RETRACTED ARTICLE: The dose-response relationship of amrinone in increasing the contractility of fatigued diaphragm in dogs

Abstract

We studied the dose-related effects of amrinone on the contractility of a fatigued diaphragm in 16 anesthetized, mechanically ventilated dogs. The animals were divided into two groups: the control group (Group C,n=8) and the amrinone group (Group A,n=8). Diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20 Hz applied for 30 min. The contractility of the diaphragm was assessed from changes in transdiaphragmatic pressure (P di). After inducing fatigue,P di at low-frequency (20 Hz) stimulation decreased significantly compared with the pre-fatigue values (P<0.05), whereas no change was observed at high-frequency (100 Hz) stimulation. In Group A, after producing fatigue,P di at 20 Hz stimulation increased significantly with a bolus injection (0.75 mg·kg(-1)) followed by continuous infusion of amrinone (2.5, 5 and then 10μg·kg(-1)min(-1)) IV (P<0.05).P di at 100 Hz stimulation increased significantly with an administration of amrinone (10μg·kg(-1)min(-1) IV (P<0.05). There was a significant positive correlation betweenP di at both stimuli and amrinone dose (P<0.01). In Group, C, the speed of recovery ofP di at 20 Hz stimulation was relatively slower. The integrated electric activity of the diaphragam (E di) in each group did not change at any frequency of stimulation throughout the experiment. We conclude that amrinone exerts a dose-dependent enhancement of the contractility of a fatigued diaphragm in dogs.