Can a 55kg adult with hypertension, managed by losartan, undergoing spinal decompression T6-L1 with Intraoperative Neurophysiological Monitoring (IONM), use Total Intravenous Anesthesia (TIVA) with propofol and fentanyl?

TIVA with Propofol and Fentanyl for Spinal Decompression with IONM

Yes, TIVA with propofol and fentanyl is appropriate and recommended for this patient undergoing T6-L1 spinal decompression with IONM, with specific protocol modifications to optimize neuromonitoring and manage hypertension. 1, 2, 3

Recommended TIVA Protocol

Use propofol target-controlled infusion (effect-site target 0.5-1 mcg/mL) combined with remifentanil infusion (0.05-0.3 mcg/kg/min) rather than intermittent fentanyl boluses for this prolonged spine surgery with IONM. 1, 2 This approach provides superior hemodynamic stability and facilitates neuromonitoring compared to traditional fentanyl bolusing. 4, 5

Induction Protocol

• Propofol via TCI at effect-site concentration 0.5-1 mcg/mL, avoiding bolus dosing to prevent hemodynamic instability in this hypertensive patient. 1, 2
• Rocuronium 0.9-1.2 mg/kg for intubation (or succinylcholine 1-2 mg/kg as alternative). 1, 2
• Establish invasive arterial blood pressure monitoring before induction when feasible, with vasopressors immediately available (ephedrine or metaraminol). 1, 3 This is particularly important given the patient's hypertension managed with losartan, as propofol decreases cardiac output and systemic vascular resistance in a dose-dependent manner. 3

Maintenance Strategy

Propofol TCI at 0.5-1 mcg/mL combined with remifentanil 0.05-0.3 mcg/kg/min provides optimal conditions for IONM while reducing propofol requirements by approximately 30%. 1, 4 If using fentanyl instead of remifentanil, administer 0.5-1.0 mcg/kg boluses titrated to effect, but recognize this provides less stable analgesia for prolonged procedures. 1, 3

Consider adding dexmedetomidine (0.5-1 mcg/kg bolus then 0.2-0.7 mcg/kg/h) and ketamine (0.5 mg/kg bolus followed by 0.1-0.2 mg/kg/h) to further reduce propofol requirements and improve postoperative analgesia. 1 This multimodal approach is specifically recommended for 4-6 hour endoscopic spine surgery to minimize intraoperative hypotension and postoperative pain. 1

Critical Monitoring Requirements for IONM

Maintain BIS between 40-60 throughout the procedure to prevent awareness while avoiding excessive depth that could impair neuromonitoring. 1, 3 Propofol-based TIVA is superior to volatile anesthetics for IONM because it produces less suppression of motor evoked potentials. 4, 5

Standard monitoring must include:

• Continuous pulse oximetry and waveform capnography 3
• ECG and non-invasive blood pressure measured at least every 5 minutes 3
• Core temperature monitoring 3
• Quantitative neuromuscular monitoring if muscle relaxants used, documenting train-of-four ratio ≥0.90 before extubation 1, 2, 3

Hypertension Management Considerations

The patient's baseline hypertension managed with losartan requires specific attention. 6 Propofol increases vasopressor requirements in hemodynamically challenged patients, and the combination with opioids can cause significant hypotension. 6, 3 Have vasopressors immediately available and consider continuing the patient's morning losartan dose on the day of surgery with a small sip of water, though this should be coordinated with the surgical team. 6

Avoid simultaneous neuraxial and general anesthesia, as this combination is associated with precipitous intraoperative blood pressure falls. 6, 3 For this extensive T6-L1 decompression, general anesthesia alone is appropriate.

Critical Pitfalls to Avoid

Never use nitrous oxide, as it increases postoperative nausea/vomiting and may interfere with neuromonitoring. 2, 3

Do not use propofol if the patient has egg, soy, or sulfite allergies (propofol contains 10% soybean oil and 1.2% purified egg phosphatide). 3

Avoid bolus dosing of propofol or remifentanil during maintenance to prevent hemodynamic instability and respiratory depression. 1, 2, 3

Do not rely on opioid analgesics as the sole adjunct to anesthesia due to greater risk of respiratory depression and postoperative confusion. 6, 3

Adjunctive Medications

Administer dexamethasone 0.15-0.25 mg/kg (maximum 0.5 mg/kg) at induction to reduce postoperative swelling and inflammation. 1 For a 55kg patient, this would be 8.25-13.75 mg.

TIVA with propofol significantly reduces postoperative nausea and vomiting compared to volatile anesthetics. 1, 2

Emergence and Postoperative Management

Ensure complete return of airway reflexes and adequate tidal volumes before extubation, with the patient fully awake. 1, 3 Propofol has rapid clearance with predictable emergence. 3

For breakthrough pain in PACU, titrate fentanyl 0.5-1.0 mcg/kg to effect, with alternatives including morphine 25-100 mcg/kg or ketamine 0.25-0.5 mg/kg. 1

Transition to multimodal oral analgesia as soon as possible, with scheduled acetaminophen 10-15 mg/kg every 6 hours and scheduled NSAIDs if not contraindicated. 1 Reserve opioids for severe breakthrough pain only. 1

Evidence Supporting TIVA for Spine Surgery with IONM

Recent evidence demonstrates that dexmedetomidine as an adjuvant to propofol in TIVA reduces propofol requirements by approximately 30% without affecting IONM recordings, while ensuring stable hemodynamics and decreasing opioid requirements. 4 Additionally, dexmedetomidine displays superior efficacy in alleviating pain and postoperative pain management for 48 hours after spinal fusion compared to remifentanil alone. 5

Low-certainty evidence suggests TIVA may reduce postoperative cognitive dysfunction compared to inhalational anesthesia (OR 0.52,95% CI 0.31 to 0.87). 7 This is particularly relevant for maintaining optimal cognitive function for postoperative neurological assessment.