What target‑controlled infusion (TCI) effect‑site concentrations of remifentanil are recommended for anesthesia, sedation, awake fiberoptic intubation, and spinal procedures in adult ASA I‑III patients?

Remifentanil TCI Effect-Site Concentrations for Different Clinical Scenarios

For awake fiberoptic intubation, use remifentanil TCI at an effect-site concentration of 1–3 ng/mL, avoiding bolus dosing to minimize respiratory depression risk. 1

Awake Fiberoptic Intubation

The Difficult Airway Society 2020 guidelines provide the definitive recommendation for remifentanil during awake tracheal intubation 1:

• Target effect-site concentration: 1–3 ng/mL
• Onset: 1 minute
• Duration: 3–5 minutes
• Critical warning: Avoid bolus dosing due to respiratory depression risk
• Must be combined with adequate topical anesthesia

Clinical Context from Research

While one observational study suggested higher concentrations (mean 6.3 ng/mL for nasal endoscopy, 8.06 ng/mL for intubation) when remifentanil was used as a single agent without premedication or topical anesthesia 2, this approach contradicts guideline recommendations and carries unacceptable respiratory depression risk. The guideline-recommended range of 1–3 ng/mL assumes proper topical anesthesia and represents safer practice 1.

General Anesthesia (Induction and Maintenance)

For anesthesia induction, the FDA label recommends 0.5–1 mcg/kg/min infusion rate (not TCI effect-site targeting) 3. However, when using TCI systems:

Induction Dosing

• Effect-site concentration ~4 ng/mL achieves drug administration consistent with FDA-recommended initial doses across patient populations 4
• For older patients using effect-site targeting: ~2 ng/mL for induction
• Research shows Ce50 of 5.0 ng/mL blocks sympathetic response to intubation in 50% of patients when combined with BIS-guided propofol 5

Maintenance Dosing

• FDA-approved ranges (weight-based):

  • With nitrous oxide: 0.4 mcg/kg/min (range 0.1–2)
  • With isoflurane: 0.25 mcg/kg/min (range 0.05–2)
  • With propofol: 0.25 mcg/kg/min (range 0.05–2) 3

• TCI equivalent: ~4 ng/mL effect-site concentration for starting maintenance 4

• Research demonstrates Ce50 of 2.1 ng/mL blocks sympathetic response to skin incision in 50% of patients 5

Pediatric Considerations (Ages 1–12 years)

• Maintenance: 0.25 mcg/kg/min (range 0.05–1.3) with volatile agents 3

Spinal Anesthesia/Sedation

For conscious sedation during spinal anesthesia, target remifentanil TCI at 3.0 ng/mL effect-site concentration 6:

• 3.0 ng/mL provides effective sedation and anxiolysis without significant side effects
• Lower concentrations (1.0–2.0 ng/mL) produce inadequate sedation
• Higher concentration (3.5 ng/mL) significantly increases respiratory depression and PONV risk
• This achieves Observer's Assessment of Alertness/Sedation (OAA/S) scale of ~3.96

Postoperative Analgesia

For continuation into immediate postoperative period: 0.1 mcg/kg/min (range 0.025–0.2) 3:

• Must be under direct supervision of anesthesia practitioner
• Bolus dosing NOT recommended for postoperative pain
• Not studied in pediatric patients for this indication

Critical Safety Considerations

Respiratory Depression Risk

• Primary concern across all applications
• Risk increases with:
  • Bolus administration (avoid in all scenarios)
  • Concomitant sedatives (propofol >1.5 mcg/mL particularly dangerous) 1
  • Higher concentrations (>3 ng/mL for sedation, >5 ng/mL for anesthesia)

Drug Interactions

• Reduce doses of co-administered anesthetics by up to 75% when using remifentanil 3
• Applies to: thiopental, propofol, isoflurane, midazolam

Common Pitfalls

• Never use remifentanil as sole agent for general anesthesia—cannot assure loss of consciousness and causes high incidence of apnea, muscle rigidity, and tachycardia 3
• Avoid bolus dosing in awake procedures—titrate via continuous infusion only
• Clear all IV tubing at discontinuation—context-sensitive half-time means rapid offset
• Consider atropine pretreatment to blunt bradycardia, especially in pediatric patients 3

Model Selection for TCI

When using TCI systems, plasma target concentrations of 3.1–5.3 ng/mL are suitable for initial dosing across Minto, Eleveld, and Kim models 4. The Minto model shows acceptable performance for most applications, though prolonged infusions (>24 hours) demonstrate significant bias (median performance error -34.7%) with tendency toward overestimation 7.