Case Study

A 36-year-old woman at 39 weeks’ gestation presented in spontaneous labor. Her initial cervical examination showed 3 cm of dilation and 80 percent effacement, and she was contracting every 3 minutes. Her medical history was significant for two prior spontaneous vaginal deliveries, for which she received epidural analgesia. The rest of her history, physical examination, and airway examination were unremarkable.

Pain relief was requested, and an epidural technique was performed without difficulty. Patient-controlled epidural analgesia was started with an infusion of 0.1% bupivacaine and 2 μg/ml fentanyl, resulting in adequate labor analgesia. During the course of labor, the patient required one manual epidural bolus of 10 ml of 0.125% bupivacaine due to an inadequate sensory level. Twenty minutes after this bolus, the patient reported adequate analgesia and was found to have a T7 level to cold bilaterally.

The rest of the patient’s labor course proceeded uneventfully, resulting in a vaginal delivery. One hour after delivery, the patient proceeded to the OR for a postpartum tubal ligation. The epidural catheter was incrementally dosed with a 20-ml mixture of 2% lidocaine, 1:200,000 epinephrine, and 2 ml sodium bicarbonate. Twenty minutes later, the patient had a T10 sensory level to pinprick bilaterally, and an additional 10 ml of the lidocaine, epinephrine, bicarbonate mixture was administered, resulting in a T7 sensory level to pinprick bilaterally. Because of the inadequate surgical anesthesia, a decision was made to proceed with general anesthesia. After administration of sodium citrate and preoxygenation, rapid-sequence induction was performed, and the patient was intubated. The rest of the procedure proceeded uneventfully.

Key Points

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  Despite requiring one additional clinician-administered epidural bolus of medication, this patient’s epidural catheter appeared to be functioning appropriately for labor analgesia.

  
  
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  Because a functioning labor epidural catheter was a convenient option for providing a surgical level of anesthesia for this patient, the anesthesia provider bolused the catheter with an appropriate dose of local anesthetic.

  
  
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  However, when surgical anesthesia was not achieved after epidural administration of 30 ml 2% lidocaine with epinephrine 1:200,000 and 2 ml sodium bicarbonate, general anesthesia was administered to enable completion of the procedure.

Discussion

Tubal sterilization is a highly effective form of female birth control, with a failure rate of less than 1 percent.¹ Performing tubal sterilizations during the postpartum period offers several surgical, anesthetic, and socioeconomic advantages, as well as some disadvantages^2–4 (Table 26.1). With the advantages outweighing the disadvantages, it is not surprising that more than 50 percent of tubal sterilizations are performed during the early postpartum period, resulting in obstetric anesthesia providers being frequently called on to provide care for this procedure.²

The American Society of Anesthesiologists (ASA) Task Force on Obstetric Anesthesia has published guidelines for the anesthetic management of obstetric patients undergoing postpartum tubal sterilizations⁵ (Table 26.2). These guidelines are meant to assist the anesthesia provider in the optimal management of this patient population. In addition to these guidelines, all anesthesia providers should review each patient’s peripartum course (including blood loss from delivery) prior to proceeding with the procedure because changes may have occurred in the interim. Finally, because pregnancy-induced physiologic changes persist into the postpartum period, anesthesia providers need to be aware of these changes and their impact on anesthetic management (Table 26.3).

Both neuraxial and general anesthesia may be used successfully for postpartum tubal sterilization. The decision of which anesthetic technique to use depends on several factors, including patient and provider preference, time interval between delivery and tubal sterilization, obstetric and anesthetic risk factors, and presence of a functioning epidural catheter.

Neuraxial anesthesia represents the most common anesthetic technique for postpartum tubal sterilizations in the United States.⁶ Compared with general anesthesia, advantages of a neuraxial technique include the ability to maintain an intact airway reflexes to protect against gastric aspiration, avoidance of airway manipulation and maternal hypoventilation, and lack of volatile agent–induced uterine atony. For women who received labor epidural analgesia, additional benefits include use of the epidural catheter for surgical anesthesia and the ability to provide effective postoperative analgesia. Regardless of which neuraxial technique is used, a T4 sensory level is required to block visceral stimulation from fallopian tube manipulation.

The chief benefit of an epidural technique for these procedures is that a functioning labor epidural catheter can easily be augmented to a surgical level of anesthesia, obviating the need to perform another anesthetic technique. However, ASA guidelines suggest that epidural catheters placed for labor may be more likely to fail with longer delivery-to-reactivation intervals.⁵ This observation is supported by several studies suggesting a lower likelihood of failed epidural catheter reactivation when the delivery-to-reactivation interval is less than 4–8 hours in duration.^7–9 Overall, successful epidural reactivation is seen in 74–95 percent of catheters, with the highest success rate occurring when the block is extended less than 4 hours after delivery.^7–9

One reason why epidural catheters reactivated at longer intervals have a higher failure rate is the larger incidence of catheter migration or dislodgement observed. In the peripartum period, significant catheter migration occurs in 36–54 percent of patients.^{10, 11} Single-orifice epidural catheters tend to have a higher rate of dislodgement when inserted 2 cm within the epidural space but a higher risk of unilateral block when inserted 6–8 cm.¹² For multiorifice epidural catheters, insertion of catheters 5 cm in the epidural space is associated with the highest incidence of satisfactory labor analgesia.¹³ Therefore, to optimize the success rate of epidural catheter reactivation for postpartum tubal sterilization, insertion of the epidural catheter 4–6 cm within the epidural space is recommended. Additionally, securing the epidural catheter to the skin when the patient is in a nonflexed position is recommended, especially in obese parturients, because catheter position within the epidural space may change significantly when the patient moves from the flexed position.¹⁴

As demonstrated in the Case Study, some patients with functioning labor epidural catheters that are reactivated within a reasonable time interval may still not achieve a surgical level of anesthesia. Anesthetic options for this scenario include placement of a spinal anesthetic, replacement of the epidural catheter, a combined spinal-epidural technique, or general anesthesia. Each of these options has its own inherent benefits and risks.

Use of a spinal anesthetic technique after epidural catheter failure is controversial. Compared with an epidural technique, benefits of this technique include higher reliability, faster onset, denser sensory block, and lower local anesthetic doses. However, the exact dose of intrathecal local anesthetic required to achieve a surgical level of anesthesia in this scenario is difficult to predict and depends on several factors, including epidural space distension and its effect on intrathecal drug distribution, interpatient variability in response to intrathecally and epidurally administered medications, and patient body habitus.^{15, 16} Additionally, due to declining maternal progesterone levels, postpartum patients typically require higher doses of local anesthetics to achieve an adequate surgical level of anesthesia compared with pregnant patients.¹⁷ Consequently, if the amount of intrathecal medication administered is not enough to achieve surgical anesthesia, the patient will likely need to undergo general anesthesia.

The more concerning issue with placement of a spinal anesthetic after failed epidural catheter reactivation is the occurrence of high or total spinal anesthesia. Several case reports have described the occurrence of total spinal anesthesia in this scenario, with a reported incidence of 0.8–11 percent.^{15, 18} Mechanisms for this increased risk include decreased size of the intrathecal space due to epidural space distension, passage of epidural medications through a dural hole from the subsequent spinal, and diffusion of epidural medications into the intrathecal space. Several techniques have been proposed to avoid high spinals in this scenario, but none has been demonstrated to decrease the incidence of total spinal anesthesia or conversion to general anesthesia.^{19, 20}

For situations in which reactivation of the epidural catheter has failed, replacement of the epidural catheter is another option. Benefits of this technique include extension of anesthesia for longer procedures and use of the epidural catheter for postoperative analgesia. However, these benefits are likely not to be clinically useful because postpartum tubal sterilizations are relatively short procedures compared with other operations, and postoperative pain requirements are moderate in intensity and often well controlled with systemic multimodal analgesia. The downsides of replacing the epidural catheter, however, are more clinically significant and potentially have a greater impact on patient safety. These drawbacks include increased risk of local anesthetic toxicity (especially if a large volume of local anesthetic has already been administered), failure of the replaced epidural catheter, and prolonged time to achieving adequate surgical anesthesia.

A combined spinal-epidural (CSE) technique using a lower intrathecal dose of local anesthetic is a third option. Use of this technique will likely decrease the risk of total spinal anesthesia but still allow for additional epidural dosing if the spinal component is inadequate for surgery or if the procedure lasts longer than expected. However, opponents of this technique voice concern about the presence of an “untested” epidural catheter. While this is a theoretical concern, evidence suggests a lower incidence of rescue analgesia with a CSE versus an epidural technique because the anesthesia provider is able to confirm placement of the epidural needle within the epidural space by obtaining CSF through the spinal needle.^{21, 22}

Although there is insufficient evidence to compare the benefits of neuraxial anesthesia versus general anesthesia for postpartum tubal sterilizations, there are certain situations (e.g., patient preference, coagulopathy) in which general anesthesia may be superior.⁵ If general anesthesia is selected, several considerations must be taken into account. First, pregnancy-induced changes in pharmacokinetics are likely to still be present and affect anesthetic management. In particular, decreases in minimum alveolar concentration requirements, as well as changes in the response of postpartum patients to depolarizing and nondepolarizing neuromuscular blockers, will likely affect management of these patients under general anesthesia.^{23, 24} Second, changes in cardiopulmonary physiology not only may affect a patient’s hemodynamics under general anesthesia but also may make mask ventilation and intubation difficult. Third, alterations in gastric physiology may increase a postpartum patient’s risk of aspiration. As such, providers should treat the patient as a “full stomach” patient by adhering to NPO requirements, administrating gastric acid prophylaxis, and using a rapid-sequence induction technique with cricoid pressure, at least on the first postpartum day (gastric emptying appears to be normal on the second day). Finally, standard ASA monitors should be used for all patients, especially monitors for oxygenation and ventilation, to help decrease the morbidity and mortality associated with general anesthesia.

Propofol presents an excellent pharmaceutical option for the induction of general anesthesia in this patient population. With its reliable fast onset of action and rapid recovery, propofol has been shown to have similar pharmacokinetics during both the intrapartum and postpartum periods.²⁵ Thiopental also has a long history of efficacy and safety as an induction agent in the obstetric patient population, but its lack of access, especially in the United States, may limit its use.²⁶

Maintenance of general anesthesia for postpartum tubal ligations can be done either by a total IV technique or with volatile halogenated agents. One significant downside of using volatile agents during the immediate postpartum period is their ability to cause uterine relaxation in a dose-dependent fashion, thereby increasing the risk of postpartum hemorrhage (PPH).²⁷ In order to minimize this risk, anesthesia providers could use 1.0 minimum alveolar concentration (MAC) or less of volatile agent and supplement with IV agents as needed to decrease the risk of intraoperative recall during these procedures. It is unclear how long after delivery the risk of volatile agent–induced PPH persists.

Succinylcholine is often used for muscle relaxation for postpartum tubal sterilization due to its rapid onset and offset of action. Compared with nonpregnant women, parturients show lower activity of pseudocholinesterase, which reaches its nadir around postpartum day 3.²⁸ Clinically, this results in a 25 percent prolonged recovery time from succinylcholine-induced muscle relaxation in postpartum women.²⁹ This prolonged recovery time may be especially important in “cannot intubate/cannot ventilate” scenarios, where rapid recovery from the effects of succinylcholine is essential. Conversely, nondepolarizing muscle relaxants exhibit a mixed response in postpartum patients. Compared with its use in nonpregnant control individuals, vecuronium demonstrates greater than 50 percent prolongation of action during the postpartum period, whereas rocuronium shows no change in its duration of action, and cisatracurium has a shorter duration due to increased elimination and clearance from pregnancy-induced physiologic changes.^30–32

Postoperative analgesia is ideally achieved with multimodal analgesia, typically using a combination of oral and/or parental opioids and nonsteroidal anti-inflammatory drugs. This method results in improved pain control and patient satisfaction, minimizes opioid-related side effects, and promotes earlier hospital discharge.³³ The use of neuraxial morphine for postoperative analgesia has also been shown to provide effective analgesia after postpartum tubal sterilizations.^{34, 35} However, the benefits of neuraxially administered morphine need to be weighed against the increased risk of nausea, vomiting, and pruritus, as well as the need for a 24-hour period of observation after administration to monitor for delayed respiratory depression.^34–36