Case Study
A term nulliparous woman presented at 3–4 cm dilated in labor with irregular contractions. An epidural was established with 16 ml 0.1% bupivacaine and fentanyl 2 µg/ml in two equal divided doses and maintained using patient-controlled epidural analgesia (PCEA) of 8-ml boluses of the same low-dose mixture available every 15 minutes as required. Labor progress was slow, and an oxytocin infusion was started. On reexamination, the patient’s cervix was found to be 6 cm dilated. The cardiotocograph (CTG) became nonreassuring, demonstrating late decelerations for 15 minutes occurring with over 50 percent of contractions. A decision was made to perform a fetal scalp blood sample, but while sampling in the supine position a prolonged deceleration to 65 beats/min occurred. The obstetrician ordered a Category I emergency cesarean delivery (immediate threat to life of woman or fetus) with a maximum intended decision-delivery interval of 30 minutes.
While in the labor room, intrauterine resuscitation was instituted (syntocinon infusion stopped, left lateral position adopted, 0.25 mg terbutaline injected subcutaneously [a tocolytic beta-agonist], oxygen by mask, and rapid IV infusion of 1 liter crystalloid solution). The fetal bradycardia recovered partially to 110 beats/min with these measures. The anesthetist arrived in the delivery room and rapidly assessed the epidural to determine the suitability and safety of an epidural top-up to provide surgical anesthesia. Analgesia during contractions had been complete, and the last PCEA bolus was administered 35 minutes previously. Then 20 ml of a top-up mixture containing 17 ml 2% lidocaine with 1 ml 1:10,000 epinephrine and 2 ml 8.4% preservative-free sodium bicarbonate was prepared in the room by the anesthetist. After a negative aspiration test, a fractionated epidural top-up was given. A 3-ml test dose was given with a check for signs of spinal placement after 30 seconds, and then a further 3-ml test dose was given, observing for signs of IV placement after 30 seconds. The remaining 14 ml then was given over 90 seconds in the labor room. By this time, the patient was ready for transfer, and the anesthetist accompanied her to the OR. The epidural block was checked using ethyl chloride spray, and complete loss of cold sensation was found between T4 (nipples) and S5 (perianal). The anesthetist gave the all-clear to start surgery, an emergency cesarean delivery was performed, and the neonate was delivered safely. Three milligrams of diamorphine was administered via the epidural catheter at the end of the operation for postoperative analgesia, and the epidural was then removed before discharge from the OR.
Key Points
An abnormal CTG that requires early delivery is often preceded by nonreassuring changes, allowing advanced preparations for surgery.
Intrauterine resuscitation measures will often lead to partial or complete recovery of fetal heart decelerations or bradycardia.
Good function of the epidural block for labor analgesia is an indicator that surgical anesthesia for operative delivery is likely to be successful.
Epidural top-up for surgery should include fractionation of the drug dose and assessment for misplacement.
If the epidural catheter is topped up in the delivery room, the anesthetist should accompany the patient during transfer to the OR.
Discussion
Although the primary aim of epidural analgesia is to provide relief from painful uterine contractions, the secondary purpose is to provide surgical anesthesia should this be necessary for cesarean delivery, operative vaginal delivery, or postpartum procedures. As surgery becomes more likely, the obstetric anesthetist should make a judgment as to whether the labor epidural will work to provide anesthesia for surgery; if he or she is not confident about the function of the epidural, then he or she should consider whether it should be resited if time allows or accept that an alternative method of anesthesia will have to be used.
Initial Assessment of Epidural Function
The assessment of whether an epidural is likely to give effective analgesia for the duration of labor and anesthesia for surgery should be made early and continued during labor. Quick onset of analgesia, bilateral cutaneous sensory changes between the midthoracic and sacral dermatomes, and bilateral autonomic motor block evidenced through increased foot temperature are all desirable features. Very frequent epidural top-ups may be indicators that the epidural is functioning poorly, with two provisos. The first is that women who are anxious or wish to have no sensation at all may self-administer frequent PCEA boluses; this will be demonstrated by low pain scores and no breakthrough pain. The second is that obstructed labor (dystocia) is more painful than normal labor, and therefore, breakthrough pain may occur even with a good epidural.1, 2 This is a difficult situation to clarify; sometimes this is only shown when an oxytocin infusion is switched off at the point of an obstetric decision to attempt operative delivery, when the epidural function immediately becomes normal.
Good communication with the attending midwife/obstetric nurse is important to monitor the effectiveness of analgesia and to identify any problems early. If an epidural is functioning poorly, the anesthetist should have a low threshold for resiting, unless straightforward vaginal delivery is imminent.
Urgency and Intrauterine Fetal Resuscitation
The four-category urgency classification for cesarean delivery is well established in the United Kingdom.3 Category I is defined as immediate threat to life of woman or fetus. The use of these categories is a useful start to communication by the obstetrician to the rest of the team, but he or she should also communicate important details of the case, such as presence and severity of maternal and fetal compromise, and any response to resuscitation (see below) to the anesthetist. This will help the anesthetist to make an appropriate decision on the type of anesthetic to be used.
Most cases of Category I cesarean delivery for fetal bradycardia are likely to be associated with a transient cause, and therefore, the use of intrauterine resuscitation allows the best chance of reversing the process, allowing extra time to review the surgery and anesthesia4, 5 (Figure 24.1). For high-risk women, it may be necessary for junior anesthetic staff to await the assistance of a senior anesthetist. Even if the process is irreversible and immediate general anesthesia is required, administration of oxygen and IV fluid prepares for this eventuality.
Clear communication between obstetrician and anesthetist must be maintained; a Category I situation can be downgraded to Category II when the fetal condition is reassessed (and improves) in the OR and vice versa (when the fetal status worsens).
Assessment of the Epidural Block before Surgery
It is rare that the anesthetist cannot consider the possibility of providing regional anesthesia for operative delivery. It is undeniable that starting an epidural top-up in the delivery room allows the maximum length of time for the block to develop, although there is debate over the safety of this practice.6, 7 The concerns relate to the potential for a high/total spinal or IV misplacement and the lack of monitoring during transfer.6, 7
The chance that an epidural catheter is misplaced is greatest when first inserted and decreases after initial establishment of block and assessment. Although it is sometimes assumed that correct epidural placement is guaranteed by continued function during labor, a recent report shows that this is incorrect; in one case, an epidural that provided satisfactory analgesia during labor was found, on review by the anesthetist, to be in the spinal space, and surgical anesthesia was provided using 2.5 mg bupivacaine. In a second case, 75 mg bupivacaine administered after a negative aspiration test was followed by total spinal and cardiorespiratory arrest.8
A national survey of Obstetric Anaesthetists’ Association members found that almost two-thirds did not use a test dose when topping up an epidural for emergency cesarean delivery.9 However, in contrast, we recommend a systematic approach to evaluating the patient and rapid but fractionated administration of the epidural top-up solution with attention to adverse changes indicating misplacement (Figure 24.2).10 An initial assessment should be performed to ensure that the epidural catheter is sited correctly, seeking signs that the epidural is working excessively (possible spinal placement) or inadequately (possible IV placement). If indicated, the insertion site should be assessed for signs of leakage. The epidural catheter should be aspirated to check for free flow of CSF or blood. At this stage, the anesthetist may decide that topping up the epidural is likely to be ineffective or dangerous and should plan on performing general or spinal anesthesia (Figure 24.3).
