Intravenous terbutaline and simultaneous β1-blockade for advanced premature labor

Abstract

Seventeen patients in advanced premature labor (cervical dilatation ≥3 cm and effacement ≥50%) were randomized in a double-blind protocol to receive metroprolol (a β1-adrenergic antagonist) or a placebo in conjunction with intravenous and oral terbutaline (a β2-agonist) in an attempt to inhibit the side effects of terbutaline. Both groups of patients had a dose-related increase in heart rate and systolic blood pressure and a decrease in diastolic blood pressure. Laboratory studies revealed significant hyperglycemia, hypokalemia, hypocalcemia, and acidosis during the intravenous terbutaline infusion, all of which normalized during oral terbutaline therapy. There were no significant differences in the cardiovascular or metabolic responses to terbutaline between the metroprolol and placebo patients. The mean delay in delivery was 5.7 days, with 59% of patients having delivery delayed for 48 hours or more. The mean prolongation time was shorter, but not statistically significant, for those patients receiving metroprolol. Despite the use of high-dose terbutaline, there were no significant complications of therapy. There was little efficacy of infusion dosages above 40 μg/min or repeated courses of intravenous tocolysis. Although recent reports do not recommend tocolysis in these patients, this study suggests that combined β-mimetics and glucocorticoids may be the optimal care for patients in advanced premature labor, in particular, those with infants of very low birth weight.