The circulatory effects of epinephrine infusion in the anesthesized piglet

Abstract

There are few published data regarding the circulatory effects of systemic epinephrine infusions in newborn subjects. We therefore instrumented six piglets aged 5 to 10 d while they were under pentobarbitone anesthesia for determination of cardiac output, left anterior descending coronary artery flow, systemic and pulmonary pressures, and mixed venous, arterial and coronary sinus gases. Systemic, coronary, and pulmonary vascular resistances, coronary oxygen consumption, and myocardial oxygen extraction ratio were calculated. Epinephrine was infused at doses from 0.2 to 3.2 micrograms/kg/min doubling at 15-min intervals, and measurements were taken after stability had been obtained. Cardiac output increased at the lowest dose investigated, i.e. 0.2 micrograms/kg/min, and progressively increased as the dose was advanced up to 1.6 micrograms/kg/min, decreasing significantly at 3.2 micrograms/kg/min. Blood pressure increased progressively, being significantly above baseline at 0.8, 1.6, and 3.2 micrograms/kg/min and having increased by approximately 81% at the highest dose investigated. Pulmonary arterial pressures were also increased at 1.6 and 3.2 micrograms/kg/min, but only by 35% at the highest dose of 3.2 micrograms/kg/min. Systemic and pulmonary vascular resistances both decreased at the three lower doses investigated and then began to increase progressively; however, the systemic vascular resistance increased to a significantly greater degree than pulmonary vascular resistance. Coronary oxygen consumption increased progressively as the epinephrine dose was increased; however, coronary blood flow and coronary oxygen delivery increased more than oxygen consumption, leading to a progressive reduction in myocardial oxygen extraction ratio and a progressive increase in coronary sinus oxygen content. Whole-body oxygen consumption was increased, but to a lesser extent than systemic oxygen transport.(ABSTRACT TRUNCATED AT 250 WORDS)