- The most common morbidities encountered in
obstetrics are severe hemorrhage and severe preeclampsia.
- Regardless of the time of last oral intake, all
obstetric patients are considered to have a full stomach and to
be at risk for pulmonary aspiration.
- Nearly all parenteral opioid analgesics and sedatives
readily cross the placenta and can affect the fetus. Regional anesthetic
techniques are preferred for management of labor pain.
- Using a local anesthetic–opioid mixture
for lumbar epidural analgesia during labor significantly reduces
drug requirements, compared with using either agent alone.
- Optimal analgesia for labor requires neural blockade
at T10–L1 in the first stage of labor and T10–S4
in the second stage.
- Continuous lumbar epidural analgesia is the most
versatile and most commonly employed technique, because it can be
used for pain relief for the first stage of labor as well as analgesia/anesthesia
for subsequent vaginal delivery or cesarean section, if necessary.
- When dilute mixtures of a local anesthetic and
an opioid are used epidural analgesia has little if any effect on
the progress of labor.
- Even when aspiration does not yield blood or
cerebrospinal fluid, unintentional intravascular or intrathecal
placement of an epidural needle or catheter is possible.
- Hypotension is the most common side effect of
regional anesthetic techniques and must be treated aggressively
with ephedrine and intravenous fluid boluses to prevent fetal compromise.
- Techniques using combined spinal epidural analgesia
and anesthesia may particularly benefit patients with severe pain
early in labor and those who receive analgesia/anesthesia
just prior to delivery.
- Spinal or epidural anesthesia is preferred to
general anesthesia for cesarean section because regional anesthesia
is associated with lower maternal mortality.
- Spinal anesthesia for cesarean section is easier
to perform and results in more rapid and intense neural blockade
than epidural anesthesia. Epidural anesthesia allows greater control
over sensory level and results in a more gradual fall in arterial
- Systemic, local anesthetic toxicity during epidural
anesthesia may be best avoided by slowly administering dilute solutions
for labor pain and fractionating the total dose for cesarean section into
- In general anesthesia for cesarean section,
if endotracheal intubation fails, the life of the mother takes priority
over delivery of the fetus.
- Maternal hemorrhage is one of the most common
severe morbidities complicating obstetric anesthesia. Causes include
placenta previa, abruptio placentae, and uterine rupture.
- Pregnancy-induced hypertension describes one
of three syndromes: preeclampsia, eclampsia, and the HELLP syndrome.
- Common causes of postpartum hemorrhage include
uterine atony, a retained placenta, obstetric lacerations, uterine
inversion, and use of tocolytic agents prior to delivery.
- Intrauterine asphyxia during labor is the most
common cause of neonatal depression. Fetal monitoring throughout
labor is helpful in identifying which babies may be at risk, detecting
fetal distress, and evaluating the effect of acute interventions.
Obstetric anesthesia is a demanding but gratifying subspecialty
of anesthesiology. The widespread acceptance and use of regional
anesthesia for labor has made obstetric anesthesia a major part
of most anesthetic practices. The guidelines of the American College
of Obstetricians and Gynecologists and American Society of Anesthesiologists
require that anesthesia service be readily available continuously
and that cesarean section be started within 30 min of the recognition
for its need. Moreover, high-risk patients, such as those undergoing
a trial of vaginal birth after a previous cesarean delivery (VBAC),
may require the immediate availability of anesthesia services.
Although most parturients are young and healthy, they nonetheless
represent a high-risk group of patients for all the reasons discussed
in the preceding chapter.
This chapter focuses on the practice of obstetric anesthesia;
techniques for analgesia and anesthesia during labor, vaginal delivery,
and cesarean section are presented. The chapter ends with a review
of neonatal resuscitation. The suggested procedures are intended
to serve only as guidelines consistent with our current understanding
of maternal and fetal physiology.
To understand anesthetic risk in obstetric patients it is important
first to fully appreciate obstetric risk in general. Although the
majority of women of childbearing age are healthy and would be considered
to be at very good operative surgical risk, pregnancy, certain maternal/fetal
factors, and preexisting medical conditions significantly increase
surgical and obstetric risks.
Pregnancy-related mortality is usually calculated as the number
of pregnancy-related deaths divided by the number of live births.
Although this number has decreased nearly 100-fold since 1900, it
has not changed appreciably since 1982. In fact, perhaps due to
better reporting, it has risen slightly in the United States to
11.8 deaths per 100,000 live births in the period 1991–1999. Roughly
similar rates (between 6.1 and 12 per 100,000) have been reported
from Canada and the United Kingdom. Figure 43–1A shows
cause of death based on the Pregnancy Mortality Surveillance System
of the Centers for Disease Control. Overall mortality was higher
for women > 35 years old, black patients, and patients without prenatal
care. The leading causes of death associated with a live birth were
pulmonary embolism (21%), pregnancy-induced hypertension
(19%), and other medical conditions (17%). Major
causes of death associated with a stillbirth were hemorrhage (21%),
pregnancy-induced hypertension (20%), and sepsis (19%).
Only 34% of patients died within 24 h of delivery, whereas
55% died between 1 and 42 days, and another 11% died
between 43 days and 1 year.
A: Causes of pregnancy-related
mortality, based on data from the Centers for Disease Control and Prevention.
Medical conditions exacerbated by pregnancy were primarily cardiovascular,
pulmonary, and neurological diseases. (Deaths associated with undelivered,
ectopic, and molar pregnancies as well as abortions are excluded.) B: Direct
causes of maternal deaths, based on Maternal and Infant Health Section–PPHB–Health Canada
from http://www.hc-sc..ca/ (Excludes
Quebec). Data for ectopic pregnancy and septic abortion have been
excluded. PIH, pregnancy-induced hypertension.
Direct causes of maternal deaths are more clearly detailed from