| The Study of Preoxygenation on the Maternal and Neonatal Arterial Blood Gas Analysis in General Anesthesia for Cesarean Section. |
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Chi Hyo Kim, Jong Hak Kim, Choon Hi Lee, Hyun Ju Lee |
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Department of Anesthesiology, College of Medicine, Ewha Womans University, Seoul, Korea. |
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| Abstract |
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Preoxygenation is a standard anesthetic technique for preventing a significant hypoxemia during the induction of anesthesia. Complete denitrogenation is especially important in clinical situations of difficult intubation or in patients with decreased functional residual capacity, and in situations where oxygen saturation is critical. Methods for preoxygenation before induction of anesthesia have raised from tidal breathing of 100% O2 to taking four maximal breaths. Pregnancy produces significant physiologic changes in the respiratory system. Oxygen consumption in pregnancy is markedly increased and functional residual capacity decreases by 20-30% at term as compared to the nonpregnant stage. It is important to evaluate how long parturient women can withstand apneic hypoxemia during induction of general anesthesia. The aim of this study is to understand better how pregnancy effects preoxygenation with boths tidal breathing of 100% O2 for 3 min and four maximally deep inspiration of 100% O2 within 30 seconds technique. Twenty ASA 1 and 2 patients scheduled for elective cesarean section under general anesthesia selected for the study. After premedication with atropine sulfate 0.5 mg, we randomly divide the patients into two groups : Group 1 was preoxygenated by tidal breathing of 100% O2 for 3 min (n =10). Group 2 was preoxygenated by taking four maximally deep inspirations of 100% O2 within 30s (n = 10). We administered O2 to both groups at a flow rate of 8 Vmin via a semiclosed circle anesthesia system and a tight-fitting face mask. We performed a rapid-sequence induction of general anesthesia with thiopental 4 mg/kg iv followed by succinylcholine 1.2 mg/kg iv and intubated the trachea. We sampled maternal arterial blood immediately umbilical blood at delivery for blood gas analysis. And induction to delivery time, uterine incision to delivery time, neonatal birth weight, Apgar score were measured. The results were as follows, 1) Induction to delivery times, uterine incision to delivery times and birth weight were similarand no infant had an Apgar score of less than 8 at 1 or 5 min between two groups. 2) There were no significant differences in maternal blood gas values between the two groups. 3) Umbilical artery and venous blood gas values were similar in both groups. In conclusion, either tidal breathing of 100% O2 for 3 minutes or four maximally deep inspiration of 100% O2 within 30 seconds technique improve arterial oxygenation and similar protection against apneic hypoxemia in rapid sequence induction of general anesthesia for Cesarean section. |
| Key Words:
Obstetric anesthesia; Preoxygenation; Blood gas analysis |
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