Diaphragmatic
fatigue may contribute to the development of
respiratory failure. We studied the dose-range effects of
propofol on the contractility of fatigued diaphragm in dogs. Animals were divided into three groups of eight each. In each group, diaphragmatic
fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20-Hz stimulation for 30 min. Immediately after the end of a
fatigue-producing period, Group 1 received no study drug; Group 2 was infused with small-dose
propofol (0.1 mg/kg initial dose plus 1.5 mg x kg(-1) x h(-1) maintenance dose); Group 3 was infused with large-dose
propofol (0.1 mg/kg initial dose plus 6.0 mg x kg(-1) x h(-1) maintenance dose). We assessed diaphragmatic contractility by transdiaphragmatic pressure (Pdi). After the
fatigue-producing period, in each group, Pdi at low-frequency (20-Hz) stimulation decreased from baseline values (P < 0.05), whereas there was no change in Pdi at high-frequency (100-Hz) stimulation. In Groups 2 and 3, with an infusion of
propofol, Pdi at 20-Hz stimulation decreased from fatigued values (P < 0.05). Compared with Group 1, Pdi at 20-Hz stimulation decreased from fatigued values (P < 0.05) during
propofol administration in Groups 2 and 3. The decrease in Pdi was more in Group 3 than in Group 2 (P < 0.05). We conclude that
propofol decreases the contractility of fatigued canine diaphragm in a dose-related fashion.
IMPLICATIONS:
Propofol is a widely used IV
anesthetic for the induction and maintenance of
general anesthesia and sedation. It decreases, in a dose-related fashion, the contractility of fatigued diaphragm in dogs.