What are the anesthetic considerations for a 62-year-old female patient with an incomplete spinal cord injury and hypertension undergoing surgical intervention under neuromonitoring with Total Intravenous Anesthesia (TIVA) using propofol and fentanyl infusion?

Anesthetic Considerations for Spinal Surgery Under Neuromonitoring with TIVA

For a 62-year-old female with incomplete spinal cord injury and hypertension undergoing spinal surgery with neuromonitoring, use propofol infusion at 50-100 mcg/kg/min combined with fentanyl boluses (0.5-1 mcg/kg as needed), with mandatory processed EEG monitoring (BIS 40-60) and quantitative neuromuscular monitoring if muscle relaxants are used. 1, 2

Critical Monitoring Requirements

When administering TIVA with neuromuscular blockade, processed EEG monitoring (BIS or Entropy) and quantitative neuromuscular monitoring are mandatory. 1

• Maintain BIS between 40-60 to prevent awareness while avoiding excessive depth 2
• Standard monitoring includes continuous pulse oximetry, waveform capnography, ECG, and non-invasive blood pressure measured at least every 5 minutes 1
• Core temperature monitoring should be used routinely 1
• Consider invasive arterial blood pressure monitoring before induction when feasible, with transducer at tragus level 2
• If using muscle relaxants, document train-of-four ratio ≥0.90 before extubation 3

Propofol Infusion Management

Maintain propofol at 50-100 mcg/kg/min for neurosurgical procedures, with reduced induction doses in elderly patients. 2, 4

• Avoid rapid bolus administration in this 62-year-old patient to minimize cardiorespiratory depression, including hypotension, apnea, and oxygen desaturation 4
• For induction in patients with potential increased intracranial pressure from spinal cord injury, use slow bolus of approximately 20 mg every 10 seconds instead of rapid boluses 4
• Propofol decreases cardiac output, systemic vascular resistance, and arterial pressure in a dose-dependent manner 2
• In neurosurgical cases, propofol decreases cerebral blood flow, cerebral metabolic rate for oxygen, and intracranial pressure 2

Opioid Selection and Dosing

Use fentanyl boluses of 0.5-1 mcg/kg as needed rather than continuous infusion, avoiding opioids as the sole adjunct. 1, 2

• The Association of Anaesthetists does not support opioid analgesics as the sole adjunct due to greater risk of respiratory depression and postoperative confusion in older patients 1
• Alternative short-acting opioids include alfentanil at 5 mcg/kg initial bolus, then 1-3 mcg/kg as required, or sufentanil at 0.5-1 mcg/kg 2, 5
• If using remifentanil infusion, maintain at 0.05-0.3 mcg/kg/min, avoiding bolus dosing to prevent respiratory depression 5, 3
• Co-administration of opioids potentiates propofol's sedative effect and increases cardiorespiratory depression 4

Hemodynamic Management

Have vasopressors immediately available (ephedrine or metaraminol) before induction, as propofol causes dose-dependent hypotension. 2, 4

• Fluid deficits should be corrected prior to propofol administration 4
• When additional fluid therapy is contraindicated, consider elevation of lower extremities or pressor agents 2, 4
• Monitor closely for hypotension as elderly patients are more sensitive to propofol's cardiovascular effects 3
• Avoid significant decreases in mean arterial pressure to maintain adequate spinal cord perfusion pressure 4

Special Considerations for Spinal Cord Injury

Be prepared for autonomic hyperreflexia, particularly if the injury level is T6 or above, with nicardipine 1 mg IV available for sudden hypertensive episodes. 6

• Autonomic hyperreflexia can manifest as sudden severe hypertension (>220/120 mmHg), bradycardia, and skin eruptions during surgical manipulation 6
• Nicardipine 1 mg IV followed by 2 mcg/kg/min infusion effectively controls autonomic hyperreflexia 6
• Maintain stable hemodynamics throughout to ensure adequate spinal cord perfusion in the setting of incomplete injury 6

Neuromonitoring Compatibility

TIVA with propofol-fentanyl is superior to volatile anesthetics for neuromonitoring, providing better signal quality for somatosensory and motor evoked potentials. 7, 8, 9

• Propofol-based TIVA allows reliable monitoring of both SSEPs and tcMEPs throughout the procedure 8, 9
• Avoid volatile anesthetics as they significantly suppress motor evoked potentials and may compromise monitoring reliability 7, 9
• TIVA provides practical advantages including better control of anesthetic depth and improved surgical field conditions 7
• In severe neurological injury, TIVA provides better brain relaxation and lower intracranial pressure compared to inhalational anesthesia 10

Infusion Device Safety

Ensure infusion pumps have audible alarms enabled by default for high-pressure, cessation of infusion, empty syringe, disconnection from mains, and low battery. 1

• Visual display must indicate infusion is in progress 1
• Keep the intravenous cannula visible throughout the procedure when practical 1
• Check infusion devices before use and ensure proper function 1

Hypertension Management

Adjust propofol and opioid dosing carefully in this hypertensive patient, as both agents affect blood pressure regulation. 4

• Propofol's hypotensive effects may be beneficial but require careful titration 4
• Avoid rapid boluses that cause precipitous blood pressure drops 4
• Continue antihypertensive medications perioperatively unless specifically contraindicated 4

Common Pitfalls to Avoid

• Never use simultaneous neuraxial and general anesthesia, as this is associated with precipitous intraoperative blood pressure falls 1
• Avoid nitrous oxide, as it increases postoperative nausea/vomiting and may interfere with neuromonitoring 3
• Do not use propofol in patients with egg, soy, or sulfite allergies (propofol contains 10% soybean oil and 1.2% purified egg phosphatide) 2
• Avoid excessive anesthetic depth (BIS <35) in this 62-year-old patient to reduce postoperative delirium risk 3
• Never extubate without confirming adequate neuromuscular recovery if muscle relaxants were used 3

Emergence and Extubation

Ensure complete return of airway reflexes and adequate tidal volumes before extubation, with the patient fully awake. 3

• Propofol has rapid clearance with predictable emergence and fast return of airway reflexes 3
• Extubate in sitting position when feasible 3
• Abrupt discontinuation may result in rapid awakening with anxiety and agitation 4
• Consider maintaining light sedation until 10-15 minutes prior to extubation 4