[Clinical study on bispectral index in monitoring the depth of desflurane anesthesia in the elderly]

Abstract

Objective: To evaluate the values of bispectral index (BIS) in mornitoring the depth of desflurane anesthesia in the elderly by observing the changes of BIS at various end-tidal desflurane concentrations.

Methods: BIS was used to monitor the depth of desflurane anesthesia in the elderly without surgery stimulation. Forty ASA physical status I approximately III patients undergoing general anesthesia were divided into 2 groups with 20 in each group:Group Elderly ( > or =65 years) and Group Youth ( 18 approximately 55 years). Anesthesia was induced with propofol 2. 0 mg/kg and vecuronium 0. 1 mg/kg including the endotracheal topical anesthesia with 2% lidocaine. After the desflurane in oxygen, each concentration of desflurane was maintained for 20 minutes. The changes of mean arterial blood pressure (MAP), heart rate (HR) and BIS were recorded simultaneously. The timepoints setting for observation were: preanesthesia, 2 minutes after the anesthesia, endotracheal intubation, 2 minutes after the intubation, and end-tidal concentration of desflurane at 0. 6 MAC, 1.0 MAC and 1. 3 MAC.

Results: During anesthesia of desflurane, MAP and HR did not change significantly in the 2 groups with increasing end-tidal desflurane concentration from 0. 6 MAC to 1. 3 MAC (P > 0.05). BIS decreased significantly than that at preanesthesia in the 2 groups during anesthesia of desflurane ( P < 0.05 ). The changes of BIS were different in the 2 groups during the whole anesthesia (P < 0.05). As the concentration of desflurane increased, BIS decreased gradually but there were no significant changes on BIS in the 2 groups ( P > 0. 05 ). In general, BIS highly correlated with the end-tidal desflurane concentration. The coefficient of product-moment correlation (r) between BIS and the end-tidal desflurane concentration was -0. 996 and -0. 946 in Group Elderly and Youth (P < 0. 05 ).

Conclusion: BIS highly correlates with the end-tidal desflurane concentration which is used to evaluate the depth of desflurane anesthesia in the elderly and youth. There is different depth of anesthesia by BIS in the elderly or youth at the same end-tidal desflurane concentration.