Anesthesia for Nonobstetric Surgery in the pregnant patient

1. Anesthesia for Nonobstetric Surgery in the pregnant patient October 21, 2003 Ri 黃雅萍 卓岱慶 / R3 彭育仁 / VS 王永彬

2. Basic Data • Name : 粘 x x • Age : 39-year-old • Gender : Female • High and weight: 162 cm & 43 kg • Past history: denied any systemic disease • Family history: her father was a cancer patient

3. Brief History (I) • Last menstrual period was on July 6, 2003 • Pregnancy with G1P0 was confirmed in July. • Sonography: • a left ovarian cystic tumor in size of 9.4cm * 5.4cm. • with septum and hair-like and dirty material inside. • Tumor size was enlarged to 11.3cm *6.89cm in Oct. • Admission for operation on Oct 13. • Operation was performed on Oct 14.

4. Brief History (II) • Anesthesia • Spinal anesthesia with an epidural catheter inserted. • 麻醉紀錄

6. Brief History (III) • Operation • Left salpingo-oophoectomy • Incidental appendectomy. • Pathology • Mucinous cystadenoma. • Postoperative analgesia • Epidural morphine injection for pain control • She was discharged on Oct 17.

7. Discussion

9. Goals Maternal consideration • Maternal safety Fetal consideration • Avoiding fetal asphyxia • Maintain uterine perfusion and fetal oxygenation • Anesthesia agent teratogenicity • Prevention of preterm labor • Inhibit uterine contraction

10. Maternal consideration

11. Maternal safety (I) Respiratory System • ↑Minute ventilation, and ↓RV, FRC • ↓Oxygen reserve • Develop hypoxia and hypercapnia more rapidly with hypoventilation or apnea • Airway management by mask, or tracheal intubation can be technically difficult. • Increased anteroposterior chest wall diameter, breast enlargement, laryngeal edema, and weight gain • Affects the soft tissues of the neck

12. Maternal safety (II) Cardiovascular System • ↓ Blood pressure • ↑Plasma volume, cardiac output • ↓ Peripheral vascular resistance and placenta resistance • Hypotensive syndrome is associated with supine positionsince mid-gestation • ↑Aortic and venal cava compression • Physiologic compensation for aortocaval compression can be compromised by anesthetic techniques

13. Maternal safety (III) Gastrointestinal System • ↑Risk for gastric acid aspiration with anesthetic induction or unconscious sedation. • ↓Gastroesophageal sphincter tone • Gastric motility is impaired by opioid administration, onset of labor, pain, trauma, and so forth.

14. Maternal safety (IV) Responses to Anesthesia Drugs • ↓Anesthetic requirements • ↓MAC since 8 or 12 wks gestation • ↓Intravenous drugs for induction of GA • ↓Dose of spinal or epidural local anesthetics • ↓Volume of the spinal or epidural space • Higher incidence of dural puncture • Maternal never fibers are more sensitive

15. Fetal considerations

16. Avoiding fetal asphyxia (I) • Avoided to decrease uterine blood flow or its oxygen content • Adequate oxygenation • Avoid excessive maternal mechanical hyperventilation • Avoid vasoactive medication • Fetal and uterine monitor

17. Avoiding fetal asphyxia (II) Adequate oxygenation • The asphyxiated fetus cannot increase oxygen extraction • Maternal administration of increased inspired oxygen will increase fetal oxygenation • Fetus is never at risk for hyperoxia.

18. Avoiding fetal asphyxia (III) Avoid maternal mechanical hyperventilation • Hyperventilation can reduce venous return and thereby cardiac output, which reduces uterine blood flow.

19. Avoiding fetal asphyxia (IV) Avoidvasoactivemedication • The uterine circulation is not autoregulated and remains sensitive to vasopressors. • Vasoactive medication reduces uterine blood flow • Uterine displacement, fluid bolus, Trendelenburg position, leg elevation, the use of compression stockings, or any combination of these may be used for maternal hypotension. • Ephedrine remains first choice for maternal hypotension.

21. Summary (I) Maternal safety • Develop hypoxia and hypercapnia more rapidly with hypoventilation or apnea • Airway management can be technically difficult. • Supine Hypotensive syndrome • ↑Risk for gastric acid aspiration • ↓Anesthetic requirements • ↓Dose of spinal or epidural local anesthetics

22. Summary (II) Avoiding fetal asphyxia • Adequate oxygenation: Fetus is never at risk for hyperoxia. • Avoid excessive maternal mechanical hyperventilation • Avoid vasoactive medication • Fetal and uterine monitor

23. Teratogenicity (I) • Teratogen:A substance causes an increase in the incidence of a particular defect in a fetus that cannot be attributed to chance. • Congenital anomalies in humans:3% • Most vulnerable period to teratogenic effects:Organogenesis takes place between the 15th to 56th days of gestation. • Exceptions:Central nervous system continues to develop even after birth.

24. Teratogenicity (II) • Most commonly used anesthetic and sedative drugs are teratogenic in some animal species (in larger doses than used clinically). • Careful, well-controlled human teratogenicity studies are nearly impossible to perform. • All surveys of women who have received anesthesia for operations during pregnancy have failed to indict any anesthetic as a teratogen. • It is not clear whether the hazard is due to the surgery or the anesthetic.

25. Teratogenicity (III) • Nitrous oxide: Most controversial inhalation anesthetic in terms of safe use during pregnancy. • Nitrous oxide →inhibit methionine synthetase → impair DNA synthesis. • Fetal methionine synthetase ↓, Miscarriage rate ↑, impaired growth and poor skeletal development after maternal exposure to greater than 50% nitrous oxide over prolonged periods in animal model. • Other volatile anesthetics: There is no evidence of teratogenicity.

26. Teratogenicity (IV) • BZD: Use of BZD during pregnancy also provide conflicting results. • Maternal use of BZD (meprobamate, chlordiazepoxide and diazepam) showed an association with higher incidence of oral clefts, cleft lip and palate in some studies. • Avoid BZD use throughout gestation and most especially during the first trimester.

27. Teratogenicity (V) • Local anesthetics: No teratogenic effect in human. • Local anesthetics may have minor neurobehavioral effects on the early neonate, but they are not likely to be clinically meaningful. • Opioids: No teratogenic effect in human when used in limited dose in the perioperative period. • The neonate is at risk of respiratory depression, sedation and psychomotor impairment only when delivery occurs at the same time as the surgery.

28. Teratogenicity (VI) • Muscle relaxants: No teratogenic effect in human and do not cross the placenta to any significant extent. • Induction agents: Thiopental can cause neonatal sedation and decreased fetal heart rate variability. (not likely to be clinically meaningful) • Oxygen and Carbon dioxide: Hypoxia has been showed to be teratogenic in animal model. • Hypercapnia can interfere with fetal development.

29. Prevention of Preterm Labor • Increased incidence of spontaneous abortion, premature labor, and preterm delivery may be due to surgery itself. • The lowest risk for preterm labor: During the 2th trimester and for surgeries that not manipulate the uterus. • Halogenated anesthetics can produce uterine relaxation and decreased myometrial irritability, may be beneficial. • Prophylactic use of tocolytic agents: No proof of efficacy.

30. Summary(I) • Specific risk of anesthetic techniques are no able to be defined. • Primary goal: Decrease fetal drug exposure. • The drugs for general anesthesia: Should have a long history of safety. • Regional anesthesia are preferred than general anesthesia. • Spinal anesthesia was preferred than epidural anesthesia due to lower dosage.

31. Summary(II) • The biggest risk of spinal anesthesia during pregnancy: Hypotension→ Uterus blood flow and perfusion of fetus↓ • Ephedrine: Drug of choice for this situation. • Elective surgery: Should not be performed. • The optimal time for necessary surgery: The 2th trimester. • The primary goal is always to preserve the life of the mother first. • Fetal and uterine monitoring: Intra- and post-op

32. Thanks for your attention!