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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

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anesthesia for non obstetric surgery in pregnancy

Anesthesia forNon-Obstetric Surgery in Pregnancy

Joe Dietrick, CRNA, M.A.

Have A Nice Day Anesthesia, LLC

Chillicothe, MO

objectives
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
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%)
introduction 2 of 3
Introduction(2 of 3)
  • Most common procedures5:
    • Appendectomy
    • Cholecystectomy
    • Ovarian disorders
    • Trauma
    • Breast / cervical dz
    • Bowel obstruction
introduction 3 of 3
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
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
teratogenicity general
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.
teratogenicity research issues
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
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
teratogenicity mr la
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
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
teratogenicity n 2 o
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?
teratogenicity inhalation agents
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?
teratogenicity non drug factors
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

intrauterine fetal asphyxia 1 of 4
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
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
intrauterine fetal asphyxia 3 of 4
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
intrauterine fetal asphyxia 4 of 4
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
preterm labor 1 of 2
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)
preterm labor 2 of 2
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
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
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 detail 3
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)
intraoperative fhr 3
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.
laparoscopic surgery 4
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
laparoscopic surgery 426
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
mac issues 5
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
plan 5
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
plan 529
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
plan 530
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
references
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.