Norepinephrine in shock
Norepinephrine has both α- and β-adrenergic activity. Patients with severe shock may need an increase in systemic vascular resistance, and vasopressors (drugs like norepinephrine that cause vasoconstriction and therefore increase systemic vascular resistance) are given to increase preload.
However, because there is also an increase in afterload on the heart, it is also desirable to increase the stroke volume. This increase in cardiac muscle performance can overcome the increase in afterload.
Because norepinephrine is a potent vasoconstrictor, it should be administered with caution, in view of decreases in mesenteric and renal blood flow.
Which of the following is an effect of epinephrine?
Extra info: Epinephrine is a mild bronchodilator (β2 agonism), relaxes the bladder detrusor (β2 agonism), relaxes the gastrointestinal tract (α agonism and β2 agonism), and enhances glycogenolysis (α1 agonism and β2 agonism).
Which of the following drugs belongs to the group of β-sympathomimetic drugs?
Extra info: Salbutamol is a specific β2-receptor agonist. Propranolol is a β-antagonist; lidocaine is an anesthetic which blocks sodium channels; and dopamine acts on D1-receptors and in higher concentration on β1 and α1-receptors.
Slow i.v. infusion of a low to moderate dose of epinephrine will elicit each of the following responses EXCEPT
Extra info: Epinephrine is a potent agonist of β1 (increasing heart rate) and β2 (increasing stroke volume). Taken together epinephrine increases the cardiac output (=HRxSV).
Which of the following statements is FALSE?
Extra info: Vasoconstriction results in decreased blood flow and, hence, perfusion. All the other statements are true.