1

What options are available to the mother for labor analgesia?

Many techniques have been used to reduce the perception of pain during labor. In addition to systemic medications, inhalation agents, neuraxial anesthesia, hypnosis, psychoprophylaxis, acupuncture, and transcutaneous electrical nerve stimulation have been used.

Systemic opioids can be used to attenuate labor pains; however, they do not completely eliminate the pain. The opioids meperidine, morphine, fentanyl, and the agonist-antagonist butorphanol have been used. Opioids can be administered as an intravenous bolus or with intravenous patient-controlled analgesia. The choice of opioid varies by institution and local experience. Remifentanil can also be used with intravenous patient-controlled analgesia. The advantage of remifentanil is that its onset and duration of action are shorter than those of other opioids. However, it is also very potent, and close maternal respiratory monitoring, preferably with pulse oximetry, is required.

Inhalation analgesia during labor is another option. The goal is to achieve analgesia without depressing airway reflexes. Typically, the mother, using a hand-held device, self-administers nitrous oxide at the beginning of each contraction. Although this technique provides moderately good analgesia, it is not commonly used because of the risk of maternal aspiration with deep levels of anesthesia.

Epidural and combined spinal-epidural (CSE) neuraxial anesthesia techniques have become popular modalities for labor analgesia because of their safety and efficacy profile.

2

What are the advantages and disadvantages of various neuraxial anesthetic techniques for labor and delivery?

Rational use of neuraxial anesthesia necessitates an understanding of the pain pathways involved during labor. Labor is traditionally divided into three distinct stages ( Table 54-1 ):

• •
  

  First stage begins with the onset of regular contractions and ends with complete cervical dilation.

  
  
• •
  

  Second stage begins when the cervix is completely dilated and ends with delivery of the fetus.

  
  
• •
  

  Third stage begins after delivery of the fetus and concludes with delivery of the placenta.

The first stage of labor is associated with uterine and cervical pain mediated by spinal segments T10-L1 ( Figure 54-1 ). Local anesthetics administered to the epidural, spinal, or caudal spaces readily anesthetize these pain pathways. In addition, subarachnoid opioids and paracervical blocks can be used for pain relief during the first stage of labor. Caudal anesthesia is rarely used because of the risk of inadvertent fetal scalp penetration and the associated high fetal levels of local anesthetic.

Schematic drawing of parturition pain pathways. First-stage labor pain is due to uterine contraction and cervical dilation. Afferent pain fibers from the uterus and cervix accompany sympathetic fibers and enter the spinal cord from T10-L1. Second-stage labor pain originates from the vagina and perineum. Afferent pain fibers from the vagina and perineum course with the pudendal nerves, S2-S4.

(From Stoelting RK, Miller RD. Basics of anesthesia, 3rd ed. New York: Churchill Livingstone; 1994. p. 364, with permission.)

The second stage of labor is associated with perineal and vaginal distention mediated by spinal segments S2-S4. Epidural, spinal, and caudal anesthetics are also effective during the second stage of labor. In addition, pudendal nerve blocks can be used for second-stage analgesia.

Epidural analgesia is the most popular technique for the relief of labor pain. The popularity of epidural analgesia is due to its efficacy. Women can obtain almost complete relief from the pain of labor. From the anesthesiologist’s perspective, because a catheter is threaded into the epidural space, it is also a versatile technique. During the earlier stages of labor, dilute solutions of local anesthetic can be used to achieve analgesia. As labor progresses, a more concentrated solution of local anesthetic may be necessary or an adjunct, such as an opioid, may be needed. Additionally, the epidural catheter can be used to maintain a low dermatomal level of anesthesia for labor (T10-L1) and, when needed, the dermatomal level can be raised to T4 for cesarean section.

Patient-controlled epidural analgesia (PCEA) is a technique that allows the patient to self-administer medication, controlling her own analgesia. Compared with continuous infusion or intermittent bolus techniques, PCEA is associated with lower total dose of local anesthetic, less motor blockade, fewer interventions by anesthesiologists, and greater patient satisfaction. We routinely use PCEA for all our patients.

A commonly used PCEA regimen is bupivacaine 0.0625% and fentanyl 2 μg/mL with the following PCEA settings: basal rate of 10 mL per hour, bolus dose of 5 mL, 10-minute lockout, and maximum of four bolus injections per hour. Theoretical risks of PCEA, such as high dermatomal levels or overdose, have been described in patients undergoing general surgery. Overdose occurs because of catheter migration into the subarachnoid space or from excessive administration by the patient or a family member. To date, these complications have not been reported in the parturient during labor.

Many disadvantages associated with labor epidural analgesia have prompted the search for alternative techniques. One disadvantage is the time it takes to provide analgesia to the patient. The time from epidural catheter placement until the patient is comfortable varies but depending on the local anesthetic used can be 15–30 minutes. Other disadvantages of labor epidural analgesia include maternal hypotension, inadequate analgesia (15%–20% of cases), and motor blockade, even with the very dilute local anesthetic solutions.

Subarachnoid opioids offer rapid, intense analgesia with minimal changes in blood pressure or motor function. Most patients can ambulate with this technique. The opioid is usually administered as part of a CSE technique where a spinal and an epidural are performed at the same time. After locating the epidural space in the usual manner, a long small-gauge spinal needle is inserted through the epidural needle into the subarachnoid space. An opioid (usually fentanyl 25 mcg or sufentanil 5 mcg), either alone or in combination with a local anesthetic, is administered through the spinal needle. The spinal needle is removed, and an epidural catheter is inserted for future use. Analgesia begins within 3–5 minutes and lasts 1–1.5 hours ( Table 54-2 ).

TABLE 54-2

Advantages and Disadvantages of Spinal versus Epidural Anesthesia

	Spinal	Epidural
Advantages	Reliable and rapid onset	Better control of spread
		Mitigates precipitous decrease in blood pressure
		Unlimited duration
Disadvantages	Potential for hypotension Inability to control spread Limited duration Postdural puncture headache	Prolonged time to achieve adequate surgical anesthesia Local anesthetic toxicity

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