How do you prepare a fentanyl (synthetic opioid analgesic) infusion?

Preparing a Fentanyl Infusion

For continuous IV fentanyl infusion, administer an initial bolus of 1-2 mcg/kg IV slowly over several minutes in opioid-naïve patients, then initiate a continuous infusion individualized based on response, with additional bolus doses available every 5 minutes as needed. 1

Initial Bolus Administration

• Administer the initial bolus slowly over several minutes (2-3 minutes minimum) to prevent glottic and chest wall rigidity, which can occur with doses as low as 1 mcg/kg with rapid administration. 1, 2
• For brain-injured patients requiring intubation, use higher bolus doses of 3-5 mcg/kg, but reduce doses in hemodynamically unstable patients. 1
• Allow sufficient time (2-3 minutes) for fentanyl to take effect before administering additional medications. 1
• The onset of action is 1-2 minutes with a duration of effect of 30-60 minutes. 3, 2

Continuous Infusion Initiation

• Start the infusion after achieving initial pain control with boluses. 1
• For opioid-tolerant patients, calculate the 24-hour opioid requirement, convert to morphine equivalents, and initiate fentanyl at an appropriate rate with a 25-50% dose reduction to account for incomplete cross-tolerance. 1

Dose Escalation Protocol

• Double the infusion rate if the patient requires two bolus doses within one hour. 1
• Reassess patients after 2-3 days at steady state and adjust the basal infusion rate based on average daily breakthrough medication requirements. 1
• Calculate rescue doses as 10-20% of the total 24-hour opioid dose. 1

Conversion from Other Opioids

When converting from continuous IV morphine to fentanyl:

1. Calculate the 24-hour morphine dose. 1
2. Use a fentanyl:morphine potency ratio of 60:1 (multiply morphine dose by 1/60). 3, 1
3. Divide by 4 to correct for morphine's longer half-life. 3, 1
4. Administer this amount intravenously in 6 divided doses every 4 hours on day 1. 3
5. Titrate the morphine dose for adequate effect over 12 to 24 hours. 3

Critical Safety Monitoring

• Monitor patients for at least 24 hours after dose initiation or increase due to fentanyl's mean half-life of approximately 17 hours. 1
• Be prepared to administer naloxone (0.1 mg/kg IV or 0.2-0.4 mg for adults) and provide respiratory support at all times. 3, 1, 2
• Monitor oxygen saturation continuously. 1
• There is significantly increased risk of apnea when fentanyl is combined with benzodiazepines or other sedatives—exercise extreme caution with co-administration. 1, 2
• Respiratory depression may last longer than the analgesic effect of fentanyl. 3, 2

Essential Preparations

• Have vasoconstrictors (ephedrine or metaraminol) immediately available to treat hypotension. 1
• Naloxone has a half-life of 30-45 minutes, so supplemental doses may be required after 20-30 minutes. 3
• Sequential doses or a continuous infusion of naloxone may be necessary due to its short half-life. 4

Common Pitfalls to Avoid

• Never administer fentanyl rapidly—this is the most common cause of chest wall rigidity. 1, 2
• Do not use fentanyl infusions for acute or postoperative pain management, as pain may decrease more rapidly than fentanyl blood levels can be adjusted, leading to life-threatening hypoventilation. 4
• Avoid underestimating the duration of respiratory depression, which can persist well beyond the analgesic effect. 3, 2