What are the recommended doses of Total Intravenous Anesthesia (TIVA) propofol and fentanyl for a 55kg patient undergoing a spine endoscopic procedure?

TIVA Dosing for 55kg Patient Undergoing Spine Endoscopy

For a 55kg patient undergoing spine endoscopy with TIVA, start with propofol 1.17 mg/kg (approximately 65 mg) for induction followed by 81 µg/kg/min (approximately 4.5 mg/kg/hr or 250 mg/hr) maintenance infusion, combined with fentanyl 1-2 µg/kg (55-110 µg) boluses as needed for analgesia. 1

Propofol Dosing Calculations

Induction Dose

• Standard induction: 1.17 mg/kg = 64 mg for your 55kg patient 1
• This is lower than traditional recommendations (2-2.5 mg/kg) but reflects actual requirements in spine surgery patients using target-controlled infusion 1
• Administer slowly over 40 seconds to minimize apnea risk 2
• Age-adjusted dosing: If patient is elderly (>65 years), reduce to 1.7 mg/kg = 94 mg 3

Maintenance Infusion

• Standard maintenance: 81 µg/kg/min = 4.5 mg/kg/hr = 247 mg/hr for 55kg patient 1
• Alternative dosing range: 10-15 mg/kg/hr (550-825 mg/hr), though this may be excessive based on recent spine surgery data 2, 1
• Target effect-site concentration: 2.34 µg/ml at induction, maintaining 3.5-4.5 µg/ml during surgery 1, 2

Recovery Planning

• Stop infusion when: Effect-site concentration reaches approximately 1.0 µg/ml (roughly 50% of induction concentration) 1
• Expected recovery time: 7-14 minutes to eye opening 1, 3

Fentanyl Dosing Calculations

Critical Principle

Propofol has zero analgesic properties—fentanyl is mandatory for painful spine procedures. 4, 5

Dosing Regimen

• Initial bolus: 1-2 µg/kg = 55-110 µg given 1 minute before propofol infusion 2
• Intraoperative boluses: 50-100 µg as needed for inadequate analgesia signs (hypertension, tachycardia, movement) 6
• Total typical dose range: 25-100 µg for endoscopic procedures, though spine surgery may require higher end 4

Administration Protocol

Pre-Induction

1. Establish large vein access (antecubital fossa preferred to minimize injection pain) 2
2. Administer fentanyl 55-110 µg IV 2
3. Wait 1 minute for fentanyl onset 2

Induction Sequence

1. Propofol 64 mg IV over 40 seconds 2, 1
2. Monitor for apnea (occurs in 25% of patients) 2
3. Expect 35% incidence of spontaneous movements during induction—this is normal 2
4. Anticipate blood pressure decrease in all patients 2

Maintenance Phase

1. Start propofol infusion at 247 mg/hr (4.5 mg/kg/hr) 1
2. Titrate to maintain state entropy 50-60 if monitoring available 1
3. Administer fentanyl 50-100 µg boluses for signs of inadequate analgesia 6
4. Maintain effect-site concentration 3.5-4.5 µg/ml 2

Emergence

1. Stop propofol when effect-site concentration reaches 1.0 µg/ml 1
2. Expect eye opening at 7-14 minutes 1, 3
3. Expect full orientation at 13 minutes (concentration ~1.3 µg/ml) 2

Mandatory Safety Monitoring

Continuous monitoring must include: 4

• Pulse oximetry (mandatory)
• Blood pressure and heart rate
• Capnography for early hypoventilation detection
• Dedicated provider performing no other tasks during sedation
• Supplemental oxygen administration

Critical Safety Warnings

Cardiovascular Effects

• Expect dose-dependent decreases in cardiac output, systemic vascular resistance, and blood pressure in all patients 5, 2
• Hypotension (BP <80 mmHg systolic) occurs in 10-15% during induction 7
• Have vasopressors immediately available 6

Respiratory Depression

• Propofol + fentanyl produces synergistic respiratory depression beyond either agent alone 4
• Apnea occurs in 25% during induction 2
• Have airway management equipment and bag-mask ventilation ready 6
• Naloxone must be immediately available for fentanyl reversal 4

Common Pitfalls to Avoid

1. Never use propofol alone for painful procedures—the lack of analgesia will require excessive propofol doses leading to deep sedation and hemodynamic instability 4, 5
2. Avoid bolus dosing during maintenance—use continuous infusion to prevent respiratory depression 4
3. Do not use traditional high-dose recommendations—actual requirements are 30-40% lower than older literature suggests 1
4. Maintain vascular access throughout and until recovery—complications can occur during emergence 4

Age-Specific Adjustments

Elderly Patients (>65 years)

• Increase induction dose to 1.7 mg/kg = 94 mg 3
• Reduce maintenance to 8.6 mg/kg/hr = 473 mg/hr 3
• Expect longer recovery time: 14 minutes vs 8 minutes in younger patients 3
• Use depth of anesthesia monitoring (BIS target 50) to avoid delirium 6

Younger Patients (25-40 years)

• Use standard dosing: 2.2 mg/kg induction = 121 mg 3
• Maintenance: 10 mg/kg/hr = 550 mg/hr 3
• Expect more pronounced side effects but faster recovery 3

Contraindications and Precautions

Absolute contraindications: 5

• Egg allergy
• Soy allergy
• Sulfite allergy

Use with extreme caution: 5

• Pulmonary hypertension (risk of hemodynamic instability)
• Hypovolemia or shock states
• Severe cardiac dysfunction