Uterine inversion is a relatively uncommon obstetric emergency that occurs in about one in 2,000 obstetric patients. The uterus actually turns inside out with this condition; the condition may range from first degree (incomplete inversion) to third degree (complete inversion), when the uterus extends to the perineum. It has been associated with multiparity, placenta accreta and a short umbilical cord. Possible causes include excessive cord traction in the third stage of labor and fundal pressure. Because maternal hemorrhage can be rapid and fatal with uterine inversion, prompt recognition and management are important.
Initial treatment of uterine inversion is the immediate manual replacement of the uterus (Johnson maneuver), administration of tocolytics and fluid replacement. In some instances, the uterus becomes entrapped in the cervical ring, making manual replacement difficult. General anesthesia, laparotomy or incision of the contracted cervical ring may be required. Since being synthesized in 1846, nitroglycerin has been used successfully in the management of uterine inversion, as well as other obstetric problems such as retained placenta and breech delivery.
Nitroglycerin has an onset of action of 30 to 95 seconds and will relax the smooth muscle within the cervix and uterus. Hicks recently reported a case in which nitroglycerin spray was used to treat a patient with uterine inversion. The patient was a 38-year-old gravida 2, para 1, who delivered a 2,005 g (4 lb, 6 oz) female infant at 33 weeks' gestation. Placental delivery did not occur after one hour, so gentle traction was applied to the umbilical cord. A complete inversion of the uterus followed, and manual reinsertion could not be accomplished, even after administration of intravenous terbutaline. While waiting for obstetric and anesthesia backup, the clinician administered fentanyl, midazolam and cefotetan. Noting that the base of the uterus was trapped by the contracted cervix, the patient was given two sprays of sublingual nitroglycerin (total dose, 400 μg). This medication quickly relaxed the cervix and allowed for manual reduction of the uterus. The patient was given oxytocin and two units of packed red blood cells but did not require surgical intervention. She was discharged on the second postpartum day.
The author notes that the literature suggests using intravenous nitroglycerin at doses of 50 to 200 mg for uterine inversion; however, that is not a drug that would routinely be found in most obstetric units. In addition, nursing staff may not be familiar with its use. Sublingual nitroglycerin has an unpredictable shelf life and thus would not be practical to maintain for an infrequent obstetric emergency. The spray form of nitroglycerin has a shelf life of two years, and one spray delivers 200 μg of the medication. The time to systemic absorption is about two minutes. The author suggests that the advantages of this medication make it worth having on hand at birthing centers.