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A282
October 18, 2008 2:00 PM - 4:00 PM Room Hall E2-Area N, |
| Sparing Effect of Nitrous Oxide on Propofol and Remifentanil Closed-Loop Anesthesia. |
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Ngai Liu, M.D., Nathalie Boichut, M.D., Thierry Hérail, M.D., Jean Bussac, M.D., Marc Fischler, M.D. Department of Anesthesiology, Hôpital Foch, Suresnes, France |
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Background: We have demonstrated, using a dual-closed-loop controller, that the Bispectral Index (BIS) can automatically steer propofol and remifentanil administration1. Nitrous oxide (N2O) has a hypnotic and analgesic effect. We investigated whether the coadministration of N2O would reduce the amount of propofol and remifentanil required to maintain BIS in the range 40-60 during intravenous anesthesia maintenance. Methods: This prospective randomized multicenter trial was performed with IRB approval and patients' written consent. 225 ASA I-IV patients who were scheduled for minor or major surgery, were randomized after induction of general anesthesia to receive 60 % nitrous oxide - 40 % oxygen (N2O group) or air-oxygen (fraction of inspired oxygen = 40%, Air Group). In both groups, the Dual-loop controller was used to provide induction and maintenance of general anesthesia according to the BIS. Anesthesia depth between groups was evaluated by measuring the percentage of time in which the BIS was in the range 40-60 during maintenance. Data is presented as mean ± SD. Statistical analysis was performed using Student-t or Chi-squared tests; p<0.05 was considered significant. Results: The preliminary results of the study are as follows. 95 patients were included in the N2O Group, 106 in the Air group and 24 were excluded. There were no differences in demographics (N2O group vs Air group): age (56 ± 15 vs 56 ± 19 yr), weight (73 ± 15 vs 74 ± 16 kg), height (169 ± 8 vs 167 ± 9 cm), duration of surgery (190 ± 135 vs 167 ± 111 min). Dual-loop controller was able to provide anesthesia induction and maintenance for all patients. Propofol (1.2 ± 0.5 vs 1.3 ± 0.6 mg.kg-1) and remifentanil (2.3 ± 1.3 vs 2.4 ± 1.6 mcg.kg-1) induction doses were similar. During anesthesia maintenance, use of neuromuscular blocking agent (35 vs 37 % of patients), percentage of time during which the BIS was between 40-60 (78 ± 12 vs 75 ± 12 %), propofol (4.9 ± 1.8 vs 5.5 ± 1.9 mg.kg-1.h-1) and remifentanil (0.20 ± 0.09 vs 0.22 ± 0.10 mcg.kg-1.min-1) consumption were all similar. The percentage of time of too light anesthesia (BIS>60) was lower in the N2O group (4 ± 3 vs 5 ± 4 %, p=0.002). No cases of awareness with recall were recorded. Conclusions: The Dual-loop controller allowed an unbiased administration of propofol and remifentanil. These preliminary results suggest the absence of significant sparing effect of N2O coadministration on propofol and remifentanil consumption during intravenous general anesthesia maintenance. Reference: 1. Anesthesiology 2006 ; A854. Anesthesiology 2008; 109 A282 |