Relative Amnesic Potency of Five Inhalational Anesthetics Follows the Meyer-Overton Rule
- 1 August 2004
- journal article
- research article
- Published by Ovid Technologies (Wolters Kluwer Health) in Anesthesiology
- Vol. 101 (2), 417-429
- https://doi.org/10.1097/00000542-200408000-00023
Abstract
Doses of volatile anesthetics around 0.3 minimum alveolar concentration (MAC) inhibit learning. However, threshold amnesic doses and relative potencies between agents are not well established. The authors determined amnesic potency in rats for four common volatiles and nitrous oxide. After institutional review board approval, adult Sprague-Dawley rats received inhibitory avoidance training during exposure to either air or various subanesthetic doses of desflurane, sevoflurane, isoflurane, halothane, or nitrous oxide (4–21 rats/dose). Animals were trained to remain in a starting “safe” compartment for 100 consecutive seconds by administering a foot shock (0.3 mA) each time they entered an adjacent “shock” compartment. Memory was assessed at 24 h. Anesthetic effects on pain thresholds were separately determined. Learning: Only relatively higher doses of sevoflurane, halothane, and desflurane increased the number of shocks required for task acquisition. Memory: Significantly decreased retention performance (P sevoflurane ≥ isoflurane >> halothane, (rank-ordered ED50 values as %MAC). Amnesic potency correlated with oil:gas partition coefficients (r = −0.956, P P Amnesic potency differs between agents; nitrous oxide is most potent and halothane is least potent relative to MAC. The amnesic threshold ranges from 0.06 to 0.3 MAC. The correlation between potency and oil:gas partition coefficients suggests a fundamental role for hydrophobicity in mediating amnesia, similar to its association with MAC. Some agents (e.g., halothane) may enhance aversive memory retention at doses typically encountered during emergence.Keywords
This publication has 51 references indexed in Scilit:
- The Concentration of Isoflurane Required to Suppress Learning Depends on the Type of LearningAnesthesiology, 2001
- Awareness during AnesthesiaAnesthesiology, 2000
- Awareness during AnesthesiaAnesthesiology, 1999
- Learning and Memory during General AnesthesiaAnesthesiology, 1997
- Patients' memories of events during general anaesthesia.Anaesthesia, 1997
- HypothesisAnesthesia & Analgesia, 1997
- Effects of Subanesthetic Concentrations of Isoflurane and Their Interactions with Epinephrine on Acquisition and Retention of the Rabbit Nictitating Membrane ResponseAnesthesiology, 1994
- Nitrous oxide: Sensory, motor, associative, and behavioral tolerance effects in classical conditioning of the rabbit nictitating membrane responsePharmacology Biochemistry and Behavior, 1994
- Effects of Isoflurane and Nitrous Oxide in Subanesthetic Concentrations on Memory and Responsiveness in VolunteersAnesthesiology, 1992
- Minimum Alveolar Anesthetic ConcentrationAnesthesiology, 1965