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Case Discussion: Postpartum Tubal Ligation

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A 36-year-old woman is scheduled for bilateral tubal ligation 12 h after delivery of a healthy baby.

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Is This Patient Still at Increased Risk for Pulmonary Aspiration?

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Controversy exists over when the increased risk for pulmonary aspiration diminishes following pregnancy. Certainly, many factors contributing to delayed gastric emptying are alleviated shortly after delivery: mechanical distortion of the stomach is relieved, labor pains cease, and the circulating progesterone level rapidly declines. In addition, a period of 8–12 h of elective fasting is possible. Some studies suggest that the risk of pulmonary aspiration as judged by gastric volume and gastric fluid pH (see the section on Gastrointestinal Effects) normalizes within 24 h. Unfortunately, even these studies report up to a 30–60% incidence of either a gastric volume greater than 25 mL or a gastric fluid pH less than 2.5. Therefore, most clinicians still consider the postpartum patient at increased risk for pulmonary aspiration and take appropriate precautions (see Chapters 15 and 43). It is not known when the risk returns to that associated with elective surgical patients. Although some physiological changes associated with pregnancy may require up to 6 weeks for resolution, the increased risk of pulmonary aspiration probably returns to “normal” well before that time.

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Other Than Aspiration Risk, What Factors Determine the “Optimal” Time for Postpartum Sterilization?

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The decision when to perform postpartum tubal ligation (or laparoscopic fulguration) is complex and varies according to patient and obstetrician preferences as well as local practices. In addition, the decision may be based on whether the patient had a vaginal delivery or cesarean section and whether an anesthetic was administered for labor (epidural anesthesia) or delivery (epidural or general anesthesia).

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Postpartum tubal ligation or fulguration may be (1) performed immediately following delivery of the baby and repair of the uterus during a cesarean section, (2) delayed 8–48 h following delivery to allow an elective fasting period, or (3) deferred until after the postpartum period (generally 6 weeks). Many obstetricians are reluctant to do immediate postpartum sterilizations because the patient may change her mind later, particularly if something untoward happens to the baby. Furthermore, they want to ensure that the patient is stable, particularly after a complicated delivery. On the other hand, sterilization is technically much easier to perform in the immediate postpartum period because of the enlargement of the uterus and tubes. Postpartum sterilizations following natural vaginal delivery are generally performed within 48 h of delivery, because bacterial colonization of the reproductive tract thereafter is thought to increase the risk of postoperative infection.

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What Factors Determine Selection of an Anesthetic Technique for Postpartum Sterilization?

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When continuous epidural anesthesia is administered for labor and vaginal delivery, the epidural catheter may be left in place up to 48 h for subsequent tubal ligation. The delay allows a period of elective fasting. A T4–5 sensory level with regional anesthesia is usually necessary to ensure a pain-free anesthetic experience. Lower sensory levels (as low as T10) may be adequate but sometimes fail to prevent pain during surgical traction on viscera.

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When the patient has not had anesthesia for delivery, postpartum sterilization may be performed under either regional or general anesthesia. Because of the increased risk of pulmonary aspiration, regional anesthesia usually is preferred for bilateral tubal ligation via a minilaparotomy. Many clinicians prefer spinal over epidural anesthesia in this setting because of the risk of unintentional intravascular or intrathecal injections with the latter (see Chapter 16). Moreover, the risk of a precipitous decrease in blood pressure following spinal anesthesia may be significantly diminished following delivery (particularly when preceded by an intravenous fluid bolus). In addition, the incidence of postdural puncture headache is as low as 1% when a 25-gauge or smaller pencil-point needle is used. Dosage requirements for regional anesthesia generally return to normal within 24–36 h after delivery. Tetracaine, 7–10 mg, bupivacaine, 8–12 mg, or lidocaine, 60–75 mg, may be used for spinal anesthesia. For epidural anesthesia, 15–20 mL of lidocaine 1.5–2% or chloroprocaine 3% is most commonly used.

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In contrast, when laparoscopic tubal fulguration is planned, general endotracheal anesthesia is usually preferred. Insufflation of gas during laparoscopy impairs pulmonary gas exchange and predisposes the patient to nausea, vomiting, and possibly pulmonary aspiration. Endotracheal intubation generally ensures adequate ventilation and protects the airway.

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What Considerations Are Important for Postpartum Patients Undergoing General Anesthesia?

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Preoperative concerns include a decreased blood hemoglobin concentration and the persistent increased risk of pulmonary aspiration. Anemia is nearly always present as a result of the physiological effects of pregnancy combined with blood loss during and following delivery. Hemoglobin concentrations are usually greater than 9 g/dL, but levels as low as 7 g/dL are generally considered safe. Fortunately, sterilization procedures are rarely associated with significant blood loss.

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The risk of pulmonary aspiration is diminished by a minimum of 8 h of fasting, premedication with an H2 histamine blocker (ranitidine), a clear antacid (sodium citrate), or metoclopramide (see Chapters 15 and 43). In addition, induction of anesthesia should employ a rapid-sequence technique with cricoid pressure prior to endotracheal intubation, and the patient should be extubated only when she is awake. Decreased plasma cholinesterase levels persist after delivery (see the section on Hepatic Effects) and generally modestly prolong the effect of succinylcholine and mivacurium. The duration of vecuronium but not atracurium (or cisatracurium) has also been reported to be prolonged in postpartum women. High concentrations of volatile agents should be avoided because of the at least theoretical risk of increasing uterine blood loss or inducing postpartum hemorrhage secondary to uterine relaxation. Intravenous opioids may be used to supplement inhalational agents. Intravenous drugs administered intraoperatively to mothers who are breast-feeding appear to have minimal if any effects on their neonates. Nonetheless, it may be prudent to avoid breast-feeding 12–24 h following general anesthesia.

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