Continuing Education Activity

Uterine atony is a principal cause of postpartum hemorrhage, an obstetric emergency. Globally, it is one of the top 5 causes of maternal mortality. Uterine atony refers to the inadequate contraction of the corpus uteri myometrial cells in response to endogenous oxytocin release. Postpartum hemorrhage can occur because spiral arteries are uniquely devoid of musculature and dependent on uterine contractions to mechanically squeeze them into hemostasis. After delivery, in the absence of uterine contraction, spiral arteries may continue to bleed, resulting in postpartum hemorrhage. This activity reviews the evaluation and management of uterine atony and highlights the role of interprofessional team members in collaborating to provide well-coordinated care and enhance outcomes for affected patients.

Objectives:

• Explain how to detect uterine atony.

• Explain the risks associated with uterine atony.

• Describe how to manage uterine atony.

• Explain the importance of improving care coordination, with particular emphasis on communication between interprofessional medical teams, to enhance to prevent hemorrhage in patients with uterine atony.

Introduction

Uterine atony refers to the corpus uteri myometrial cells inadequate contraction in response to endogenous oxytocin that is released in the course of delivery. It leads to postpartum hemorrhage as delivery of the placenta leaves disrupted spiral arteries which are uniquely void of musculature and dependent on contractions to mechanically squeeze them into a hemostatic state. Uterine atony is a principal cause of postpartum hemorrhage, an obstetric emergency. Globally, this is one of the top 5 causes of maternal mortality.[1]

Etiology

Risk factors for uterine atony include prolonged labor, precipitous labor, uterine distension (multi-fetal gestation, polyhydramnios, fetal macrosomia), fibroid uterus, chorioamnionitis, indicated magnesium sulfate infusions, and prolonged use of oxytocin. Ineffective uterine contraction, either focally or diffusely, is additionally associated with a diverse range of etiologies including retained placental tissue, placental disorders (such as morbidly adherent placenta, placenta previa, and abruption placentae), coagulopathy (increased fibrin degradation products) and uterine inversion. Body mass index (BMI) above 40 (class III obesity) is also a recognized risk factor for postpartum uterine atony.[2]

Epidemiology

The absence of effective contraction of the uterus after delivery complicates 1 in 40 births in the United States and is responsible for at least 75% of cases of postpartum hemorrhage.[3]

Pathophysiology

Contraction of the myometrium that mechanically compresses the blood vessels supplying the placental bed provides the principal mechanism uterine hemostasis after delivery of the fetus, and the placenta is concluded. The process is complemented by local decidual hemostatic factors such as tissue factor type-1 plasminogen activator inhibitor as well as by systemic coagulation factors such as platelets, circulating clotting factors.

History and Physical

At prenatal history and examination, risk factor discernment is key to optimal risk management. Identification of risks allows for planning and availability of resources that might be needed including personnel, medication, equipment, adequate intravenous access, and blood products. The American College of Obstetricians recommends that women be identified prenatally as high risk for postpartum hemorrhage based on the presence of placenta accreta spectrum, pre-pregnancy BMI greater than 50, clinically significant bleeding disorder, or other surgical-medical high-risk factors. Part of the planning should be to develop a plan that allows delivery at a facility with an appropriate level of care for these patients' needs.

The diagnosis is made during the physical exam immediately upon conclusion of an obstetric vaginal or cesarean delivery. Direct palpation at cesarean delivery (typically after the closure of the uterine incision) or indirect examination at bimanual examination after a vaginal delivery reveals a boggy, soft, and an unusually enlarged uterus, typically with co-existent bleeding from the cervical os (harder to appreciate at cesarean deliveries). An expeditious exclusion of retained gestational products or obstetric lacerations quickly excludes additional co-concomitant etiologies. The possibility of coagulopathies is considered and pursued if clinically indicated. The physical examination suggested above may involve obstetric ultrasound imaging.

Evaluation

Diagnosis of diffuse uterine atony is prompted typically by finding of more than usual blood loss during examination demonstrating a flaccid and enlarged uterus, which may contain a significant amount of blood. With focal localized atony, the fundal region may be well contracted while the lower uterine segment is dilated and atonic, which may difficult to appreciate on abdominal examination, but may be detected on vaginal examination. A digital exploration of the uterine cavity (if adequate anesthesia is available), or bedside obstetric ultrasound imaging to reveal an echogenic endometrial stripe is an essential examination, as is a timely examination with adequate lighting to exclude an obstetric laceration.

Treatment / Management

Prenatal Readiness

If the woman is at a medium risk for intrapartum, blood should include be typed and screened. Women with a medium risk factor for uterine atony-related postpartum hemorrhage include prior uterine surgery, multiple gestation, grand multiparity, prior PPH, large fibroids, macrosomia, body mass index greater than 40, anemia, chorioamnionitis, prolonged second stage, oxytocin longer than 24 hours, and magnesium sulfate administration. Those assessed to be high risk should be typed and cross-matched for those at high risk of PPH. High-risk criteria include placental previa or accreta, bleeding diathesis, 2 or more medium risk factors for uterine atony. Use of a cell saver (blood salvage) should be considered for women at increased risk of postpartum hemorrhage, but this is not cost-effective to be routine.

Intrapartum Prevention

This includes optimal management of the third stage of labor. Active management of the third stage includes uterine massage with concomitant sustained low-level traction on the umbilical cord. Simultaneous oxytocin infusion is helpful, although it is reasonable to defer it to after delivery of the placenta.

Initial Medical Treatment

If uterine atony occurs, healthcare providers should be ready for initial medical management which is directed to the use of medications to improve tone and induce uterine contractions. Massaging the uterus is also effective, as is ensuring an empty cavity. Maternal support with intravenous (IV) fluids is commenced through preferably an u8-gauge, intravenous catheter. A team approach is initiated with the summoning of the needed personnel through a standardized built-in alert system. Medications used for postpartum hemorrhage secondary to Uterine atony include the following:

1. Oxytocin (Pitocin) can be given IV 10 to 40 units per 1000 ml or 10 units intramuscularly (IM). The rapid undiluted infusion may cause hypotension.
2. Methylergonovine (Methergine) given IM 0.2 mg. Given every 2 to 4 hours. Should be avoided in patients with hypertension.
3. 15-methyl-PGF2-alpha (Hemabate) given IM 0.25 mg. Given every 15 to 90 minutes for a maximum of 8 doses. Should be avoided in asthmatics. May cause diarrhea, fevers, or tachycardia. It is expensive.
4. Misoprostol (Cytotec): 800 to 1000 mg placed rectally. May cause a low-grade fever. It has a delayed action.
5. Dinoprostone (Prostin E2) 20 mg vaginal or rectal suppository may be given every 2 hours.

Surgical Treatment

Should the medications fail with persisting excess bleeding, then surgical management is engaged.[4]

Tamponade Techniques

1. Uterine packing with gauze (with vaginal packing to ensure its retention, thus a uterovaginal packing) with Foley catheter insertion to allow bladder drainage. The uterine packing should be tight and uniform, and it is a quickly and efficiently achieved with rolled gauze ribbons.
2. Bakri balloon (with vaginal packing to ensure its retention) with Foley catheter insertion to facilitate bladder drainage.

Surgical Management Techniques

1. Uterine curettage for retained products
2. Uterine artery ligation (O' Leary), with an option to for extending arterial ligation to tubo-ovarian vessels.
3. Compression sutures such as the B-Lynch are typically reserved for clinical scenarios where bimanual compression of the uterus leads to arrest in bleeding.
4. Hypogastric artery ligation (performed by Gyn/Onc)
5. Hysterectomy

Differential Diagnosis

The typical physical findings elude detection in the presence of uterine eversion when the endometrial surface everts into the vagina and allowed by uterine atony. This typically occurs after a vaginal delivery, and the usual findings of an enlarged boggy uterus are unavailable and replaced by findings of an intra-vaginal mass that is cherry colored (endometrium) and should be immediately replaced back into the uterine cavity, after which restoration of uterine tone prevents its recurrence.

Prognosis

Women with a prior PPH have as much as a 15% risk of recurrence in a subsequent pregnancy. The risk of recurrence depends, in part, on the underlying cause and associations such as class 3 obesity may have a higher recurrence risk. 

Postoperative and Rehabilitation Care

Postpartum anemia is common after an episode of uterine atony and postpartum hemorrhage. Severe anemia due to PPH may require red cell transfusions, depending on the severity of anemia and the degree of symptomatology attributable to anemia. A common practice is to offer a transfusion to symptomatic women with a hemoglobin value less than 7 g/dL. In most cases of uterine atony-related postpartum hemorrhage, the amount of iron lost is not fully replaced by the transfused blood. Oral iron should thus be also considered. Parenteral iron therapy is an option as it accelerated recovery. Most women with mild to moderate anemia, however, resolve the anemia sufficiently rapidly with oral iron alone and do not need parenteral iron.

Pearls and Other Issues

In recognition that the majority of the cases of postpartum hemorrhage are due to uterine atony, implementation of a systemic approach in birthing units is advocated by all leading professional bodies.

Enhancing Healthcare Team Outcomes

The Joint Commission recommends that obstetrical staff undergo interprofessional team training to teach staff to work together and communicate more effectively when postpartum hemorrhage (most due to uterine atony) occurs. The Commission is in favor of clinical drills to help staff prepare for the clinical event, as well as conducting debriefings after such events to evaluate team performance and identify areas for improvement. Simulation team training can help to identify areas that need strengthening, and regular, unannounced, simulated, postpartum hemorrhage scenarios in real-life settings, such as the labor and delivery units or post-anesthesia care units, may also increase comfort with the protocols and teamwork required in such emergencies. Such a systemic approach creates a positive trajectory toward improved obstetric outcomes and is also endorsed by the Association of Women's Health, Obstetric and Neonatal Nurses (AWHONN). An interprofessional team approach will provide the best patient outcomes. [Level V]