Brain Injury Management

TBI Pathophys & Assessment - Brain Under Pressure

• Pathophysiology:
  • Primary Injury: Immediate mechanical damage (contusion, Diffuse Axonal Injury - DAI). Irreversible.
  • Secondary Injury: Evolves post-trauma; key factors: hypoxia (PaO₂ <60 mmHg), hypotension (SBP <90 mmHg), ↑Intracranial Pressure (ICP), cerebral edema. Potentially treatable.
  • Monro-Kellie Doctrine: Intracranial volume (Brain parenchyma, Blood, CSF) is fixed. An ↑ in one component requires a ↓ in others to maintain normal ICP.
  • ICP: Normal 5-15 mmHg. Sustained ↑ICP >20 mmHg is critical & requires treatment.
  • Cerebral Perfusion Pressure: $CPP = MAP - ICP$. Target 50-70 mmHg. Avoid CPP <50 mmHg.
• Assessment:
  • Glasgow Coma Scale (GCS): Eye (E1-4), Verbal (V1-5), Motor (M1-6). Total 3-15.
    • Severe TBI: GCS 3-8 (Intubate if GCS ≤8)
    • Moderate TBI: GCS 9-12
    • Mild TBI: GCS 13-15
  • Pupillary Examination: Size, symmetry, reactivity to light. Unilateral fixed dilated pupil suggests uncal herniation.

⭐ Cushing's Triad (late sign of markedly ↑ICP & impending brainstem herniation):

1. Hypertension (often with widened pulse pressure)
2. Bradycardia
3. Irregular respirations (e.g., Cheyne-Stokes)

Anesthetic Goals & Pre-op - Code Grey Guardian

• Physiological Targets (Maintain Homeostasis):
  • ICP: < 20-22 mmHg.
  • CPP: 60-70 mmHg ($CPP = MAP - ICP$).
  • MAP: > 80 mmHg (adults), age-specific for peds.
  • PaO2: > 100 mmHg (avoid hypoxia).
  • PaCO2: 35-40 mmHg (normocapnia; avoid routine hyperventilation).
  • Glucose: 140-180 mg/dL.
  • Temperature: Normothermia (36-37.5°C).
• Pre-anesthetic Management (📌 "CRANIUM"):
  • C-spine: Assume injury, Manual In-Line Stabilization (MILS) for intubation.
  • RSI: Preferred for airway control.
    • Induction: Etomidate (0.3 mg/kg, neuroprotective, hemodynamically stable) or Ketamine (1-2 mg/kg, if hypotensive; use with caution if ICP known to be very high).
    • Paralytic: Rocuronium (1.2 mg/kg) or Succinylcholine (1.5 mg/kg, beware fasciculations/ICP rise).
  • Avoid Hypotension & Hypoxia: Critical to prevent secondary brain injury.
  • Neurological Assessment: GCS, pupils, deficits.
  • ICP Monitoring/Management: Elevate head of bed 30°, neutral neck.
  • Urine Output & Fluids: Maintain euvolemia.
  • Mannitol/Hypertonic Saline: If signs of herniation or acutely ↑ICP.

⭐ The 'lethal triad' in trauma-acidosis, hypothermia, and coagulopathy-significantly worsens TBI outcomes by exacerbating secondary brain injury and complicating neurosurgical interventions.

Intraoperative Management - Neuro-Anesthesia Navigator

• Key Goals: Maintain CPP >60-70 mmHg; MAP >80 mmHg; PaO2 >100 mmHg; PaCO2 35-40 mmHg; Normothermia; Euglycemia.
• Anesthetic Choices (Effects on ICP, CBF, CMRO2, MAP):

  Agent Type	Agent	ICP	CBF	CMRO2	MAP	Note
  IV	Propofol	↓↓↓	↓↓↓	↓↓↓	↓	Neuroprotective
  	Etomidate	↓	↓	↓	↔	Stable hemodynamics
  	Ketamine	↑/↔	↑	↔/↑	↑	Preserves CPP; caution
  Volatile	(e.g., Sevo)	↔/↑	↑	↓	↓	Low MAC; ICP↑ dose-dependent

• ICP Control Agents:
  • Mannitol: 0.25-1 g/kg IV.
  • Hypertonic Saline (HTS): e.g., 3% (2-5 mL/kg).

  ⭐ Hyperventilation (PaCO2 30-35 mmHg) for acute ↑ICP is temporizing; prolonged use risks ischemia.

• Acute Intraoperative ↑ICP Management:

Postoperative Care & Complications - TBI Aftermath Alert

• ICU: Maintain CPP >60-70 mmHg; ICP <20-22 mmHg; $PCO_2$ 35-45 mmHg.
• Optimize sedation, analgesia; ensure adequate oxygenation.
• Prophylaxis: DVT, stress ulcers. Seizure prophylaxis (e.g., phenytoin for 7 days if high-risk).
• Monitor for complications:
  • Cerebral edema, hematoma re-accumulation.
  • Seizures (early/late onset).
  • Vasospasm (typically days 4-14).
  • Hydrocephalus (communicating/obstructive).
  • Infections (VAP, meningitis).
  • Electrolyte disturbances (SIADH, DI).

⭐ Tight glycemic control (target glucose <180 mg/dL) and aggressive fever management (maintain normothermia, e.g., temp <37.5°C) are critical to prevent secondary brain injury and improve outcomes after TBI.

High‑Yield Points - ⚡ Biggest Takeaways

• Maintain ICP < 20-22 mmHg and CPP 60-70 mmHg.
• Avoid prophylactic hyperventilation (PaCO2 < 30 mmHg); reserve for imminent herniation.
• Use isotonic fluids; avoid hypotonic solutions and dextrose. Maintain euvolemia.
• Prefer IV anesthetics for ICP control. Ketamine generally safe. Avoid N2O.
• Mannitol or hypertonic saline for acute ↑ICP; monitor serum osmolality.
• Prevent hyperthermia; maintain normothermia.
• Seizure prophylaxis (e.g., phenytoin) for severe TBI to prevent early seizures.