The effects of age and anesthetic solubility on anesthetic-induced opisthotonus in mice.

In our previous report which indicated volatile anesthetics-induced opisthotonus in mice, we hypothesized that opisthotonus might relate with the rapidity of anesthetic induction, i.e., the blood/gas partition coefficient of the agent. To confirm this, we determined the incidence of opisthotonus induced by four different halogenated ethers (2.0% sevoflurane, 1.3% isoflurane, 2.0% enflurane, and 0.5% methoxyflurane) and 1.0% halothane, a haloalkane, in male ddN mice. The effect of age on opisthotonus was also evaluated by using young (10±2 weeks), middle-aged (6±1 months), and elderly (12±1 months) groups of male ddN mice. In each age group, the incidence of opisthotonus occurred in the following order: sevoflurane > isoflurane > enflurane > methoxyflurane > halothane. This partly supports our hypothesis as far as halogenated ethers are concerned. Halothane rarely produced opisthotonus. In the sevoflurane, isoflurane, and methoxyflurane groups, incidence was lower in middle-aged than in young or elderly mice, while incidence increased with age in the enflurane group.