Plasma Fentanyl Concentrations and Clinical Observations during and after Operation

Abstract

Thirty patients undergoing major abdominal gynaecological surgery were anaesthetized with a standard technique including nitrous oxide in oxygen and myoneural blockade. The lungs were ventilated with large tidal volumes (10 ml kg" 1 ) but i-'aco, remained within normal limits. Fentanyl was given as a loading dose of 10 | xg kg" 1 or 25 (xg kg" 1 i.v. at the start of the anaesthetic. The lower dose was followed by either an infusion of fentanyl 2 ng min" 1 or by fentanyl given as increments of 100 (ig after 30 min and 50 (ig after 1 h. Significant (2% level) second peaks of plasma fentanyl (increases greater than 0.49 ng ml" 1 ) occurred within 45 min of the end of surgery in 60% of patients receiving the infusion, in 40% of patients receiving the high dose and in 20% of patients receiving increments of fentanyl. Analgesia was required in the first 3 h after operation in 70% of patients in the infusion group, in 60% in the high dose group and in 80% in theincrement group. The mean times for administration of postoperative analgesia in these three groups were 102, 80 and 55 min respectively. After operation .Pao, was less than 8 kPa in 60-67% of patients. It is suggested that particular care should be given to patients who are breathing air and recovering from anaesthesia in which fentanyl in large or recurring amounts has been used, since administration of analgesics after operation may produce additive effects and further arterial hypoxaemia.

Pharmacokinetics, induction of anaesthesia and safety characteristics of Propofol 6% SAZN vs Propofol 1% SAZN and Diprivan®‐10 after bolus injection

“…Secondary peaks in the drug concentration profile occurring at the time of awakening have been observed previously for propofol [ 22, 23] and for other lipophilic intravenous anaesthetic agents such as fentanyl [ 30]. Since the majority of propofol eliminated from the blood during the first 2 h is accounted for by the uptake into peripheral compartments (62%) and not by metabolism [ 31] we hypothesized that alterations in cardiac output at awakening may have led to the release of propofol from lipid tissues [ 32].…”

Reproductive and Teratogenic Effects of Nitrous Oxide, Fentanyl and Their Combination in Sprague-Dawley Rats

“…In a previous study (Fujinaga, Stevenson and Mazze, 1986), we administered fentanyl either 10 or 100 ug kg" 1 / day to Sprague-Dawley rats throughout pregnancy or 500 ug kg~yday on days 3-17 of pregnancy using chronically implanted, subcutaneous, osmotic minipumps. The 500-ug kg'yday dose was associated with plasma fentanyl concentrations of 8.5 ng ml" 1 (clinical therapeutic range: 0.5-2.5 ng ml" 1 in general surgery (McQuay et al, 1979); 5-10 ng ml" 1 in cardiac surgery (Bovill and Sebel, 1980)) and was the largest dose we could administer with osmotic minipumps without producing respiratory depression. In our study, no adverse reproductive effects were observed with any dose of fentanyl.…”

Sedation for Stereotactic Headframe Application: A Randomized Comparison of Two Techniques

“…Fentanyl is a potent, short-act ing narcotic which is frequently used in the practice of neurosurgical anesthesia. Like all narcotics, its use may precipitate respiratory de pression and/or nausea [1,3]. Chest wall rigidity has also been re ported with fentanyl use [4].…”