RETRACTED ARTICLE: Nicardipine enhances diaphragmatic fatigue

The effects of nicardipine, a calcium channel blocker, on diaphragmatic fatigue were studied in 20 anaesthetized, mechanically ventilated dogs divided into two groups: control group (Group C, n = 10) and nicardipine group (Group N, n -10). Diaphragmatic fatigue was induced by intermittent supramaximal electric stimulation to bilateral phrenic nerves at a frequency of 20 Hz for 30 min. In Group N, 5 μg · kg^?1· min^?1 nicardipine iv was infused continuously during this fatigueproducing period. Transdiaphragmatic pressure (Pdi) produced by electrical stimulation (10–100 Hz) of the phrenic nerves was used as an index of diaphragmatic contractility. After a fatigueproducing period, the Pdi in both groups decreased at low frequency (10–30 Hz) stimulation compared with pre-fatigue values (P < 0.05), whereas no change in Pdi was observed at high-frequency (50–100 Hz) stimulation. The decrease of Pdi at low-frequency stimulation was larger in Group N (P < 0.05). The integrated diaphragmatic electric activity (Edi) in both groups did not change at any frequency of stimulation throughout the experiment. We conclude that nicardipine enhances diaphragmatic fatigue.