O. Ziegler1, K. Anderson1, Y. Liu1, V. Pavlov1, J. Fingleton1, A. Ehsan1, N. Sodha1, A. Usheva1, J. Feng1, F. Sellke1 1The Warren Alpert Medical School of Brown University,Cardiovascular Research Center,Providence, RI, USA
Introduction: Challenges in blood pressure management during and after cardiac surgery are a significant cause of morbidity and mortality. Previously our lab has found that cardioplegic arrest and cardiopulmonary bypass (CP/CPB) is associated with impaired arteriolar responsiveness to phenylephrine. However, concomitant changes in alpha adrenergic receptor abundance and localization were not observed. Here, we further investigate the role of beta adrenergic mediators in skeletal muscle arterioles pre- and post- CP/CPB as well as beta receptor abundance and localization to arterioles in skeletal muscle.
Methods: Skeletal muscle arterioles (90-150 µm in diameter) were collected pre- and post- CP/CBP from patients undergoing cardiac surgery (CABG or AVR). Ex vivo microvascular reactivity was measured in response to the beta adrenergic receptor agonist isoproterenol (concentrations 10-9 to 10-4 M).
Results: Isoproterenol induced dose-dependent relaxation response in both pre-and post-CP/CPB vessels. Post-CP/CPB vessel relaxation response to isoproterenol was significantly attenuated (p < 0.05 vs pre-CP/CPB). There were no significant changes in localization of beta 1, beta 2, or beta 3 adrenergic receptors to arterioles of skeletal muscle as assayed by immunohistochemistry between these groups. Nor were there significant changes in beta receptor abundance as assayed by western blotting.
Conclusion: These findings suggest there is diminished peripheral arteriolar responsiveness to beta adrenergic stimuli after CP/CBP, though this is not explained by beta adrenergic receptor abundance or localization. This further suggests that CP/CPB is associated with vasoplegia in the peripherial microvasculature early after cardiac surgery.
