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Effects on the fetus and newborn of maternal analgesia and anesthesia

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Effects on the fetus and newborn of maternal analgesia and anesthesia

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    1. Effects on the fetus and newborn of maternal analgesia and anesthesia R1 ??? / AP ??? April 30th, 2009

    2. Outlines Labor pain Analgesic techniques for labor Labor epidurals and outcome Anesthetic techniques for Cesarean section Postpartum pain management

    5. Labor pain

    6. Analgesic techniques for labor Systemic opioids Agonist-antagonist opioids N2O Neuraxial analgesia Opioids Local anesthetics Combining opioids, local anesthetics and pain-relieving adjuvants

    7. Systemic opioids Lipid-soluble weak bases Placental transfer: free, not protein-bound Placental blood flow, degree of maternal protein binding Degree of placental uptake, metabolism and clearance Alter maternal MV or uterine tone

    9. Systemic opioids Decreased baseline FHR and reduce variability Neonatal respiratory depression Decreased neonatal alertness Inhibition of sucking and delay in feeding No sufficient evidence to affect primary and secondary outcome

    10. Systemic opioids Meperidine (Demerol)? Plateau 1-5 hrs Multiple doses: accumulation of normeperidine (T1/2=17-25 hrs, >60hrs in fetus) Respiratory depression: not reversible by naloxone Seizure

    11. Systemic opioids Sufentanil Most lipid soluble(enhence placental transfer) bind to maternal protein conc. rise slowly in fetus, plateau in 45-80 mins Useful in second stage pain relief (fetal delivery < 45 mins) Remifentanil Most rapid onset of peak effect, shortest context-sensitive half-time, greatest clearance conc.? by 50% within 3-5 mins Rapidly cross placenta, metabolized by fetal esterases ? FHR variability. No report of low Apgar scores, or respiratory depression necessitating naloxone use

    12. Systemic opioids Naloxone Reverse respiratory depression Contraindicated for infants of narcotic-dependent mothers Precipitate acute withdrawal and seizure No evidence to ? assisted ventilation or ?admission to special care unit No study on time to spontaneous effective respiration or long-term outcome

    13. Agonist-antagonist opioids Nalbuphine Severe perinatal cardiovascular and respiratory depression Estimated T1/2= 4.1 hrs in neonates Immature hepatic function Buprenorphine Treat opiate-dependent pregnant women Little or no neonatal abstinence syndrome

    14. N2O Readily crosses the placenta Maternal-fetal conc. ratio reach 0.8 within 15 mins No effect on uterine contractions or FHR Not metabolized, quickly eliminated by lung Not affect Apgar scores or sucking behavior

    15. Neuraxial analgesia Neuraxial opioids Affect balance in circulating catecholamines (norepinephrine>epinephrine) due to ?-activation of smooth muscle receptor ? ?Uterine muscle tone and vascular resistance ?FHR due to ?uteroplacental blood flow

    16. Neuraxial analgesia Neuraxial LA Dose-dependent ?Concentrated, ?motor block Fetal malposition, maternal inability to push, instrumental delivery Epidural LA alone v.s. intrathecal opioid alone No differences in maternal and fetal outcomes

    17. Neuraxial analgesia Combining opioids, LA, and pain-relieving adjuvants Different mechanism: Na+ blocking agents, opioid-receptor agonists, ?-adrenergic agonists and/or acetylcholinesterase inhibitors Afford analgesia with minimal motor blockade and other relevant side effects CSE bupivacaine+sufentanil v.s. intrathecal sufentanil alone Equally fast pain relief But no nonreassuring FHR tracings in the former group

    18. Labor epidural and outcome Instrumental vaginal delivery Less in LA+opioid than LA group (Preserve motor tone) Mild neonatal depression in LA+opioid group due to cumulative effect of opioid No difference in 5-min Apgar scores or admission to NICU Maternal fever Altered thermoregulation No ?risk of sepsis

    19. Anesthetic techniques for Cesarean section General anesthesia Regional anesthesia Fetal effects of maternal oxygen administration

    20. General anesthesia Factors affecting neonatal outcomes: Elapsed time between induction and clamping of umbilical cord (< 10 mins) Time from incision to delivery (< 3 mins) Placental transfer of drugs Physical-chemical properties of drugs Characteristics of maternal, placental and fetal circulation Placental anatomy and physiology

    21. GA - Sedatives Midazolam and propofol Longer induction times, lighter plane of anesthesia and lower Apgar scores Thiopental and methohexital Peak in umbilical arteries at 3-5 mins and declines rapidly Little neonatal depression Ketamine should be avoided due to significant maternal hemodynamic changes. Minerva Anestesiol. 2009 Apr;75(4):185-90.

    22. GA - Muscle relaxant Quaternary ammonium ion: across placenta S.C.C. degraded rapidly by plasma cholinesterase Non-depolarizing muscle relaxant 7 to 22% to cross placenta If high dose: ventilation support or reversal agents may be needed

    23. GA - inhalation agents Desflurane and sevoflurane cross placenta and equilibrate more rapidly than isoflurane Potentially more depressed neonate Desflurane: irritating to airway and may result in laryngospasm Desflurane 3% with N2O-O2 Higher desflurane delayed time to sustained respiration in the newborn Isoflurane 0.5% v.s. sevoflurane 1% Similar maternal and neonatal results. Cord gas and Apgar

    24. Regional anesthesia Advantages Less neonatal exposure to drugs Mother participate in birth of baby Better maternal analgesia Disadvantages Hypotension

    25. Regional anesthesia Fetal acidemia Associate with maternal hypotension Not correlated with Apgar scores Poor outcome indicator Base excess: correlated with neonatal outcome BE < -12 mmlol/L : moderate to severe newborn encephalopathy Prevention of hypotension minimize neonatal acid-base status

    26. Regional anesthesia Maintain uteroplacental perfusion: Left lateral tilt position, lower leg compressive stockings, IV fluid loading Ephedrine Mixed ?? agonist Fetal acidemia, lower umbilical arterial pH Phenylephrine Pure ? agonist Avoidance of hypotension

    27. Fetal effects of maternal O2 Oxidative stress: NEC, ROP, PVL, CLD Air v.s. O2-enriched group Greater free radicals activity in the latter group No means of linking free radical formation with neonatal outcomes No published trial of maternal O2 therapy for fetal distress

    28. Postpartum pain management Implications on breastfeeding Neonatal dose of most medication obtained through breastfeeding is 1 to 2% of maternal dose AAP: Acetaminophen, NSAIDs, morphine are compatible with breastfeeding

    29. Outlines Labor pain Analgesic techniques for labor Systemic opioids Agonist-antagonist opioids N2O Neuraxial analgesia Labor epidurals and outcome Anesthetic techniques for Cesarean section Postpartum pain management

    30. Thank you for your attention

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