A Comparison between the Effects of Total Intravenous Anesthesia and Inhalational Anesthesia on Postoperative Pulmonary Function Test

Every surgery is followed by some changes in postoperative pulmonary function tests which can dramatically influence this period. Although the type of the surgery and its vicinity to diaphragm are the main determinants of these changes, anesthetic techniques are also responsible. Among different probable factors through which anesthesia could influence postoperative pulmonary function tests, we planned to evaluate the effects of drugs used during the maintenance stage of anesthesia on postoperative pulmonary function tests. Patients & This is a single blind randomized clinical trial in which the patients ranged in age from 15 to 35 and presented with ASA I(American Society of Anesthesiology). All the operations were elective extremity or lower abdominal surgeries and their length was between one and two hours. All the patients had normal preoperative pulmonary function tests. The total number of the subjects was sixty and they were randomly divided into two equal groups(n=30). For the maintenance stage of anesthesia, inhalational agents(N2O 50%, Halothane 0.5-1%) were used in one group and intravenous drugs in the other one (Midazolam 0.1mg/kg/h, Alfentanil 0.5µg/kg/min). 24 hours postoperatively, pulmonary function tests(PFT) were performed and the deviations of three indices(FEV1=Forced Expiratory Volume in 1 sec, FVC=Forced Vital Capacity, VC=Vital Capacity) from their preoperative values were measured and compared. Students’ t-test was used for statistical analysis. FEV1, FVC and VC decreased by 16.3%, 13.5% and 12.5% in the inhalational group and by 12%, 12.9% and 12% in the intravenous group respectively. Comparing the results showed no significant difference between the two groups. Among the factors which are related to anesthesia and can affect postoperative pulmonary indices, the above-mentioned drugs that we used for the maintenance stage, whether inhalational or intravenous, exert no significant influence on postoperative pulmonary function tests.