Differential relaxant effect of high concentrations of intravenous anesthetics on endothelin-constricted proximal and distal canine coronary arteries.
This study determined the direct effect of three intravenous anesthetics on isolated canine coronary arteries constricted with the potent endogenous vasoconstrictor endothelin. Arteries were divided into groups of large (1.3-2.5 mm) and small (250-500 microns) vessels, and arterial rings were suspended in tissue baths. The rings were stretched to an optimal resting tension and then preconstricted with an EC50 concentration of endothelin that was equivalent for both groups. Incremental concentrations (5 x 10(-6) M to 1.6 x 10(-2) M) of thiopental, ketamine, and propofol were added to the baths, and the relaxant responses were recorded. Small arteries demonstrated greater vasodilation at equivalent drug concentrations than did large arteries. These results demonstrate antagonism of the vasoconstrictor endothelin by intravenous anesthetics. Distal vessels are more sensitive than proximal vessels to the relaxant effects of the intravenous anesthetics studied. Direct effects on coronary vascular tone, however, are only apparent at concentrations above those seen clinically. Despite the potential for a differential effect on proximal and distal coronary arteries, we conclude that thiopental, ketamine, and propofol do not possess a direct effect on the tone of large or small canine coronary arteries at concentrations seen in routine clinical practice.
Coughlan
M G
MG
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226.
Flynn
N M
NM
Kenny
D
D
Warltier
D C
DC
Kampine
J P
JP
D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects* / Q000502:physiology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D016232:Endothelins / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D007275:Injections, Intravenous; D007649:Ketamine / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D011189:Potassium Chloride / Q000494:pharmacology; D015742:Propofol / Q000494:pharmacology; D013874:Thiopental / Q000494:pharmacology
D000777:Anesthetics; D016232:Endothelins; D011189:Potassium Chloride; D007649:Ketamine; D013874:Thiopental; D015742:Propofol