Hypotension with dobutamine: beta-adrenergic antagonist selectivity at lowdoses of carvedilol

OBJECTIVE: To report a case of marked hypotension resulting from the concom itant use of low-dose carvedilol and intravenous dobutamine, CASE SUMMARY: A 54-year-old white man with severe heart failure was placed on carvedilol 3.125 mg orally twice a day; three days later the dosage was increased to 6.25 mg orally twice a day. His symptoms of heart failure wors ened with increasing fluid retention, orthopnea, paroxysmal nocturnal dyspn ea, and elevated blood urea nitrogen and creatinine. He was admitted for tr eatment of decompensated heart failure with intravenous dobutamine. With ea ch increase in intravenous dobutamine, systolic blood pressure fell. Dobuta mine was discontinued when systolic blood pressure reached 56 mm Hg. In a s ubsequent admission for decompensated heart failure, when the patient was n ot taking carvedilol, he was treated with intravenous dobutamine and systol ic blood pressure increased. DISCUSSION: Although carvedilol is a nonselective beta-adrenergic antagonis t, at low doses it is a selective beta(1)-adrenergic antagonist. Dobutamine is a beta(1)-, beta(2)-, and alpha(1)-adrenergic agonist. Typically, patie nts with heart failure treated with intravenous dobutamine have a small inc rease in systolic blood pressure. We propose that the drop in blood pressur e with dobutamine in this patient was caused by a fall in systemic vascular resistance due to vascular beta(2)-adrenergic receptor activation. The nor mal increase in cardiac output was partially blocked by selective beta(1)-a drenergic blockade at low doses of carvedilol. CONCLUSIONS: beta-adrenergic blockade with carvedilol is now common therapy for patients with congestive heart failure. Intravenous dobutamine is ofte n used when these patients have worsening heart failure. Recognition that t reatment with dobutamine in patients taking low doses of carvedilol may res ult in hypotension is important for appropriate monitoring and therapy.