The Characteristics of Clinical Anesthesia Based on the Duration of Lateral Decubitus in Low Dose Hyperbaric Bupivacaine Induced Unilateral Spinal Block / 대한마취과학회지

BACKGROUND: When attempting a unilateral spinal anesthesia, many factors must be considered including patient's position, density and amount of the local anesthetics, needle design, injection speed. We evaluated a duration of lateral decubitus with low dose hyperbaric bupivacaine for maximizing the benefit. METHODS: Hyperbaric 0.5% bupivacaine 6 mg was administered slowly through a 25-gauge Whitacre needle to 60 ASA 1-2 patients undergoing unilateral lower extremity surgery. The patients were randomly allocated to four groups based on the duration of lateral decubitus after spinal anesthesia: 5 minutes in Group I; 10 minutes in Group II; 15 minutes in Group III; 20 minutes in Group IV. Circulatory variables, sensory and motor block level were recorded. RESULTS: The circulatory variables were stable in all patients. In the Group I, the success rate of unilateral motor block was significantly lower than other groups. In the Group IV, the success rate of unilateral sensory block was significantly higher than group I. In the Group II, III, IV, the patient's satisfaction scores were significantly higher than Group I. CONCLUSIONS: When unilateral spinal anesthesia was attempted with 0.5% hyperbaric bupivacaine 6 mg, cardiovascular stability was achieved in the groups that patients are kept in a lateral decubitus for more than 5 minutes after spinal injection, and patient's higher satisfaction scores were achieved in the unilateral motor block and in the groups that patients are kept in a lateral decubitus for more than 15 minutes after spinal injection.

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.