Analgesia and Anesthesia in Labor

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Analgesia and Anesthesia in Labor

• Obstetrics and Gynecology Clinics
• of North America 32(2005) 231-244
• Reported by R3 ???

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Purpose of this article

• To review the various pharmacologic and
  nonpharmacologic options for obstetric pain
  management in the United States
• Analgesia refers the reduction of pain
  anesthesia refers to reduce the sensation or
  feeling

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History

• 1840s
• ? the first use of anesthestics for labor
• 1900s
• ? the first case of regional anesthesia in
• labor

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Physiology and anatomy

• Uterine innervation
• Sympathetic nerves
• T7-T8
• Internal iliac plexi
• Parasympathetic nerves
• S2S4
• Cervical ganglion of Frankenhauser
• Visceral afferent (pain)
• Uterine corpus ?T11-T12
• Cervix, vagina, and perineum ? S2-S4

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Nonpharmacologic interventions

• Acupuncture
• Massage
• Intracutaneous sterile water block
• Water immersion
• Others

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• Intracutaneous sterile water block
• Injection of
• sterile water
• Four sites of
• sacral area

• 3 posterior superior iliac spine

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Intravenous analgesia

• Morphine
• Meperidine (Demerol)
• Fentanyl
• Butorphanol

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• Morphine
• the first pure opioid administered for labor
  analgesia
• Usual dose 1 to 4 mg
• Peak effect 20 min IV, 1 - 2 hr IM
• Duration 4 to 6 hr
• Neonate effects respiratory depression
• Maternal effects respiratory depression,
  sedation, nausea, emesis, dizziness
• Rarely used in USA

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• Meperidine (Demerol)
• The most commonly used opioid for pain relief in
  labor
• Typical dose 50 to 100 mg IM, 25 to 50 mg IV
• Peak effect 10 min IV, 50 min IM
• Duration 4 hr
• Neonate effects
• respiratory depression (less than morphine)
• The neonate is less likely to be affected if
  delivered less than 1 hour after dosing or more
  than 4 hour after dosing
• Metabolite of meperidine has long half-life

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• Fentanyl
• Synthetic opioid
• Usual dose 50 to 100 ug IM, 25 to 50 ug IV
• Peak effect 2 to 3 min IV
• Duration 60 min
• Side effects constipation, dry mouth, urinary
  retention, pruritus, neonatal respiratory
  depression

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• Fentanyl
• Improvement in
• Neonate effects
• Does not alter Apgar scores or umbilical cord
  blood gases
• Decreased transport to fetal system
• Maternal effects
• Sedation?decreased
• Nausea? decreased

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• Butorphanol
• Opioid agonist-antagonists
• Usual dose 1 to 2 mg IV, 2 to 4 mg IM
• Peak effect 4 to 5 min IV, 30 to 60 min IM
• Duration 3 to 4 hr
• Nalbuphine
• Opioid agonist-antagonists
• Usual dose 10 mg IV or IM
• Peak effect 2 to 3 min IV, lt 15 min IM
• Duration 3 to 6 hr

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• Butorphanol Nalbuphine
• Neonate respiratory depression
• Ceiling effect
• Limit their impact on maternal respiratory
  depression
• Caution
• Acute withdrawal in patients who are on chronic
  narcotics or drug abusers

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• Sedatives, like barbiturates
• To reduce maternal anxiety may reduce the
  perception of pain
• Disadvantage long half-lives, does cross the
  placenta, maternal respiratory depression
• Not recommended for use during labor

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• Antiemetics
• Promethazine (Phenergan)
• Treat nausea associated with opioids
• some sedation for maternal anxiety without
  suppressing maternal respiratory drive
• does cross the placenta, but no effects on the
  neonate
• Hydroxyzine (Vistaril)
• H1 antagonist
• treat pruritus, antiemetic, mild sedative

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Paracervical block

• Administration of a local anesthetic (1
  lidocaine) on the cervix
• Advantage
• Availability
• Simplicity
• Disadvantage
• fetal bradycardia
• Lidocaine toxicity

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Regional anesthesia

• Epidural anesthesia
• Spinal anesthesia
• Spinal and epidural technique

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• Epidural anesthesia
• Medication
• Analgesics (opioids)
• Anesthetics
• Combination

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• Analgesics (opioids)
• Morphine
• Long onset time, moderate efficacy
• Meperidine
• Risk of seizure
• Fentanyl and sufentanyl

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• Anesthetics
• Bupivacaine
• Long duration, low placental transfer,good effect
  both in early and late stages of labor
• Side effect ? cardiotoxicity
• Lidocaine
• shorter duration of action and less effective
  pain relief
• Lower risk of cardiotoxicity
• Ropivacaine
• More rapid clearance and larger margin of safety
  against cardiotoxicity

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• Regional anesthesia
• Side effect
• Pruritus
• inability to void
• Hypotension
• The effects of regional anesthesia
• Not increase the rate of primary cesarean section
• increase the rate of oxytocin administration,
  operative vaginal delivery, episiotomy, and
  antibiotic use
• increase the length of both the first and second
  stages of labor

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• The end !