The Changes of Propofol Concentration over Time in a Propofol-Lidocaine or Propofol-Ketamine Mixtures / 대한마취과학회지

BACKGROUND: Pretreatment or addition of lidocaine or ketamine have been reported to reduce pain on injection. However, the stability of propofol following the addition of lidocaine or ketamine is not yet known. Therefore, we checked compatibility and stability of propofol-lidocaine or propofol-ketamine mixtures. METHODS: After mixing 9 ml of 1% propofol and 0, 5, 10, 15, or 20 mg of 2% lidocaine or 10, 20 mg of ketamine, the samples (0.9 ml) were divided into 10 glass vials and stored at room temperature. Macroscopic and microscopic changes, and propofol concentrations were measured at 0, 1/4, 1/2, 1, 2, 3, 4, 5, 6, and 24 hours after mixing. Premedicated 100 ASA classification I or II patients scheduled for elective surgery were randomly allocated into one of three groups(Group 1: propofol only, Group 2: propofol + lidociane 20 mg, Group 3: propofol + ketamine 10 mg). Intensity and frequency of injection pain was checked during induction (150 ml/hr). Intensity of injection pain was evaluated with a pain score (1: no pain, 2: mild, 3: moderate 4: severe). RESULTS: Macroscopic and microscopic changes were only seen in propofol-lidocaine mixtures (more than 15 mg after 1 hour) in a time-dependent manner. In the mixtures with lidocaine 15 or 20 mg, the propofol concentration decreased linearly and significantly compared to the control (time 0) in a time-dependent manner from 1 hour to 24 hours. However, the propofol concentration was not changed in the propofol-ketamine mixtures. The pain score at 20 mg of lidocaine or 10 mg of ketamine were significantly lower than propofol only group and there was no difference in pain score between group 2 and group 3. CONCLUSIONS: Lidocaine (more than 15 mg), but not ketamine, added to 90 mg of propofol reduced the propofol concentration linearly in a time-dependent manner and showed microscopic changes from l hour after mixing. Therefore, this mixture seems to be inappropriate for long-standing storage and thus propofol-ketamine mixtures are more appropriate for this purpose.

Effects of Flow Rate and Dilution during Anesthesia Induction with Propofol / 대한마취과학회지

BACKGROUND: The Pharmacokinetic parameter and the degree of dilution can have an effect on induction time and vital signs during general anesthesia with propofol. Induction time, induction dose and vital signs according to various flow rates and the degrees of dilution during anesthesia induction with propofol were studied. METHODS: After institutional review board approval, and informed consent, One hundred and eighty ASA I or II adult patients undergoing elective surgery were assigned to one of four groups according to their degree of dilution. One group was undiluted and another 3 groups were diluted with 5% D/W (1:1, 1:2, 1:3). Each group was divided into 3 subgroups according to their flow rates of 25, 50, 100 mg/kg/hr. No premedication was given. With routine monitoring including radial arterial cannulation, propofol was infused using a syringe or infusion pump (Becton Dickinson pump, Franklin Lakes New Jersey, USA) in the previously designed manner. Induction time defined as loss of eyelash reflex, induction dose, and vital signs were checked. RESULTS: The faster the flow rate and the more diluted a drug, the shorter the induction time. The faster the flow rate and the less diluted a drug, the greater the induction dose. The more diluted a drug, the less the decrease in systolic blood pressure. Flow rate has little influenced decreasing systolic blood pressure. CONCLUSIONS: We concluded that it is reasonable to reduce flow rate and dilute propofol when the hemodynamic changes of the patient should be minimal during propofol based sedation/anesthesia.

The Effect of Inhaled Desflurane Concentrations on the Bispectral Index / 대한마취과학회지

BACKGROUND: The bispectral index (BIS) has been designed to objectively measure the degree of sedation and hypnosis for several anesthetics. The aim of this study was to evaluate the changes of the BIS during desflurane-N2O-O2 anesthesia. METHODS: With Institutional Review Board approval and informed consent, forty premedicated (atropine 0.5 mg, IM) male and female adult patients (ASA class 1 or 2, 18 55 yrs) scheduled for elective surgery were studied. After intubation with the aid of propofol (2.0 mg/kg) and vecuronium (0.15 mg/kg), anesthesia was maintained with desflurane in combination with 50% N2O and 50% O2. Several transitions between 3.0 and 12.0 vol% were performed. During anesthesia, the BIS was checked at least 30 min after induction to avoid the residual effect of propofol and after 15 min maintenance of a certain inhaled concentration for equilibration. RESULTS: The values of BIS were correlated closely with the desflurane concentrations (r = 0.88). Steep changes in the BIS were shown between 1.5 6.0 vol% and a ceiling effect regarding the BIS over 6.0 vol% was observed. CONCLUSIONS: The BIS is valuable for measuring the degree of sedaton and hypnosis in desflurane anesthesia. Above 6.0 vol%, desflurane showed a ceiling effect regarding the BIS.

The Effect of Concentration of Nitrous Oxide on Bispectral Index and Sedation Score / 대한마취과학회지

BACKGROUND: Bispectral index (BIS) has been designed to measure objectively the degree of sedation and hypnosis for several anesthetics. It is predicted that sedation and hypnosis during nitrous oxide inhalation affect BIS in an unusual manner due to a different mechanism compared to usual hypnotics. The aim of this study was to evaluate the effect of different concentration of nitrous oxide inhalation on BIS and sedation score. METHODS: Forty unpremedicated ASA physical status I or II patients scheduled for lower extremity surgery were studied. After performing epidural anesthesia, patients inhaled gradually increasing concentrations of nitrous oxide from 0 to 67% (15 minutes for each concentration) via a tightly sealed face mask. At the end of each inhalation, BIS and OAA/S scale (Observers's Assessment of Alertness/ Sedation scale) were assessed. RESULTS: The increasing concentrations of inhaled nitrous oxide resulted in significant reduction of the OAA/S scale but in no change of BIS. Concentrations of nitrous oxide exceeding 50% affected behavior or emotion of the patients. CONCLUSIONS: Following increasing concentrations of inhaled nitrous oxide, sedation score was reduced significantly but BIS was not affected.

The Effect of Induction Mode on Various Parameters and Vital Signs during Anesthesia Induction with Propofol Using a Target Contolled Infusion / 대한마취과학회지

BACKGROUND: Anesthesia induction time is related to speed of injection, injected volume, and Keo. In the case of target controlled infusion, induction time can be controlled by adjusting the induction time mode. The aim of this study was to estimate the effect of induction time mode on variable parameters and vital signs during anesthesia induction with propofol using a target controlled infusion (TCI). METHODS: Sixty unpremedicated adult patients (ASA class I or II, 18 55 yrs) scheduled for elective surgery were randomly allocated to four groups according to induction mode. Group 1 was assigned a flash induction mode, and groups 2, 3 and 4 were assigned 2, 3 and 4min respectively. The end point of anesthesia induction was loss of eyelash reflex. Various parameters including induction time, infused volume, current/effect concentration at induction, and vital signs were compared. RESULTS: As the induction time mode was prolonged, induction time was delayed, but there was no difference in infused volume. Also, the current concentration decreased gradually, but the effect concentration did not show any difference. The vital signs were more stable in groups 3 and 4 compared with groups 1 and 2. CONCLUSIONS: For anesthesia induction, a rapid induction mode showed more rapid induction and low current concentration, but vital signs were relatively unstable and the effect concentration at induction showed no difference. For critically ill patients or patients with unstable hemodynamics, a more gradual induction mode for anesthesia induction in propofol TCI is recommended.