Bolus tocolysis: treatment of preterm labor with pulsatile administration of a beta-adrenergic agonist.

The treatment of premature labor with beta-adrenergic substances is complicated by side effects. Although most human control mechanisms are pulsatile, therapy is usually administered continuously. We designed a microprocessor-controlled pump to allow pulsatile tocolytic infusion, hoping to reduce the total dose and thus the side effects. In 33 patients pulsatile bolus tocolysis was compared with continuous tocolysis in a control group of 38 patients. Bolus tocolysis required considerably less beta-sympathomimetic agent for comparable therapeutic success (median dosage 3.0 versus 15.9 mg, p less than 0.001). Duration of therapy under bolus tocolysis was also significantly shorter (p less than 0.05). Birth weight was higher after bolus tocolysis (median 3070 versus 2580 gm, p = 0.05). Additional indicators favored bolus tocolysis but were not statistically significant: a longer gestational period, fewer infants weighing less than 2500 gm, and a lower incidence of respiratory distress syndrome. Pulmonary edema occurred in one patient during continuous tocolysis.