Respiratory effects of epidural fentanyl

Abstract

Respiratory, function following single bolus doses as well as continuous infusions of epidural fentanyl were studied in 21 patients. Respiratory rate decreased significantly and end-tidal CO₂ showed a non significant increase following single doses of epidural fentanyl (1.5 μg/kg). These changes occurred within minutes of injection, hut could not be attributed solely to rapid systemic absorption of fentanyl from the epidural space. Prior administration of parenteral morphine resulted in significantly higher end-tidal CO₂ concentrations and lower respiratory rates following epidural fentanyl. Continuous epidural fentanyl infusion (0.5 μg/kg/hour) started 60 minutes after the bolus dose had no effect on end-tidal CO₂ concentration or respiratory rate for up to 18 hours. Infusions were continued after the study terminated for up to 9 days, during which there was no clinically significant respiratory depression.