Okada K, Nakayama H, Aizawa J, Okada H, Nunokawa N, Wakusawa R
Department of Anesthesiology, Iwate Medical University, School of Medicine, Morioka.
Masui. 1999 May;48(5):500-5.
Low flow anesthesia (LFA) at a fresh gas flow (FGF) level of 10 ml.kg-1.min-1 with oxygen flow set at 0.5 ml.kg-1.min-1: 0.5 ml.kg-1.min-1 nitrous oxide and 3% isoflurane was performed using time-cycled ventilator on 10 patients of ASA class I or II, with age of 55 +/- 13 (mean +/- SD) years and body weight of 55 +/- 10 kg for 5 h. Excessive anesthetic gases from the anesthesia gas monitor were led to an expiratory breathing tube. After rapid induction and tracheal intubation, denitrogenation was performed for about 5 min using a 100% oxygen flow of 6 l.min-1 before LFA. The inspired/expired oxygen concentration decreased gradually from 96 +/- 2%/90 +/- 2% at beginning of LFA to 42 +/- 3%/37 +/- 4% at 5 h. The operation was started after 29 +/- 10 min of beginning of LFA. The nitrous oxide concentration reached 37 +/- 4%/35 +/- 4% at the beginning of operation and further increased to 55 +/- 3%/53 +/- 3% at 5 h. The isoflurane concentration reached 1.0 +/- 0.1%/0.8 +/- 0.1% at the beginning of operation and further increased to 1.2 +/- 0.1%/1.0 +/- 0.1% at 5 h. The anesthetic potency was 1.2 +/- 0.1 MAC/1.0 +/- 0.2 MAC at the beginning of operation. The isoflurane vaporizer setting was changed only once in two cases from 3% to 2% exceeding 1.5% in inspired concentration. There was no need to change the flow of oxygen and nitrous oxide for 5 hrs. No SpO2 lower than 95% was observed during this study. This method is a clinically safe, easily applicable anesthesia method and used the smallest FGF reported in LFA without occurrence of low FIO2.
对10例ASA I级或II级患者进行低流量麻醉（LFA），新鲜气体流量（FGF）为10 ml·kg⁻¹·min⁻¹，氧气流量设定为0.5 ml·kg⁻¹·min⁻¹，氧化亚氮流量为0.5 ml·kg⁻¹·min⁻¹，异氟烷浓度为3%，使用时间切换通气机，患者年龄55±13（平均±标准差）岁，体重55±10 kg，麻醉时长5小时。麻醉气体监测仪排出的多余麻醉气体接入呼气呼吸管。快速诱导和气管插管后，在进行低流量麻醉前，使用6 l·min⁻¹的纯氧流量进行约5分钟的去氮操作。吸入/呼出氧浓度从低流量麻醉开始时的96±2%/90±2%逐渐降至5小时时的42±3%/37±4%。低流量麻醉开始29±10分钟后开始手术。手术开始时氧化亚氮浓度达到37±4%/35±4%，5小时时进一步升至55±3%/53±3%。手术开始时异氟烷浓度达到1.0±0.1%/0.8±0.1%，5小时时进一步升至1.2±0.1%/1.0±0.1%。手术开始时麻醉效能为1.2±0.1 MAC/1.0±0.2 MAC。仅2例患者的异氟烷蒸发器设置从3%改为2%，因为吸入浓度超过了1.5%。5小时内无需改变氧气和氧化亚氮的流量。本研究期间未观察到SpO₂低于95%。该方法是一种临床安全、易于应用的麻醉方法，采用了低流量麻醉中报道的最小新鲜气体流量，且未出现低氧分压情况。
