Explain the risk factors, presentation, and treatment of uterine atony

Explain the risk factors, presentation, and treatment of uterine atony.

Any condition associated with overdistention of the uterus, such as multiple births, polyhydramnios, or a large baby, is a risk factor for uterine atony. Other risk factors include multiparity, retained placenta, prolonged labor, previous tocolysis, β-agonists, prolonged general anesthe-sia with potent inhaled anesthetic agents, ruptured uterus, and chorioamnionitis.

Uterine atony presents as continued painless vaginal bleeding after delivery. The noncontracting uterus appears boggy and large. Obstetric management is aimed at increasing myometrial tone. Massaging the uterus through the abdominal wall or directly via the vagina is initially attempted to induce contractions. If massaging does not work, oxytocin and ergot derivatives are administered intravenously as well as prostaglandin F_2α directly into the uterus to induce contractions.

Anesthetic management is initially aimed at maternal resuscitation. Intravascular volume is restored with crystal-loid, colloid, and/or blood. Massive blood loss may lead to shock. Coagulation factor replacement may be required. Vaginal examination and suturing in attempts to stop the bleeding require anesthesia; however, conduction techniques are hazardous in the face of hypovolemia. Intravenous sedation with small amounts of fentanyl, ketamine, and/or midazolam generally suffices. If sedation is inadequate, a rapid sequence induction of general anesthesia with endo-tracheal intubation is required to reduce the risk of mater-nal aspiration.

Continued hemorrhage may require hypogastric artery ligation or hysterectomy, which necessitate general anes-thesia. Anesthetic management for these procedures is the same as for placenta previa. Pelvic artery embolization, usually performed in the radiology suite, can sometimes reduce the bleeding and prevent the need for a hysterectomy. Although general anesthesia is not required, maternal fluid resuscitation must be continued during embolization.

Frequent vital sign monitoring is required and resuscitative equipment must be available.

Successful intraoperative cell salvage (cell saver) have been reported in obstetrics. The major concern with its usage is that the amniotic fluid will not be completely removed during the centrifuging and cleansing process leading to iatrogenic amniotic fluid embolism. Recommendations for its use include discarding all surgi-cal field fluids before collecting blood with the cell saver device. Use of this technique should be reserved for situa-tions where there is no other blood available or the patient refuses autologous blood transfusion (Jehovah’s witness).