The subjective, behavioral and cognitive effects of subanesthetic concentrations of isoflurane and nitrous oxide in healthy volunteers

Abstract

A prospective, crossover, double-blind trial was conducted in nine healthy volunteers in which the subjective, psychomotor and memory effects of isoflurane (0.0, 0.3 and 0.6%) and nitrous oxide (N2O) (0, 20 and 40%) were examined. Dependent measures included visual analog scales and a standardized drug effects inventory (subjective effects), reaction time and eye-hand coordination (e.g., psychomotor performance), and immediate and delayed free recall (memory). There were some similarities in subjective effects between the two inhaled drugs (e.g., increased ratings of "drunk" and "spaced out"), but isoflurane had effects which N2O did not have. Isoflurane but not N2O increased visual analog scale ratings of "confused," "sedated," and "carefree," and decreased ratings of "in control of thoughts" and "in control of body." An odor was detected with isoflurane and it was disliked. Psychomotor performance was more grossly impaired during isoflurane inhalation than during N2O inhalation. Psychomotor recovery from both agents was rapid and complete so that 5 min after the inhalation period had ceased, performance had returned to baseline levels. Both isoflurane and nitrous oxide impaired immediate and delayed free recall. The feasibility of using isoflurane in conscious sedation procedures is discussed.

Cognitive properties of sedation agents: comparison of the effects of nitrous oxide and midazolam on memory and mood

“…One study using a similar concentration of nitrous oxide to that reported here, also reported nonsignificant increases in reaction time. 23 While other studies have revealed significant increases in reaction time, such effects were dose-dependent, and reaction time slowing may only be seen at the highest doses. 17 On the other cognitive measures, nitrous oxide inhalation led to mild performance impairments, which did not differ significantly from performance in the control sessions.…”

Anosmia after general anaesthesia: a case report

“…An animal study examining the behavioural and electrophysiologic effects of four anaesthetic agents infused into the cerebral ventricles of conscious rats demonstrated depressed olfactory responses following propofol and fentanyl, with propofol producing the strongest effect [2]. Another study in humans assessing [15]. Standard brain and sinus imaging studies (CT scan, MRI) of patients with loss of smell are usually normal except for a relatively small number of cases with nasal pathology, e.g.…”

Inhibition de l’apprentissage et de la mémoire par les anesthésiques généraux

“…55 Sub-sedative doses of isoflurane (0.3%) and nitrous oxide (20%) also impaired immediate and delayed word recall. 56 Memory for emotional encounters was blocked by sub-anesthetic concentrations of sevoflurane (0.25%), desflurane (1.5-2 times MAC-awake), and propofol (1.5-2 times MAC-awake). 57,58 At MAC-equivalent concentrations, some anesthetics are more effective than others at preventing memory.…”