[Low flow anesthesia at a fresh gas flow of 10 ml.kg-1.min-1 for hours using time-cycled ventilator].
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.
Okada
K
K
Department of Anesthesiology, Iwate Medical University, School of Medicine, Morioka.
Nakayama
H
H
Aizawa
J
J
Okada
H
H
Nunokawa
N
N
Wakusawa
R
R
D000328:Adult; D000368:Aged; D000769:Anesthesia, Inhalation / Q000295:instrumentation* / Q000379:methods; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage*; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage*; D010100:Oxygen / Q000008:administration & dosage; D013514:Surgical Procedures, Operative; D013997:Time Factors; D012122:Ventilators, Mechanical
D018685:Anesthetics, Inhalation; D007530:Isoflurane; D009609:Nitrous Oxide; D010100:Oxygen