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.

Changes in Bispectral Index during Coinduction with Intravenous Anesthetics Using Synergistic Interaction / 대한마취과학회지

BACKGROUND: Coinduction according to a hypnotic synergistic effect of intravenous anesthetics has an advantage of reducing hemodynamic change, induction dose and side effects of each drug. Meanwhile, the bispectral index has been used to monitor objective measurement of the hypnotic effect of intravenous anesthetics. The aim of this study was to evaluate the changes in the bispectral index during coinduction with two intravenous anesthetics that were known to have synergistic interactions. METHODS: Sixty ASA I or II adult patients undergoing elective surgery were assigned to one of three groups according to induction methods: group 1, thiopental + propofol; group 2, thiopental + midazolam; group 3, midazolam propofol. Anesthesia induction was performed by injecting half of a hypnotic ED50 dose of both drug according to the known time to peak effect. For example, in group 1, propofol was injected first, and then thiopental 1 min. later. The Bispectral index, vital signs, and SpO2 were checked every minute for 5 minutes after injection of a drug. RESULTS: Each group showed the lowest point of the BIS at time to peak effect, but the reduction of the BIS for each group showed no regular pattern between time and amount of degree compared to the lowest BIS of the two drugs when they were used alone. CONCLUSIONS: The BIS has limitations in expressing a synergistic interaction phenomenon when anesthesia induction with two intravenous anesthetics that have a synergistic interaction.

Comparison of Poloxamer-407 to Soybean Oil as an Emulsifying Agent for Propofol: Histamine Release and Plasma Lipid Levels / 대한마취과학회지

BACKGROUND: To reduce side effects (hyperlipidemia, pain on injection, etc.) of the present formation of propofol, many attempts to change the emulsifying agent for propofol have been tried. This study was designed to examine the poloxamer-407 as an emulsifying agent for propofol compared to soybean oil regarding histamine release and plasma lipid levels. METHODS: Twelve Beagle dogs weighing 12 - 16 kg were randomly assigned to one of two groups according to the formulation of propofol. Group 1 received Diprivan propofol 1% (AstraZeneca Co. UK), and group 2 received poloxamer-407 formulated propofol by a continuous intravenous infusion at 30 mg/kg/h for 3 hours. Three, 6, 9 and 12 hours after discontinuing the propofol infusion, venous blood samples from the cranial tibial vein were analysed by an ELISA kit for the histamine level. Also, blood lipid levels were checked 3 hours after the infusion and blood propofol concentration were checked every hour during the infusion. RESULTS: Group 2 showed significantly less histamine release than group 1 at 3, 6 and 9 hours after the infusion (P < 0.05). In the plasma lipid study, there was no difference in high-density lipoprotein (HDL) between the two groups, but triglyceride and cholesterol were significantly higher in group 2 (P < 0.05). There was no difference in propofol concentrations between the two groups. CONCLUSIONS: Poloxamer-407 as an emulsifying agent for propofol showed no advantage compared to a present formulation regarding hyperlipidemia, and even decreased the histamine level.

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.

Recognition of Kind and Concentration of a Drug Using an Optical Signal Sensor in a Target Controlled Infusion of Intravenous Anesthetics / 대한마취과학회지

BACKGROUND: An automatic procedure to detect and recognize the specified drugs for a target controlled infusion system based on the absorption ratio of the optical signals (red and infrard light) was proposed. METHODS: A red (660 nm) and infrared (925 nm) light emitting diode (R-IR LED) and photodiode was established at two perforated holes on a 50 ml syringe horizontally and opposite. The syringe was isolated from extra-light sources, such as sun-light or fluorescent light, with a dark sheet. First, the light of the R-IR LED was emitted into free space without insertion of any other syringe. After measuring the intensity of radiation, a 30 ml syringe containing a drug solution was pushed into the 50 ml syringe and again the intensity of light was measured. We measured intensities of light for 1% or 2% propofol and 0.5% thiopental sodium three times and compared it to the measurement of the free space. In order to investigate mechanical error, we measured it again two days later. We calculated errors among each measurement, simple errors and ratios between first and second time measurements and whether the error was within a permissible error range (less than 1%). After all of this, we evaluated the accuracy and clinical usefulness of this new method. RESULTS: Ratio of intensities of transmission of light in each drug solution to free space showed thiopental, 1% propofol and 2% propofol in order. Considering permissible error between the first and second time measurements, this method showed no problem in recognition of kinds and concentrations of drugs. CONCLUSIONS: We supposed that this simple optical method for drug recognition can be applied for target controlled infusion operation instead of the currently available magnetic recognition tag combined to a syringe.

Production and Accumulation of Plasma Carboxyhemoglobin in Minimal Flow Anesthesia / 대한마취과학회지

BACKGROUND: Minimal flow anesthesia (total inflow rate 0.5 L/min) has been known to increase carbon monoxide production and accumulation in the breathing circuit. We tried to investigate the differences that minimal flow anesthesia shows in the production and elimination of plasma carboxyhemoglobin as compared with high-flow anesthesia. METHODS: Fifty patients were divided into smokers and non-smokers. The smokers were allocated into two groups; high flow (Hs, n = 10) or minimal flow (Ms, n = 13). Non-smoker were also allocated the same way; high flow (Hns, n = 12) or minimal flow (Mns, n = 15). The values (%) of COHb were measured at the preanesthetic baseline, 50 min (30 min after reducing inflow rate in minimal flow), 80 min and 140 min. All values along the time were compared with their baseline within a group. RESULTS: Non-smokers showed a COHb level that didn't change at each time interval as compared with the baseline in group Mns (p = 0.91) and group Hns (p = 0.365). Smokers showed a decreased COHb level at 50 min which increased at 80, 140 min compared with the baseline in group Ms (p = 0.004), but decreased at 50, 80 and 140 min as compared with baseline in group Hs (p < 0.001). CONCLUSIONS: Minimal flow anesthesia does not produce plasma COHb more than high flow anesthesia, but an increase of COHb would be expected in risky groups such as heavy smokers because elimination of carbon monoxide in the breathing circuit was slower than with high flow anesthesia.

Does Lidocaine Mixture for Preventing The Pain on Propofol Injection Affect Anesthetic Induction and Hemodynamic Responses to Tracheal Intubation / 대한마취과학회지

Background: We hypothesized that intravenous lidocaine mixed with propofol may have an influence on anesthesia induction and hemodynamic responses to propofol induction and endotracheal intubation as well as propofol-induced pain on injection. Methods: Seventy-five patients were allocated to group L1 (2% lidocaine 1.5 mg/kg, n=25), group L2 (2% lidocaine 2 mg/kg, n=25) or group C (normal saline 0.05 mL/kg, n=25) according to the lidocaine dosage mixed with propofol 2 mg/kg. The pain on injection was scored as none, mild, moderate, and severe. The site of pain and recall of pain were also recorded. Loss of verbal response was observed during induction. Mean arterial blood pressure (MAP) and heart rate (HR) were recorded before anesthetic induction (baseline value), immediately before and after endotracheal intubation, and every min until 5 min thereafter. Results: Ninety-two percent of patients reported pain upon injection in group C, whereas 8% of the patients in group L1 and no patient in group L2. Loss of verbal response before injection of total dose of propofol was observed in 44% in group L2, 36% in group L1 and 28% in group C. Lowered MAP caused by propofol increased significantly after endotracheal intubation in all three groups (p<0.05). HR increased immediately and 1 min after endotracheal intubation in all three groups (p<0.05). Conclusions: Our results indicate that intravenous lidocaine 1.5 mg/kg or 2 mg/kg mixed with propofol 2 mg/kg significantly reduces the incidence and the degree of pain, but does not affect anesthesia induction and hemodynamic responses to propofol and tracheal intubation.