What is the recommended Total Intravenous Anesthesia (TIVA) protocol for a 55kg patient with hypertension on losartan (angiotensin II receptor antagonist) maintenance, undergoing spinal decompression T6-L1 with Intraoperative Neurophysiological Monitoring (IONM)?

TIVA Protocol for 55kg Patient on Losartan Undergoing T6-L1 Spinal Decompression with IONM

Anesthetic Maintenance Regimen

Use propofol-based TIVA with remifentanil for this case, as TIVA is compatible with IONM and may reduce postoperative cognitive dysfunction in this patient population. 1

Induction Protocol

• Propofol: 0.5 mg/kg followed by 10 mg every 10 seconds (approximately 27.5 mg initial bolus for 55kg patient) 2
• Remifentanil: 1 mcg/kg bolus (55 mcg for this patient) followed immediately by infusion at 0.5 mcg/kg/min 2, 3
• Rocuronium: 0.9-1.2 mg/kg (50-66 mg) for intubation 4

Maintenance Protocol

Five minutes after intubation, adjust to maintenance dosing: 2, 3

• Propofol infusion:

  • First 10 minutes: 10 mg/kg/h (550 mg/h = 9.2 mg/min)
  • Second 10 minutes: 6 mg/kg/h (330 mg/h = 5.5 mg/min)
  • Thereafter: 4 mg/kg/h (220 mg/h = 3.7 mg/min)

• Remifentanil: Reduce to 0.125 mcg/kg/min (6.9 mcg/min) after initial 5 minutes 3

• Oxygen/Air mixture: 50%/50% O₂/Air (avoid nitrous oxide as it increases PONV and delays bowel function) 4

IONM-Specific Considerations

Maintain processed EEG monitoring (BIS) throughout the case, as this is mandatory when using TIVA with neuromuscular blockade. 4

• Target BIS: 40-60 (avoid burst suppression and excessively deep anesthesia) 4
• Avoid volatile anesthetics: While 3% desflurane (0.5 MAC) can be used with IONM 5, pure TIVA is preferred as it provides more stable SSEP and tcMEP monitoring without the confounding effects of halogenated agents 5
• Neuromuscular monitoring: Use quantitative TOF monitoring at hand muscles (not facial) throughout, maintaining TOF ratio ≥0.90 before extubation 4

Hemodynamic Management for Patient on Losartan

This patient requires careful blood pressure management due to chronic ARB therapy and the high-risk nature of multilevel spinal surgery (T6-L1). 4

Blood Pressure Targets

• Avoid deliberate hypotension in this multilevel spine case, as the procedure carries high risk for perioperative visual loss 4
• Maintain MAP within 20% of baseline: Check preoperative baseline blood pressure and maintain intraoperative pressures near this level 4
• Continuous arterial line monitoring: Strongly recommended for this multilevel case with anticipated prolonged duration and blood loss 4

Managing Propofol-Induced Hypotension

Propofol can increase vasopressor requirements, particularly in patients on chronic ARB therapy: 4

• Have vasopressors immediately available: Phenylephrine 50-100 mcg boluses or norepinephrine infusion 0.02-0.1 mcg/kg/min
• Treat prolonged significant decreases in blood pressure immediately 4
• Consider lower propofol infusion rates if hypotension persists despite vasopressor support 4

Monitoring Requirements

Mandatory monitoring for this case includes: 4

• Continuous arterial blood pressure (invasive line recommended)
• Pulse oximetry with plethysmograph
• ECG (5-lead preferred)
• End-tidal CO₂ waveform capnography
• Temperature (every 30 minutes minimum)
• Processed EEG (BIS or equivalent) - mandatory with TIVA and neuromuscular blockade 4
• Quantitative neuromuscular monitoring (TOF at adductor pollicis)
• Airway pressure, tidal volume, respiratory rate
• Hemoglobin/hematocrit monitoring: Check periodically during surgery given substantial blood loss risk in multilevel decompression 4

Ventilation Strategy

Use lung-protective ventilation: 4

• Tidal volume: 6-8 mL/kg ideal body weight (330-440 mL for 55kg patient)
• PEEP: 6-8 cm H₂O
• Target end-tidal CO₂: 35-40 mmHg

Analgesia and Adjuncts

Multimodal Analgesia

Implement opioid-sparing multimodal analgesia to facilitate recovery: 4

• Acetaminophen: 1000 mg IV at induction (baseline treatment for all pain intensities) 4
• Dexamethasone: 4-8 mg IV at induction (reduces PONV and may provide analgesic benefit) 4
• Consider ketamine: 0.2-0.5 mg/kg bolus at induction, then 2-5 mcg/kg/min infusion (may reduce chronic postoperative pain and provides opioid-sparing effect) 4

PONV Prophylaxis

This patient is high-risk for PONV (opioid use, spine surgery, prone positioning): 4

• Ondansetron: 4 mg IV near end of case
• Dexamethasone: 4-8 mg IV at induction (dual benefit for PONV and analgesia)
• TIVA itself reduces PONV compared to volatile anesthetics 2, 3

Neuromuscular Blockade Management

After initial intubating dose of rocuronium (50-66 mg): 4

• Maintenance: Redose rocuronium 10-15 mg as needed based on TOF monitoring
• Target: 1-2 twitches on TOF during surgery for IONM compatibility
• Reversal: Sugammadex 2-4 mg/kg (110-220 mg) at case end to achieve TOF ratio ≥0.90 before extubation 4
• Document TOF ratio ≥0.90 before extubation (mandatory) 4

Fluid Management

For this multilevel spine case with anticipated blood loss: 4

• Crystalloid: Balanced crystalloid solution (lactated Ringer's or Plasma-Lyte)
• Colloid consideration: Higher colloid percentage may reduce risk of ischemic optic neuropathy in high blood loss cases 4
• Transfusion threshold: Maintain hemoglobin >8-9 g/dL given risk of perioperative visual loss in multilevel spine surgery 4
• Monitor urine output: Target >0.5 mL/kg/h

VTE Prophylaxis

Initiate mechanical prophylaxis: 4

• Sequential compression devices on lower extremities
• Continue throughout hospitalization

Temperature Management

Maintain normothermia (36-37°C) throughout the case: 4

• Forced-air warming blanket
• Warmed IV fluids
• Monitor temperature every 30 minutes minimum 4

Recovery and Emergence

TIVA with propofol-remifentanil provides rapid emergence: 2, 3

• Expected time to spontaneous ventilation: 2-4 minutes after stopping infusions 3
• Expected time to extubation: 3-4 minutes 3
• Expected time to eye opening: 4-6 minutes 3

Critical: Initiate postoperative analgesia immediately, as remifentanil provides no residual analgesia after discontinuation. 3

Common Pitfalls to Avoid

• Do not use nitrous oxide: Increases PONV and delays bowel function 4
• Do not use volatile anesthetics >0.5 MAC: May interfere with IONM reliability, though 3% desflurane has been used successfully 5
• Do not forget processed EEG monitoring: Mandatory with TIVA and neuromuscular blockade 4
• Do not allow deliberate hypotension: High risk for perioperative visual loss in multilevel spine surgery 4
• Do not delay postoperative analgesia: Remifentanil has no residual effect; pain management must begin immediately 3
• Do not extubate without TOF ≥0.90: Document complete reversal of neuromuscular blockade 4