The Effect of Non - rebreathing Oxygen Mask on Arterial Blood Gas Tension during Epidural Anesthesia

Kim, Ae Ra; Cheun, Jae Kyu

Abstract

This investigation was undertaken to examine the effect of nonrebreathing oxygen mask on arterial blood gas tension during epidural anesthesia. 35 patients who were undergone total hystrectomies were studied. After the induction of epidural anesthesia, thiopental 200 mg and Entobar 25 mg were intravenouly injected. 35 patients were divided into four groups i. e:group 1(n=9) with no oxygen mask (contol), group 2(n=12) with oxygen of 3L/min, group 3(n=8) with 4L/min, and group 4(n=6) with 5L/min through the non-rebreathing oxygen mask. Arterial blood samples were taken one hour after the start of surgery for the measurement of PaO2, PaCO2 and O2 sat. The results were as follows: 1) In control group, the mean value of PaO2, was 86.6(13.4) torr but two patients showed less than 70 torr. 2) In group 2, 3, 4, PaO2, and 02, sat increased significantly compared with the control group (P< 0.05). 3) PaO2, and 02, sat were not significantly different in connection with oxygen flow rates between group 2, 3, 4. 4) The changes of PaCO2, were not significant in comparison with the control group between group 2, 3, 4 but PaCO2, was above 45 torr in eleven patients due to respiratory depression. Non-rebreathing oxygen mask increased PaO2, significantly at the oxygen flow rates of 3-5 L/min. However, PaCO2 did not seem to be influenced by the oxygen flow rates but the minute ventilation. Therefore, we concluded that the most important thing we should do for CO2 accumulation is careful observation to the patients for respiratory depression and obstruction.