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Nitrous oxide does not produce a clinically important sparing effect during closed-loop delivered propofol-remifentanil anaesthesia guided by the bispectral index: A randomized multicentre study

par Liu, Ngai;Le Guen, Morgan;Boichut, Nathalie;Genty, Antoine;Herail, Thierry;Schmartz, Denis ;Khefif, G.;Landais, Amaelle;Bussac, J.J. J.J.;Charmeau, A.;Baars, Jan Harald J.;Rehberg, Benno;Tricoche, Stéphanie;Chazot, Thierry;Sessler, Daniel D.I.;Fischler, Manuel
Référence British Journal of Anaesthesia, 112, 5, page (842-851)
Publication Publié, 2014

Article révisé par les pairs

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Résumé :

Background Nitrous oxide (N2O) offers both hypnotic and analgesic characteristics. We therefore tested the hypothesis that N 2O administration decreases the amount of propofol and remifentanil given by a closed-loop automated controller to maintain a similar bispectral index (BIS). Methods In a randomized multicentre double-blind study, patients undergoing elective surgery were randomly assigned to breathe 60% inspired N2O (N2O group) or 40% oxygen (AIR group). Anaesthesia depth was evaluated by the proportion of time where BIS was within the range of 40-60 (BIS40-60). The primary outcomes were propofol and remifentanil consumption, with reductions of 20% in either being considered clinically important. Results A total of 302 patients were randomized to the N2O group and 299 to the AIR group. At similar BIS40-60 [79 (67-86)% vs 76 (65-85)%], N2O slightly decreased propofol consumption [4.5 (3.7-5.5) vs 4.8 (4.0-5.9) mg kga1 ha1, P=0.032], but not remifentanil consumption [0.17 (0.12-0.23) vs 0.18 (0.14-0.24) μg kg a1 mina1]. For the subgroups of men, at similar BIS 40-60 [80 (72-88)% vs 80 (70-87)%], propofol [4.2 (3.4-5.3) vs 4.4 (3.6-5.4) mg kga1 ha1] and remifentanil [0.19 (0.13-0.25) vs 0.18 (0.15-0.23) μg kga1 mina1] consumptions were similar in the N2O vs AIR group, respectively. For the subgroups of women, at similar BIS40-60 [76 (64-84)% vs 72 (62-82)%], propofol [4.7 (4.0-5.8) vs 5.3 (4.5-6.6) mg kga1 ha1, P=0.004] and remifentanil [0.18 (0.13-0.25) vs 0.20 (0.15-0.27) μg kga1 mina1, P=0.029] consumptions decreased with the co-administration of N2O. Conclusions With automated drug administration titrated to comparable BIS, N2O only slightly reduced propofol consumption and did not reduce remifentanil consumption. There was a minor gender dependence, but not by a clinically important amount. Clinical trial registration This study was registered at ClinicalTrials.gov, number NCT00547209. © 2014 The Author. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved.