K. Tomi et al., ALTERATIONS IN PAIN THRESHOLD AND PSYCHOMOTOR RESPONSE ASSOCIATED WITH SUBANAESTHETIC CONCENTRATIONS OF INHALATION ANESTHETICS IN HUMANS, British Journal of Anaesthesia, 70(6), 1993, pp. 684-686
We studied the effects of six inhalation anaesthetics at subanaestheti
c concentrations of 0.2 MAC on pain threshold and psychomotor function
in six healthy volunteers. When compared with 100% oxygen inhalation,
nitrous oxide and methyoxy-flurane significantly increased pain thres
hold as measured by a radiant heat algometer, and prolonged the respon
se time to auditory stimuli. In contrast, halothane, enflurane, isoflu
rane and servo-flurane produced prolongation of the response time to a
uditory stimuli but did not influence pain perception. The pain thresh
old with nitrous oxide remained significantly increased 30 min after i
ts discontinuation, while the response time returned to the preinhalat
ion value. We conclude that nitrous oxide and methoxyflurane possess b
oth analgesic and hypnotic actions but halothane, enflurane, isofluran
e and sevoflurane do not have an analgesic action at subanaesthetic co
ncentrations, and the analgesic action of nitrous oxide persists after
its elimination.