1 % –2 % of women will experience a condition requiring surgery during pregnancy. In the early to mid second trimester, procedures requiring anesthesia include insertion of cervical suture for incompe- tent cervix, and an array of nonobstetric operations and procedures (e.g., laparosocopy or laparotomy for acute appendicitis or cholecysti- tis or ovarian cyst accidents, neurosurgery for cerebrovascular events, operations for traumatic or other injury, and oncological operations).
With embryo or fetal demise, evacuation of retained products of conception may be necessary.
Early pregnancy loss (mainly prior to 13 weeks gestation) is common (incidence 15 % –20 % of all pregnancies). Although not all women require evacuation of retained products of conception, this is a very common operation for which general anesthesia is usually provided.
Termination of pregnancy is also a common procedure in some countries, but general anesthesia is used infrequently; sedation, with or without regional anesthesia (e.g., paracervical block), is often deliv- ered by non-anesthesiologists.
Whenever continued fetal viability is desired, and particularly during initial embryo development and organogenesis (days 14 to 56), remember that:
Drugs may have both direct (pharmacologic) and indirect effects on
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the fetus (e.g., vasoactive drugs may affect placental blood fl ow).
Adequate uteroplacental perfusion must be assured by maintaining
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maternal blood pressure and cardiac output and avoiding peripheral vasoconstriction.
Obstetric Anesthesia185 Anesthetic Principles and Management
Epidemiological studies suggest that the risk of loss of a viable preg- nancy, and premature or low birth weight delivery, are increased by surgery but not infl uenced by anesthesia or anesthetic technique.
Other factors that are likely more important are maternal illness and current disease, with fetal loss more likely after operations on the genital tract (e.g., cervical suture), abdomen, or pelvis.
During early pregnancy, the teratogenic and carcinogenic potential of anesthetic or sedative drugs assumes particular importance. The anesthesiologist must understand potential effects of anesthetic and analgesic drugs on pregnancy, so that sound decisions can be made and so that informed consent can be obtained from the patient.
A joint statement on Non-obstetric surgery during pregnancy by the American College of Obstetricians and Gynecologists and the American Society of Anesthesiologists notes: “No currently used anesthetic agents have been shown to have any teratogenic effects in humans when using standard concentrations at any gestational age.”
Midazolam, opioids (e.g., IV fentanyl or remifentanil), propofol and
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the inhalational anesthetic agents are popular and appear safe.
The primary concern during nonobstetric surgery during pregnancy is always the safety of the mother.
Aspiration prophylaxis should be considered based on the gesta-
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tional age; prior to 16 weeks gestation, the risk of aspiration prob- ably does not differ greatly from nonpregnant patients.
Aortocaval compression is a possibility after the uterus rises out of
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the pelvis at approximately 20 weeks gestation (or earlier if multiple pregnancy).
The effect of anesthesia on the fetus remains a prime consideration,
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both up to the time of viability (23–24 weeks gestation) and in the weeks thereafter, when premature delivery has substantial morbid- ity and mortality implications (see Chapter 11); preterm delivery potentially involves costly health care, severe parental psychologi- cal stress, and sometimes lifelong impact on the child’s health.
Whenever possible, elective surgery should be postponed until
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after pregnancy. (Though never demonstrated in humans, drugs have potential nonteratogenic effects on developing fetal organ systems, especially the central nervous system.)
Essential but nonurgent surgery should be deferred until after fetal
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viability (although inevitably, urgent surgery will be mandated by surgical and medical emergencies).
186Anesthesia for Surgery
Fetal monitoring should be considered on a case-by-case basis. Prior to viability, at 22–24 weeks estimated gestational age, ascertaining the fetal heart rate prior to and after surgery is suffi cient. If the fetus is considered viable and the situation allows, expert advice should be sought but simultaneous electronic fetal heart rate and contraction monitoring can be performed before and after the procedure to assess fetal well-being and the absence of contractions.
Intraoperative electronic fetal monitoring may be appropriate when the following apply:
The fetus is viable.
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It is physically possible to perform intraoperative electronic fetal
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monitoring.
A provider with obstetrical surgery privileges is available and willing
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to intervene during the surgical procedure for fetal indications.
The woman has given informed consent to emergency cesarean
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delivery.
Loss of beat-to-beat variability and fetal bradycardia are effects of anesthetic drugs and hypothermia, so interpretation of fetal heart rate patterns requires special expertise.
After fetal death in utero, a coagulopathy may develop over time but does not usually become clinically relevant for 3–4 weeks.
Although not evidence-based, the core principles of anesthesia are listed in Table 6.1 and a management plan outlined in Figure 6.1 .
Table 6.1 Key Principles of Anesthesia from Early to Term Pregnancy
Communicate with the surgeon regarding the urgency of surgery Postpone elective surgery until after pregnancy
If possible, defer non-elective surgery until after fetal viability (22–24 weeks)
During assessment, be aware of the changes resulting from pregnancy and the exposure of the fetus to radiation during imaging
Avoid drugs with potential for fetal harm Avoid drugs that stimulate uterine contractility Maintain normal pregnant physiology
Consider the merit of continuous intraoperative fetal monitoring If suitable, use regional anesthesia whenever possible (to minimize maternal risks and fetal drug exposure)
Provide effective postoperative analgesia