Background: Minimizing the time of anesthesia emergence can facilitate faster patient turnover in the operating rooms of a busy surgery center. According to Lin's new concept of inhalation uptake, after turning off the vaporizer under close-circuit anesthesia (CCA) with a very low fresh gas flow rate, the concentration of desflurane decreases at a slow rate. The aim of this study was to determine if earlier cessation of desflurane supply would shorten the emergence time and at the same time register the changes of desflurane concentration in the circuit after turning off the vaporizer.
Methods: 30 patients were randomly assigned to two groups, i.e., the control group and the study group. In the control group, the desflurane supply was continued up till the end of the operation, while in the study group the desflurane supply was cut off prior to the suturing the skin. In the study group, data regarding the hemodynamic changes, time from turning off desflurane with high flow washout to wakefulness, and the inspired as well as the expired desflurane concentrations at the low-flow anesthetic phase were collected. The time required from high flow washout to emergence was recorded in all patients. Inter-group and intra-group data were analyzed with nonparametric 2-independent-samples Mann-Whitney test and 2 related-samples Wilcoxon signed ranks test, respectively.
Results: Under CCA with similar surgical duration, the patients in the study group emerged from anesthesia significantly faster than those in the control group (5.6 +/- 1.9 min versus 8.8 +/- 2.3 min; P < 0.05), without molestation of stable hemodynamic signs. At the low-flow wash-in stage, the inspired desflurane concentrations were significantly higher than the expired ones from 0 to 2nd min; no significant difference was noted from the 3rd to 6th min, but after which the expired concentrations were significantly higher. Desflurane concentrations decreased most noticeably during the first 5 min (0.35 +/- 0.14%), and then the decrease was moderating from 6th to 10th min (0.21 +/- 0.58%) and staggered from 11th to 15th (0.14 +/- 0.06%). The mean duration of low flow wash was 25.6 +/- 11.6 min. No patient reported awareness during surgery.
Conclusions: Ceasing desflurane supply earlier in CCA (250 mL/min) significantly shortens emergence time without significant hemodynamic changes.