Document Detail


Cholinergic reversal of isoflurane anesthesia in rats as measured by cross-approximate entropy of the electroencephalogram.
MedLine Citation:
PMID:  14576549     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
BACKGROUND: Pharmacologic modulation of the state of consciousness is of interest for clinical practice and for a better understanding of anesthetic mechanisms. The cholinergic activating system is an important regulator of the state of consciousness during general anesthesia. Entropy of the electroencephalogram has been proposed as a promising measure of anesthetic depth. The authors have shown that volatile anesthetics decrease cross-approximate entropy (C-ApEn) of the bihemispheric frontal electroencephalogram in rats. The effect of cholinergic agents on C-ApEn has not been examined. Here, the authors test the hypothesis that cholinergic activation reverses the effect of isoflurane anesthesia on C-ApEn. METHODS: An electroencephalogram in the 1- to 100-Hz range was recorded bipolarly, with epidural leads from the frontal cortex of both hemispheres, and used to calculate C-ApEn, which reflects statistical independence of bihemispheric electroencephalographic activity. Cholinesterase inhibitor, neostigmine (25 mug), or the muscarinic agonist oxotremorine (25 mug) were infused intracerebroventricularly while the rats were inhaling 1.0% (0.7 minimum alveolar concentration) isoflurane. In other animals, isoflurane was lowered to 0.4% (0.3 minimum alveolar concentration) to assess the electroencephalogram in a sedated, waking state. RESULTS: At 1.0% isoflurane, C-ApEn decreased by 54% compared with that at 0.4%, but the motor reflex response to tail pinch was still present. Cholinergic agents reversed the electroencephalogram-depressant effect of isoflurane, i.e., C-ApEn rose to the level measured at 0.4% isoflurane. The rise in C-ApEn was paralleled by the appearance of spontaneous limb and orofacial explorative movements, suggesting a return of consciousness. In contrast, cholinergic agents fully blocked the motor reflex to tail pinch. CONCLUSIONS: C-ApEn of the bihemispheric electroencephalogram correlates with the return of spontaneous motor signs but not with the nociceptive reflex. Cerebral cholinergic activation dissociates central and peripheral anesthetic effects. C-ApEn, a novel measure of interhemispheric electroencephalogram independence, is a promising correlate of depth of sedation and state of consciousness.
Authors:
Anthony G Hudetz; James D Wood; John P Kampine
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Anesthesiology     Volume:  99     ISSN:  0003-3022     ISO Abbreviation:  Anesthesiology     Publication Date:  2003 Nov 
Date Detail:
Created Date:  2003-10-24     Completed Date:  2003-11-20     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  1300217     Medline TA:  Anesthesiology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1125-31     Citation Subset:  AIM; IM    
Affiliation:
Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA. ahudetz@mcw.edu
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MeSH Terms
Descriptor/Qualifier:
Algorithms
Anesthesia, Inhalation*
Anesthetics, Inhalation / antagonists & inhibitors*
Animals
Cholinergic Agents / pharmacology*
Electroencephalography / drug effects*
Entropy
Injections, Intraventricular
Isoflurane / antagonists & inhibitors*
Male
Movement / drug effects
Muscarinic Agonists / pharmacology
Neostigmine / pharmacology*
Oxotremorine / pharmacology
Pulmonary Alveoli / drug effects,  metabolism
Rats
Rats, Sprague-Dawley
Grant Support
ID/Acronym/Agency:
GM-56398/GM/NIGMS NIH HHS; MH-51358/MH/NIMH NIH HHS
Chemical
Reg. No./Substance:
0/Anesthetics, Inhalation; 0/Cholinergic Agents; 0/Muscarinic Agonists; 26675-46-7/Isoflurane; 59-99-4/Neostigmine; 70-22-4/Oxotremorine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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