Abstract
The effects of dobutamine on diaphragmatic contractility were studied in 24 dogs anaesthetized with secobarbital and receiving mechanical lung ventilation. The phrenic nerves were stimulated supramaximally for two seconds with electrodes placed around the fifth and sixth cervical roots when the airway was closed at the level of FRC. The stimulating frequency ranged from 10 to 100 Hz. Transdiaphragmatic pressure gradient (Pdi) generated by the electrophrenic stimulation was used as an index of diaphragmatic contractility. The electrical activity of the diaphragm during the stimulation (Edi) was also measured with needle electrodes inserted in the right hemidiaphragm percutaneously. During an infusion of dobutamine (10 μ ·kg−1 ·min−1 for 20 min), Pdi increased by 15 ±2.1% of control value at 20 Hz stimulation (P < 0.01), and by 13 ±1.2% at 100 Hz stimulation (P < 0.01). The Edi was not altered by dobutamine infusion. This enhancement of Pdi by dobutamine was abolished by simultaneous infusion of nicardipine, a Cachannel blocker, but was not affected by prostaglandin E1. These results suggest that dobutamine has a stimulating effect on canine diaphragmatic contraction, and this action may be related to the increased inward movement of extracellular calcium.
Résumé
Les effets de la dobutamine sur la contractilité diaphragmatique ont été étudiés sur 24 chiens anesthésiés avec du sécobarbital et ventilés artificiellement. A lors que les voies aériennes étaient obstruées en position de capacité résiduelle fonctionelle, les nerfs phréniques recevaient un stimulus supramaximal durant deux secondes au moyen d’électrodes entourant les cinquièmes et sixièmes racines cervicales. La fréquence de stimulation s’étalait de 10 à 100 Hz. Le gradient de pression transdiaphragmatique (Pdi) génére par la stimulation électrophrénique était utilisé comme indice de contractilité diaphragmatique. L’activité électrique du diaphragme durant la stimulation (Edi) était aussi mesurée et cela au moyen d’électrodes insérées au niveau de l’hémidiaphragme droit par voie percutanée. Durant une perfusion de dobutamine (10 μ ·kg−1 ·min−1 durant 20 min), le Pdi a augmente de 15 ±2,1% de sa valeur initiale pour une stimulation a 20 Hz (P < 0,01), et de 13 ±1,2% pour une stimulation a 100 Hz(P < 0,01). Le Edi n’etait pas modifié par la perfusion de dobutamine. Cette amelioration du Pdi par la dobutamine était abolie lors de l’administration concomitante de nicardipine, un bloqueur de canaux calciques, mais elle n ’était pas affectee par la prostaglandine E1. Ces résultats suggèrent que la dobutamine possède un effet stimulant sur la contraction diaphragmatique chez le chien, et cette action peut être reliée à une rentrée accrue du calcium extracellulaire.
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Ebata, T., Fujii, Y. & Toyooka, H. Dobutamine increases diaphragmatic contractility in dogs. Can J Anaesth 39, 375–380 (1992). https://doi.org/10.1007/BF03009049
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DOI: https://doi.org/10.1007/BF03009049