Grand Rounds - Hammersmith Hospital (beta) Adrenergic agonists and pulmonary oedema in preterm labour Must be used with care

Ritodrine and other β adrenergic agonists relax uterine smooth muscle and have been widely used to manage preterm labour. The effect of these drugs on birth weight and perinatal mortality remains controversial. Several side effects, including maternal pulmonary oedema, have been described. A 34 year old woman with primary infertility for 10 years had in vitro fertilisation, resulting in a twin pregnancy. She was normally fit and well with no history of cardiac disease. At 24 weeks of pregnancy she developed intermittent vaginal bleeding and was admitted to hospital. Initial assessment showed no evidence of uterine activity, but later the same day she developed contractions and the cervix was found to be 2 cm dilated, although the membranes were intact. Preterm labour was diagnosed and a ritodrine infusion was started at a dose of 200 μg/min, given in 500 ml of normal saline every four hours. She was also given dexamethasone (two 12 mg doses) and thyrotrophin releasing hormone (400 μg eight hourly over 48 hours) to improve fetal lung maturation and reduce the risk of hyaline membrane disease. Over the next 24 hours the contractions became less frequent and although she had a resting tachycardia, her chest was clinically clear. During the next day the contractions became more frequent and she was given ritodrine in 500 ml of normal saline every four hours. The contractions continued and on the fourth day she became increasingly breathless with a tachycardia of 135 beats/min, bilateral basal crackles, and some peripheral oedema. Pulmonary oedema was diagnosed clinically and she responded to oxygen and a bolus of intravenous frusemide. The ritodrine infusion was stopped and twins were delivered a few hours later. Thirty minutes after delivery she became acutely breathless and started coughing up pink frothy sputum. She had severe tachycardia with chest crepitations …