Traumatic Brain Injury anaesthetic management and critical care management along with exam oriented points
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"traumatic brain injury" AND "anesthetic management"
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Traumatic Brain Injury (TBI): Anaesthetic & Critical Care Management
CLASSIFICATION OF TBI (Exam Point)
By GCS score:
| Severity | GCS |
|---|---|
| Mild | 13-15 |
| Moderate | 9-12 |
| Severe | 3-8 |
By mechanism: Blunt vs. Penetrating. Penetrating injury traversing the midbrain bilaterally is generally fatal.
By CT (Marshall Scale - exam favourite):
| Category | Definition |
|---|---|
| Diffuse Injury I | No visible pathology |
| Diffuse Injury II | Cisterns present, midline shift 0-5 mm, no lesion >25 mL |
| Diffuse Injury III | Compressed cisterns, midline shift 0-5 mm |
| Diffuse Injury IV | Midline shift >5 mm |
| Mass lesion evacuated | Any lesion surgically evacuated |
| Mass lesion non-evacuated | High/mixed density lesion >25 mL, not evacuated |
PATHOPHYSIOLOGY (Foundation for All Management)
Primary injury: Occurs at the time of impact - contusions, lacerations, diffuse axonal injury (DAI), hematomas. Not remediable.
Secondary injury: The major target of management. Caused by:
- Raised ICP
- Hypotension (SBP <90 mmHg - single most avoidable cause of secondary injury)
- Hypoxia (SpO2 <90% or PaO2 <60 mmHg)
- Hyperthermia
- Hyperglycemia / hypoglycemia
- Hyponatremia
- Seizures
Monroe-Kellie Doctrine (Exam Point): The cranial vault is rigid. Its contents = brain (80%) + CSF (10%) + blood (10%). Any increase in one must be offset by decrease in another to maintain normal ICP.
Normal ICP: 7-15 mmHg. Treatment threshold: >22 mmHg (Brain Trauma Foundation, BTF).
CPP = MAP - ICP. Target: 60-70 mmHg.
ANAESTHETIC MANAGEMENT
A. AIRWAY & INITIAL STABILIZATION
Indications for emergency intubation:
- GCS ≤8
- Loss of protective airway reflexes
- Hemodynamic instability with impaired consciousness
- Impending herniation signs (Cushing's triad: hypertension + bradycardia + irregular breathing)
Rapid Sequence Intubation (RSI) is the technique of choice - all TBI patients are presumed full stomach + have raised ICP risks.
Key RSI principle: Avoid succinylcholine-induced fasciculations raising ICP in known raised ICP? This is now nuanced - succinylcholine remains acceptable in emergency airway. Rocuronium (1.2 mg/kg) is the alternative.
Cervical spine precautions must be maintained (assume C-spine injury until cleared).
Pre-oxygenation is mandatory - even brief hypoxia worsens outcome.
ETCO2 target during ventilation: 35-45 mmHg (normocapnia). Avoid both:
- Hyperventilation (causes cerebral vasoconstriction, ischemia)
- Hypoventilation (raises ICP via vasodilatation)
Exception: Active herniation - brief hyperventilation to ETCO2 30-35 mmHg as temporizing bridge.
B. INDUCTION AGENTS (Exam Favourite)
| Drug | Effect on ICP / CBF | Notes |
|---|---|---|
| Propofol | Decreases ICP, CBF, CMRO2 | Drug of choice; can cause hypotension (worsen CPP) - use cautiously, titrate |
| Thiopental | Decreases ICP, CBF, CMRO2 | Historically used; causes myocardial depression, hypotension |
| Etomidate | Minimal effect on MAP; reduces ICP | Haemodynamically stable - preferred in shocked TBI patients |
| Ketamine | Once feared to raise ICP (now controversial) | Recent evidence shows it may be safe/beneficial in ventilated patients; raises BP (protects CPP); useful in hypotensive TBI |
| Midazolam | Lowers ICP | Can cause hypotension |
Key Exam Point: Etomidate is the most haemodynamically stable induction agent in TBI. Ketamine's reputation for raising ICP has been revised - it may be safe in RSI when the patient is ventilated.
C. MAINTENANCE OF ANAESTHESIA
- Avoid N2O (increases CMRO2 and CBF; expands air-containing spaces)
- Volatile agents (isoflurane, sevoflurane, desflurane): All cause dose-dependent cerebral vasodilation, raising CBF/ICP. Use at ≤1 MAC. Sevoflurane preferred over desflurane (desflurane most cerebrovascular).
- Total IV Anaesthesia (TIVA) with propofol + opioid is preferred for intracranial surgery - best ICP control, better cerebral metabolic suppression
- Opioids (fentanyl, remifentanil): Minimal ICP effect; maintain haemodynamic stability - allow lower doses of other agents
- Avoid succinylcholine infusion (raises ICP due to fasciculations with repeated dosing)
D. BLOOD PRESSURE / HAEMODYNAMIC TARGETS (Exam Numbers)
| Age Group | Minimum SBP |
|---|---|
| 15-49 years and ≥70 years | ≥110 mmHg |
| 50-69 years | ≥100 mmHg |
- Aggressive CPP >90 mmHg with vasopressors should be avoided (increases respiratory failure risk)
- CPP target: 60-70 mmHg
- Hypotension (SBP <90 mmHg) is strongly correlated with poor outcome - a single hypotensive episode doubles mortality
Vasopressor of choice: Norepinephrine (best CPP support). Avoid dopamine as first-line.
Fluids: Isotonic crystalloid (0.9% saline) preferred. Avoid hypotonic fluids (increase cerebral edema). Lactated Ringer's is mildly hypotonic - use with caution. Even modestly positive fluid balance worsens outcome.
E. VENTILATION IN THE OR
- Target PaO2 >60 mmHg, SpO2 >95%
- Target PaCO2 35-40 mmHg (normocapnia)
- Avoid PEEP >10 cmH2O (impairs cerebral venous drainage, raises ICP)
- Judicious PEEP for oxygenation if needed; the benefit-risk balance must be assessed
- Head 30° elevation improves venous drainage
- Avoid tight cervical collars or tight ETT ties - impair jugular venous outflow
CRITICAL CARE (ICU) MANAGEMENT
A. MONITORING
ICP Monitoring - Indications (BTF Guidelines):
- Severe TBI (GCS 3-8) with abnormal CT scan
- Severe TBI with normal CT if ≥2 of: age >40, unilateral/bilateral motor posturing, SBP <90
ICP Monitoring Methods:
| Method | Gold Standard? | Notes |
|---|---|---|
| Ventricular catheter (EVD) | YES | Also allows CSF drainage (therapeutic); increased infection risk |
| Parenchymal (Codman/Camino) | No | Less invasive; cannot drain CSF; measures local pressure |
| Subdural/epidural bolts | No | Least accurate |
ICP threshold for treatment: >22 mmHg (BTF 4th Edition)
Advanced multimodal monitoring:
- SjvO2 (Jugular venous oximetry): normal 55-75%; <50% = ischemia; >75% = hyperemia/shunting
- PbtO2 (Brain tissue oxygenation, Licox): target >15-20 mmHg
- Microdialysis: Glutamate, lactate/pyruvate ratio (LPR >40 = ischemia)
- TCD (Transcranial Doppler): Non-invasive CBF assessment; Lindegaard index >3 = vasospasm
- NIRS: Non-invasive regional cerebral oxygenation
B. TIERED ICP MANAGEMENT (SIBICC Guidelines - Exam Favourite)
Tier 0 (All TBI Patients, ICU Baseline):
- HOB elevation 30° (Reverse Trendelenburg)
- Loosen cervical collar
- Adequate analgesia (IV fentanyl 25-50 mcg q5min prn)
- Normothermia (treat fever aggressively - antipyretics + cooling)
- Normoglycemia (4-10 mmol/L)
- Prevent seizures (prophylactic phenytoin/levetiracetam for first 7 days)
- Avoid Valsalva, coughing, ventilator dyssynchrony
- Normoxia, normocapnia
Tier 1 (ICP >22 mmHg despite Tier 0):
- Sedation/Analgesia: Propofol (drug of choice - decreases CMRO2, CBF, rapidly cleared for neurological assessment) + opioid; dexmedetomidine as alternative
- CSF drainage via EVD (if present)
- Osmotherapy (bolus only, never prophylactic/scheduled):
- Mannitol: 0.25-1 g/kg IV bolus q6h; hold if serum osmolality >320 mOsm/kg or Na >160; peak effect at ~60 min; lasts 6-8 hrs
- Hypertonic saline (HTS): 3% at 30-50 mL/hr OR 23.4% HTS 30-60 mL IV via central line q6h; hold if Na >160 mEq/L
HTS vs Mannitol (Exam Point):
- HTS preferred in: hypovolemia, hypotension (no diuretic effect), hypernatremia can be corrected later
- Mannitol preferred in: fluid overload
- 30 mL of 23.4% HTS is at least as effective as mannitol for acute ICP reduction
Tier 2 (Persistent ICP >22 mmHg):
- Mild hyperventilation PaCO2 30-35 mmHg (only temporizing; cerebral hypoxia risk)
- Neuromuscular blockade (NMB) - single test dose first; if effective, proceed to infusion
- Advanced neuromonitoring (SjvO2, PbtO2) to guide therapy
- Consider repeat CT to rule out new surgical lesion
Tier 3 (Refractory ICP):
- Barbiturate coma: Pentobarbital 10 mg/kg loading over 30 min, then 1-4 mg/kg/h; titrate to EEG burst suppression; requires continuous EEG monitoring; frequently causes hypotension requiring vasopressors
- Decompressive craniectomy (bifrontal/bifrontoparietal): reserved for life-threatening ICP refractory to all medical measures; reduces mortality but may not improve functional outcome (DECRA and RESCUEicp trials)
- Continuous NMB (if test dose was effective in Tier 2)
- Therapeutic hypothermia NOT recommended for salvage ICP treatment (BTF guideline)
C. WHAT NOT TO DO (Exam Favourite - "Contraindicated Therapies")
| Therapy | Reason to Avoid |
|---|---|
| Steroids (dexamethasone) | Increase mortality in TBI (CRASH trial) - no benefit |
| Prophylactic hyperventilation | Cerebral ischemia from vasoconstriction |
| Scheduled/continuous hyperosmolar therapy | Should be bolus only |
| Therapeutic hypothermia (prophylactic) | No outcome benefit; POLAR, EUROTHERM3235 trials negative |
| CPP >90 mmHg aggressively | Worsens respiratory failure |
| Lumbar CSF drainage | Risk of cerebellar herniation in raised ICP |
| Furosemide (routine) | Not recommended |
| High-dose propofol (>5 mg/kg/h) | Propofol infusion syndrome (PRIS) |
D. SPECIFIC ICU PRIORITIES
Glucose: Target 4-10 mmol/L. Both hypoglycemia and hyperglycemia worsen outcome.
Temperature: Normothermia strictly. Every 1°C rise increases CMRO2 by ~7%. Fever management: paracetamol + cooling blanket.
Seizure Prophylaxis:
- Phenytoin or levetiracetam for first 7 days only (prevents early posttraumatic seizures)
- No evidence prophylaxis reduces late seizures
- NMB patients require continuous EEG monitoring (masks seizures)
Nutrition:
- Begin enteral nutrition within 24-48 hours of injury
- Full nutrition by day 7
- TBI patients are hypermetabolic and hypercatabolic for weeks to months
VTE Prophylaxis:
- Mechanical (compression stockings/pneumatic devices): immediately
- Pharmacological (LMWH): begin 24-48 hours after injury once hemorrhage is stable on imaging
Paroxysmal Sympathetic Hyperactivity ("Storming"):
- Features: tachycardia, hypertension, hyperthermia, diaphoresis, tachypnea, posturing
- Common in diffuse axonal injury
- Treatment: morphine, bromocriptine, β-blockers (propranolol), clonidine
Tracheostomy:
- Early tracheostomy within 5-7 days if prolonged mechanical ventilation anticipated
- Reduces VAP, ICU stay
Amantadine: Dopamine agonist; improves cognitive recovery post-TBI especially if given early.
E. SURGICAL MANAGEMENT
Epidural Hematoma (EDH):
- "Biconvex lens" on CT; typically from middle meningeal artery rupture
- Classic: LOC → lucid interval → rapid deterioration
- Evacuate urgently - good prognosis if evacuated early
Subdural Hematoma (SDH):
- Crescent-shaped, crosses suture lines
- Acute SDH: bridging vein tear; high mortality
- Surgical threshold: thickness >10 mm, midline shift >5 mm, or ICP >20 despite treatment
Intracerebral contusion/hematoma:
- Surgical if progressive neurological deterioration + surgically accessible lesion
Decompressive Craniectomy:
- Primary (immediate) or secondary (for refractory ICP)
- DECRA trial: reduced ICP but worse functional outcome
- RESCUEicp trial: reduced mortality at cost of increased severe disability - patient selection important
KEY EXAM MNEMONICS & HIGH-YIELD POINTS
"4 Hs" to avoid in TBI ICU:
- Hypotension (SBP <90 mmHg)
- Hypoxia (SpO2 <90%)
- Hypocarbia (PaCO2 <35, except herniation)
- Hypercarbia (PaCO2 >45)
ICP Waveforms (Lundberg):
- A waves (Plateau waves): 50-80 mmHg, 5-20 min duration - PATHOLOGICAL, cerebral ischemia
- B waves: 20-50 mmHg, 0.5-2 min - may precede A waves
- C waves: <20 mmHg, 4-8/min - relatively benign
Monroe-Kellie: Foundation of all ICP management.
Cushing's Triad (=impending herniation, not just raised ICP): Hypertension + Bradycardia + Irregular respirations
CPP = MAP - ICP; target 60-70 mmHg
ICP treatment threshold = 22 mmHg (BTF 4th Ed)
CRASH trial = steroids harm TBI patients
DECRA trial = decompressive craniectomy reduced ICP but worsened functional outcomes
Propofol infusion syndrome (PRIS): Metabolic acidosis + rhabdomyolysis + renal failure + cardiac failure. Avoid >5 mg/kg/h or prolonged high-dose infusions. Switch to midazolam or barbiturate.
RSI drug of choice in stable TBI: Propofol or thiopental | In haemodynamically unstable TBI: Etomidate or ketamine
Osmotherapy monitoring:
- Mannitol: hold if osmolality >320 mOsm/kg
- HTS: hold if Na >160 mEq/L
Traumatic SAH: Occurs in up to 60% of TBI; ~20% develop vasospasm
REFERENCES
- Miller's Anesthesia, 10th Ed (Ch. 62, 80) - Trauma and Neurocritical Care
- Sabiston Textbook of Surgery, 21st Ed (Ch. 41) - TBI Critical Care
- Rosen's Emergency Medicine - ICP Management
- Adams & Victor's Principles of Neurology, 12th Ed - Raised ICP Management
- Systematic Review: Intraoperative Anesthetic Care for Intracranial Hypertension/Herniation (2026, PMID 39793097)
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