RETRACTED ARTICLE: Effects of nicardipine on diaphragmatic fatigue in the dog: The relationship between dosage and fatigability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 (P_di). After induction of diaphragmatic stimulation at low-frequency (20 Hz), P_di decreased significantly in all groups compared with the prefatigue value (P<0.05), whereas no change was observed in P_di at high-frequency (100 Hz) stimulation. The P_di at 20 Hz stimulation was significantly lower in groups N₁ and N₂ compared with that in group C (P<0.05). The decrease in P_di at 20 Hz stimulation was significantly larger in group N₂ than in group N₁ (P<0.05). The speed of recovery of P_di at 20 Hz stimulation was dose dependent. The integrated diaphragmatic electric activity (E_di) 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.