RETRACTED ARTICLE: Dobutamine increases contractility of fatigued diaphragm in dogs: The relationship between dose and diaphragmatic contractility.

The dose-related effects of dobutamine (DOB) on the contractility of fatigued diaphragm were studied in 16 anesthetized, mechanically ventilated dogs. The animals were divided into two groups of eight: the control (group C) and the DOB (group D). Diaphragmatic fatigue was induced by intermittent supramaximal electrophrenic stimulation at a frequency of 20 Hz applied for 30 min. Diaphragmatic contractility was assessed from changes in transdiaphragmatic pressure (Pdi). After the induction of diaphragmatic fatigue, Pdi at low-frequency (20-Hz) stimulation decreased significantly compared with the prefatigue values (P<0.05), whereas no change in Pdi was observed at high-frequency (100-Hz) stimulation. In group D, after producing fatigue, Pdi at 20-Hz stimulation increased significantly with a continuous infusion of DOB (5 and 10 μg·kg(-1)·min(-1)) i.v. (P<0.05). The Pdi at 100-Hz stimulation increased significantly with administration of DOB 10 μg·kg(-1)·min(-1) i.v. (P<0.05). There was a significant correlation between dose of DOB and Pdi at both stimuli (P<0.05). In group C, the speed of Pdi recovery at 20-Hz stimulation was relatively slower. The integrated diaphragmatic electric activity (Edi) in each group did not change at any frequency of stimulation throughout the study. It is concluded that DOB increases the contractility of fatigued diaphragm in a dose-dependent manner.