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 Results of Effect Site Targeting on Anesthetic Induction Using Propofol-Target Controlled Infusion (TCI) / 대한마취과학회지

BACKGROUND: The effect site is the theoretical compartment in which a drug exerts its action and thus the concentration at this site is a direct determinant of a drug,s effect. This study was performed to compare effect site targeting with plasma targeting with regard to induction phenomena and vital sign changes using propofol target controlled infusion (TCI). METHODS: Forty patients were randomly assigned to one of two groups. Groups were defined as propofol administered via TCI to either a target plasma propofol concentration (group P) or to a target effect site (group E) propofol concentration. We used Master TCI for plasma targeting and a stelpump program for effect site targeting. The concentration targeted for all subjects was 5.7 microgram/ml. We compared the time to loss of consciousness, change of concentration, BP and pulse pressure between groups until the effect site concentration was reached at 5.7 microgram/ml. RESULTS: The median time to LOC in group P was 58.1 +/- 11.8 s and 35.8 +/- 7.9 s in group E (P <0.05). The mean time to achieve the effect site concentration of 5.7 microgram/ml was 18.5 +/- 0.1 min in group P and 3.6 +/- 0.1 min in group E (P < 0.05). Systolic and diastolic blood pressure showed significant changes in group E. CONCLUSIONS: We concluded that anesthetic induction time can be significantly reduced when the effect site concentration is targeted. However, we recommended effect site targeting in anesthesia induction with propofol TCI only in cases of healthy young patients because of possible undesirable hemodynamic changes.

The Bispectral Index and Modified Observer's Assessment of Alertness/Sedation Scale Comparable to Effect Site Concentration of Propofol in Koreans / 대한마취과학회지

BACKGROUND: Propofol has been frequently used for sedation or hypnosis in anesthesia and is relatively accurate in the dose-response relationship for hypnosis. The aim of this study was to define the bispectral index and modified observer's assessment of alertness/sedation (OAA/S) scale at various effect site concentrations (Ce) of propofol in Koreans. METHODS: Fifty premedicated (atropine 0.5 mg, I.M.) adult patients (ASA class I or II, 20 55 yrs) scheduled for elective orthopedic surgery were studied. Propofol was infused until 2 min after the target concentration equilibrated with the effect site concentration (Ce) of propofol using Master TCI. The target concentration of propofol was stepwise increased at intervals of 0.5 microgram/ml until BIS reached 40, BIS and OAA/S at each Ce of propofol were checked. If SpO2 decreased below 90%, oxygen (4 l/min) was given via nasal cannula. RESULTS: BIS was 97.9 +/- 0.2 and OAA/S 5 +/- 0.0 at a Ce of propofol of 0 microgram/ml; the Ce of propofol was 3.5 microgram/ml and OAA/S 0.1 +/- 0.3 at a BIS of 41.1 +/- 2.5. Also, systolic BP at a Ce of propofol above 1.0 microgram/ml and diasolic BP at a Ce of propofol above 1.5 microgram/ml significantly decreased compared to the control (P < 0.05). However, heart rate did not show any difference compared to the control value. Above a 1.0 microgram/ml Ce, fifty-eight percent of patients showed SpO2 < 90%, but there was no incidence of apnea. There were significant correlations between Ce of propofol, BIS and OAA/S. CONCLUSIONS: BIS showed a significant correlation with Ce of propofol (Spearman's r = 1.0) (P < 0.0001). The Ce of propofol was above 3.0 microgram/ml for BIS50.

The Effect Site Concentration of Propofol Comparable to BIS 50 and Awakening in Pediatric Patients / 대한마취과학회지

BACKGROUND: Propofol offers the advantages of rapid onset of action and recovery. However, the pharmacokinetics of propofol in children is different from that of adults. Therefore, infusion of propofol by target-controlled infusion (TCI) has same difficulties in use. Also, bispectral index has shown a close relationship with plasma concentration of propofol. In this study, we measured the effect site concentration comparable to Bispectral index (BIS) 50 during induction and the awakening concentration. Furthermore, we tried to demonstrate age-related differences. METHODS: Forty five premedicated (atropine 0.02 mg/kg) children (ASA class I) scheduled for elective surgery were assigned to one of three groups (Group 1: 1-5 years, Group 2: 6-10 years, Group 3: 11-15 years). After intravenous injection of lidocaine 0.5 mg/kg, a propofol infusion was started at a target concentration of 6 microgram/ml by using a Stelpump. Anesthesia was maintained with propofol 4-6 microgram/ml and 67% nitrous oxide in oxygen. During anesthesia induction, we checked the effect site concentration comparable to BIS 50 and plasma/effect concentration for awakening during an emergence period. RESULTS: The effect site concentrations comparable to BIS 50 were 5.7 +/- 0.5 microgram/ml (group 1), 4.9 +/- 0.8 microgram/ml (group 2) and 3.8 +/- 1.1 microgram/ml (group 3), so there are significant differences among the groups (P < 0.05)(Table 2). At the moment of awakening, the current/effect site concentration in group 1 (2.0 +/- 0.1 microgram/ml, 2.6 +/- 0.2 microgram/ml) was significantly higher than those of group 3 (1.6 +/- 0.2 microgram/ml, 2.0 +/- 0.30 microgram/ml). CONCLSIONS: The effect site concentration comparable to BIS 50 showed significantly age-related differences and was higher in younger children. The current/effect site concentration at awakening was highest in group 1.

A Case of Cerebral Infarction and Chronic Subdural Hematoma in Essential Thrombocythemia

Essential thrombocythemia is one type of the related chronic myeloproliferative disorders that also include poly-cythemia vera, chronic myelogenous leukemia, and idiopathic myelofibrosis. It is a rare disorder of unknown origin characterized by thrombocytosis, excessive megakaryocytes, hemorrhage, and thrombotic complication. Several cases of ischemic stroke in essential thrombocythemia have been reported, but cerebral infarction combined with cerebral hemorrhage has been very rare and has not been reported in Korea. We report a case of cerebral infarction and chronic subdural hematoma in a pateint with essential thrombocythemia. A 59-year-old woman with essential thrombocythemia was admitted with mild left hemiparesis that developed 3 days prior. She had a history of minor trauma 15 days prior. A brain MRI showed an infarction in the right temporal lobe and a chronic subdural hematoma in the right frontoparietal area. A cerebral angiography revealed an occlusion of the M2 portion of the right middle cerebral artery.

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.

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.

A Case of Total Intravenous Anesthesia Using a Propofol-Fentanyl Computer Asssisted Continuous Infusion: A case report / 대한마취과학회지

The technique of computer-assisted continuous infusion (CACI) has revolutionised the administration of drugs by intravenous infusion. A stable blood concentration is achieved rapidly with CACI, allowing the anesthesiologist to monitor therapeutic effect and titrate drug concentrations accordingly. Propofol and opioids can be administered by CACI for the induction and maintenance of anesthesia in adult patients. Also, the ability to maintain a constant blood concentration of drugs is also extremely important for studying the pharmacodynamic interactions of drugs, and research in the area has increased with advent of CACI. We experienced a case of total intravenous anesthesia which was totally conducted by CACI, using a Master TCI for propofol and Stelpump program for fentanyl infusion.

Anesthesia Induction with Propofol Using a Target Controlled Infusion (TCI) / 대한마취과학회지

BACKGROUND: Target Controlled Infusion (TCI) is designed to achieve a predicted target blood concentration based on population pharmacokinetics and it provides the closest approximation for any individual patients. This study determined which target is appropriate for propofol induction using a TCI in korean adullt patients premedicated with midazolam. METHODS: Sixty six patients (ASA I or II, 18~55 years) premedicated with midazolam were allocated randomly to receive an infusion to achieve and maintain a target blood concentration of 3, 4, 5 and 6 microgram/ml using a TCI. Induction time was measured as the interval from the start of the infusion to loss of verbal contact and induction within 3 min was considered as successful. Calculated concentration, induction dose, context sensitive decrement time, vital signs, pain score and side effects were checked and compared each other during induction period. RESULTS: The success rate when the target was 3 microgram/ml was 25%, 58.8%, 77.8% and 100% when targets were 4 microgram/ml, 5 microgram/ml and 6 microgram/ml respectively. EC50 for induction was 3.87 microgram/ml and EC95 was 5.71 microgram/ml. Calculated concentration, induction dose, context sensitive decrement time in 3, 4, 5 microgram/ml group showed no differences among groups, but 6 microgram/ml group showed statistically significant differences compared with other groups. Vital signs, pain score and side effects showed no differences among groups. CONCLUSIONS: Target concentration of 5~6 microgram/ml would successfully induce anesthesia in the majority of patients premedicated with midazolam without major hemodynamic changes.