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.

Dose Response and Hypnotic Interaction of Propofol and Ketamine for Anesthesia Induction in Korean / 대한마취과학회지

BACKGROUND: Both propofol and ketamine are useful hypnotics for induction of anesthesia, and the combination of propofol and ketamine has been used for total intravenous anesthesia. The aim of this study was to evaluate the dose response of propofol, ketamine and combination of these drug, and determine possible interaction between two drugs in patients. METHODS: The effect of ketamine on the dose response curve for propofol was studied in unpremedicated 165 ASA physical status I or II patients who were scheduled for elective operation. As an endpoint of hypnosis, ability to open eyes on verbal command was checked. Dose response curves for propofol and ketamine were determined with a probit procedure and their type of pharmacologic interaction was determined by fractional and isobolographic analysis. RESULTS: At the hypnotic endpoint, the ED50s were 1.13 mg/kg propofol, 0.66 mg/kg ketamine, and the ED95s were 1.67 mg/kg propofol, 1.09 mg/kg ketamine. The type of interaction between two drugs for hypnosis was found to be additive and ketamine was 1.7 times potent than propofol as an equieffective dose of hypnosis. CONCLUSIONS: The type of interaction between propofol and ketamine for hypnosis was additive.

Hypnotic Dose Response of Etomidate Using a Bispectral Index during Anesthesia Induction / 대한마취과학회지

INTRODUCTION: Several methods, including loss of eye lash (eyelash) reflex and loss of verbal contact, have heen used as criteria for estimating the optimal hypnosis for anesthesia induction. However, these methods are too objective. We examined the hypnotic dose response of etomidate, using a bispectral index as a more subjective criterion for anesthesia induction. METHODS: Fourty-Five ASA I or II adult patients scheduled for elective orthopedic surgery were randomly allocated to three groups according to induction dose of etomidate. They were Group 1: 0.1 mg/kg ; Group 2: 0.15 mg/kg; Group 3: 0.2 mg/kg (n = 15 for each group), respectively. Etomidate diluted as 10 ml in a syringe injected through an 18G forearm intravenous catheter, using a syringe pump at the rate of 20 ml/min. Observer's Assessment of Alertness/sedation (OAA/S) scale of 1 was considered optimal for hypnosis. Bispectral index, OAA/S scale, and vital signs were checked every minute until spontaneous eye opening after end of drug infusion. Also, the correlation coefficient between BIS and OAA/S scale was checked for evaluating the bispectral index; this was a useful tool for estimating the degree of hypnosis. RESULTS: BIS and OAA/S showed their lowest scores around 60 sec. after the etomidate injection, which was very different from time to peak effect known to be the 2 min. The correlation coefficient (r) between BIS and OAA/S was 0.84 on average, suggesting the BIS as an good subjective indicator of optimal hypnosis for anesthesia induction. Vital signs were stable in all groups. Hypnotic ED50 and ED95 were 0.12 and 0.19 mg/kg, respectively. CONCLUSIONS: Bispectral index can be a useful tool for estimating the optimal hypnosis for anesthesia induction. Hypnotic ED50 of etomidate was 0.12 mg/kg.

Hypnotic Dose Response of Etomidate Using a Bispectral Index during Anesthesia Induction / 대한마취과학회지

INTRODUCTION: Several methods, including loss of eye lash (eyelash) reflex and loss of verbal contact, have heen used as criteria for estimating the optimal hypnosis for anesthesia induction. However, these methods are too objective. We examined the hypnotic dose response of etomidate, using a bispectral index as a more subjective criterion for anesthesia induction. METHODS: Fourty-Five ASA I or II adult patients scheduled for elective orthopedic surgery were randomly allocated to three groups according to induction dose of etomidate. They were Group 1: 0.1 mg/kg ; Group 2: 0.15 mg/kg; Group 3: 0.2 mg/kg (n = 15 for each group), respectively. Etomidate diluted as 10 ml in a syringe injected through an 18G forearm intravenous catheter, using a syringe pump at the rate of 20 ml/min. Observer's Assessment of Alertness/sedation (OAA/S) scale of 1 was considered optimal for hypnosis. Bispectral index, OAA/S scale, and vital signs were checked every minute until spontaneous eye opening after end of drug infusion. Also, the correlation coefficient between BIS and OAA/S scale was checked for evaluating the bispectral index; this was a useful tool for estimating the degree of hypnosis. RESULTS: BIS and OAA/S showed their lowest scores around 60 sec. after the etomidate injection, which was very different from time to peak effect known to be the 2 min. The correlation coefficient (r) between BIS and OAA/S was 0.84 on average, suggesting the BIS as an good subjective indicator of optimal hypnosis for anesthesia induction. Vital signs were stable in all groups. Hypnotic ED50 and ED95 were 0.12 and 0.19 mg/kg, respectively. CONCLUSIONS: Bispectral index can be a useful tool for estimating the optimal hypnosis for anesthesia induction. Hypnotic ED50 of etomidate was 0.12 mg/kg.

Effect of Ketamine Pretreatment on Injection Pain and Hemodynamic Changes during Anesthesia Induction with Propofol / 대한마취과학회지

BACKGROUND: Propofol is useful agents for anesthesia induction and maintenance, but pain on injection and possible hypotension are a commonly encountered problems during induction. Meanwhile, ketamine has potent analgesic and sympathomimetic effect. Therefore, we evaluated the effect of ketamine pretreatment on injection pain and hemodynamic changes during induction with propofol. METHODS: Premedicated one hundred and twenty ASA physical status I or II patients scheduled for elective surgery were randomly allocated into one of four groups (group 1; propofol only, group 2, 3, 4; pretreatment with 25%, 50%, 75% dose of hypnotic ED50 of ketamine, respectively) groups. Intensity and frequency of injection pain, mean arterial pressure and pulse rate were checked for evaluation of ketamine pretreatment on injection pain and hemodynamic changes during induction with propofol. RESULTS: Incidence of pain on injection was significantly reduced in group 2,3 and 4 compared with group 1. Group 2 and 3 showed more stable hemodynamic changes than Group 1 and 4. CONCLUSIONS: 25-50% of hypnotic ED50 of ketamine (0.17-0.33 mg/kg) pretreatment reduced pain on injection and hemodynamic changes during propofol induction significantly.

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.