The electrophysiological effects of alpha-chloralose anesthesia in the intact dog: (1) alone and (2) in combination with verapamil.
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 less than 0.02); (2) the A-H from 98 +/- 12 msec to 108 +/- 16 msec (P less than 0.04); (3) the AV nodal effective refractory period from 136 +/- 16 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 length from 228 +/- 54 msec to 248 +/- 43 msec (P less than 0.04). Chloralose anesthesia also increased the ventricular refractory period from 139 +/- 13 msec to 161 +/- 22 msec (P less than .03) and the QTc interval from 273 +/- 22 to 306 +/- 32 msec (P less than 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 chloralose 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.
Schwartz
J B
JB
Section of Cardiology, Baylor College of Medicine, Houston, Texas.
Herre
J M
JM
D000768:Anesthesia, General; D000818:Animals; D001283:Atrioventricular Node / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002698:Chloralose / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D004285:Dogs; D004594:Electrophysiology; D006327:Heart Block / Q000139:chemically induced; D006329:Heart Conduction System / Q000187:drug effects*; D008991:Monitoring, Physiologic; D014700:Verapamil / Q000008:administration & dosage / Q000009:adverse effects / Q000097:blood / Q000494:pharmacology*
D002698:Chloralose; D014700:Verapamil