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Awakening Propofol Concentration with and without Blood-Effect Site Equilibration after Short-term and Long-term Administration of Propofol and Fentanyl Anesthesia

1998; Lippincott Williams & Wilkins; Volume: 88; Issue: 4 Linguagem: Inglês

10.1097/00000542-199804000-00012

1528-1175

Tomiei Kazama, Kazuyuki Ikeda, Koji Morita, Yoshimitsu Sanjo,

Anesthesia and Neurotoxicity Research

The propofol awakening concentration can vary. However, the effect site awakening propofol concentration will be a fixed value. The purpose of this study was to determine the awakening propofol concentrations obtained from infusion Schede using abrupt discontinuation of propofol (half-maximal effective concentration [EC50]) or a descending decrease in concentration to allow blood-effect site equilibration (EC50eq).Patients undergoing short-term (group 1) and long-term (group 2) elective surgery were anesthetized with computer-assisted continuous infusion of propofol and fentanyl, with both groups receiving the same propofol (3 microg/ml) and fentanyl (1 ng/ml) concentrations 20-30 min before the end of surgery until the end. Then both groups were further divided into two subgroups: subgroup A abrupt discontinuation, and subgroup B descending concentrations of propofol (15-min duration per concentration). In the A subgroups, the response to verbal command was evaluated every 30 s. In the B subgroups, the blood propofol concentrations just permitting and just preventing response to command were averaged individually. The EC50 and EC50eq values were determined by probit analysis.The EC50 of group 1A was 1 microg/ml, which was significantly less than the 1.6 microg/ml of group 2A (P < 0.05). The awakening time of group 1A was 5.2 +/- 1.8 min, which was significantly shorter than the 9.3 +/- 3.5 min of group 2A (means +/- SD). The EC50eq of both groups 1B and 2B was 2.2 microg/ml.The EC50eq was independent of propofol infusion length, compared with the EC50. Thus the potential for hysteresis during emergence from propofol anesthesia was confirmed.