Anesthesia for Non-Obstetric Surgery in Pregnancy

1. Anesthesia forNon-Obstetric Surgery in Pregnancy Joe Dietrick, CRNA, M.A. Have A Nice Day Anesthesia, LLC Chillicothe, MO

2. Objectives • Identify the most common procedures • Identify factors of: maternal safety, fetal teratogenicity, intrauterine asphyxia, & preterm labor • Intraoperative FHR monitoring • Laparoscopic surgery • Anesthetic management

3. Introduction(1 of 3) • Surgeon’s approach to surgery in pregnancy: • 1990: If medical or surgical treatment plan usually followed for a nonpregnant woman is altered because of pregnancy, there must be strong justification for its modification. • Occurrence: Approx 50K/yr (1-2%)

4. Introduction(2 of 3) • Most common procedures5: • Appendectomy • Cholecystectomy • Ovarian disorders • Trauma • Breast / cervical dz • Bowel obstruction

5. Introduction(3 of 3) • 4 Areas of Unique Concern: • Maternal safety • Fetal teratogenicity • Intrauterine fetal asphyxia • Preterm labor • Appropriate anesthetic care will require understanding of the current knowledge of these areas.

6. Maternal SafetySignificant changes after 1st trimester • Uterine enlargement • AO/VC compression: LUD > 20 wks • Respiratory • Increased VO2 + decreased reserve risks HYPOxia • Chronic resp alkalosis (PaCO2 ≈ 32) • Potential AW difficulty • CNS • Up to 40% decrease in MAC • Increased LA sensitivity • GI • Increased aspiration risk from physical and biochemical changes > 18-20 wks

7. Teratogenicity: general • Fetal risk: • 0-15d  usually embryotoxic (EGA 2-4 wks) • 15-60d (organogenesis)  great risk to fetus. • 31-71d EGA (4-10 wks) • Then functional deficits • Nearly all drugs have been demonstrated to be teratogenic in some species at some dose.

8. Teratogenicity: Research Issues • Difficulty in applying animal & human studies to practice: • Variations in susceptibility between species • Human studies are retrospective • Difficulty in controls • Confounding multiple variables • Small numbers inadequate for statistical significance

9. Teratogenicity: BZD, Opioids • BZD/minor tranquilizers: • Associated with increased anomalies • BZD • Initally associated with increased cleft palates • Later studies: no relationship • FDA (1975): minor tranquilizers should almost always be avoided in 1st trimester • Single dose: no effect • Synthetic opioids: animal studies not teratogenic

10. Teratogenicity: MR, LA • Muscle relaxants: • minimal placental transfer • Local Anesthetics: • Lidocaine used in PG rats w/o complication • No evidence of problems in humans • Cocaine is a known teratogen • IUGR, preterm delivery, and increased risk of abruptio placentae

11. Teratogenicity: Induction Agents • Induction Agents: • Ketamine – not teratogenic • >1 mg/kg  ↑risk of preterm labor • Thiopental – not teratogenic in conventional doses • Propofol in pregnant ewe1 • No adverse fetal effects compared to thiopental • Propofol + Succinylcholine demonstrated cases of severe maternal bradycardia in ewe

12. Teratogenicity: N2O • N2O: • Theoretical risk is decreased but reversible DNA synthesis • Pretreatment with folinic acid is not proven effective in preventing neurogenic teratogenicity in animals • Conclusion • Teratogenic only under extreme conditions; however, slightly increased abortion risk?

13. Teratogenicity: Inhalation Agents • Volatile anesthetics: • Shown teratogenic in some species • VA + N2O in PG rats showed no anomalies at any gestational age • Like N2O, slightly increased risk of abortion?

14. Teratogenicity: non-drug factors • Anesthesia &/or surgery may cause • HYPOxia • HYPOtension • HYPERcapnia • ↑ temp • ↑ / ↓ BS • Effects may be teratogenic With a critical event, pose greatest fetal risk

15. Intrauterine Fetal Asphyxia(1 of 4) • Avoided by maintaining the following variables of fetal respiration • Maternal oxygenation • Maternal carbon dioxide tension • Uterine blood flow

16. Intrauterine Fetal Asphyxia(2 of 4) • Maternal oxygenation • HYPOxia can occur with either regional or general anesthesia • HYPERoxia does not promote either fetal HYPOxia from UA constriction, or retrolental fibroplasia • Fetal pO2 <=60 due to maternal/placental mismatch and high placental VO2

17. Intrauterine Fetal Asphyxia(3 of 4) • Maternal CO2 • Fetal CO2 related to maternal level • HYPOcapnia • Increased ventilation may reduce venous return or provoke UA vasoconstriction, and cause a fall in UBF • Alkalosis reduces release of O2 from maternal hemoglobin • Target EtCO2≈ 32-34 mmHg

18. Intrauterine Fetal Asphyxia(4 of 4) • Uterine blood flow • HYPOtension may be caused by • anesthetics (GA or RA) • AO/VC compression • Vasoconstriction may be caused by endogenous or exogenous sympathetic activity, including injection of ketamine (> 2mg/kg) • Neostigmine (anti-Ach-ase) • Glyco, then slow admin with FHR monitoring

19. Preterm Labor(1 of 2) • Anesthetic effect on preterm labor unknown • Surgical procedures in abdomen and especially near uterus are associated with preterm labor • >24 wks: 22% delivered 1st week post-op appendectomy (1991, N=778)

20. Preterm Labor(2 of 2) • Pre-emptive pro-gestational drugs • Have not been demonstrated effective at preventing preterm labor or abortion • Ketamine, vasopressors, & anticholinesterases • increase uterine tone and therefore increase risk. • Volatile agents • decrease uterine tone & may have benefit

21. Intraoperative FHR monitoring • Horrigan, et al (1999)2 reviewed 12 articles • Conclusion: 20 years experience  no documented evidence that FHR monitoring intraoperatively is required. • Letter in response, by Kendrick & Neiger • 18 cases, 10 non-cardiac • Uterine activity requiring tocolysis 3/10 • One episode of bradycardia assoc. with EBL • Must individualize decision

22. ACOG Opinion # 474 (02/2011)3 • “The decision to use fetal monitoring should be individualized and, if used, should be based on gestational age, type of surgery, and facilities available. Ultimately, each case warrants a team approach (anesthesia and obstetric care providers, surgeons, pediatricians, and nurses) for optimal safety of the woman and the fetus.”

23. More detail…3 • If FHR used: • + Neonatal/ped serv • CS capability available • Qualified individual for FHR interpretation • When • Previable: FHR before & after • Viable: FHR & Toco before & after (minimum)

24. Intraoperative FHR?3 • The fetus is viable. • It is physically possible to perform intraoperative electronic fetal monitoring. • A health care provider with obstetric surgery privileges is available and willing to intervene during the surgical procedure for fetal indications. • When possible, the woman has given informed consent to emergency cesarean delivery. • The nature of the planned surgery will allow the safe interruption or alteration of the procedure to provide access to perform emergency delivery.

25. Laparoscopic Surgery4 • No difference in indications • Timing • Elective – avoid • Optimal – Early 2nd trimester • Performed as late as 34 wks EGA • Initial trocar approach • No difference between open & blind • Midline: ≥ 6 cm above fundus

26. Laparoscopic Surgery4 • Adverse effects of CO2 insufflation: • Maternal  fetal acidosis • Pneumoperitoneum 8 – 12 mmHg (< 15) • Avoid: N2O (or < 50%), extreme position • EtCO2 32 -34 mmHg • Hyperventilation deleterious

27. MAC Issues5 • Risk of hypoventilation  fetal acidosis • Difficulty in evaluating resp status • Potential difficulty with emergent AW •  risk of aspiration • Compounded by co-existing morbidities

28. Plan5 • Timing • Avoid if possible • Risk vs benefit; OB consult • Non-emergent: early/mid 2nd trimester • Perioperative monitoring • Con’t FHR & uterine activity if possible. • FHR >18 wks6 or > 23 wks • Ability to perform emergent CS • Plan action for persistent fetal ↓ HR

29. Plan5 • Anesthesia • Both GA & RA used • Maintaning variables of fetal well-being most important • Regional generally preferred • > 16 wks • Aspiration prophylaxis • Resolve dehydration / hypovolemia • LUD • Maintain variables of fetal well-being

30. Plan5 • Pneumatic compression devices perioperatively • Postoperative management • Opiates & antiemetics as needed • Avoid NSAIDs, esp >32 weeks • Emergent delivery • Effects of anesthetics may require neonatal support • Muscle relaxants do NOT cross placenta

31. FDA Pregnancy Categories

32. References Unless otherwise noted all information is from the OB text: • Naughton, N & Cohen, S. (2004). Non-obstetric Surgery in Pregnancy. In Chestnut, D. (Ed), Obstetric Anesthesia, Principles & Practice, 3rd Ed ( Pg 255-272) Other references • Alon, et al. Effects of propofol and thiopental on maternal and fetal cardiovascular and acid-base variables in the pregnant ewe. Anesthesiology. 1993 Mar;78(3):562-76 • Horrigan TJ, Villarreal R, Weinstein L. Are obstetrical personnel required for intraoperative fetal monitoring during nonobstetric surgery? J Perinatol. 1999 Mar;19(2):124-6. • ACOG Committee Opinion Number 284: Non-obstetric surgery in pregnancy. Obstet Gynecol. 2011;117:420-21. • Stany, M, et al. Laparoscopic surgery in pregnancy. Retrieved 04/01/2011) from UpToDate. Website: http://www.uptodate.com/contents/laparoscopic-surgery-in-pregnancy?source=search_result&selectedTitle=1%7E150 • Norwitz, E., & Joong, S. Management of pregnant women undergoing non-obstetric surgery. Retrieved 04/01/2011) from UpToDate. Website: http://uptodateonline.com/online/content/topic.do?topicKey=pregcomp/21735&selectedTitle=1~150 • Ni Mhuircheartaigh RN, O’Gorman DA. Anesthesia in the pregnant patient for non-obstetric surgery. J Clin Anesth 2006;18:60- 6.