The effects of different dobutamine infusion rates on hypercapnic depression of diaphragmatic contractility in pentobarbital-anesthetized dogs.

Abstract

Previously, we demonstrated that dobutamine was more effective than dopamine for the improvement of diaphragmatic contractility during hypercapnia. Here, we studied the effects of different dobutamine infusion rates on hypercapnic depression of diaphragmatic contractility in pentobarbital-anesthetized dogs. Animals were divided into four groups of six each. In each group, hypercapnia (80-90 mm Hg) was produced by adding 10% CO2 to inspired gas. When hypercapnia was established, group Dob 0 received no study drug; group Dob 5 was induced with dobutamine 5 microg x kg(-1) x min(-1); group Dob 10 was induced with dobutamine 10 microg x kg(-1) x min(-1); group Dob 15 was induced with dobutamine 15 microg x kg(-1) x min(-1). Study drugs were administered IV for 60 min. Diaphragmatic contractility was assessed by measurement of transdiaphragmatic pressure (Pdi). In the presence of hypercapnia, in each group, Pdi at low-frequency (20 Hz) and high-frequency (100 Hz) stimulation decreased from baseline (P < 0.05). In group Dob 0, Pdi to each stimulus did not change from hypercapnia-induced values. In groups Dob 5, Dob 10 and Dob 15, during the study drug administration, Pdi at both stimuli increased from hypercapnia-induced values (P < 0.05). There was a significant positive correlation between dobutamine infusion rates and Pdi at both stimuli (P = 0.0001). Dobutamine effectively improves hypercapnic depression of diaphragmatic contractility in an infusion rate-dependent manner in pentobarbital-anesthetized dogs.