Careful monitoring called key to tocolysis: pulmonary status, vital signs

OB/GYN News, Dec 15, 2003 by Nancy Walsh

ATLANTA -- The rational use of tocolysis requires close monitoring of pulmonary status, vital signs, and fluid balance--but first ensuring that the patient is indeed in preterm labor, Dr. Washington C. Hill said.

"When a patient is experiencing increased uterine activity without cervical change or dilation, we don't want to start doing aggressive tocolytic therapy," Dr. Hill said at a conference on high-risk obstetrics sponsored by Symposia Medicus.

Prediction of preterm birth relies heavily on fetal fibronectin testing and cervical sonography. These tests have good negative predictive value, and they can be helpful in identifying those patients who do not need tocolysis, said Dr. Hill, who is chairman of the department of obstetrics and gynecology and director of maternal-fetal medicine, Sarasota (Fla.) Memorial Hospital.

But for patients presenting with a viable fetus of 20-36 weeks' gestation, intact membranes, and no obstetric or medical contraindications to continued pregnancy, tocolysis--even if it doesn't work for very long--can provide enough time for steroids to get on board, he said.

All the available tocolytics are associated with adverse effects for both mother and fetus. Beta-mimetics can cause tachycardia and other cardiac effects, pulmonary edema, and hyperglycemia in both. Magnesium sulfate can cause maternal respiratory depression and alterations in cardiac conduction, as well as alterations in heart rate variability in the fetus. Indomethacin is associated with gastrointestinal irritation in the mother and oligohydramnios in the fetus. Nifedipine can cause maternal and fetal tachycardia, as well as hypotension in the mother and altered uteroplacental blood flow to the fetus.

"There are no clear first-line drugs, so know your own tocolytic 'cocktail' well," said Dr. Hill, also of the department of obstetrics and gynecology, University of South Florida, Tampa.

Rational use of tocolysis requires special precautions when there are multiple fetuses or when the mother has diabetes mellitus or anemia. "'If you give a diabetic patient terbutaline, her blood sugar will go up. That doesn't mean you can't use it, but you need to be aware that will happen and treat it appropriately," he said. Pulse oximetry can be helpful in monitoring for pulmonary edema, he said.

Consider infection or abruption if the patient does not respond to tocolysis, and discontinue treatment in 48 hours if possible. Prolonged maintenance with oral terbutaline is not effective, he said.

The patient also needs to carefully monitor her own uterine activity. If she has more than four contractions in an hour, she should empty her bladder, lie down, and carefully monitor the activity. If she again has more than four, she should come to labor and delivery, Dr. Hill said.

"But we need to get rid of the term Braxton Hicks contractions," he said, referring to the intermittent, usually painless contractions felt by many women in mid-pregnancy. "Patients do not know the difference between so-called Braxton Hicks contractions and the real thing.

"Too many times patients will come into labor and delivery saying 'I was having Braxton Hicks contractions so I just stayed home,'" Dr. Hill said.