The effect of olprinone compared with milrinone on diaphragmatic muscle function in dogs

We compared the effect of olprinone with milrinone on the contractility of fatigued diaphragms in dogs. Animals were divided into four groups of 10 each. In each group, diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20 Hz applied for 30 min. After producing fatigue, Group I received only maintenance fluids; Group II was given a bolus injection (50 microg/kg) followed by continuous infusion (0.5 microg x kg(-1) x min(-1)) of milrinone; Group III was infused with olprinone (10 microg/kg initial dose plus 0.3 microg x kg(-1) x min(-1) maintenance dose); Group IV was infused with nicardipine (5 microg x kg(-1) x min(-1)) during olprinone administration. After the fatigue-producing period in each group, transdiaphragmatic pressure (Pdi) at low-frequency (20 Hz) stimulation decreased from the prefatigued values (P < 0.05), whereas there was no change in Pdi at high-frequency (100-Hz) stimulation. In Groups II and III, during study drug infusion, Pdi at both stimuli increased from fatigued values (P < 0.05). The increase in Pdi was larger in Group III than in Group II (P < 0.05). In Group IV, the augmentation of Pdi by olprinone was abolished in the fatigued diaphragm with an infusion of nicardipine. We conclude that olprinone is more effective than milrinone for the improvement of contractility in he fatigued diaphragm and that the potentiating mechanism of olprinone may be closely related to the transmembrane calcium movement.

Diaphragmatic fatigue may contribute to the development of respiratory failure. Compared with milrinone, olprinone improves the contractility in fatigued diaphragm in dogs.