Pain Relief in Labor

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Pain Relief in Labor
Khalid A. Yarouf
. www.4MedStudents.com
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Pain pathways during labor

• Pain is sensation of discomfort resulting from
  stimulation of specialized nerve endings.
• During labor, pain sensation is relayed to the
  spinal cord from T10, L1, S1-S4. These sensory
  fibers make synaptic connections in dorsal horn
  of spinal cord with cells that provide axons that
  make up the spinothalamic tract.

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• Early 1st stage before fetal head reaches zero
  station, pain impulses arise primarily from
  uterus ? via visceral afferents enter spinal cord
  at T10-L1.
• Late 1st stage 2nd stage pain impulses arise
  from uterus, pelvic structures, vagina,
  perineum.
• 3rd stage of labor is usually well tolerated with
  spontaneous placental delivery.

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Analgesia

• Psychoprophylaxis physical analgesia
• Nature childbirth (e.g. Lamaze prenatal
  classes) whereby informed mother utilizes
  relaxation techniques to stimulate descending
  inhibitory pathways.
• Whirlpool baths, transcutaneous nerve stimulation
  acupuncture inhibit nociceptive impulses
  reduce pain propagating muscle tension.
• Especially effective in early stages of labor.

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Cont Analgesia

• Systemic medications
• Narcotics
• Although narcotics provide both analgesic
  sedation, their S.E are
• Maternal Orthostatic hypotension, nausea,
  vomiting.
• Fetal ? beat-to-beat variability of FHR.
• Neonatal respiratory depression ? Rx Naloxone
  (Narcan).

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Cont Analgesia

• Meperidine (Demerol or Pethidine)
• Best use in early stages of labor, less effective
  once labor is well established.
• If IV (25-50 mg) ? peak effect 7-8 min.
  Duration 1.3-3 hrs.
• If IM (50-100 mg) ? peak effect 2-4 hrs.

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Cont Analgesia

• Fentanyl
• Most frequently used for parturient in active
  labor.
• Administered in 2-3 divided doses of 25 µg given
  5 min apart.
• Peak analgesic effect 5-6 min after each IV
  injection. Duration 30-60 min.

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Cont Analgesia

• Sedative-Tranquillizers
• These agents given in combination with a
  narcotic.
• The phenothiazine Promethazine (Phenergan)- 25
  mg IM or 12.5 mg IV.
• Relieves anxiety, controls nausea vomiting, ?
  narcotic requirements during labor.

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Cont Analgesia

• Inhalational analgesia (NO)
• Provides partial pain relief during labor as well
  as _at_ delivery.
• 50 NO in O2. Its administered with a mask /
  mouthpiece in a manner such that the parturient
  remains awake, cooperative in control of her
  airway ? to prevent pulmonary aspiration of
  gastric contents.
• Does not prolong labor or interfere with uterine
  contractions but administration gt 20 minutes may
  result in neonatal depression.
• A/w lt risk of neonatal depression when compared
  with narcotics.

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Anesthesia (Regional anesthesia)

• Peripheral nerve block
• Local infiltration for episiotomy (Lidocaine).
• Pudendal block.
• Central nerve block
• Epidural anesthesia.
• Spinal (subarachnoid) block.

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Cont Anesthesia

• Pudendal block
• Administered shortly before delivery to
  anesthetize pudendal nerve.
• Insert needle ? aspirate with syringe to check
  for absence of blood ? inject 1 Lidocaine on
  each side.
• Analgesia produced in lower birth canal
  perineum provides maternal comfort for low
  forceps delivery episiotomy.
• Advantages easy to administer, not a/w maternal
  hypotension/ fetal distress.
• Disadvantage incomplete analgesia _at_ time of
  delivery, since pain of uterine contraction is
  unaffected.

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Cont Anesthesia

• Epidural anesthesia
• Most commonly used technique for both labor
  delivery.
• 19 gauge indwelling catheter inserted into lumbar
  epidural space _at_ L3-4.

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Cont Anesthesia

• Does not prolong 1st stage, but may reduce
  maternal expulsive efforts, therefore usually
  used in earlier stages of labor (lt4 cm).

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Cont Anesthesia

• During early labor, analgesia is established with
  Fentanyl small dose of Bupivacaine (Marcaine).
• Epidural opiate (Fentanyl) ? provides effective
  analgesia for visceral pain arising from uterus.
• Local anesthetic (Bupivacaine) ? relieves somatic
  pain of labor, which begins once fetal head
  engages pelvis (at zero station).
• If perineal anesthesia (for muscle relaxation) is
  needed to facilitate difficult vaginal delivery ?
  2 Lidocaine (Xylocaine).

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Cont Anesthesia

• Certain precaution must be taken
• Preload mother with 5 mL IV fluid to prevent ?
  assess pt for evidence of spinal shock (e.g.
  rapid loss of sensory function).
• If no spinal shock ? give another 5 mL ? assess
  for signs of intravascular injection (dizziness,
  tinnitus) ? if nothing happens, rest of dose is
  given _at_ rate of 5 mL/min.
• Cx inadvertent total spinal with cardiovascular
  collapse resp arrest, intravascular injection
  with seizures, post-ictal depression possible
  cardiac arrest.

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Cont Anesthesia

• Spinal (subarachnoid) block
• Injection of local anesthetic (Tatracaine,
  Bupivacaine, or Lidocaine) into subarachnoid
  space thru a spinal needle placed in L3-4
  interspace.
• Fastest onset.
• Least drug exposure for fetus because small dose
  required.
• Beware of rapid hypotension preload mother with
  1000 mL IV fluid.

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Anesthesia (General)

• Not used to vaginal deliveries, because
  unconscious pt is at high risk of pulmonary
  aspiration of gastric contents.
• Indications
• C-Section in certain circumstances.
• For shoulder dystocia.
• Undiagnosed twins.
• Breech presentation.

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• Rapid sequence induction should be done ? to
  prevent aspiration.
• Pre-oxygenate mother with 100 O2 as she is prone
  to hypoxia during intubation 2º to ? Functional
  Residual Capacity ? O2 consumption.
• High concentration of Halothane 2 or Isoflurane
  3 is used if uterine relaxation is necessary.