The Comparison of Minimum Alveolar Concentration and BIS50 of Inhalation Anesthetics for Evaluation of Anesthetic Potency / 대한마취과학회지

BACKGROUND: The bispectral index (BIS) has been designed to objectively measure the degree of sedation and hypnosis for anesthesia. Although it has been well-known that BIS correlates highly with the concentration of inhalation anesthetics, it is not clear whether analgesic potency expressed as MAC is comparable to hypnotic potency described as BIS50 in inhaled anesthetics. This study was conducted to examine the degree of correspondence by correlating the changes of BIS according to the different MAC of commonly used inhalation anesthetics. METHODS: One hundred ASA class 1 or 2 patients, scheduled for laparoscopic knee surgery were included. Patients were equally divided into 4 groups (n = 25 each) according to the inhalational agent enflurane, isoflurane, desflurane, or sevoflurane. Anesthetic depth for each individual agent was controlled to 2.0, 1.75, 1.5, 1.25, 1.0, 0.75 and 0.5 MAC, respectively. After equilibration for each concentration, BIS values were measured three times at 30 second intervals and an average was obtained. In addition, MAC values for each agent were measured when the bispectral index showed 50. RESULTS: The concentrations of inhaled agents vs. BIS showed high negative correlations (enflurane; -0.91, isoflurane; -0.94, desflurane; -0.84, and sevoflurane; -0.86). BIS50 for each agent was enflurane, 0.93 (1.6 vol%); isoflurane, 0.71 (0.9 vol%); desflurane, 0.95 (5.7 vol%); and sevoflurane, 0.84 MAC (1.7 vol%). Isoflurane-BIS50 showed a significant difference to the others (P<0.05). CONCLUSIONS: We concluded that the MAC of inhalation anesthetics showed poor correlation with BIS, suggesting a difference between the hypnotic and analgesic potency of individual inhaled anesthetic agents.

Atypical Increases of BIS according to Effect Site Concentration of Propofol in Severely Burn Patients Undergoing Early Escharectomy / 대한마취과학회지

BACKGROUND: This bispectral index, which is used for intravenous anesthetics and inhalation anesthesia, is a scale of sedation and hypnotic effect, which is widely used in clinics. Atypical changes in BIS are expected due to increased cardiac output, decreased blood albumin concentrations and renal function in severe burn patients undergoing early escharectomy. The aim of this study was to compare BIS according to effected site concentrations of propofol during anesthetic induction using propofol TCI in severe burn and nonburn patients. METHODS: Forty patients were classified as twenty nonburn elective surgical patients (group 1) and twenty burn patients scheduled for escharectomy (group 2). For induction, a propofol TCI device incorporating a prefilled syringe was adjusted to a target concentration of 6mug/ml in flash mode. The bispectral index was checked before induction and at each effect site concentration of propofol (0.5mug/ml interval) until an effect site concentration of 4.5mug/ml. Other suspected contributory factors such as cardiac index, creatinine clearance and albumin were checked simultaneously. The unpaired t-test and repeated measures ANOVA were performed for the statistical analysis. RESULTS: Below an effect site concentration of propofol of 3mug/ml, no BIS difference was evident between group 1 and group 2. However, at 3.5mug/ml, group 1 was 41.1+/-13.5 and group 2 was 54.7+/-16.6 and at 4mug/ml, group 1 was 40.1+/-2.6 and group 2 was 50.1+/-13.1. Among the suspected contributing factors, cardiac index and albumin showed significant differences between groups 1 and 2 (cardiac index: 3.4+/-0.5 L/min/m2 vs 2.7+/-0.3 L/min/m2, albumin: 4.1+/-0.3 g/dl vs 2.6+/-0.3 g/dl, P<0.05). Creatinine clearance showed no significant difference between the groups. CONCLUSIONS: Severe burn patients who are expecting early escharectomy had higher BIS values than nonburn patients from an effect site concentration of propofol of 3.5mug/ml. This study suggest that cardiac index should be considered as a factor that influences propofol.

Temporary Cardiac Arrest during a Pulmonary Lobectomy / 대한마취과학회지

A 49-year-old man with a left upper lobe mass lesion was admitted for evaluation. An open thoracotomy biopsy confirmed tuberculosis. A left upper lobectomy was then performed under general anesthesia. The operative procedure was remarkable for a 15-second acute episode of cardiac asystole during the aortopulmonary window lymph node dissection. After injection of epinephrine and open cardiac massage, sinus rhythm was restored. The rest of the patient's hospital course was uneventful. A vasovagal reflex due to the operative procedure, anesthetic medications, and undiagnosed underlying heart disease could be considered for the possible etiology.

Comparison of Transesophageal Doppler Monitor vs. Pulmonary Artery Catheter in the Hemodynamic Indices of Major Burn Patients Undergoing an Extensive Escharectomy / 대한마취과학회지

BACKGROUND: In major burn patients, many invasive monitors including a pulmonary artery catheter (PAC) are often required to assess hemodynamic status. An esophageal Doppler monitor (EDM), as a noninvasive method of measuring hemodynamic parameters, may be a substitute for a PAC in this clinical circumstance. This study was conducted to evaluate the validity of Doppler derived hemodynamic indices in comparison to that of a PAC. METHODS: A total of 20 critically ill, severe burn patients, scheduled for an elective escharectomy and application of artificial dermis, were enrolled for the placement of a PAC and EDM. Simultaneous data was collected in regular intervals and the various parameters were compared between the two methods. RESULTS: A total of 158 pairs of data in 20 patients were gathered. Among all the parameters, cardiac output (CO) and stroke volume (SV) showed consistently 20% less in EDM. Correlation coefficients of heart rate (HR), CO, SV and systemic vascular resistance (SVR) were 0.97, 0.54, 0.62, and 0.68 respectively. Corrected flow time (FTc) had poor correlations with central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP). In the mean time, significant, but very weak correlations with FTc vs. CO and SV were demonstrated. CONCLUSIONS: EDM may be a substitute for a thermodilution (TD) PAC technique, it can be used with usefulness for hemodynamic and preload assessment in major burn patients.