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The Electrophysiological Effects of Alpha‐Chloralose Anesthesia in the Intact Dog: (1) Alone and (2) in Combination with Verapamil
Author(s) -
SCHWARTZ JANICE B.,
HERRE JOHN M.
Publication year - 1989
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.1989.tb02661.x
Subject(s) - verapamil , refractory period , chloralose , medicine , anesthesia , electrophysiology , effective refractory period , cardiology , blood pressure , calcium
The electrophysiological effects of alpha‐chloralose anesthesia were determined in 13 chronically instrumented dogs and compared to baseline electrophysiological parameters in the conscious state. Alpha‐chloralose anesthesia (75 mg/kg of a 4% solution in polyethylene glycol (PEG) delayed conduction and prolonged refractoriness of the AV node: (1) the P‐R interval increased from 108 ± 14 msec (mean ± SD) in the conscious state to 125 ± 23 msec ( P < 0.02); (2) the A‐H from 98 ± 12 msec to 108 ± 16 msec (P < 0.04); (3) the AV nodal effective refractory period from 136 ± 36 to 153 ± 29 msec (P = .05) and the AV nodal functional refractory period from 232 ± 58 to 247 ± 46 msec (P = 0.07); and (4) the AV block cycle iength from 228 ± 54 msec to 248 ± 43 msec ( P < 0.04). Chloralose anesthesia also increased the ventricular refractory period from 139 ± 13 msec to 161 ± 22 msec (P < .03) and the QTc interval from 273 ± 22 to 306 ± 32 msec fP < 0.0002). To determine whether these effects on AV nodal conduction would influence experimental results, responses to verapamil were studied in the conscious state and during chloraiose anesthesia. During chloralose anesthesia, (1) no relationship was detected between the sinus cycle length and verapamil concentrations; (2) a greater increment in AV conduction time was seen for a given verapamil concentration; and (3) AV block occurred at verapamil concentrations associated with 1:1 conduction in the conscious state. We conclude that chloralose anesthesia has significant electrophysiological effects and that these effects must be taken into consideration during the interpretation of experiments performed in animals during chloralose anesthesia. (PACE, Vol. 12 February 1989)