[Study on general anesthesia for cesarean section--condition of ventilation and inhaled O2 concentration]

The effects of ventilation on the fetus during general anesthesia for elective cesarean section were evaluated.

62 healthy parturients (37-42 weeks) were divided into two groups, 40 received general anesthesia (G group) and 22 received spinal anesthesia (C group). All were given pre-operative infusion, journey tilt position and LUDD application. The G group was further divided according to the combination of O2 concentration and respiratory rate. General anesthesia was maintained by N2O-O2-halothane (0.5%). The C group was given 0.3% dibucaine with 100% O2 inhalation. ABM was used to monitor blood pressure, pulse rate, EMG, EEG, NMT and EtCO2. Maternal arterial blood (MA) and umbilical arterial and venous blood (UA, UV) were taken at delivery for measurement of PO2, PCO2, pH and B.E..

No significant change in blood pressure was found. There were positive correlations in EtCO2, MAPCO2 and UVPCO2. MAPCO2 decreased when the respiratory rate was increased. UVPCO2 and UVPO2 were not affected when MAPCO2 was below 23mmHg. When the O2 concentration was increased, MAPO2 also increased. Thus, pre-operative infusion, journey tilt position and LUDD application help to prevent hypotension. ABM, and especially, EtCO2, provides useful information. Slight hyperventilation and hyperoxygenation are better for the fetus.