Anesthesia for Supratentorial Craniotomy

Preoperative Assessment & Goals - Brainy Prep Work

• Neurological Status: Baseline GCS, focal deficits, seizure history/control.
• ICP Assessment: Signs of ↑ICP (headache, N/V, papilledema). Cushing's triad (late).
• Airway: Standard assessment; consider difficult airway with ↑ICP or cervical spine issues.
• Systemic Review: CV (HTN, IHD), Respiratory (pulmonary edema risk), Renal function.
• Medications: Continue anticonvulsants. Steroids (e.g., dexamethasone). Manage anticoagulants/antiplatelets.
• Investigations: Recent MRI/CT. Baseline bloods (FBC, U&E, Coags).
• Anesthetic Goals:
  • Maintain CPP ($CPP = MAP - ICP$; use CVP if higher). Target >60-70 mmHg.
  • Control ICP (target <20 mmHg).
  • Smooth induction & emergence.
  • Rapid recovery for neuro assessment.

⭐ Patients on long-term phenytoin may exhibit resistance to non-depolarizing muscle relaxants due to enzyme induction.

Induction & Neuromonitoring - Setting the Stage

• Primary Goals:
  • Maintain hemodynamic stability (MAP within 20% of baseline).
  • Control ICP (target < 20 mmHg).
  • Ensure adequate CPP (target 60-70 mmHg; $CPP = MAP - ICP$).
• Induction Protocol:

• Airway & Positioning: Head up 15-30° (promotes venous drainage), neutral neck.
• Essential Monitoring:
  • Standard ASA (ECG, NIBP, SpO2, EtCO2, Temp).
  • Invasive Arterial BP (A-line): For continuous MAP & ABGs.
  • Neuromuscular monitoring (TOF).
  • Consider: CVP, EEG/BIS, SSEP/MEP if eloquent areas involved.

  ⭐ Rapid Sequence Intubation (RSI) is generally avoided due to risk of ICP spike with succinylcholine; a modified rapid sequence with rocuronium is preferred if aspiration risk is high.

Intraoperative Anesthetic Management - Skull Session Secrets

• Brain Relaxation:
  • Head elevation: 15-30°.
  • Hyperventilation: PaCO₂ 30-35 mmHg.
  • Osmotic diuretics: Mannitol (0.25-1 g/kg) or Hypertonic Saline (HTS).
  • Loop diuretics: Furosemide (0.5-1 mg/kg).
  • CSF drainage (if available).
• Anesthetic Choice:
  • TIVA (Propofol + Remifentanil) favored: ↓ICP, rapid emergence.
  • Volatiles: Maintain <1 MAC if used.
• Hemodynamic Goals:
  • Maintain Mean Arterial Pressure (MAP) within 20% of baseline.
  • Cerebral Perfusion Pressure (CPP) >60-70 mmHg.
• Fluid Management:
  • Isotonic crystalloids (Normal Saline preferred). Avoid hypotonic & glucose solutions.
• ⚠️ Key Complications & Management:
  • Venous Air Embolism (VAE): Sudden ↓ETCO₂, ↓SpO₂, hypotension. Mgmt: Notify surgeon, flood field with saline, 100% O₂, aspirate from CVC, left lateral decubitus (Durant's maneuver).
  • Intraoperative Seizures: Propofol, thiopental, levetiracetam.

⭐ During craniotomy, a sudden decrease in End-Tidal CO₂ (ETCO₂) accompanied by hypotension should immediately raise suspicion for Venous Air Embolism (VAE).

Emergence & Postoperative Care - Waking Up Well

• Goal: Smooth emergence, stable hemodynamics, early neuro-assessment.
• Smooth Emergence Strategies:
  • Lidocaine IV (1-1.5 mg/kg) or LTA.
  • Short-acting opioids (e.g., remifentanil, fentanyl).
  • Dexmedetomidine infusion.
  • Avoid $N_2O$ at closure (prevents pneumocephalus expansion).
• Extubation Criteria: Awake, follows commands, adequate ventilation (TOF > 0.9).
• Immediate Postoperative Care (PACU/Neuro-ICU):
  • Frequent neurological checks (GCS, pupils, motor function).
  • Strict BP control (e.g., SBP < 140-160 mmHg, avoid hypotension).
  • Multimodal analgesia (paracetamol, opioids; NSAIDs with caution).
  • Antiemetics (e.g., ondansetron).
  • Maintain normothermia, normocapnia, normoglycemia.
• Key Complications to Monitor: Hematoma, seizures, ↑ICP, PONV, delayed awakening.

⭐ Delayed emergence or neurological deterioration post-craniotomy mandates urgent CT scan to exclude intracranial hematoma or acute hydrocephalus.

High‑Yield Points - ⚡ Biggest Takeaways

• ICP management is crucial: target PaCO2 30-35 mmHg, mannitol, and consider CSF drainage.
• Maintain Cerebral Perfusion Pressure (CPP) at 60-70 mmHg by optimizing MAP and ICP.
• Anesthetic choices: TIVA or volatile agents (<1 MAC); strictly avoid Nitrous Oxide.
• Ensure smooth emergence to prevent coughing, straining, and subsequent ICP elevation.
• Key complications: Venous Air Embolism (VAE), seizures, and intracranial hematoma.
• Preoperative: assess neurological deficits, ICP signs, and steroid/anticonvulsant use.