Nitrous oxide reduces thiopental-induced prolongation of survival in hypoxic and anoxic mice

Arnfred's mouse model was used to test the effect of thiopental during hypoxia (5% O₂) and anoxia, with and without simultaneous administration of nitrous oxide. As found by Arnfred and others, thiopental without N₂O more than doubled survival time during hypoxia (from 5.2 ± 0.6 to 13.9 ± 2.6 min). This effect was completely offset by simultaneous use of N₂O (from 13.9 ± 2.6 to 4.8 ± 0.7 ,om). Thiopental without N₂O also increased survival time during complete anoxia (from 26 ± 1 to 59 ± 1 sec). This effect was diminished by 58% when N₂O was added (from 59 ± 1 to 40 ± 1 sec). The authors conclude that nitrous oxide diminishes the effect of barbiturates upon survival time in hypoxic and anoxic mice.