Management of Acute and Subacute Puerperal Uterine Inversion with Intravenous Nitroglycerin

Introduction

Acute inversion of the uterus is a rare—but potentially fatal—obstetrical emergency that can occur in the third stage of labor. Although the exact cause for this inversion is unclear, active management of the third stage of labor is recommended to avert maternal morbidity and mortality. To minimize the hazards of acute puerperal inversion, the uterus must be repositioned immediately, but manual efforts are often hampered by cervical constriction. To relax the constriction ring, halothane is commonly administered, but this weak uterine relaxant reduces uterine responsiveness to oxytocin and the ergot alkaloids. In recent years, intravenous (IV) nitroglycerin has come to the attention of obstetricians as a potent uterine relaxant.

This article describes two case reports of puerperal uterine inversion in which manual replacement of the uterus were facilitated by the use of IV nitroglycerin.

Cases

Results

Both cases were treated successfully with the use of IV nitroglycerin. Surgeons were able to reposition these patient's uteri manually, thus, avoiding the need for surgical intervention.

Discussion

Uterine inversion occurs when the uterine fundus prolapses within the endometrial cavity. Uterine inversion is an unpredictable entity with more than one-half of cases reported without detectible precipitants. Hemorrhage can be rapid and life-threatening, requiring prompt recognition and aggressive management. The incidence of uterine inversion varies, depending upon the patient's geographic location and varies from 1:5000 to 1:6407 following vaginal birth. The maternal mortality is as high as 15%. ¹

Puerperal uterine inversion has been classified as first degree, in which the fundus has inverted but has not passed through the cervix; second degree, in which the inverted fundus has passed through the cervix into the vagina; and third degree, in which the fundus is inverted and is outside the vulva. ² Inversion has also been classified as acute when it has occurred without contraction of the cervix, subacute when the cervix has contracted, and chronic when >4 weeks have elapsed. ³

Uterine inversion can occur in both obstetrical (puerperal) and gynecologic (nonpuerperal) settings. Uterine inversion has been linked to a number of etiologic factors, although there may be no obvious cause. Factors associated with puerperal uterine inversion are multiparity, fundal location of the placenta, an abnormally adherent placenta, a uterine structural anomaly, uterine atony, a short umbilical cord, antepartum use of tocolysis such as magnesium sulfate, precipitate labor, and poor management of third stage of labor because of premature cord traction prior to placental separation. ⁴

The diagnosis of uterine inversion is usually clinical. When there is complete inversion, the diagnosis is made most easily by palpating the inverted fundus at the external cervical os or vaginal introitus. Profuse bleeding, absence of the uterine fundus, or an obvious defect of the fundus noted on abdominal examination, as well as evidence of shock with severe hypotension will provide the clinician with further diagnostic clues.

Treatment modalities involve immediate repositioning of the uterus (the Johnson maneuver), ⁵ use of tocolytics, and replacement of lost fluid. In some patients, contraction of the cervical ring around the uterus renders repositioning of inverted uteri difficult. ¹ In 10%–15% of patients, general anesthesia is required to allow repositioning of the uterus. ² What is rarer still is that laparotomy, with traction or incision of the contracted ring, has been used in refractory cases.

Treatment of uterine inversion consists of manual manipulation of the uterus and the use of pharmacologic agents to assist in uterine relaxation for achieving correction (e.g., tocolytics, such as MgSO₄, terbutalin). Furthermore, agents are then given to cause uterine contraction to prevent reinversion and to decrease blood loss. If these methods fail, surgical intervention might be necessary. The two most commonly used procedures are the Huntington ⁶ and Haultain ⁷ procedures.

At the PGIMS, general anesthesia (halothane) is used to induce uterine relaxation. Halothane is cardio-depressant and is associated with hypotension. In addition, halothane increases aspiration of gastric contents especially during pregnancy.^8,9 However, nitroglycerin does not produce these side-effects. Thus, nitroglycerin is ideal for treating inversion of the uterus, because of this agent's powerful uterine-relaxant effect and short plasma half-life (∼2 minutes). With a low dose of nitroglycerin, the degree and duration of uterine relaxation can be controlled easily without maternal side-effects. In this way, the significant risk of needing general anesthesia may circumvented. ⁸

First synthesized in 1846, nitroglycerin has been used in many ways in medicine. Obstetrical use of nitroglycerin dates back to the late 1800s. Since that time it has been used successfully for treating internal podalic version, retained placenta, and breech delivery. ¹⁰ Nitroglycerine's usefulness in the obstetrical field lies in its ability to relax smooth muscle within the cervix and uterus. Nitroglycerine, a nitric oxide donor and potent smooth-muscle relaxant, acts on smooth muscle by elevating cyclic guanosine monophosphate. Uterine relaxation occurs within 30–95 seconds, and the medication has a half-life of 1–3 minutes.

This short duration of action makes nitroglycerin useful at times when the prolonged effects of tocolytics might be hemodynamically disadvantageous to the patient. Nitroglycerin can be administered by various non-IV routes (lingual, sublingual, intranasal, intrabuccal, oral, and topical) or can be given through IV infusion. Although nitroglycerin can cause hypotension and headache, therapeutic doses are generally well-tolerated.

The data on using IV nitroglycerin for treating uterine inversion suggests infusing doses ranging from 50 μg to 200 μg, with success noted at all dosing levels. ¹¹ The current authors have corrected uterine inversion successfully at a minimum dose of 50 μg without any side-effects.

Conclusions

Nitroglycerin is a useful tool in the obstetrical armamentarium. Its short duration of action and rapid absorption make it ideal for expeditious uterine and cervical relaxation.