1-1-12 one-step wash-in scheme for desflurane low flow anesthesia: performance without nitrous oxide.
BACKGROUND
We reported a 1-1-12 wash-in scheme for desflurane-nitrous oxide (N2O) low flow anesthesia that is simple, rapid, and predictable. There remain some situations where N2O should be avoided, which limits the generalizability of this wash-in scheme. The objective of our study was to determine the performance of this scheme in contexts where N2O is not used.


METHODS
We recruited 106 patients scheduled for elective surgery under general anesthesia. After induction and intubation, wash-in was started with a fresh gas flow of air:O2 1:1 L/min and a vaporizer concentration of desflurane of 12%. Controlled ventilation was then adjusted to maintain PACO2 at 30-35 mmHg.


RESULTS
The alveolar concentration of desflurane (FAD) rose rapidly from 0% to 6% in 4 minutes in the same pattern as observed in our previous study in which N2O was used. An FAD of 7% was achieved in 6 minutes. An FAD of 1% to 7% occurred at 0.6, 1, 1.5, 2, 3, 4, and 6 minutes. The rise in heart rate during wash-in was statistically significant, although not clinically so. There was a slight but statistically significant decrease in blood pressure, but this had no clinical significance.


CONCLUSIONS
Performance of the 1-1-12 wash-in scheme is independent of the use of N2O. Respective FADs of 1%, 2%, 3%, 4%, 5%, 6%, and 7% can be expected at 0.6, 1, 1.5, 2, 3, 4, and 6 minutes.
Department of Anesthesiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
Thepakorn
T
Sathitkarnmanee
Department of Anesthesiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
Sirirat
S
Tribuddharat
Department of Anesthesiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
Duangthida
D
Nonlhaopol
Department of Anesthesiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
Maneerat
M
Thananun
Department of Anesthesiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
Wilawan
W
Somdee
D000293:Adolescent; D000328:Adult; D000768:Anesthesia, General / Q000379:methods*; D001794:Blood Pressure / Q000187:drug effects; D000077335:Desflurane; D005260:Female; D006331:Heart Diseases / Q000601:surgery; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D008171:Lung Diseases / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage*; D055815:Young Adult
D000077335:Desflurane; D007530:Isoflurane; D009609:Nitrous Oxide
air; desflurane; low flow anesthesia; wash-in