Clinical obstetric anesthesia is most commonly associated with delivery of an infant; however, there are a number of other obstetric procedures and surgeries where the use of anesthesia can optimize maternal and fetal outcomes. Miscarriage or termination of pregnancy may occur in up to 30% of pregnancies, and when accompanied by retained fetal or placental tissues, removal is accomplished with a dilation and curettage (D&C) or dilation and evacuation (D&E); these typically occur within the first 12 weeks following conception. Between 1% and 2% of pregnancies are associated with an incompetent cervix; a minority of these cases will require cervical cerclage, which is typically placed during the second trimester. Percutaneous umbilical blood sampling (PUBS) is most commonly performed in the second or third trimester for fetal indications, and late in the third trimester, external cephalic version may be attempted to turn a breech fetus into the cephalic position. Tubal ligations are most frequently performed within the first 48 hours’ postpartum, with a second peak occurrence at 6 to 8 weeks’ postpartum, when most of the pregnancy-related changes have resolved. Knowledge of the anatomic and physiologic alterations with different stages of pregnancy, as well as the relevant innervation (Figure 13-1), can optimize the planning and conduct of anesthesia; such knowledge will improve the ability of these procedures to be conducted safely and successfully, and augment the patients’ experience, comfort, and satisfaction.
Innervation (and relevant obstetric procedure) of the female reproductive organs. The fallopian tubes (tubal ligation) are innervated by T11–L1 via the hypogastric nerves. The uterus (cerclage, dilation and curettage or dilation and evacuation, and external cephalic version) is innervated by T10–L1 and S2–S4 by the uterovaginal and sacral plexus. The umbilical cord (percutaneous umbilical blood sampling) has been observed to be devoid of innervation. Relevant sensory blockade by local, regional, or neuraxial anesthesia techniques may need to include additional sensory levels to account for the placement of surgical instrumentation and the possibility for referred pain.
POSTPARTUM TUBAL LIGATION
Tubal ligation is a highly effective form of permanent sterilization and is among the most popular methods of contraception in the United States. Data from the National Survey of Family Growth for the 2006-2008 period showed that 21% of married women have undergone a tubal ligation procedure.1 However, there has been a recent decline in tubal sterilization rate, possibly explained by improved alternative long-acting and reversible methods of contraception.
Tubal ligation can be performed either in the immediate postpartum period or at any time unrelated to pregnancy (ie, interval sterilization). Tubal sterilization in the early postpartum period has several advantages over an interval sterilization: