Clinical Study Of Isoflurane For Low-flow Closed Circuit Anesthesia

Objective: To investigate low-flow closed circuit anesthesia (LFCCA) with isoflurane made in china to implement low-flow inhalated anesthetic techniques. To evaluate the relations among inspired or expired isoflurane concentration (Ci,Ce) and the vaporizer output concentration adjust to 4% in the anesthesia duration, in addition,to investigate the relativity between vaporizer concentration setting(Cn) and actual inspiratory concentration. Methods: Forty ASA grade Ⅰ-Ⅱ patients were randomly divided into two groups(A and B). Anesthesia were performed with rapid induction intubation andmaintained with 4% Isoflurane at oxygen flow rate of 0.8L/min and 2L/min respectively. The Ci and Ce were monitored, the rising speed and difference of alveolar concentration were observed, the time(Te) and the concentration(Cmax) were recorded as soon as Ci and Ce got equilibrium. The relative coefficient and regression equation between Cmax and Cn were work out by linear logical regression. Results: The ratio of Ce/Ci both increased following Te in two groups. There was linear correlation among Ci , Ce and anesthesia duration. In group B, there is the higher Co and the higher sloope of the equation, meanwhile Ci and Ce increased more rapidly. The lineal regression equation in group A and B is Y=0.443+0.01577 and Y=1.043+0.02067 respectively.To analysis through conjecture changes the deal and achieve two straight lines of different sloope,Te that was calculated in group A and B is 4.9±0.2min and 7.2O±0.3min respectively. Oxygen flow rate can not obviously influence Te that alveolar concentration and Ci got equilibrium, but lead to alveolar concentrationincreased rapidly. The time of alveolar concentration that got to 0.9% is quicker in group B than in group A. Conclusion: During low-flow isoflurane anesthesia, the concentration of the alveoli and the Ci Can got to balanced rapidly. The low-flow isoflurane anesthesia is safe, feasible and cheap.