These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Effects of alpha-adrenergic blockade on regional myocardial function in canine ischemic myocardium during beta-adrenergic blockade.
    Author: Kono M, Morita S, Rubsamen R.
    Journal: J Cardiothorac Vasc Anesth; 1995 Oct; 9(5):525-33. PubMed ID: 8547553.
    Abstract:
    OBJECTIVE: The contribution of alpha-adrenergic receptor subtypes in mediation of coronary vasoconstriction during ischemia remains controversial. This study investigated the effects of alpha-adrenergic subtypes blockade on regional myocardial function in a canine ischemic model. DESIGN: Prospective, randomized, controlled trial. SETTING: Experimental animal laboratory in a university medical center. PARTICIPANTS: Thirty-two adult dogs, weighing 13 to 22 kg. INTERVENTIONS: The animals were prepared with pentobarbital, oxygen, enflurane and pancuronium. Two selective alpha 1-adrenergic antagonists (bunazosin, 50 micrograms/kg/min, n = 8, and prazosin, 25 micrograms/kg/min, n = 8) and the alpha 2-adrenergic antagonist (yohimbine, 15 micrograms/kg/min, n = 8) were administered after the partial occlusion of the left circumflex coronary artery (LCX) during beta-adrenergic blockade (propranolol, 1 mg/kg). MEASUREMENTS AND MAIN RESULTS: Myocardial systolic segment shortening (%SS) and a myocardial lactate extraction ratio (LER) were used as indices of regional myocardial and metabolic function. Compared with poststenotic condition, coronary blood flow of the LCX was increased by 123% with bunazosin and 138% with prazosin (p < 0.05, respectively). Both %SS and LER in the ischemic myocardium were significantly improved after treatment with both alpha 1-adrenergic antagonists (in the bunazosin group, %SS, 8.3 +/- 1.9 to 10.4 +/- 2.2%, p < 0.05; LER, -12.8 +/- 12.3 to 6.2 +/- 15.9%, p < 0.01; in the prazosin group, %SS, 8.5 +/- 1.6 to 10.3 +/- 1.9%, p < 0.05; LER, -10.2 +/- 5.7 to 3.6 +/- 10.2%, p < 0.05). In contrast, coronary blood flow of the LCX, %SS and LER were not different from poststenotic condition during alpha 2-adrenergic receptor blockade with yohimbine. The salutary effect of bunazosin was also observed after mechanically controlling for the afterload reduction produced by alpha 1-adrenergic blockade (n = 8). Prazosin and yohimbine were found to produce a significant increase in plasma norepinephrine levels in contrast to bunazosin, which had no significant effect. CONCLUSIONS: These data indicate that alpha 1-adrenergic blockade increases coronary blood flow and improves regional myocardial function during myocardial ischemia.
    [Abstract] [Full Text] [Related] [New Search]