Effects of Halothane on Left Ventricular Function and Distribution of Regional Blood Flow in Dogs and Primates

Abstract

Left ventricular and regional vascular effects of halothane were assessed in dogs and primates in which coronary, mesenteric, renal, and iliac blood flows, arterial blood pressure, left ventricular diameter and pressure, dD/dt (i.e., the velocity of myocardial fiber shortening), and dP/dt were continuously measured in the control resting state, while the conscious animals were breathing O 2 , and during halothane-O 2 anesthesia maintained at 1% or at 2% for 90 minutes (separate experimental days). Halothane caused a concentration-dependent depression of myocardial contractility: (dP/dt)/P fell 68 ± 5% during 2% halothane anesthesia and left ventricular end-diastolic diameter rose. Halothane also caused a redistribution of regional blood flows. At a concentration of 1% halothane, the most intense vasodilatation occurred in the renal bed (renal resistance fell 46 ± 5%), but mesenteric resistance rose (42 ± 15%). With 1% halothane regional vascular resistances tended to rise with time, but with 2% halothane regional blood flows rose with time. A direct vasodilating action of halothane was observed following direct intra-arterial injection of the drug. Probably this action was responsible for the renal and iliac vasodilatations and for the opposition to the metabolically induced vasoconstriction in the coronary bed. Thus, the administration of the most commonly employed potent inhalation anesthetic, halothane, substantially alters myocardial contractility and regional blood flows and resistances. These effects are, in many instances, a function of the concentration of the anesthetic and the duration of its administration. KEY WORDSanesthesia renal flow mesenteric flow iliac flow myocardial contractility baboon chimpanzee

Regional myocardial functional and electrophysiological alterations after brief coronary artery occlusion in conscious dogs.

“…The increase after a 15-min occlusion was not significantly greater than that after a 5-min occlusion. (8,9). Bugge-Asperheim et al (19), Hawthorne (18)., and Theroux et al (14) have utilized techniques that are applicable to the study of regional myocardial function in the intact, conscious animal.…”

“…It was considered important to conduct this study in the conscious animal in which the myocardial depressant effects of a general anesthetic and recent operation were not present (8,9 (Fig. 1).…”

Cellular mechanisms of impaired adrenergic responsiveness in neonatal dogs.

“…More recently, studies in conscious, chronically instrumented animal models, which obviate the potential, widespread autonomic effects of general anesthesia (11)(12)(13), have indicated a subnormal neonatal vascular reactivity to infused adrenergic agonists (14,15), as well as blunting of the baroreceptor reflex responses to induce carotid sinus hypotension (16). Nevertheless, the cellular developmental events that comprise normal autonomic maturation have been incompletely identified.…”

Effects of isoproterenol on regional myocardial function, electrogram, and blood flow in conscious dogs with myocardial ischemia.

“…Since general anesthesia and the trauma of operation affect myocardial function substantially (3,4), the animals were studied in the conscious state several weeks after recovery from operation. The specific goals of this study included the examination of the effects of isoproterenol on the normal, border, and ischemic zones of the myocardium and also determination of the conditions in which isoproterenol either improves or impairs function in these zones, in the presence of obstruction to flow through one major coronary vessel.…”