Fentanyl Standard dose for induction
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Here is a complete, textbook-sourced breakdown of fentanyl dosing for induction:
Fentanyl - Induction Doses
Standard / Adjunct Dose (most common clinical use)
| Context | Dose | Route | Timing |
|---|---|---|---|
| Pre-induction adjunct (blunt laryngoscopy response) | 1-2 mcg/kg | IV | 3-5 min before induction |
| Sedation adjunct (e.g., cardioversion, procedural) | 1-1.5 mcg/kg | IV | 3 min before induction |
| Combined with propofol or benzodiazepine | 1.5 mcg/kg | IV | Reduces required dose of co-induction agent |
Source: Roberts and Hedges' Clinical Procedures in Emergency, Table 12.1 - IV fentanyl 1.5 mcg/kg administered 3 minutes before induction.
High-Dose Fentanyl Anesthesia (cardiac / major surgery)
| Technique | Dose | Notes |
|---|---|---|
| Bolus (rapid or slow) | 5-75 mcg/kg | Achieves plasma levels of 10-30 ng/mL; provides hemodynamic stability throughout induction/intubation |
| Continuous infusion | 0.1-1.0 mcg/kg/min | Used up to and through cardiopulmonary bypass (CPB) |
| Pediatric cardiac surgery | 25-50 mcg/kg | Combined with isoflurane 0.2-0.4% to obtund hemodynamic/stress responses |
| Fast-track cardiac | 8-12 mcg/kg total | Sufficient analgesia with early extubation in OR |
Source: Miller's Anesthesia, 10e - Section on Fentanyl / High-Dose Opioid Anesthesia.
Key Clinical Points
- Standard adjunct (1-2 mcg/kg): Most common use - given before propofol or thiopental to attenuate the sympathetic surge from laryngoscopy. Fentanyl at this dose also reduces the required induction dose of propofol (synergistic effect on Cp50).
- High-dose technique (5-75 mcg/kg): Reserved for cardiac surgery; does NOT reliably produce unconsciousness on its own - always combine with a hypnotic agent.
- Chest wall rigidity ("wooden chest"): Risk increases with rapid injection of high doses (>5 mcg/kg); treat with succinylcholine or naloxone.
- Onset: 1-2 minutes IV; peak effect at 3-5 minutes.
- Respiratory depression: Reversible with naloxone; dose-dependent.
- Elderly/compromised patients: Reduce dose; altered pharmacokinetics and pharmacodynamics.
In summary: For routine general anesthesia induction, fentanyl 1-2 mcg/kg IV given 3 minutes before induction is the standard adjunct dose. High-dose opioid techniques (5-75 mcg/kg) are reserved for cardiac and major surgery settings.
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