| The Appropriate Inflow Rates of Oxygen and Nitrous Oxide in Adult General Anesthesia. |
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Il Sook Seo, Ki Seok Son, Byeung Yong Lee, Jun Man Park, Sae Yeun Kim, Bon Up Koo, Dae Pal Park, Se Hun Park |
1Department of Anesthesiology, College of Medicine, Yeungnam University, Daegu, Korea.
2Department of Anesthesiology, Pusan Armed Forces General Hospital, Pusan, Korea. |
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| Abstract |
BACKGROUND
During adult general anesthesia, we used 3~5 L/min of fresh gas flow(FGF) but low FGF are employed, the amount of anesthetic consumption and air contamination can be reduced. The aim of this study was to determine the minimal appropriate inflow rate of oxygen and nitrous oxide during semiclosed circle technique.
METHODS
We selected 40 patients, ASA group 1 or 2, scheduled for elective, nonabdominal surgery under general anesthesia with semiclosed circle system. Anesthesia was maintained with 50% oxygen, nitrous oxide and enflurane, controlled ventilation was used; rate of 10/min, tidal volume of 10 ml/kg. After induction and vital signs stabilized, FGF was changed to 4 L, 3 L, 2 L and 1L/min at interval of 30 minutes. We observed mean airway pressure and arterial blood gas tensions.
RESULTS
The changes of mean airway pressure did not correlated with fresh gas inflow rate. In arterial blood gas analysis, PaO2 showed a decreasing tendency significantly according to decreasing fresh gas inflow rate(p<0.01) but there were no clinical hypoxemia in all patients. There were no significant changes in pH, PaCO2 and base excess.
CONCLUSIONS
We consider that FGF of 1~2 L/min is appropriate during adult general anesthesia because of economic and ecological advantages. Also, we consider low flow technique with below 1L/min can be used safely and effectively under proper gas monitoring such as oxygen analyzer, capnometer. |
| Key Words:
Anesthetics; volatile nitrous oxide; Anesthetic techniques semiclosed; low flow |
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