Читать книгу Manual of Equine Anesthesia and Analgesia - Группа авторов - Страница 377

 Adrenergic agonists include vasopressors (e.g. phenylephrine) and inotropes (e.g. dobutamine).

 Most adrenergic agonists activate both α and β receptors, with the predominant pharmacologic effect being the expression of this mixed receptor activation (see Table 7.3).Table 7.2 Comparative pharmacology of selective β2 adrenergic bronchodilators.Agentβ2 selectivityPeak effect (minutes)Duration of action (hours)Albuterol+++++30–604Metaproterenol+++30–603–4Terbutaline++++604Salmeterol++++60>12Clenbuterol++++30–608–12Table 7.3 Principal sites of action of adrenergic agonists.Agentα1α2β1β2DA1DA2MechanismPhenylephrine+++++?±000directNorepinephrine+++++++++++++000directEpinephrine+++++++++++++++00directEphedrine++?+++++00indirect + directDopamine+ to +++++?+++++00directDobutamine±?++++++00directIsoproterenol00++++++++++00direct+ = increase, − = decrease, 0 = no change.

 Hemodynamic effects evoked by adrenergic agonists include changes in heart rate (chronotropism), cardiac contractility (inotropism), conduction velocity of the cardiac impulse (dromotropism), cardiac rhythm, and systemic vascular resistance (see Table 7.4).

 The effects of these drugs on capacitance veins (venous return) may be as important as their inotropic actions and more important than arteriolar effects.