What is the recommended dose of remifentanil (opioid analgesic)?

Remifentanil Dosing Recommendations

For general anesthesia in adults, remifentanil should be initiated at 0.5-1 mcg/kg IV bolus followed by a continuous infusion of 0.125-0.25 mcg/kg/min, with dose reductions of 50% in patients over 65 years of age. 1

Standard Adult Dosing by Clinical Context

General Anesthesia Induction and Maintenance

• Induction bolus: 0.5-1 mcg/kg IV over 30-60 seconds 1
• Maintenance infusion: 0.05-2 mcg/kg/min, with typical starting dose of 0.25 mcg/kg/min 1
• Optimal maintenance rate: 0.125 mcg/kg/min provides superior hemodynamic control during neurosurgery compared to lower (0.0625 mcg/kg/min) or higher (0.25 mcg/kg/min) rates 2
• Target plasma concentration: 3.1-5.3 ng/mL (approximately 4 ng/mL) achieves dosing consistent with FDA recommendations across all age groups 3

Cardiac Surgery Specific Dosing

• Induction: 1 mcg/kg/min continuous infusion through intubation 1
• Maintenance: 0.125-4 mcg/kg/min with supplemental boluses of 0.5-1 mcg/kg 1
• Pre-bypass period: 0.3-0.4 mcg/kg/min effectively suppresses hemodynamic responses to sternotomy and skin incision without severe cardiovascular depression 4
• During cardiopulmonary bypass (CPB): Maintain at least the pre-CPB dose for all opioids except remifentanil 5
• Hypothermia adjustments: Reduce dose by 30% after 20-30 minutes at 32°C, and by 60% immediately with moderate to deep hypothermia below 28°C 5

Monitored Anesthesia Care (MAC)

• Single IV dose: 1 mcg/kg administered over 30-60 seconds, given 90 seconds before local anesthetic 1
• Continuous infusion: Begin at 0.05 mcg/kg/min, starting 5 minutes before local anesthetic 1
• Maintenance: 0.025-0.2 mcg/kg/min, titrated to effect 1

Age-Specific Modifications

Geriatric Patients (>65 years)

• Reduce all doses by 50% due to doubled pharmacodynamic sensitivity 1
• Effect-site targeting: Use 2 ng/mL for induction and 4 ng/mL for maintenance to achieve appropriate dosing 3
• Critical consideration: Elderly patients maintain rapid clearance but demonstrate significantly increased sensitivity to remifentanil's effects 1

Pediatric Patients (Birth to 12 years)

• Neonates (birth to 2 months): Start at 0.4 mcg/kg/min, but may require higher rates due to 2-fold higher clearance compared to adults 1
• Children 1-12 years: Use adult maintenance dosing of 0.25 mcg/kg/min with nitrous oxide or 0.4 mcg/kg/min without nitrous oxide 1
• Recommended concentration: 20 or 25 mcg/mL for infusion preparation 1

Obese Patients (>30% over ideal body weight)

• Calculate all doses based on ideal body weight (IBW), not actual body weight 1
• This prevents overdosing due to remifentanil's pharmacokinetic properties in adipose tissue 1

Context-Specific Applications

Postoperative Pain Management

• Effective dose: 0.1 mcg/kg/min as constant infusion provides adequate analgesia with minimal rescue medication needs (6% vs 26% at lower doses) 6
• Lower dose: 0.05 mcg/kg/min requires 4 times more rescue analgesia 6
• ICU continuation: 0.05-1 mcg/kg/min for post-cardiac surgery analgesia 1
• Duration limitation: No safety data exists for use exceeding 16 hours in ICU settings 1

Intubation Without Muscle Relaxants

• Low-dose approach: 1-1.5 mcg/kg with propofol 2 mg/kg provides acceptable intubation conditions but causes 10% incidence of respiratory depression 5
• High-dose approach: 2 mcg/kg with propofol increases apnea time substantially (270s to 487s) with 10% unacceptable intubation conditions 5
• Ultra-high dose: 4 mcg/kg provides intubation conditions comparable to succinylcholine but causes significant hypotension and prolonged apnea (12.8 min vs 6.0 min) 5

Critical Safety Considerations and Common Pitfalls

Cardiovascular Management

• Hypotension risk: Higher doses (>0.3 mcg/kg/min) require more frequent phenylephrine boluses but remain well-tolerated 4
• Vasopressor availability: Have phenylephrine 100 mcg or norepinephrine immediately available 1
• Cardiac surgery caution: Up to 80% of patients may require vasopressors to maintain cerebral perfusion pressure >60 mmHg at doses ≥1 mcg/kg/min 7

Respiratory Considerations

• Apnea duration: Dose-dependent, with high doses (4 mcg/kg) causing 12.8 minutes of apnea 5
• Inadequate for airway procedures: Remifentanil infusions do not effectively block coughing responses to endotracheal suctioning even at high doses (4 mcg/kg bolus + 1 mcg/kg/min infusion) 7
• Monitoring requirement: Continuous pulse oximetry and capnography mandatory 5

Drug Interaction Warnings

• Serotonin syndrome risk: When combined with rasagiline or other serotonergic agents, use lowest effective dose for shortest duration with close monitoring for 24-48 hours 8
• Alternative consideration: Fentanyl may be safer than remifentanil in patients taking rasagiline 8

Preparation and Administration

• Reconstitution: Add 1 mL diluent per 1 mg remifentanil to create 1 mg/mL solution 1
• Final dilution: Dilute to 20,25,50, or 250 mcg/mL before administration 1
• Never administer undiluted 1
• Infusion device required: Must use calibrated infusion pump for continuous administration 1
• Stability: Stable for 24 hours at room temperature after reconstitution and dilution 1

Common Dosing Errors to Avoid

• Do not use actual body weight in obese patients—this leads to significant overdosing 1
• Do not forget 50% dose reduction in elderly—they are twice as sensitive despite normal clearance 1
• Do not maintain pre-CPB doses during hypothermia—reduce by 30-60% based on temperature 5
• Do not rely on remifentanil alone for airway procedures—it inadequately suppresses coughing reflexes 7