The effects of terbutaline on acid base, serum electrolytes, and glucose homeostasis during the management of preterm labor.

Terbutaline (T) is a beta-adrenergic compound which is commonly employed as a tocolytic agent in preterm labor. We evaluated the metabolic and biophysical consequences of infusion of T into six pregnant women in preterm labor. Our results showed that the infusion of T led to the development of hyperglycemia, hyperinsulinemia, hyperlactacidemia, hypokalemia, a fall in serum colloid osmotic pressure and pH, a rise in maternal heart rate, and a fall in maternal blood pressure. These changes in electrolytes in the serum occurred in the absence of any significant alterations in their urinary excretion. These data suggest that the infusion of T causes hyperglycemia that results in a rise in serum insulin and lactate, which, in turn, leads to a fall in serum potassium, ionized calcium, and pH. Volume expansion as manifested by a fall in colloid osmotic pressure may contribute to the reduction in the levels of ionized and total calcium. Thus, careful monitoring of electrolytes and hydration status is warranted when beta-mimetic agents are used, specifically T, for tocolytic therapy.