Effects of dibutyryl cyclic adenosine monophosphate on hypercapnic depression of diaphragmatic contractility in pentobarbital-anesthetized dogs.

BACKGROUND

Hypercapnia is associated with diaphragm muscle dysfunction that causes a reduction of diaphragmatic force generated for a constant elective myographic activity. No published data are available concerning hypercapnic depression of diaphragmatic contractility during dibutyryl cyclic adenosine monophospate (DBcAMP) administration.

OBJECTIVE

The aim of this study was to assess the effects of DBcAMP on hypercapnic depression of diaphragmatic contractility in pentobarbital-anesthetized dogs.

METHODS

This experimental study was conducted from July to December 2008 at the Department of Anesthesiology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Japan. Adult (aged >5 years) mongrel dogs weighing 10 to 15 kg were randomly divided into 3 equal groups. Hypercapnia (80-90 mm Hg) was induced with 10% carbon dioxide added to the inspired gas. When hypercapnia was established, group 1 was infused with low-dose DBcAMP (0.05 mg/kg/min); group 2 was infused with high-dose DBcAMP (0.2 mg/kg/min); and group 3 received placebo (saline). Study drug was administered intravenously for 60 minutes. Diaphragmatic contractility was assessed by transdiaphragmatic pressure (Pdi) at baseline, induction of hypercapnia, and study drug administration.

RESULTS

Twenty-one dogs were divided into 3 groups of 7. There were no significant differences observed at baseline. In the presence of hypercapnia, Pdi (mean [SD], cm H2O) at low- (20-Hz) and high-frequency (100-Hz) stimulation was significantly decreased from baseline in each group (all, P = 0.001). In groups 1 and 2, Pdi at both stimuli was significantly increased during DBcAMP administration compared with hypercapnia-induced values (group 1: 20-Hz, 13.5 [2.2] vs 15.0 [2.4], respectively, P = 0.001, 100-Hz, 21.2 [1.6] vs 22.5 [1.6], P = 0.001; group 2: 20-Hz, 13.7 [1.4] vs 19.2 [1.7], P = 0.001, 100-Hz, 21.0 [2.4] vs 27.2 [2.5], P = 0.001). The Pdi at both stimuli during DBcAMP administration was significantly higher in group 2 than in group 1 (20-Hz, 19.2 [1.7] vs 15.0 [2.4], P = 0.001, 100-Hz, 27.2 [2.5] vs 22.5 [1.6], P = 0.003). In group 3, Pdi did not significantly change in regard to either stimulus from hypercapnia-induced values.

CONCLUSION

DBcAMP, in a dose-dependent manner, was associated with improved hypercapnic depression of diaphragmatic contractility in these pentobarbital-anesthetized dogs.