Anesthesia for Traumatic Brain Injury

Anesthesia for Traumatic Brain Injury

Anesthesia for Traumatic Brain Injury

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TBI Pathophysiology - Brain Under Siege

  • Primary Injury:
    • Irreversible mechanical damage occurring at impact (e.g., contusion, laceration, Diffuse Axonal Injury (DAI)).
  • Secondary Injury:
    • Develops minutes to days post-injury; a key therapeutic target, as it is potentially preventable or reversible.
    • Exacerbated by:
      • Systemic insults: Hypotension (SBP < 90 mmHg), Hypoxia (PaO2 < 60 mmHg).
      • Intracranial events: Increased Intracranial Pressure (ICP), cerebral edema (vasogenic & cytotoxic), cerebral ischemia.
    • Cellular damage cascade: Excitotoxicity (e.g., glutamate), inflammation, free radical production, apoptosis.
    • TBI Primary and Secondary Injury Mechanisms
  • Monro-Kellie Doctrine:
    • The skull is a rigid box; the sum of intracranial volumes (brain parenchyma, blood, Cerebrospinal Fluid (CSF)) is constant.
    • An increase in one component must be compensated by a decrease in another, otherwise ICP rises.
  • Cerebral Perfusion:
    • Cerebral autoregulation is often impaired in TBI.
    • Cerebral Perfusion Pressure ($CPP = MAP - ICP$); target range is typically 50-70 mmHg.

Cushing's Triad: Represents a late and ominous sign of critically increased ICP and impending brainstem herniation. It consists of:

  • Hypertension (often with a widened pulse pressure)
  • Bradycardia
  • Irregular respirations (e.g., Cheyne-Stokes breathing)

Preoperative Management - TBI Triage Time

  • Airway: Secure early (RSI if GCS ≤8). Avoid hypoxia (SpO₂ >94%) & maintain normocapnia (PaCO₂ 35-45 mmHg).
  • Breathing: Optimize oxygenation; mechanical ventilation often needed.
  • Circulation:
    • Maintain SBP >100 mmHg (adults), age-adjusted for pediatrics.
    • Aggressive fluid resuscitation (isotonic crystalloids: NS, RL).
    • Target CPP >60-70 mmHg; $CPP = MAP - ICP$.
  • Disability: Neurological assessment (GCS, pupils).
    • Glasgow Coma Scale Scoring
  • Exposure/Environment: Prevent hypothermia (target >36°C). Control glucose.

High-Yield: Indications for ICP monitoring in severe TBI (GCS 3-8 with abnormal CT) OR (GCS 3-8 with normal CT but 2+ of: age >40 yrs, SBP <90 mmHg, or motor posturing).

📌 Mnemonic (ABCDE): Airway, Breathing, Circulation, Disability, Exposure/Environment control for secondary injury prevention during the "Golden Hour".

Intraoperative Anesthesia - Neuro-Protective Shield

  • Primary Goals: Maintain CPP (50-70 mmHg), control ICP (<22 mmHg), ensure cerebral oxygenation.
  • Induction Agents:
    • Propofol (↓ICP; caution: hypotension).
    • Etomidate (hemodynamic stability).
    • Lidocaine (1.5 mg/kg) IV to blunt intubation response.
  • Maintenance Strategy:
    • TIVA (Propofol + Remifentanil): Preferred for ↓CMRO2, ↓CBF, ↓ICP.
    • Volatiles (Isoflurane, Sevoflurane <1 MAC): Use cautiously; dose-dependent ↑CBF/ICP.
  • Muscle Relaxants: Non-depolarizing (e.g., Rocuronium). Avoid suxamethonium if ↑ICP suspected.
  • Ventilation: Target normocapnia (PaCO2 35-40 mmHg).

    ⭐ The cautious and transient use of hyperventilation to PaCO2 30-35 mmHg for acute ICP rise.

  • Fluid Management: Isotonic crystalloids (e.g., Normal Saline). Avoid hypotonic solutions.
  • Key Adjuncts:
    • Maintain normothermia (36-37.5°C).
    • Strict glucose control (target 140-180 mg/dL).

Anesthetic effects on CMR and CBF

Postoperative Care - Recovery & Risks

  • ICU Management: Neuro-ICU ideal.
    • Maintain CPP > 60-70 mmHg, ICP < 20-22 mmHg.
    • Normoxia (PaO2 > 100 mmHg), normocapnia (PaCO2 35-40 mmHg).
    • Normothermia, euglycemia.
  • Neuromonitoring: Continuous ICP, CPP; serial GCS, pupils.
  • Sedation & Analgesia: Titrate carefully (e.g., propofol, opioids).
  • Ventilation & Extubation:
    • Lung-protective ventilation.
    • Cautious extubation: assess neuro status, airway reflexes; risk of ICP ↑.
  • Key Risks & Management:
    • Cerebral Edema: Mannitol (0.25-1 g/kg), hypertonic saline.
    • Seizures: Prophylaxis (e.g., Phenytoin, Levetiracetam).
    • Infections (VAP, meningitis), DVT prophylaxis.
    • Electrolyte disturbances (SIADH, CSW).

⭐ Prophylactic anticonvulsants (e.g., Phenytoin for 7 days) reduce early post-traumatic seizures (PTS) in high-risk TBI. Neuromonitoring for Traumatic Brain Injury

High‑Yield Points - ⚡ Biggest Takeaways

  • Maintain CPP > 60-70 mmHg and ICP < 20-22 mmHg.
  • Avoid hypotension (SBP < 90 mmHg) and hypoxia (PaO2 < 60 mmHg).
  • Mild hyperventilation (PaCO2 30-35 mmHg) is temporary for ↑ ICP; avoid prolonged use.
  • Mannitol (0.25-1 g/kg) or hypertonic saline (e.g., 3%) reduce ICP.
  • Propofol/barbiturates ↓ CMRO2, ICP; risk hypotension, monitor hemodynamics.
  • Optimize head position (midline, elevated 30°), avoid neck compression.
  • Ketamine: cautiously used if CPP maintained; can ↑ ICP in some patients.

Practice Questions: Anesthesia for Traumatic Brain Injury

Test your understanding with these related questions

A case of trauma comes to the emergency. On examination there is evidence of head injury, BP is 90/60 mmHg, and pulse is 150/min. Which of the following anesthetic agent should be used for induction?

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Flashcards: Anesthesia for Traumatic Brain Injury

1/5

_____ is safe to use in head trauma as it is not associated with rise in ICP

TAP TO REVEAL ANSWER

_____ is safe to use in head trauma as it is not associated with rise in ICP

Etomidate::Anaesthetic

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