Ventilatory depression related to plasma fentanyl concentrations during and after anesthesia in humans.
Twenty-four patients were allocated randomly into four groups for the study of the pharmacokinetics of, and effects on postoperative ventilation of, two doses of fentanyl (10 micrograms/kg or 25 micrograms/kg) administered at the start of general anesthesia in which ventilation was controlled at a fixed volume, but arterial PCO2 was adjusted to a range of either 38-42 torr, or 20-25 torr. During the first 2 hr after anesthesia, ventilatory depression (CO2 responsiveness decreased to less than 50% of awake values, PaCO2 greater than 48 torr) occurred only in patients who had received 25 micrograms/kg fentanyl, and was more marked in patients who were hyperventilated to a low PaCO2 during anesthesia. Plasma fentanyl concentrations associated with 50% depression of CO2 responsiveness were in the range 1.5-3.0 ng/ml, the lower values found in patients hyperventilated to a low PaCO2. Whole-body clearance of fentanyl was significantly decreased by hypocapnic hyperventilation.
D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D005283:Fentanyl / Q000009:adverse effects* / Q000097:blood; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011897:Random Allocation; D012119:Respiration / Q000187:drug effects*
D002245:Carbon Dioxide; D005283:Fentanyl