Comparative effects of dopamine and dobutamine on hypercapnic depression of diaphragmatic contractility in dogs

The present study was undertaken to evaluate the effects of dopamine and dobutamine on diaphragmatic contractility in dogs with induced hypercapnia. Animals were divided into three groups of ten each. In each group, hypercapnia (80-90 mmHg) was produced by adding 10% CO2 to the inspired gas. When hypercapnia was established, Group I received no study drug; Group II was infused with dopamine 10 microg/kg/min; Group III was infused with dobutamine 10 microg/kg/min. Study drugs were administered intravenously for 60 min. Diaphragmatic contractility was assessed by 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 Groups II and III, during the study drug administration, Pdi at both stimuli increased from hypercapnia-induced values (P<0.05). The increase in Pdi was more than in Group III than in Group II (P<0.05). In Group I, Pdi to each stimulus did not change from hypercapnia-induced values. In conclusion, compared with dopamine, dobutamine is effective in improving hypercapnic depression of diaphragmatic contractility in dogs.