The Study Of Target-controlled Infusion For Conscious Sedation In Patients Undergoing Spinal Anesthesia

Object To investigate the feasibility of target-controlled infusion(TCI) with propofol , midazolam for sedation in patients undergoing spinal anesthesia and determine the required target concentration. And to search the correlation between Bispectral index(BIS) and the target concentration of propofol or midazolam .Methods 45 patients undergoing lower limb operations were randomly divided into three groups: group P-propofol (n=15), group M-midazolam (n=15) and group P/F-propofol plus fentanyl (n=15). Patients with psychiatric disorders, hearing abnormalities o r s evere c ardiopulmonary d iseases w ere e xcluded. A fter getting satisfied spinal anesthesia, target-controlled infusion was established. Marsh pharmacokinetic parameters were used in group P and group P/F , and Avram pharmacokinetic parameters were used in group M . The effect site concentration w as c hosen a s t argeted c oncentration . The 1 evel o f s edation w as evaluated using observer's assessment of alertness/sedation(OAA/S) scale. Target propofol concentration was initially set at 0.6 M g/ml and adjusted in increment of 0.1ug/ml until the patients' OAA/S score reduced to 3. Target midazolam concentration was initially set at 40 ng/ml and adjusted in increment of 10 ng/ml until the patients' OAA/S score reduced to 3. In group P/F, the patients were given fentanyl 50 ug before using propofol TCI. Then target propofol concentration was initially set at 0.6 ug/ml and adjusted in increment of 0.1 M g/ml until the patients' OAA/S score reduced to 3. Target concentration ,hemodynamic parameters, BIS and satisfaction of sedation of patients were recorded. The target concentration at different O AA/S and t he c orrelation w ith B IS w ere d etermined. All d atas w ere analyzed by SPSS 10.0.Results The target propofol concentration for conscious sedation (OAA/S 3)was 1.01 +0.12 ug/ml. There was a good correlation between BIS and target propofol concentration(r=-0.600,p<0.05). The target midazolam concentration for conscious sedation (OAA/S 3) was 57.33+ 14.38 ng /ml. There was a good correlation between BIS and target midazolam concentration(r=-0.689,p<0.05). Fentanyl decreased target propofol concentration significantly . All patients express great satisfaction with the sedation.Conclusion TCI with propofol or midazolam for conscious sedation in patients undergoing spinal anesthesia has the advantages of good control, appropriate sedation and hemodynamic less influence and can be used clinically. BIS is the sensitive parameter to monitor the conscious sedation during spinal anesthesia.