Regional techniques during pregnancy and delivery

Perspectives

The anesthesia care of obstetric patients is dominated by regional anesthesia and analgesia, primarily neuraxial techniques (spinal, epidural, combined spinal-epidural). The anesthetic care of the obstetric patient must also consider effects on the fetus/neonate. In general, neuraxial compared to systemic analgesia/anesthesia results in less drug transfer across the placenta to the fetus.

Neuraxial analgesia is the only analgesic technique that can provide complete analgesia for labor and vaginal delivery. Given that labor lasts a variable duration (less than an hour to several days), a continuous technique is optimal. Neuraxial labor analgesia is typically initiated with a bolus injection of local anesthetic combined with a lipid-soluble opioid into the subarachnoid or epidural space. An epidural catheter (rarely a spinal catheter) is sited and used to maintain analgesia throughout labor and delivery. Other regional techniques and nerve blocks may be performed, often by the obstetrician (bilateral paracervical blocks, bilateral pudendal nerve blocks), but these techniques are not continuous and do not provide complete analgesia. Paracervical blocks provide analgesia for the first stage of labor, when pain impulses originate from the cervix and lower uterine segment. Pudendal nerve blocks are useful for the second stage of labor as the fetus descends in the birth canal, when pain originates from the vagina and perineum. Only neuraxial analgesia can block these pain impulses simultaneously.

Neuraxial anesthesia is considered the optimal technique for cesarean delivery, both scheduled and intrapartum deliveries. Advantages compared with general anesthesia include: 1) it is safer for the mother (no need to manipulate the airway), 2) less drug(s) crosses the placenta and depresses the fetus/neonate, and 3) it allows the mother to be awake and father to be present for the delivery of their child. Single-shot spinal anesthesia is frequently used for elective procedures. Combined spinal-epidural anesthesia is used when long case duration is anticipated (e.g., repeat procedure, obese body habitus). Epidural anesthesia is a common technique for intrapartum cesarean delivery in women who have an indwelling epidural catheter sited for labor analgesia; epidural analgesia is transitioned to epidural anesthesia .

Postcesarean delivery analgesia is most often provided using multimodal analgesia—a common component of multimodal analgesia is single-shot neuraxial morphine analgesia. In women who are not able to receive neuraxial morphine (e.g., general anesthesia is used), the transversus abdominal plane block (see Chapter 36 ), and the quadratus lumborum block (see Chapter 38 ) have been shown to supplement systemic analgesia. However, these blocks do not improve the analgesia provided by neuraxial morphine and are therefore not indicated in women who receive spinal or epidural morphine.

Patient selection

Most obstetric patients are candidates for neuraxial analgesia/anesthesia. Contraindications mimic those for nonpregnant patients. Absolute contraindications include patient refusal, coagulopathy, infection at the site of needle placement, and uncorrected maternal hypotension (e.g., in the setting of hemorrhage). Systemic infection is a relative contraindication, although most clinicians will proceed with a neuraxial technique once antibiotics have been administered and the patient is not exhibiting signs of frank septicemia. Thromboembolic disease is a major cause of maternal morbidity and mortality; thus many pregnant women receive pharmacologic anticoagulation. Guidelines for the initiation of neuraxial procedures in women who have received pharmacologic anticoagulation generally mimic those for the nonobstetric population, although a thorough risk-benefit analysis should be individualized to each patient. Several obstetric conditions are associated with a frank consumptive coagulopathy, including placental abruption and amniotic fluid embolism. Coagulopathy should be ruled out in these women before proceeding with a neuraxial procedure.