| Objective: To investigate the effect of different carrier gas flow rate and composition on the performance of Tec6 desflurane vaporizer and give a reference to the low-flow and minimum-flow inhaled anesthesia.Method: Thirty-one ASA I - II patients undergoing elective surgery were selected. The patients were preme-dicated with intramuscular diazepam 10mg and atropine 0.Stag.Anesthesia was induced with midazolum 0.2mg/kg, fentanyl 3.0ug/kg and vecuronium 0.1mg/kg. After tracheal intubation the patients were mechanically ventilated with Penlon Prima 103 anesthesia machine and Ohmeda Tec 6 desflurane vaporizer. Controlled ventilation parameter were set up as follows: vital volume 8ml/kg, respiratory rate 12 times per minute, I:E 1:2 ,and maintained the end tidal CO2 pressure between 4.5-5.0kPa. During the initial stage of the anesthesia,vaporizer were set up at 12% and O2 1L/min to satisfy the rapid wash-in and the high absorption of vessel-rich constitutions. After 5-8min the vaporizer were set up at 6% according to BP and pulse rate of the patients. Fresh gas flow rates were set up at 5.0, 3.0, 1.0 and 0.5L/min by turns. Under each flow rate use the following three different carrier gases:100%O2, 70%O2+30%N20, 30%O2+70%N20 by tums. FGF 0.5L/min group use 100%O2, 70%Oz+30%N2O only. The gases were rapidly switched at 5-min interval. When light anesthesia occurred during the operation, such as high blood pressure (MAP> 125% pre-induction value or MAP>100 mmHg) or tachycardia (HR>125% pre-induction value or HR>100 beat/min),fentanyl 3.0ug/min were bolus intrave-nously.When BP decreased (MAP<75% pre-induction value or MAP<60mmHg) efedrina 10mg or atropine 0.5mg bolus intravenously. All the data were obtained in this study from the same operating theater, anesthesia machine and agent analyzer. The ambient temperature were maintained at 22 4- 1C and excluded the aptitude influence on the performance of desflurane vaporizer. All the bonds in the anesthesia machine were reinforced and the leaking quantity of the breathing circuit was measured. Every morning leaking test was performed before the experiment. This study used Atima agent analyzer. Its principle was based on the fact that different gas absorbs various wavelength of infrared light. The sensor of the analyzer was connected with the common gas outlet of the anesthesia machine and the desflurane, O2, N20 concentrations were continuously analyzed. The gases were rapidly switched at 5-min intervals and recording the output concentrations at 3-min and 5-min and their average values.During the study BP, HR, SpO2 and ECG of the patients were continuously monitored. All the data were processedstatistically. For this study, an analysis of variance was performed, which treated each patient as a blocking factor. Various gas flow and composition crossed and made up each treat factor. All main effects were equally assigned to each block. SAS 6.12 statistic software was used to do the variance analysis. Student-Newman-Keuls test was used to conduct the pair comparison. Result: Carrier gas flow rate and composition affected deflurane vaporizer performance significantly (p<0.001). At high flow rate 51/min of carrier gas, the average desflurane output was 6.03%, 5.83% and 5.54% for the carrier gases 100%O2, 70%O2+30%N20, 30%O2+70%N20 respectively. Turning the high flow rate to the middle flow rate 3L/min,desflurane output decreased to 5.81%, 5.53%, 5.28% with the same gases respectively and the lowest point was reached with the gas of 30%O2+70%N20. Turning the middle flow rate to the low flow rate 1L/min, the desflurane output further decrease to 5.45%, 5.20%, 5.00% respectively and the lowest point was reached with the gas of 30%O2+70%N20 just as the high-flow, mid-flow group. Compared with the above flow rates, the output of minimum flow group was the lowest concentration, when carrier gas was 5L/min 100%02, desflurane output reached the highest value. Accompanying the decrease of the 02 concentration in the carrier gases, de... |
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