What is a recommended Total Intravenous Anesthesia (TIVA) protocol using propofol, ketamine, and fentanyl for endoscopic spine surgery?

TIVA Protocol for Endoscopic Spine Surgery Using Propofol, Ketamine, and Fentanyl

For endoscopic spine surgery lasting 4-6 hours, use propofol target-controlled infusion (effect-site target 0.5-1 mcg/mL) combined with ketamine (0.5 mg/kg bolus followed by 0.1-0.2 mg/kg/h infusion) and fentanyl (5 mcg/kg loading dose with 2 mcg/kg supplemental boluses as needed), maintaining BIS 40-60 throughout the procedure. 1

Pre-Induction Preparation

• Establish invasive arterial blood pressure monitoring before induction when feasible, with transducer positioned at tragus level 2
• Have vasopressors immediately available (ephedrine or metaraminol) to treat propofol-induced hypotension 2
• Ensure quantitative neuromuscular monitoring equipment is ready for use 1, 2

Induction Protocol

Administer medications in the following sequence:

• Fentanyl: 5 mcg/kg IV bolus over 2-3 minutes 3
• Ketamine: 0.5 mg/kg IV bolus 1, 4
• Propofol: 2 mg/kg IV bolus for rapid onset, avoiding excessive bolus dosing to prevent hemodynamic instability 3, 2
• Rocuronium: 0.9-1.2 mg/kg for intubation (or succinylcholine 1-2 mg/kg if rocuronium unavailable) 1, 2

Maintenance Protocol

Propofol:

• Target-controlled infusion (TCI) with effect-site concentration of 0.5-1 mcg/mL 1, 2
• Avoid bolus dosing during maintenance to prevent hemodynamic instability 2
• Never exceed 1.5 mcg/mL as this significantly increases risk of over-sedation and hypoventilation 2

Ketamine:

• Continuous infusion at 0.1-0.2 mg/kg/h (equivalent to 1 mcg/kg/min) 1, 4
• This co-administration prevents opioid-induced hyperalgesia while maintaining hemodynamic stability 4

Fentanyl:

• Supplemental boluses of 2 mcg/kg as needed for inadequate analgesia 3
• Titrate based on hemodynamic response and surgical stimulation 3

Adjunctive Medications:

• Dexamethasone: 0.15-0.25 mg/kg (maximum 0.5 mg/kg) at induction to reduce postoperative swelling and inflammation 1, 4
• Dexmedetomidine (optional): 0.5-1 mcg/kg bolus followed by 0.2-0.7 mcg/kg/h infusion to reduce opioid requirements and provide sympatholysis 1, 4

Intraoperative Monitoring Requirements

Mandatory monitoring includes:

• BIS monitoring: Target 40-60 throughout procedure; avoid values below 35 in patients over 60 years to reduce postoperative delirium risk 1, 2
• Quantitative neuromuscular monitoring: Document train-of-four ratio ≥0.90 before extubation 1, 4, 2
• Standard ASA monitoring: Pulse oximetry, capnography, ECG, invasive arterial blood pressure 3
• Core temperature monitoring: Use routinely throughout the case 3

Critical Pitfalls to Avoid

• Never use nitrous oxide as it increases PONV and delays bowel function 4, 2
• Avoid propofol boluses during maintenance as they cause precipitous hypotension 2
• Do not use remifentanil monotherapy without ketamine co-administration, as this leads to opioid-induced hyperalgesia 4
• Avoid burst suppression patterns on EEG in elderly patients (>60 years) to reduce delirium risk 2

Emergence and Extubation

• Discontinue propofol and ketamine infusions 5-10 minutes before anticipated end of surgery 1
• Ensure return of airway reflexes and adequate tidal volumes before extubation 1, 2
• Document train-of-four ratio ≥0.90 with quantitative monitoring 1, 4, 2
• Extubate patient awake in sitting position 2

PACU Pain Management

For breakthrough pain, titrate to effect:

• Fentanyl: 0.5-1.0 mcg/kg IV boluses as first-line 1, 4
• Ketamine: 0.25-0.5 mg/kg IV as alternative 4
• Morphine: 25-100 mcg/kg IV depending on age (use cautiously) 4

Postoperative Analgesia Transition

Multimodal oral analgesia should begin as soon as possible:

• Acetaminophen (paracetamol): 10-15 mg/kg every 6 hours scheduled 3, 1, 4
• NSAIDs: Scheduled dosing if not contraindicated 3, 1, 4
• Opioids: Reserve for severe breakthrough pain only 1, 4

Advantages of This TIVA Protocol

• Significantly reduced PONV compared to volatile anesthetics 1, 2, 5
• Less postoperative pain and reduced opioid consumption compared to desflurane-based anesthesia 5
• Hemodynamic stability when ketamine is combined with propofol, counteracting propofol's hypotensive effects 6, 7, 8
• Absence of psychic disturbances from ketamine when combined with propofol 7
• Rapid, predictable emergence with fast return of airway reflexes 2

Special Considerations for Prolonged Cases (>4 hours)

• Monitor for propofol infusion syndrome (rare but serious): watch for metabolic acidosis, rhabdomyolysis, cardiac dysfunction 1
• Consider propofol dosing based on lean body weight in obese patients 2
• Elderly patients (>60 years) are more sensitive to propofol's cardiovascular effects; monitor closely for hypotension 2
• Maintain adequate depth of anesthesia (BIS 40-60) but avoid excessive depth (BIS <35) in elderly patients 1, 2