Fourly adult healthy patients were separately anesthetlzed with (1 )0. 95% isoflurane; (2) fentanyl 5g/kg and thiopentone 4 mg/kg; (3) upper thoracic epidural blockage and (4 ) lumbar epidural blockage,Continuous 5 min ECG were recorded before and a fier anesthesia with spectral analysis of heart rate varlability (HRV) performed by computer program. For power spectral measurement,three frequency band of HRV were evaluated and the effects of each anesthesia were compared. HRV reduced markedly in patients using 0. 95 % isoflurane. with decreases of frequency by 91. 7% (low frequency ), 84. 4% (mid frequency ). and 82% (high-frequency) respectively. In patients after administration of fentanyl 5g/kg, mid and high-frequency components declined 63. 4 % and 65. 4 %. Upper thoracic epidural block restrained the mid and low frequency components by 66 % and 65 % respectively, Following lumbar epidural block the pattern of HRV components did not change. It is concluded that different anesthesia techniques may have significant different effects on autonomic reflexes as presented by HRV.

Objective Using accurate monitoring,and high precision anesthetic machine and vapourizer,and guided with a simple mathematics formula to implement low-flow inhaled anesthetic techniques.Methods Ten healthy patients under going craniotomy,thoracotomy or laparotomy were assigned to receive isoflurane by low-flor of fresh gas and high vapourizer output.After intubation,the vapourizer dial was set at 5% and the patients were delivered with 1L/min total fresh gas flow of oxygen.The expiratory(F E) and inspired(F 1) concentration of isoflurane were monitored continuously.The data were recorded with computer once every 10. The concentrations were plotted against the time and the predicted regression equation were calculated.Results The F E reached 1.05% 10 min after inhalation of isoflurane ,which could be predicted by curvilinear(y=0 4092(1nx)+0 0172) and lineal (y=0 083x+0 1385) regression equations from 1 to 10 min,The predicted concentration by curvilinear regression equation appeared to estimate the measured value more accurately than linear regression equation.However segmental lineal regression equation cluld predict the measured value as accurately as curvilinear regression equation.Conclusions The inhalation anesthetic induction can be completed within 10 min with low-flow of fresh gas flow and high output of vapourizer dial setting.The measured value of anesthetic can be predicted accurately.