What is the recommended remifentanil infusion dose to prevent intubation response?

Remifentanil Infusion Dose to Prevent Intubation Response

For preventing hemodynamic and airway responses to intubation, administer remifentanil 1 mcg/kg as a bolus over 30-60 seconds immediately before induction, followed by an infusion of 0.5-1 mcg/kg/min, as recommended by the FDA label. 1

Bolus Dosing for Intubation

The FDA-approved approach is to give an initial bolus of 1 mcg/kg over 30-60 seconds if endotracheal intubation will occur within 8 minutes of starting remifentanil. 1 This should be combined with a hypnotic agent (propofol or thiopental) for loss of consciousness, as remifentanil alone cannot guarantee unconsciousness. 1

Evidence-Based Dose-Response Data

The optimal dose depends on your clinical priorities:

• For adequate intubation conditions without muscle relaxants: Remifentanil 3-4 mcg/kg provides excellent conditions in 75-95% of patients when combined with propofol 2 mg/kg. 2 The 4 mcg/kg dose achieved excellent intubation conditions in 95% of patients, significantly better than lower doses. 2

• For attenuating cardiovascular responses specifically: The ED95 to prevent hypertensive response to intubation is 1.34 mcg/kg (95% CI: 1.04-2.19 mcg/kg) in high-risk patients with severe preeclampsia. 3 For general adult patients, an effect-site concentration of 3.7 ng/ml effectively blocks hemodynamic responses during desflurane induction. 4

• For pediatric patients (ages 4-11): The ED95 is 2.75 mcg/kg (95% CI: 2.59-3.35 mcg/kg) when combined with propofol 2.5 mg/kg. 5

Critical Safety Considerations

Higher doses provide better intubation conditions but carry significant risks:

• Remifentanil 4 mcg/kg causes profound hypotension and prolonged apnea (mean 12.8 minutes) compared to lower doses. 6 The Anaesthesia guidelines note this ultra-high dose provides conditions comparable to succinylcholine but at the expense of cardiovascular stability. 6

• Doses of 2 mcg/kg substantially increase apnea time to 487 seconds (8 minutes) compared to 270 seconds with 1 mcg/kg, while still resulting in 10% unacceptable intubation conditions. 6

• Rapid administration of even 1 mcg/kg can cause glottic and chest wall rigidity. 7 The FDA label emphasizes administering the bolus over 30-60 seconds to minimize this risk. 1

Recommended Practical Algorithm

For routine intubation with muscle relaxants (standard approach):

• Give remifentanil 1 mcg/kg over 30-60 seconds 1
• Follow immediately with propofol 2-2.5 mg/kg 6
• Administer muscle relaxant (rocuronium or succinylcholine) 6
• This provides optimal conditions with minimal cardiovascular instability

For intubation without muscle relaxants (when contraindicated):

• Use remifentanil 3-4 mcg/kg over 90 seconds 2
• Follow with propofol 2 mg/kg 2
• Wait 90 seconds after propofol before attempting intubation 2
• Critical caveat: Have vasopressors immediately available, as hypotension requiring treatment occurred in patients receiving ≥1 mcg/kg doses 3

For patients requiring strict cardiovascular stability (neurosurgical, cardiac, cerebrovascular disease):

• Target the ED95 of 1.34 mcg/kg 3
• This balances hemodynamic blunting with acceptable side effect profile
• The Difficult Airway Society specifically recommends remifentanil for these populations due to its cough suppressant effects and cardiovascular attenuation properties 6

Maintenance Infusion After Intubation

Following successful intubation, reduce the infusion to 0.4 mcg/kg/min when using nitrous oxide, or 0.25 mcg/kg/min when using isoflurane or propofol. 1 The FDA label provides a range of 0.05-2 mcg/kg/min for maintenance, with supplemental boluses of 1 mcg/kg every 2-5 minutes as needed for surgical stimulation. 1

Common Pitfalls to Avoid

• Never use remifentanil as the sole induction agent - it cannot guarantee loss of consciousness and causes high rates of apnea, muscle rigidity, and tachycardia. 1

• Administering propofol or a muscle relaxant before or concurrent with remifentanil dramatically reduces muscle rigidity from 20% to <1%. 1 Always give the hypnotic first or simultaneously.

• Do not assume the 1 mcg/kg FDA-recommended dose will provide adequate intubation conditions without muscle relaxants - this dose is designed for use WITH neuromuscular blockade. 1 Without relaxants, you need 3-4 times this dose. 2

• Remifentanil provides NO postoperative analgesia due to its ultra-short context-sensitive half-time. 8 Alternative analgesics must be administered before discontinuation. 8