Adult ICU, mechanically ventilated: fentanyl is mainly an analgesic, often used as part of analgosedation rather than as the sole sedative.

Avoid a routine bolus in a hemodynamically unstable or opioid-naive patient. Monitor continuous SpO₂, ventilation/EtCO₂ when applicable, blood pressure, consciousness, and signs of chest-wall rigidity, especially with rapid or high-dose administration. Reduce doses in older adults and hepatic impairment; accumulation can occur with prolonged infusions.

For procedural sedation, fentanyl is generally given as intermittent IV doses, not a maintenance infusion: 25-50 micrograms slow IV, titrated cautiously, especially if combined with midazolam or propofol because of respiratory-depression risk. The SCCM PADIS guidance supports protocolized, lowest-effective-dose opioid use for ICU pain management, and the MSD procedural-sedation reference emphasizes cautious titration with other sedatives.

This should be prescribed and titrated under local ICU/anesthesia protocol. Pediatric, non-intubated, and post-operative dosing differs substantially.

For an adult ventilated ICU patient, a typical fentanyl infusion is:

Example: 70 kg patient

Use lower starting doses in older, frail, opioid-naive, or hepatic-impaired patients. Do not rely on fentanyl alone for amnesia/deep sedation. Monitor closely for respiratory depression, hypotension, bradycardia, chest-wall rigidity, and accumulation with prolonged infusion. A published adult ICU protocol used 0.5-3 micrograms/kg/hour; see this ICU dosing study.