Effect of Continuous Infusion of Low Concentrations of Ketamine on the Bispectral Index and Recovery from Propofol-N2O-O2 Anesthesia / 대한마취과학회지

ABSTRACT

BACKGROUND: Ketamine as an analgesic adjunct in propofol-based anesthesia has the benefit of potent analgesic action and more stable vital signs due to sympathetic stimulation. However, its impact on the bispectral index and speed of recovery is still controvertial. The aim of this study was to evaluate the effects of continuous infusion of low concentrations of ketamine (0.1 microgram/ml) on the bispectral index and speed of recovery from propofol-N2O-O2 anesthesia. METHODS: Forty ASA I or II adult patients scheduled for elective orthopedic surgery were randomly allocated to one of two groups according to intraoperative ketamine use. In group P, anesthesia was induced and maintained with propofol (Ct 3 - 6 microgram/ml), 67% nitrous oxide and 33% oxygen and the target concentration of propofol was kept at 4 microgram/ml at least 20 min before the end of propofol infusion. In group P + K, the method of anesthesia was same as in group P, but the low concentration (0.1 microgram/ml) of ketamine was continuously infused until discontinuation of propofol using computer-assisted continuous infusion. Bispectral index, recovery time from anesthesia, current/effect concentration of drugs, vital signs before and at induction, end of drug infusion, eye opening time on verbal command, and orientation time were checked. RESULTS: Changes in vital signs showed no differences between the groups. For bispectral index, there was no difference between groups initially, but it was higher (4 - 8) after the end of drug infusion in group P K than in group P. Also, recovery from anesthesia was delayed significantly in group P + K (P < 0.05). CONCLUSIONS: From these observations, we concluded that the use of low concentrations of ketamine during propofol-N2O-O2 anesthesia increased BIS, delayed eye opening and recovery from anesthesia without any benefit to vital sign stability.