Anesthesia for NonObstetric Surgery in Pregnancy Joe Dietrick

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

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

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 50 K/yr (1 -2%)

Introduction (2 of 3) • Most common procedures 5: – Appendectomy – Cholecystectomy – Ovarian disorders – Trauma – Breast / cervical dz – Bowel obstruction

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.

Maternal Safety Significant changes after 1 st trimester • Uterine enlargement – AO/VC compression: LUD > 20 wks • Respiratory – Increased VO 2 + decreased reserve risks HYPOxia – Chronic resp alkalosis (Pa. CO 2 ≈ 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

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

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

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 1 st trimester – Single dose: no effect • Synthetic opioids: animal studies not teratogenic

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

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

Teratogenicity: N 2 O • N 2 O: – 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?

Teratogenicity: Inhalation Agents • Volatile anesthetics: – Shown teratogenic in some species – VA + N 2 O in PG rats showed no anomalies at any gestational age – Like N 2 O, slightly increased risk of abortion?

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

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

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 p. O 2 <=60 due to maternal/placental mismatch and high placental VO 2

Intrauterine Fetal Asphyxia (3 of 4) • Maternal CO 2 – Fetal CO 2 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 O 2 from maternal hemoglobin • Target Et. CO 2 ≈ 32 -34 mm. Hg

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 (> 2 mg/kg) • Neostigmine (anti-Ach-ase) – Glyco, then slow admin with FHR monitoring

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 1 st week post-op appendectomy (1991, N=778)

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

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

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. ”

More 3 detail… • 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)

Intraoperative 3 FHR? • 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.

Laparoscopic Surgery 4 • No difference in indications • Timing – Elective – avoid – Optimal – Early 2 nd trimester • Performed as late as 34 wks EGA • Initial trocar approach – No difference between open & blind – Midline: ≥ 6 cm above fundus

Laparoscopic Surgery 4 • Adverse effects of CO 2 insufflation: – Maternal fetal acidosis – Pneumoperitoneum 8 – 12 mm. Hg (< 15) • Avoid: N 2 O (or < 50%), extreme position • Et. CO 2 32 -34 mm. Hg – HYPERventilation deleterious

MAC Issues 5 • • • Risk of HYPOventilation fetal acidosis Difficulty in evaluating resp status Potential difficulty with emergent AW risk of aspiration Compounded by co-existing morbidities

Plan 5 • Timing – Avoid if possible – Risk vs benefit; OB consult – Non-emergent: early/mid 2 nd trimester • Perioperative monitoring – Con’t FHR & uterine activity if possible. • FHR >18 wks 6 or > 23 wks • Ability to perform emergent CS • Plan action for persistent fetal ↓ HR

Plan 5 • 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

Plan 5 • 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

FDA Pregnancy Categories

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, 3 rd Ed ( Pg 255 -272) Other references 1. 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 2. 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. 3. ACOG Committee Opinion Number 284: Non-obstetric surgery in pregnancy. Obstet Gynecol. 2011; 117: 420 -21. 4. Stany, M, et al. Laparoscopic surgery in pregnancy. Retrieved 04/01/2011) from Up. To. Date. Website: http: //www. uptodate. com/contents/laparoscopic-surgery-inpregnancy? source=search_result&selected. Title=1%7 E 150 5. Norwitz, E. , & Joong, S. Management of pregnant women undergoing non-obstetric surgery. Retrieved 04/01/2011) from Up. To. Date. Website: http: //uptodateonline. com/online/content/topic. do? topic. Key=pregcomp/21735&selected. Title=1~1 50 6. Ni Mhuircheartaigh RN, O’Gorman DA. Anesthesia in the pregnant patient for non-obstetric surgery. J Clin Anesth 2006; 18: 60 - 6.