RETRACTED ARTICLE: Effects of nicardipine on diaphragmatic fatigue in the dog: The relationship between dosage and fatigability.

We examined the dose-related effects of nicardipine on the diaphragmatic fatigability in 24 anesthetized, mechanically ventilated dogs. Animals were divided into three groups of eight each: the control group (group C), the nicardipine 3 μg·kg(-1) I.V. group (group N1) and the nicardipine 5 μg·kg(-1)·min(-1) I.V. group (group N2). Diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20 Hz applied for 30 min. In groups N1 and N2, nicardipine was continuoulsy infused intravenously during this fatigueproducing period. Diaphragmatic contractility was assessed by changes in transdiaphragmatic pressure (Pdi). After induction of diaphragmatic stimulation at low-frequency (20 Hz), Pdi decreased significantly in all groups compared with the prefatigue value (P<0.05), whereas no change was observed in Pdi at high-frequency (100 Hz) stimulation. The Pdi at 20 Hz stimulation was significantly lower in groups N1 and N2 compared with that in group C (P<0.05). The decrease in Pdi at 20 Hz stimulation was significantly larger in group N2 than in group N1 (P<0.05). The speed of recovery of Pdi at 20 Hz stimulation was dose dependent. The integrated diaphragmatic electric activity (Edi) in each group did not change at any frequency of stimulation throughout the study. Our results demonstrate that nicardipine causes a dose-dependent reduction of the contractility of the fatigued diaphragm.