JOURNAL HOME CME HOME THIS MONTH PAST ISSUES ETOC COLLECTIONS AUTHORS REVIEWERS EDITORIAL BOARD FEEDBACK RSS HELP
		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (16) Citing Articles via Google Scholar Google Scholar Articles by Antognini, J. F. Articles by Sudo, S. Search for Related Content PubMed PubMed Citation Articles by Antognini, J. F. Articles by Sudo, S.

---

GENERAL ARTICLES

Isoflurane Depresses Electroencephalographic and Medial Thalamic Responses to Noxious Stimulation via an Indirect Spinal Action

Joseph F. Antognini, MD^*, E. Carstens, PhD, Makoto Sudo, MD, and Satoko Sudo, MD

*Department of Anesthesiology and Pain Medicine, Section of Neurobiology, Physiology and Behavior, University of California, Davis, California; and Department of Anesthesiology and Resuscitology, Ehime University, Ehime, Japan

Address correspondence to Joseph F. Antognini, MD, Department of Anesthesiology, TB-170, University of California, Davis, CA 95616. Address e-mail to jfantognini{at}ucdavis.edu

Anesthetics such as isoflurane act in the spinal cord to suppress movement in response to noxious stimulation. Spinal anesthesia decreases hypnotic/sedative requirements, possibly by decreasing afferent transmission of stimuli. We hypothesized that isoflurane action in the spinal cord would similarly depress the ascending transmission of noxious input to the thalamus and cerebral cortex. In six isoflurane-anesthetized goats, we measured electroencephalographic (EEG) and thalamic single-unit responses to a clamp applied to the forelimb. Cranial bypass permitted differential isoflurane delivery to the torso and cranial circulations. When the cranial-torso isoflurane combination was 1.3% ± 0.2%–1.0% ± 0.4% the noxious stimulus did not evoke significant changes in the EEG or thalamic activity: 389 (153–544) to 581 (172–726) impulses/min, (median, 25th–75th percentile range, P > 0.05). When the cranial-torso isoflurane combination was 1.3% ± 0.2%–0.3% ± 0.2%, noxious stimulation increased thalamic activity: 804 (366–1162) to 1124 (766–1865) impulses/min (P < 0.05), and the EEG "desynchronized": total EEG power decreased from 25 ± 20 µV² to 12 ± 8 µV² (P < 0.05). When the cranial-torso isoflurane was 1.7% ± 0.1%–0.3% ± 0.2%, the noxious stimulus did not significantly affect thalamic: 576 (187–738) to 1031 (340–1442) impulses/min (P > 0.05), or EEG activity. The indirect torso effect of isoflurane on evoked EEG total power (12.6 ± 2.7 µV²/vol%, mean ± SE) was quantitatively similar to the direct cranial effect (17.7 ± 3.0 µV²/vol%; P > 0.05). These data suggest that isoflurane acts in the spinal cord to blunt the transmission of noxious inputs to the thalamus and cerebral cortex, and thus might indirectly contribute to anesthetic endpoints such as amnesia and unconsciousness.

Implications: Isoflurane action in the spinal cord diminished the transmission of noxious input to the brain. Because memory and consciousness are likely dependent on the "arousal" state of the brain, this indirect action of isoflurane could contribute to anesthetic-induced amnesia and unconsciousness.

This article has been cited by other articles:

				D. Kroeger and F. Amzica Hypersensitivity of the Anesthesia-Induced Comatose Brain J. Neurosci., September 26, 2007; 27(39): 10597 - 10607. [Abstract] [Full Text] [PDF]

				J. C. Murrell, S. L. Mitchinson, D. Waters, and C. B. Johnson Comparative effect of thermal, mechanical, and electrical noxious stimuli on the electroencephalogram of the rat Br. J. Anaesth., March 1, 2007; 98(3): 366 - 371. [Abstract] [Full Text] [PDF]

				C. Vahle-Hinz, O. Detsch, C. Hackner, and E. Kochs Corresponding minimum alveolar concentrations of isoflurane and isoflurane/nitrous oxide have divergent effects on thalamic nociceptive signalling Br. J. Anaesth., February 1, 2007; 98(2): 228 - 235. [Abstract] [Full Text] [PDF]

				M. Orth, E. Bravo, L. Barter, E. Carstens, and J. F. Antognini The differential effects of halothane and isoflurane on electroencephalographic responses to electrical microstimulation of the reticular formation. Anesth. Analg., June 1, 2006; 102(6): 1709 - 1714. [Abstract] [Full Text] [PDF]

				J. F. Antognini, S. L. Jinks, R. Atherley, C. Clayton, and E. Carstens Spinal anaesthesia indirectly depresses cortical activity associated with electrical stimulation of the reticular formation Br. J. Anaesth., August 1, 2003; 91(2): 233 - 238. [Abstract] [Full Text] [PDF]

				M. Yamauchi, S. G. Shimada, H. Sekiyama, and J. G. Collins Neither Spinal {gamma}-Aminobutyric Acid-A nor Strychnine-Sensitive Glycine Receptor Systems Are the Sole Mediators of Halothane Depression of Spinal Dorsal Horn Sensory Neurons Anesth. Analg., August 1, 2003; 97(2): 417 - 423. [Abstract] [Full Text] [PDF]

				J. F. Antognini, R. Atherley, and E. Carstens Isoflurane Action in Spinal Cord Indirectly Depresses Cortical Activity Associated with Electrical Stimulation of the Reticular Formation Anesth. Analg., April 1, 2003; 96(4): 999 - 1003. [Abstract] [Full Text] [PDF]

				C. Vahle-Hinz and O. Detsch What can in vivo electrophysiology in animal models tell us about mechanisms of anaesthesia? Br. J. Anaesth., July 1, 2002; 89(1): 123 - 142. [Abstract] [Full Text] [PDF]

				J. F. Antognini and E. Carstens In vivo characterization of clinical anaesthesia and its components Br. J. Anaesth., July 1, 2002; 89(1): 156 - 166. [Abstract] [Full Text] [PDF]

Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999