Contractility of fatigued diaphragm is improved by dobutamine.
The effects of dobutamine (DOB) on diaphragmatic fatigue were examined in 20 anaesthetized, mechanically ventilated dogs. Animals were divided into two groups: the DOB group (n = 10) and the control group (n = 10). Diaphragmatic fatigue was induced by intermittent supramaximal electric stimulation applied to bilateral phrenic nerves at a frequency of 20 Hz for 30 min. Diaphragmatic contractility was assessed with transdiaphragmatic pressure (Pdi). After diaphragmatic fatigue, Pdi decreased at low-frequency (20 Hz) stimulation (P < 0.05), whereas the decrease was minimal at high-frequency (100 Hz) stimulation. In the DOB group, after producing fatigue, the continuous administration of 10 micrograms.kg-1.min-1 dobutamine iv for 30 min produced an increased Pdi at both frequencies of stimulation (P < 0.05). The Pdi returned to pre-fatigue values after cessation of dobutamine administration. In the control group, the speed of recovery from fatigue was much slower at low-frequency stimulation. The integrated diaphragmatic electric activity (Edi) in the two groups did not change throughout the experiment at any frequency of stimulation. We conclude that dobutamine improves contractility in fatigued diaphragm.
Department of Anesthesiology, Toride Kyodo General Hospital, Ibaraki, Japan.
Y
Y
Fujii
H
H
Toyooka
T
T
Ebata
K
K
Amaha
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002302:Cardiac Output / Q000187:drug effects / Q000502:physiology; D003964:Diaphragm / Q000187:drug effects* / Q000294:innervation / Q000503:physiopathology; D004280:Dobutamine / Q000494:pharmacology*; D004285:Dogs; D004558:Electric Stimulation; D004576:Electromyography / Q000187:drug effects; D005221:Fatigue / Q000503:physiopathology*; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D010791:Phrenic Nerve / Q000502:physiology; D011312:Pressure; D015656:Respiratory Mechanics; D013997:Time Factors
D004280:Dobutamine