Abstract
Background. We propose a 1-1-12 wash-in scheme for desflurane-nitrous oxide (N2O) low-flow anesthesia. The objective of our study was to determine the time to achieve alveolar concentration of desflurane (FAD) at 1, 2, 3, 4, 5, and 6%. Methods. We enrolled 106 patients scheduled for elective surgery under general anesthesia. After induction and intubation, wash-in was started with a fresh gas flow (FGF) of N2O : O2 1 : 1 L min−1 and vaporizer concentration of desflurane (FD) of 12%. Ventilation was controlled to maintain PACO2 at 30–35 mmHg. Results. The FAD rose rapidly from 0 to 4% in 2 min in a linear manner in 0.5 min increments. An FAD of 6% was achieved in 4 min in a linear fashion from FAD of 4% but in 1 min increments. An FAD of 1 to 6% occurred at 0.6, 1, 1.5, 2, 3, and 4 min. Heart rate during wash-in showed a statistically, albeit not clinically, significant pattern of increase. By contrast, blood pressure slightly decreased during this period. Conclusions. We developed a 1-1-12 wash-in scheme using a FGF of N2O : O2 1 : 1 L min−1 and FD of 12% for desflurane-nitrous oxide low-flow anesthesia. A respective FAD of 1, 2, 3, 4, 5, and 6% can be expected at 0.6, 1, 1.5, 2, 3, and 4 min.
Highlights
The benefits of low-flow anesthesia (LFA; fresh gas flow ≤ 1 L min−1) include its economy, lower pollution, and conservation of heat and humidity [1]
Desflurane is well suited for LFA because it has low tissue solubility and there is no limitation of minimal fresh gas flow (FGF) even with older CO2 absorbers [2]
LFA needs an initial high FGF with high vaporizer concentration of desflurane (FD) in order to rapidly achieve the required concentration in the circle circuit: this is the wash-in phase [3] and many wash-in schemes have been reported
Summary
The benefits of low-flow anesthesia (LFA; fresh gas flow ≤ 1 L min−1) include its economy, lower pollution, and conservation of heat and humidity [1]. We propose a simple 1-1-12 wash-in scheme— a single step using FGF of N2O : O2 1 : 1 L min−1 and FD of 12%—that will enable the anesthesiologist to anticipate the time needed to rapidly achieve every FAD target (i.e., from 1 to 6%). We propose a 1-1-12 wash-in scheme for desflurane-nitrous oxide (N2O) low-flow anesthesia. Wash-in was started with a fresh gas flow (FGF) of N2O : O2 1 : 1 L min−1 and vaporizer concentration of desflurane (FD) of 12%. We developed a 1-1-12 wash-in scheme using a FGF of N2O : O2 1 : 1 L min−1 and FD of 12% for desflurane-nitrous oxide low-flow anesthesia. A respective FAD of 1, 2, 3, 4, 5, and 6% can be expected at 0.6, 1, 1.5, 2, 3, and 4 min
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