[A clinical dose finding study of propofol in continuous total intravenous anesthesia]

Total intravenous anesthesia (TIVA) is recommended in view of avoiding air pollution. However, intermittent administration of anesthetic agents has a disadvantage of delayed emergence time. We have suggested continuous TIVA with propofol, ketamine, vecuronium and buprenorphine (PKBp), and reported that the elder or the patients anesthetized for a long time show delayed emergence from continuous TIVA. In this study, after induction with propofol, ketamine, vecuronium and buprenorphine, the subjects were maintained with continuous intravenous administration of propofol corresponding to the age using twice step down method with ketamine (240 micrograms.kg-1.h-1), vecuronium (80 micrograms.kg-1.h-1) and buprenorphine (0.4 microgram.kg-1.h-1). Emergence was evaluated from the 2nd step down of propofol to awareness. There was a linear relationship between the emergence (2nd step down time of propofol to awareness) (Y) and the anesthetic time (X); Y = 0.175X + 3.00. We conclude that the last 1/6 (= 0.175) of anesthetic time is the point to reduce maintenance doses of propofol to achieve more rapid emergence.