Anesthesia for Normal Labor and Delivery

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Anesthesia for Normal Labor and Delivery

• Sheila E. Cohen M.B.,Ch.B. FRCA
• Stanford University School of Medicine
• Stanford, California

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McGill Pain Questionnaire
(Melzack R The myth of painless childbirth.
Pain 19321, 1984)
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Analgesia for Labor and Delivery

• Always controversial!
• Birth is a natural process
• Women should suffer!!
• Concerns for mothers safety
• Concerns for baby
• Concerns for effects on labor

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Anesthesia à la Reine
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John Snow (1853) on Queen Victorias Anesthetic
for the birth of Prince Leopold

• The inhalation lasted fifty-three minutes.
  The chloroform was given on a handkerchief in
  fifteen minim doses the Queen expressed herself
  as greatly relieved by the administration.

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The Ideal Labor Analgesic

• Good pain relief
• No autonomic block (no hypotension)
• No adverse maternal or neonatal effects
• No motor block
• No effect on labor and delivery
• No increase in C/S rate
• No increase in forceps/vacuum delivery
• Patient can ambulate
• Economical cost and personnel

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Pain Pathways in Labor and Delivery
Eltzschig, Leiberman, Camann, NEJM 348 3192003
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Labor Pain at different Stages of Labor
Eltzschig, Leiberman, Camann, NEJM 348 3192003
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Fetal pH during Labor and Delivery
pH
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Analgesia for Vaginal Delivery

• Systemic narcotics
• Tranquilizers / hypnotics
• Inhalation analgesia
• Acupuncture
• TENS
• Psychoanalgesic techniques

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Placental Transfer of DrugsMaternal, Drug,
Placental and Fetal Factors

• Lipid solubility
• Molecular size
• Total dose of drug
• Concentration gradient
• Maternal metabolism and excretion
• Degree of ionization
• pKa of drug, maternal and fetal pH
• Protein binding - mother and fetus
• Uterine blood flow
• Time for equilibrium to occur

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Factors Determining Fetal Drug Levels
(Ralston, 1987)
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Differential Protein Binding
Differential maternal and fetal protein binding
accounts for differences in total circulating
drug concentrations on both sides of placenta,
when free drug concentrations are actually equal
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UV/MV Fetal-Maternal Drug Ratios

• Bupivacaine 0.25-0.3
• Mepivacaine 0.7
• Lidocaine 0.5

Correlates with degree of protein binding, but
may not reflect total amount of drug in fetus
because of high lipid solubility leading to
significant tissue uptake
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Systemic Opioids in Labor
Advantages

• Easy administration
• Inexpensive
• No needles
• Avoids complications of regional block
• Does not require skilled personnel
• Few serious maternal complications
• Perceived as natural

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Systemic Opioids in Labor
Disadvantages

• All drugs easily cross placenta
• Pain relief inadequate in most cases
• Maternal sedation
• Nausea, vomiting, gastric stasis
• Fetal heart rate effects
• Loss of beat-to-beat variability
• Sinusoidal rhythm
• Dose-related maternal / neonatal depression
• Newborn neurobehavioral depression

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Which Systemic Opioid?Pure Agonists

• Morphine
• long half-life, neonatal depression
• Meperidine
• neonatal depression (normeperidine effect)
• nausea, vomiting
• Fentanyl
• short duration, minimal newborn effects
• Alfentanil
• newborn depression
• Remifentanil? (what surveillance is needed?)

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IV-PCA Fentanyl during Labor A suggested regimen

• Loading dose of 50-100 mcg
• No background infusion
• 10-12.5 mcg bolus
• 8-10 min lockout
• 4 hour limit - 300 mcg
• Pulse oximeter if large doses given

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Which Systemic Opioid?Agonist-Antagonists
Ceiling effect for respiration and
analgesiaMaternal sedation prominent

• Nalbuphine
• Butorphanol
• Buprenorphine

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Potential Fetal/Neonatal Effects of Maternal
Sedation

• Low 1 and 5 min Apgar scores
• Respiratory acidosis
• Naloxone, ventilatory assistance may be needed
• Neurobehavioral depression - dose dependent
• Prolonged observation in NICU occasionally needed

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Neurologic and Adaptive Capacity Score (NACS)
(Anesthesiology, 1982)
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Neonatal Neurobehavioral Effects of Maternal
Systemic Medication

• Transient, global depression of behavior related
  to presence and quantity of drug in newborn
• Most effects gone by 3rd day all by 10 days
• Important to differentiate from sinister causes

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Inhalation Analgesia for Vaginal Delivery
(N2O 30-50 very low concentration volatile
agents)

• Advantages
• Easy to administer (no needles or PDPH)
• Satisfactory analgesia variable
• Minimal neonatal depression

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Inhalation Analgesia for Vaginal Delivery
(N2O 30-50 very low concentration volatile
agents)

• Disadvantages
• Decreased uterine contractility (except N2O)
• Rapid induction of anesthesia in pregnancy
• Risk of unconsciousness and aspiration
• Difficulties with scavenging in labor rooms

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Analgesia for Labor and Delivery
Local and regional techniques

• Local infiltration
• Pudendal block
• Paracervical block
• Paravertebral (lumbar sympathetic block)
• Epidural - lumbar (caudal)
• Spinal
• Combined spinal-epidural (CSE)

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Analgesic Blocks for Labor and Delivery
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Paracervical Block
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Regional Analgesia for Labor

• Lumbar epidural
• Segmental (T10-L1)
• Extended (T10-S5)
• Caudal epidural (S5-T10)
• Spinal (LA opioids)
• CSE (opioids LA)

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Fetal / Neonatal Effects of Regional Analgesia in
Labor

• Uterine perfusion maintained
• Profound hypotension ? possible fetal compromise
• LA toxicity - extremely rare
• FHR changes
• baseline variability
• periodic decelerations (due to? maternal
  catechols?)
• Apgar scores, acid-base status, unaffected
• Neurobehavioral effects absent with current agents

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The Ideal Labor Analgesic

• Good pain relief
• No autonomic block (no hypotension)
• No adverse maternal or neonatal effects
• No motor block
• No effect on labor and delivery
• No increase in C/S rate
• No increase in forceps/vacuum delivery
• Patient can ambulate
• Economical cost and personnel

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How to Achieve Goals

• What you put in
• Drugs, concentrations, combinations
• How you deliver it
• Intermittent boluses, continuous, PCEA
• How much you give
• Low vs. high infusion rates

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Ropivacaine vs. Bupivacaine in Labor - What are
the Relative Potencies?

• Ropivacaine is only 60 as potent as bupivacaine
  (2 MLAC studies)
• Claims for reduced toxicity and motor block must
  consider relative potency
• Do very dilute agents pose risk of toxicity?
• Newer agents very expensive

(Polley et al. Anesthesiology, 1999. Capogna
et al. BJA, 1999)
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Relative Analgesic and Motor Blocking Potencies
of Epidural Bupivacaine and Ropivacaine in Labor
(Lacassie et al. Anesth Analg 200295204)
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Relative Motor Blocking Potencies of Epidural
Bupivacaine and Ropivacaine
CONCLUSIONS

• Motor block potency ratio is the same as sensory
  block potency ratio
• Ropivacaine is only 0.66 as potent as bupivacaine
• No difference in mode of delivery

(Lacassie et al. Anesth Analg 200295204)
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Potencies of Levobupivacaine and Bupivacaine in
Labor
Lyons et al. Br J Anaesth 199881 899
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Epinephrine Use in Labor

• May transiently slow labor
• Increases motor block
• Improves analgesia ( 1600K works)
• Epinephrine test dose often avoided in labor
• Low specificity - maternal heart rate very
  variable
• Low sensitivity - ? response to sympathomimetics
• Increases motor block - prevents ambulation
• Potential for ? UBF with repeated doses
• Very dilute agents - whole first dose is test
  dose.

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Epidural Opioids in Labor

• Inadequate analgesics used alone
• Synergize with local anesthetics
• Speed onset of analgesia
• Improve quality of analgesia
• Permit use of very dilute LA solutions
• Help relieve persistent perineal pain and
  unblocked segments
• Optimal recipe and maximum safe dose not
  determined

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Which Epidural Opioid in Labor?
Fentanyl and Sufentanil

• Rapid onset, few side effects
• Sufentanil slightly more effective
• No significant fetal drug accumulation (? less
  with sufentanil)
• No serious adverse neonatal effects with either

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Light or Ultra-light Analgesic Techniques

• Bupivacaine
• Ropivacaine OPIOID
• Levobupivacaine

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Continuous Infusion Epidural

• A larger volume of a more dilute agent is more
  effective for labor analgesia than a smaller
  volume of higher concentration

PCEA

• Good analgesia
• Patient autonomy
• Less need for MD interventions
• Cost effective

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Effect of Low-Dose Mobile vs. Traditional
Epidural Techniques on mode of delivery A
randomized Trial
(Comet Study UK , Lancet 200135819)



Patients
Bupivacaine 0.25
Bupivacaine 0.1 fentanyl
Bupiv 2.5 mg Fent 25 mcg
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Ultra-Light Bupivacaine-Sufentanil PCEA
technique for Labor Analgesia(Stanford Technique)

• Block initiated with 15-20 ml bolus 0.125
  bupivacaine sufentanil 10 mcg
• PCEA solution
• 0.0625 bupivacaine sufentanil 0.3-0.4 mcg/ml
• PCEA settings
• Basal infusion 10-15 ml/hour
• Bolus 12 ml
• Lockout 15 min

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Physician Administered Boluses
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IT Opioid Analgesia (CSE)
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Advantages of CSE (opioids local anesthetic)
for Labor Analgesia

• Rapid onset of intense analgesia (the patient
  loves you immediately! ???)
• Ideal in late or rapidly progressing labor
• Very low failure rate
• Less need for supplemental boluses
• Minimal motor block (walking epidural)
• Side effects vs standard epidural?

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Median Upper and Lower Level of
DecreasedPinprick Sensation after Intrathecal
Sufentanil 10 µg
10 µg
(Cohen et al. Anesth Analg, 1993)
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Onset of Analgesia CSE vs. Epidural Collis et
al. Lancet 19953451413
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Rare but Serious Problems
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The Problem
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Epinephrine Levels after Analgesia

Cascio et al. Can J Anaesth 1997 44605-609
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Fetal Bradycardia After Labor Analgesia
Pain Relief
Decreased Circulating Epinephrine
Increased Uterine Tone
Decreased Uterine Blood Flow
Fetal Bradycardia
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Fetal Heart Rate Changes after Analgesia CSE vs.
Epidural
Nielsen et al. Anesth Analg 1996 837426
Palmer et al. Anesth Analg 19988(3)577-81Riley
et al. Anesthesiology 1999 A1054Eberle et al.
Am J Obstet Gynecol 1998 179150-155
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Fetal Heart Rate after CSE - Selection Bias May
Contribute to Higher Incidence of Fetal
Bradycardia -
Riley...Cohen et al. Anesthesiology 1999 A1054
Fetal Bradycardia FHR lt 120 bpm for gt 2min
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Greater Pain Scores and Cervical Dilation Before
Analgesia May Contribute to Bias
Riley...Cohen et al. Anesthesiology 1999 A1054
(n 196)
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Management of FHR Changes

• Left uterine displacement
• Maternal position change
• O2 administration
• STOP OXYTOCIN!
• Fetal scalp stimulation
• Nitroglycerin 400 µg sublingual X 2 (or more)
• 100 µg IV repeated as needed
• Terbutaline 0.25 mg, subcutaneous
• Treat hypotension
• Ephedrine - ? epinephrine level ? UBF

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Other Problems
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Spinal Needle DesignRiley, Cohen et al.
Longer needle subsequently successful in all
these cases.
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CSE vs. Epidural Labor AnalgesiaRisk of Headache
Norris et al, Anesthesiology 200195913
(n2183)
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Strategies to Decrease Complications with CSE

• Decrease dose of opioid
• Fentanyl 15-20 µg
• Sufentanil 2.5-5 mg
• Combine with
• Local anesthetic (bupivacaine 1.25-2.5 mg)
• Epinephrine?
• Clonidine?
• (Neostigmine?)

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Current Recommendations for CSE

• Use lowest effective dose of opioid, dont repeat
• Monitor BP, FHR, Respiration, (SpO2 if indicated)
• Expect potentiation of epidural doses
• All mixtures hypobaric - avoid prolonged sitting
  position after block
• Treat hypotension and uterine hypertonus
• Naloxone and resuscitation equipment available
• Same or greater surveillance as after epidural

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Controversial Areas

• Effects on labor and delivery process
• Maternal temperature elevation
• Drug choice - are new agents better?
• Epidural vs. CSE

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Conclusions

• Individualize technique to patients goals and
  stage of labor
• Optimize management for spontaneous delivery
• Provide safe, cost-effective analgesia