Whereas analgesia for the first stage of labor (pain caused by uterine contractions) is provided by block of T10 to L1, analgesia for the second stage of labor (pain caused by distention of the perineum) is provided by block of S2 to S4.

1. Nonpharmacologic methods of labor analgesia (massage, aromatherapy, hydrotherapy, biofeedback, transcutaneous electrical nerve stimulation, acupuncture, hypnosis) remain unproven for efficacy.
2. Other Nonpharmacologic Methods. Continuous labor support is the presence during labor of nonmedical support by a trained person (shorter labors, fewer operative deliveries, fewer analgesic interventions).
3. Systemic Medication. The time and method of administration must be chosen carefully to avoid maternal and neonatal depression.
   1. Opioids
      1. Meperidine appears to produce less neonatal ventilatory depression than does morphine. Meperidine administered intravenously (IV) (analgesia in 5–10 minutes) or intramuscularly (peak effect in 40–50 minutes) rapidly crosses the placenta.
      2. Fentanyl (1 µg/kg IV) provides prompt pain relief (during forceps application) without severe neonatal depression. For more prolonged analgesia, fentanyl or remifentanil may be administered with patient-controlled delivery devices.
      3. Naloxone (10 µg/kg IV) may be administered directly to newborns to reverse excessive opioid depression.
   2. Ketamine (0.2–0.4 mg/kg IV) provides adequate analgesia without producing neonatal depression.
4. Regional Anesthesia. Regional techniques (central neuraxial blockade [spinal, epidural, combined spinal–epidural]) provide excellent analgesia with minimal depressant effects in the mother and fetus. Hypotension resulting from sympathectomy is the most frequent complication that occurs with central neuraxial blockade. (Maternal systemic blood pressure is typically monitored every 2 to 5 minutes for about 15 to 20 minutes after the initiation of the block and at regular intervals thereafter.) Regional analgesia may be contraindicated in the presence of coagulopathy, acute hypovolemia, or infection at the needle insertion site (chorioamnionitis without frank sepsis is not a contraindication). There is no difference in the rate of cesarean delivery in women receiving early neuraxial analgesia compared with systemic opioid analgesia.
   1. Epidural analgesia may be used for pain relief during labor and vaginal delivery and may be converted to anesthesia for cesarean delivery if required.
      1. Effective analgesia during the first stage of labor may be achieved by blocking the T10 to L1 dermatomes with dilute concentrations of local anesthetic with or without the use of opioids that have their effect at the opioid receptors in the dorsal horn of the spinal cord (Table 40-4: Tests to Rule out Intrathecal or Intravascular Placement of a Lumbar Epidural Catheter). For the second stage of labor and delivery, because of pain from vaginal distention and perineal pressure, the block should be extended to include the S2 to S4 segments.
      2. The first stage of labor may be slightly prolonged by epidural analgesia, but this is not clinically significant provided aortocaval compression is avoided. Epidural analgesia initiated during the latent phase of labor (2–4 cm cervical dilation) does not result in a higher incidence of dystocia or cesarean section.
      3. Prolongation of the second stage of labor by epidural analgesia (presumably related to loss of the urge to push by the patient) may be minimized by the use of an ultra-dilute concentration of local anesthetic in combination with an opioid.
      4. Analgesia for the first stage of labor may be achieved with 5 to 10 mL of bupivacaine, ropivacaine, or levobupivacaine (0.125%–0.25%) followed by continuous infusion (8–12 mL/hr) of 0.0625% bupivacaine or levobupivacaine or 0.1% ropivacaine. The addition of 1 to 2 µg/mL of fentanyl (or 0.3–0.5 µg/l mL of sufentanil) permits a more dilute local anesthetic solution to be administered. During delivery, the sacral dermatomes may be blocked with 10 mL of 0.5% bupivacaine or 1% lidocaine or if a rapid effect is needed, 2% chloroprocaine may be administered in the semirecumbent position.
      5. Patient-controlled epidural analgesia is an alternative to bolus or infusion techniques.
   2. Spinal Analgesia
      1. A single subarachnoid injection for labor analgesia has the advantages of a reliable and rapid onset of neuraxial blockade.
      2. Spinal analgesia with 10 µg of fentanyl or 2 to 5 µg of sufentanil alone or in combination with 1 mL of isobaric bupivacaine 0.25% may be appropriate in multiparous patients whose anticipated course of labor does not warrant a catheter technique.
      3. Spinal anesthesia (“saddle block”) is a safe and effective alternative to general anesthesia for instrumental delivery.
      4. There is a risk of postdural puncture headache, and the motor block may be undesirable.
   3. Combined Spinal–Epidural Analgesia
      1. Combined spinal–epidural analgesia is an ideal analgesic technique for use during labor because it combines the rapid onset of profound analgesia (spinal injection) with the flexibility and longer duration of epidural techniques.
      2. After identification of the epidural space, a long pencil-point spinal needle is advanced into the subarachnoid space through the epidural needle. After intrathecal injection (10–20 µg of fentanyl or 2.5–5 µg of sufentanil alone or in combination with 1 mL of bupivacaine 0.25% produces profound analgesia lasting 90 to 120 minutes with minimal motor block), an epidural infusion of bupivacaine 0.03% to 0.625% with added opioid is started.
      3. Women with hemodynamic stability and preserved motor function who do not require continuous fetal monitoring may ambulate with assistance. (Walking has little effect on the course of labor.)
      4. The most common side effects of intrathecal opioids are pruritus, nausea, vomiting, and urinary retention. The risk of postdural puncture headache does not seem to be increased. Fetal bradycardia may occur.
      5. The incidence of emergency cesarean delivery is no greater after combined spinal–epidural analgesia than after conventional epidural analgesia.
      6. This technique should be used with caution in women who may require an urgent cesarean section and women who are at most increased risk (morbidly obese, difficult airway).
   4. A paracervical block interrupts transmission of nerve impulses from the uterus and cervix during the first stage of labor.
   5. A pudendal nerve block may provide anesthesia for outlet forceps delivery and episiotomy repair.

Obstetrical Anesthesia

1. Physiologic Changes of Pregnancy
2. Placental Transfer and Fetal Exposure to Anesthetic Drugs
3. Anesthesia for Labor and Vaginal Delivery
4. Anesthesia for Cesarean Delivery
5. Anesthetic Complications
6. Management of High-Risk Parturients
7. Preterm Delivery
8. Human Immunodeficiency Virus and Acquired Immunodeficiency Syndrome
9. Substance Abuse
10. Fetal Monitoring
11. Newborn Resuscitation in the Delivery Room
12. Anesthesia for Nonobstetric Surgery in Pregnant Women