Transcript Analgesia for Labor and Vaginal Delivery

Analgesia for Labor and Vaginal
Delivery
Hirmanpour A . MD

Pain perception by the parturient is a dynamic
process that involves both peripheral and central
mechanisms.

On the McGill pain questionnaire, labor pain is one
of the most intense pains that a woman can
experience, and it is typically worse than a toothache,
backpain, and pain associated with a deep laceration.
Labor analgesia options are:
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Psychoprophylaxis
Transcutaneous electrical nerve stimulation(TENS)
Systemic medication
Inhalational techniques
Neuraxial blocks
Lumbar sympathic block
Paracervical and pudendal block(infrequently)
Psychoprophylaxis

“Natural childbirth” stems from a phrase coined by
Grantley Dick-Read in 1933;
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He believed that childbirth was a painless process that
did not need medical intervention.
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He opined that the pain of childbirth results from a ‘‘feartension-pain-syndrome.’’
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Fernand Lamaze introduced the Western world to
psychoprophylaxis.
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“natural childbirth” was popularized after Marjorie Karmel
described and published her childbirth experience under the
care of Dr. Lamaze. (Lamaze method)
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American society for Psychoprophylaxis was born.
Karmel M. Thank You, Dr. Lamaze: A Mother’s Experiences in Painless Childbirth. 2nd
edition. New York, Harper & Row, 1981.
Labor analgesia options are:
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Psychoprophylaxis
Transcutaneous electrical nerve stimulation(TENS)
Systemic medication
Inhalational techniques
Neuraxial blocks
Lumbar sympathic block
Paracervical and pudendal block(infrequently)
Transcutaneous Electrical Nerve Stimulation
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TENS is thought to reduce pain by nociceptive inhibition
at a presynaptic level in the dorsal horn by limiting central
transmission.
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TENS involves the transmission of low-voltage electrical
current to the skin via surface electrodes.
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It is most widely used for childbirth in Scandinavia and
the United Kingdom.
Transcutaneous Electrical Nerve Stimulation
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A systematic review of eight trials in more than 700
women concluded that evidence for TENS-mediated
reduction in pain during labor is weak.
Carroll D, Tramer M, McQuay H, et al. Transcutaneous electrical nerve
stimulation in labour pain: A systematic review. Br J Obstet Gynaecol 1997;
104:169-75.
Transcutaneous Electrical Nerve Stimulation
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Electrical stimulation activates low-threshold
myelinated nerves.
Inhibit unmyelinated small c fibers by blocking
impulses to target cells in the substantia gelatinosa of the
dorsal horn.
TENS is also thought to enhance release of
endorphins and dynorphins centrally.
Placement of electrodepads over the lower back region
in the distribution of T10-L1 may provide some
analgesia for parturients in early labor.
Labor analgesia options are:
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Psychoprophylaxis
Transcutaneous electrical nerve stimulation(TENS)
Systemic medication
Inhalational techniques
Neuraxial blocks
Lumbar sympathic block
Paracervical and pudendal block(infrequently)
Systemic Medication
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Opioids are the most commonly used class of drugs
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Sedative – transqualizer
Meperidine
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Meperidine is the most commonly used parenteral opioid
analgesic during labor.
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IM : 50 to 100 mg( peak onset of effect at 40 to 50
minutes);
IV : 25 to 50 mg ( 5 to 10 minutes).
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The analgesic effect lasts up to 3 to 4 hours.
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Fetal exposure to meperidine is highest between 2 and 3
hours after maternal administration.
Meperidine
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Cause less respiratory depression in the neonate
than morphine does; So, it is more commonly
used.
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It may cause loss of beat-to-beat variability of FHR
tracings.
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A meta-analysis failed to prove that other
opioids(tramadol, meptazinol, diamorphine, pentazocine,
nalbuphine,and butorphanol) were superior to
meperidine for labor analgesia.
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Some investigators have proposed fentanyl and remifentanil
as superior choices.
Meperidine
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Metabolized in the liver to produce normeperidine,
Normeperidine
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Pharmacologically active metabolite
A potent respiratory depressant
Crosses the placenta.
Half-life of 60 hours in the neonate.
Fentanyl
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An alternative analgesic option
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For patients in whom neuraxial anesthesia is contraindicated.
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Its short half-life makes it suitable for prolonged use in labor,
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Use as an IV bolus or as an analgesic administered by means of a
PCA delivery system.
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Provides reasonable levels of analgesia with minimal neonatal
depression.
Fentanyl
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The usual dose : 25 to 50 µg (IV).
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The peak effect occurs within 3 to 5 minutes and has
a duration of 30 to 60.
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Eisele found IV fentanyl 1 µg/kg provided good
analgesia with no appreciable hemodynamic effect
and no adverse effects on Apgar scores, fetal acidbase status, or neurobehavioral scores at 2 and 24
hours.
Fentanyl
Another advantage:
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Can be administered in non parenteral modalities,
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Subcutaneously-Orally- Patch.
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These uses, have not been adequately evaluated in
laboring patients.
Butorphanol and Nalbuphine
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Opioid agonist-antagonists
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Structurally related to oxymorphone and naloxone.
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The potential advantages of producing less nausea
and vomiting
Butorphanol
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Is a κ-agonist and a µ-antagonist
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Minimal affinity for σ-receptors.
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Dose : 1 to 2 mg IM or IV
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Duration of action up to 4 hours.
Nalbuphine
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Is a partial κ-agonist and a potent µ-antagonist
Minimal σ-receptor activity.
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A dose of 10 mg IM or IV is equivalent to 10 mg of
morphine
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IV : Onset 2 to 3 minutes
IM: Onset 10 to 15 minutes
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It can offer analgesia for up to 6 hours.
One advantage of these agents over
µ-agonists
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They demonstrate a “ceiling effect”
By increasing doses do not produce further respiratory
depression.
Unfortunately,
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The use of these drugs is limited in clinical practice
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Because of rapidly transferred across the placenta and
have produced ominous sinusoidal FHR patterns.
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The use of antagonists or agonist-antagonists may
precipitate acute withdrawal syndrome in the
mother and the newborn of an opioid-dependent
parturient.
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This syndrome has been reported after parenteral or
neuraxial routes of administration.
Naloxone
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There is no neonatal benefit to the maternal
administration of naloxone during labor or just before
delivery.
Naloxone reverses opioid depression of newborn minute
ventilation and increases the slope of the CO2-response
curve in infants affected by the maternal administration of
an opioid.
The recommended dose is 0.1 mg/kg of a 1 mg/mL or 0.4
mg/mL solution.
Not recommended during the primary steps of neonatal
resuscitation,
Naloxone
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Only use if respiratory depression continues and after PPV,
normal heart rate and color of neonate appears (In mother
received an opioid within the previous 4 hours).
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Preferred route of administration is intravenous.
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If IV access is not available, IM administration is acceptable,
although absorption may be delayed.
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Endotracheal administration of naloxone is not
recommended.
Remifentanil
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A potent, short-acting µ-opioid receptor agonist
Approved for clinical use in the US since1996.
Contains an ester linkage that allows metabolism by
nonspecific esterases throughout the blood and muscles.
This metabolism gives it a unique pharmacologic profile
in comparison to other opioids.
Remifentanil has an extremely rapid plasma clearance and
offset of action.
Half life : 1.3 mins
Remifentanil
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Prolonged administration does not cause accumulation
of this drug.
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UV/M= 0.88.
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Fetal exposure to the drug is minimized because of its
rapid metabolism or redistribution, or both.
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An attractive alternative systemic analgesic in parturients
in whom regional anesthesia is contraindicated.
Remifentanil
PCA with IV remifentanil :
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Bolus dose of 0.4 µg/kg with a lockout time of 1 minute
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Continuous infusion of remifentanil at 0.05 µg/kg/min
with a bolus of 25 µg and a lockout time of 5 minutes
provides satisfactory labor analgesia.
Systemic Medication
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Opioids are the most commonly used class of drugs
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Sedative – transqualizer
Sedative-Tranquilizers
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used for sedation,anxiolysis, or both during early
labor and before cesarean delivery.
Barbiturates
Phenothiazines
Hydroxyzine
Benzodiazepines
Secobarbital were once popular, they are currently
unfashionable because of antianalgesic effects in the
mother and prolonged depressant effects inthe neonate.
Even with small doses of barbiturates that
result in no depression of the Apgar score, the
newborn’s attention span may be depressed
for more than 4 days.
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Promethazine
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The most commonly phenothiazine used in obstetrics.
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Used with meperidine
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Doses : 25 to 50 mg to prevent emesis.
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Promethazine appears in fetal blood within 1 to 2
minutes after IV injection in the mother and reaches
equilibrium within 15minutes.
Ketamine
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N-methyl-d-aspartate (NMDA) receptor antagonist
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Produces dissociative anesthesia
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Its mechanism: With phencyclidine receptors located
in the limbic and corticothalamic areas of the brain.
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Subanesthetic doses: 0.5 to 1 mg/kg or 10 mg every 2
to 5 minutes to a total of 1 mg/kg in 30 minutes
during labor.
ketamine
In addition to its use in labor…..
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Ketamine in dose of 25 to 50 mg can be used to supplement
an incomplete neuraxial blockade for C/S.
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Its main disadvantages are the potential for hypertension
and emergence reactions.
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High doses (>2 mg/kg)can produce psychomimetic effects
and increased uterine tone, which may cause low Apgar
scores and abnormalities in neonatal muscle tone.
Benzodiazepines
can be used as sedatives and anxiolytics in labor.
 Diazepam (Valium),
 Lorazepam(Ativan),
 Midazolam (Versed),
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Disadvantages: cross the placenta, with elimination halflives as long as 48 hours for diazepam and upward of 120
hours for its main metabolite N-desmethyldiazepam.
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Exposure to BNZ early in utero may result in malformations
such as cleft lip.
Benzodiazepines
Use of BNZ during labor no effect on fetal malformations,
 But may be with other problems in the neonate:
 Sedation
 Hypotonia
 Cyanosis
 Impaired metabolic responses to stress.
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BNZ are potent amnestic agents, a parturient may not be able
to remember her birthing experience.
Many of the adverse effects can be reversed by flumazenil,
which is a competitive benzodiazepine receptor antagonist.
Labor analgesia options are:
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
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Psychoprophylaxis
Transcutaneous electrical nerve stimulation(TENS)
Systemic medication
Inhalational techniques
Neuraxial blocks
Lumbar sympathic block
Paracervical and pudendal block(infrequently)
Inhalational techniques

Definition : administration of subanesthetic concentrations
of inhaled anesthetics to relieve pain during labor.
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This pain relief technique should not be confused with
inhaled anesthesia that produces unconsciousness and loss of
protective laryngeal reflexes.
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Although inhaled analgesia provides a limited amount of pain
relief, it is not adequate to provide sufficient pain relief for
most mothers.
Inhalational techniques
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Inhaled analgesics can be administered either
intermittently (during contractions) or continuously.
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They can be self-administered, but the patient should have
a health care provider present to ensure an adequate
level of consciousness and proper use of the equipment.
Inhalational techniques
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Entonox (50 : 50 N2O/O2 mixture) has been used for
many years as both a sole analgesic and an adjuvant to
systemic and regional techniques for labor.
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Side effects include dizziness, nausea, dysphoria, and
lack of cooperation.
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The maximum analgesic effect : after 45 to 60 seconds,
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Should use in early onset of contractions and
discontinue its use after the peak of the contraction.
Entonox
Inhalational techniques
Inhalational techniques
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The lack of scavenging systems in labor may theoretically put
staff at risk of exposure to excessive levels in prolonged period.
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The administration of N2O and O2 in a 50 : 50 combination
appears to have no effect on hepatic, renal, cardiac, or pulmonary
functions.
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A recent meta-analysis by Kronberg and Thompson concludes that
inhaled N2O relieves labor pain to a significant degree in most
patients but does not provide complete analgesia for many.
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The analgesic effect of N2O is dose dependent, which supports
its analgesic efficacy during labor.
Inhalational techniques
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Desflurane (0.2%), enflurane, and isoflurane (0.2% -0.25%)
sevoflurane (0.8%)as an effective labor analgesic.
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Sevoflurane, when compared with Entonox, provided superior
pain relief but more intense sedation, without adverse effects
and which was acceptable to mothers.
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The use of these volatile analgesics is limited by drowsiness,
unpleasant smell, and high cost.
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The major risk with VA : Accidental overdose
Labor analgesia options are:
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Psychoprophylaxis
Transcutaneous electrical nerve stimulation(TENS)
Systemic medication
Inhalational techniques
Neuraxial blocks
Lumbar sympathic block
Paracervical and pudendal block(infrequently)
Regional Analgesia
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The ideal labor analgesic technique
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Safe for both the mother and the baby,
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Does not interfere with the progress of labor and
delivery
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Provides flexibility in response to changing
conditions.
Techniques of Noraxial Analgesia
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Epidural,
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Spinal,
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Combined spinal-epidural blocks.
Patient Evaluation and Preparation
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Medical and obstetric history,
Clinical examination
Evaluating the airway.
Use of herbal medications
A 7.1%incidence of herbal use by parturients after 20
weeks’gestation has been reported.
Garlic , Ginkgo, Ginseng, Ginger may have anesthetic
implications.
The anesthesiologist should explain the procedure and
the potential complications of the technique.
Neuraxial blocks
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A full check of emergency equipment should be performed
to ensure the immediate availability of resuscitative drugs
and equipment.
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An intravenous infusion should be started, and appropriate
maternal and fetal monitoring should be in place before
starting the procedure.
Epidural Analgesia
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Low doses of LA or opioid combinations are
administered(usually by infusion) to provide a continuous
T10-L1 sensory block during the first stage of labor.

Further supplementation maybe required during the late first
stage and second stage to achieve a sacral block.
Laber is divided into three stages:
 The
first stage----has two phases:
1- Latent phase ( is defined as the period between the
onset of labor and the point at which a change in cervical
dilatation is noted) and Phase of maximal dilatation(which
usually begins at approximately 3-cm dilation).
2- Active phase of labor, uterine contractions occur
approximately every 3 minutes, have a duration of about 1
minute.
 The second satage----- interval between full cervical
dilation and delivery of the infant.
 The third stage ------- delivery of the placenta.

During the first stage of labor, visceral pain impulses
entering the spinal cord at T10 to L1 must be blocked.

During the second stage of labor, somatic impulses
entering the spinal cord fromS2 to S4 must also be
blocked .
T10 & L1, lower part of the back
and perineum and the upper part
of the legs.
T11 & T 12
T10 & L1
perineum
Figure 69-7 Distribution and intensity of labor pain during each stage of labor and
delivery.
First stage of labour
Epidural Analgesia
The benefits:
 Effective
pain relief without appreciable motor block,
 Reduction in maternal catecholamines
 Decreased α & β adrenergic receptor stimulation
Result in better uteroplacental perfusion and more
effective uterine activity.
Influence of epidural analgesia on maternal plasma concentrations of catecholamines
during labor. *P < .05 comparedwith before epidural.Shnider SM, Abboud TK, Artal R,et
al. Maternal catecholamines decrease during labor after lumbar epidural anesthesia. Am J
Obstet Gynecol 1983; 147:13-5.)
contraindications
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Patient refusal
Overt maternal coagulopathy
Frank infection at the needle site
Maternal hemodynamic instability
High-risk conditions, such as fixed cardiac output
states (critical aortic stenosis),
Must be considered on a case-by-case basis, with riskbenefit analysis for each patient.
Epidural Analgesia
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The use of ultrasound is increasing .
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Ultrasound imaging of the lumbar spine can aid identification
of necessary landmarks for epidural placement and estimate
the depth of the epidural space in the pregnant patient .
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It may be especially beneficial in the obese parturient or in
patients known to have previous difficult epidural
placement.
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In a survey of 1000 consecutive women who chose a variety of
analgesic techniques for labor and vaginal delivery(including
nonpharmacologic methods, transcutaneouselectrical nerve
stimulation, intramuscular meperidine,inhalation of nitrous
oxide, epidural analgesia, and a combination of these
techniques), pain relief and overall satisfaction with the
birth experience were greater in patients who received
epidural analgesia.
Paech MJ. The King Edward Memorial Hospital 1,000 mother survey of methods
of pain relief in labour. Anaesth Intensive Care 1991; 19:393-9.
Epidural Test Dose
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Contravertial for the use of epinephrine.
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Epinephrine produces a reliable increase in HR when the
epidural has been sited in a blood vessel.
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In laboring patient, maternal HR variability from the pain
of uterine contractions may confuse interpretation of the
heart rate response, and intravenous epinephrine may have
deleterious effects on uterine blood flow.
Epidural Test Dose
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The lack of sensitivity and specificity of the test dose
calls into question its usefulness as a diagnostic
tool.
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Leighton ----- injection of 1 to 2 mL of air into the
epidural catheter while listening over the precordium
with the maternal external Doppler monitor for
evidence of air.
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If continuous infusion of dilute LA is administered and the
patient remains comfortable, without a motor block,
proper epidural catheter placement is ensured.
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That is, after several hours, if the epidural catheter were
intravascular the patient should have inadequate pain relief,
and if the catheter were subarachnoid, a solid motor
block would develop.
The safe practice of administering labor epidural
analgesia dictates
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Initial catheter aspiration,
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Incremental injections,
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Continuous monitoring for evidence of local anesthetic
toxicity.
Spinal Analgesia
Provides effective and rapid onset of labor analgesia
 In very early labor
 In a distressed parturient to enable epidural placement
under more controlled conditions.
 For instrumental deliveries in women who do not have an
indwelling epidural catheter.
 For routine labor analgesia
in some hospitals.
(No flexibility of catheter)
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Continuous spinal analgesia with a
“macrocatheter”
•
•
•
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Indications:
Considered in cases of accidental dural puncture
Very high-risk parturients
Provides excellent analgesia and the assurance of a spinal
catheter.
Reduce the incidence of post–dural puncture headache
(PDPH)after an accidental dural puncture with an epidural
needle.
Inform all personnel involved in the care of a parturient with
a spinal catheter in place to avoid accidental over dose of LA.
Continuous spinal analgesia with a
“microcatheter”
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Introduced into clinical practice in the late 1980s
Quickly gained popularity
Convenience,
Fast onset,
Potential for decreased risk of PDPH.
Reports of cauda equina syndrome associated with
their use for C/S led the FDA to withdraw these
microcatheters from clinical practice.
Explanations for the occurrence of
cauda equina syndrome
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Possible inadequate mixing of local anesthetic within
the intrathecal space
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The use of high concentrations of potentially
neurotoxic local anesthetic (5% lidocaine) that can
result in neural damage.
Combined Spinal-Epidural Analgesia
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Effective,
Rapid-onset analgesia with minimal risk of toxicity or
impaired motor block.
The ability to prolong the duration of analgesia,
If operative delivery becomes necessary, the catheter
can be used to provide operative anesthesia.
Made ambulation possible with minimal motor block
so termed “the walking epidural.”
Methods of CSE
(1) Epidural catheter insertion followed by spinal needle
placement at a lower interspace;
(2) An epidural needle beside the spinal needle at the
same interspace with the use of specially designed
needles;
(3) The most commonly used “needle-through-needle”
technique,
Combined Spinal-Epidural Analgesia Set
The epidural needle is sited in the epidural space.
The long spinal needle is passed through the epidural
needle and punctures the dura mater.
After removal of the spinal needle stylet CSF is seen
spontaneously dripping from the spinal needle.
Combined Spinal-Epidural
spinal needle
Spinal fluid
coming from
spinal needle
Slide 82
courtesy of Alex Pue, MD
epidural needle
The spinal needle is withdrawn, and the epidural
catheter is threaded through the epidural needle into
the epidural space
Advantages of CSE versus Epidural
analgesia
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No incomplete(patchy) blockade,
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No motor block,
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No poor sacral spread.
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Significantly reduced duration of the first stage
of labor in primiparous parturients.
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The original description of spinal labor analgesia
involved sufentanil or fentanyl.
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The addition of isobaric bupivacaine to the opioid
produces a greater density of sensory blockade
while still minimizing motor blockade.
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Originally,25 µg of fentanyl or 10 µg of sufentanil was
advocated,
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Later studies have suggested using smaller doses of
opioid combined with a local anesthetic.
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Many clinicians are now routinely using 5 µg of
sufentanil or 15 µg of intrathecal fentanyl.
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Other studies have suggested that ropivacaine and
levobupivacaine can be substituted for intrathecal
bupivacaine to provide labor analgesia.
Side effects of intrathecal opioid
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Pruritus,
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Nausea and vomiting,
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Urinary retention.
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Respiratory depression as a result of cephalad spread
of opioid is rare but has occurred when using lipidsoluble opioids.
Pruritus
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Unrelated to histamine release
Pruritus is mediated through central µ-opioid receptor
Antagonizing central inhibitory neurotransmitters (e.g.,
gamma-aminobutyric acid [GABA] and glycine)
Interaction with central 5-HT3 receptors.
These receptors are concentrated in areas of the CNS
with high µ-opioid receptor density (e.g., trigeminal
nerve nucleus and dorsal horn of the spinal cord).
1- Waxler B, Dadabhoy ZP, Stojiljkovic L, Rabito SF. Primer of postoperative pruritus for
anesthesiologists. Anesthesiology 2005; 103:168-78.
2- Ganesh A, Maxwell LG. Pathophysiology and management of opioid- induced pruritus. Drugs
2007; 67:2323-33.
Treatment of pruritus

The most effective treatment is a centrally acting µ-opioid
antagonist (e.g., naloxone or naltrexone) or a partial agonistantagonist such as nalbuphine (Table 23-8).
Antihistamines(e.g., diphenhydramine) are usually ineffective
because the mechanism of pruritus is not related to histamine
release.
 Ondansetron (8-16mg)
 Subhypnotic doses of propofol (10- 20 mg)

Warwick JP, Kearns CF, Scott WE. The effect of subhypnotic doses of propofol on the incidence of
pruritus after intrathecal morphine for caesarean section. Anaesthesia 1997; 52:270-5.

Use of a continuous epidural infusion of dilute local
anesthetic plus opioid (e.g.,0.0625% to 0.1% bupivacaine)
provides sensory analgesia without motor block;
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Before ambulation, however, women should be observed
for the preceding 30 minutes to ensure maternal and fetal
well-being, and they should be assessed for adequate motor
function.
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An increased frequency of FHR tracings and fetal
bradycardia occurs with CSE. fetal bradycardia is usually
short in duration and typically resolves within 5 to 8
minutes.
Etiology of fetal bradycardia after CSE (may be
related to) :
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Acute reduction in circulating maternal catecholamine
levels after the quick onset of analgesia.
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Imbalance between epinephrine/norepinephrine levels
causes α-adrenoceptor effects on uterine tone and
decreases uterine blood flow.(controversy)
Continuous Epidural Infusion

Most obstetric anesthesiologists now advocate the use of
continuous infusions of dilute LA solutions.
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Local anesthetics such as bupivacaine, ropivacaine, and
levobupivacaine in concentrations ranging from 0.0625% to
0.125% ± opioid.
The addition of epinephrine enhance the quality of the analgesia
by:
1) Reducing vascular uptake and systemic absorption of LA
2) Direct agonist effect on α2 spinal receptors.
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Patient-controlled epidural analgesia
(PCEA)
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Effective labor analgesia and excellent patient satisfaction.

It reduces total amount of LA used; so lessens unwanted
effects such as motor block and hypotension.
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It reduces the demands on staff on the labor floor,
The catheter is connected to the PCEA device and the
patient can then self-administer further boluses as
required.
Labor analgesia options are:







Psychoprophylaxis
Transcutaneous electrical nerve stimulation(TENS)
Systemic medication
Inhalational techniques
Neuraxial blocks
Lumbar sympathic block
Paracervical and pudendal block(infrequently)
Lumbar Sympathetic Blocks

Another nerve block as an alternative to central neuraxial
blocks

Block transmission of pain from the uterus during the
first stage of labor.

It is a technically difficult block to perform, it appears to
be associated with fewer complications than paracervical
blockade.
Labor analgesia options are:







Psychoprophylaxis
Transcutaneous electrical nerve stimulation(TENS)
Systemic medication
Inhalational techniques
Neuraxial blocks
Lumbar sympathic block
Paracervical and pudendal block(infrequently)
Paracervical and Pudendal Blocks

For who does not want or cannot receive a neuraxial block.

LA is injected submucosally into the fornix of the vagina lateral
to the cervix to block nerve transmission through the
paracervical ganglion, which lies lateral and posterior to the
junction of the cervix and uterus. Anesthetic agent is
injected into the cervix laterally at 3 and 9 o'clock.

Because this block does not affect somatic sensory fibers from
the perineum, it offers no pain relief for the second stage of
labor.
Technique of paracervical block.
Paracervical block
Its use in obstetrics has been limited
Because of :
 Profound
fetal bradycardia,
 Systemic local anesthetic toxicity,
 Nostpartum neuropathy,
 Infection. (Paracervical, retropsoal, or subgluteal abscess)
Paracervical block
The cause of this fetal bradycardia :
1)
Reflex Bradycardia,
2)
Uterine and/or Umbilical Artery Vasoconstriction
3)
Decreased uterine blood flow
4)
High fetal blood levels of LA.
Paracervical block
Usually, we
use:
 Lidocaine
 Chloroprocaine, 5 to 10 ml of a 1%
solution.
Bupivacaine
is contraindicated because of
an increased risk of cardiotoxicity.
Pudendal block




The pudendal nerves are derived from the lower
sacral nerve roots (S2-S4)
Sensory innervation for the lower part of the vagina,
the vulva, and the perineum,
Motor innervation to the perineal muscles.
The nerves are easily anesthetized through a transvaginal
approach, which is accomplishedby depositing local
anesthetic behind each sacrospinous ligament.
Local infiltration of the pudendal nerve.
(Transvaginal technique)
Pudendal block

Provides analgesia for vaginal delivery as well as outlet
forceps delivery, but it is not useful for labor analgesia.

However, it is generally inadequate for midforceps
delivery, repair of vaginal lacerations, or exploration of
the uterine cavity.

Maternal complications from this technique are rare, but
include systemic local anesthetic toxicity, infection, and
hematoma formation.
Local Anesthetics

Bupivacaine

Levobupivacaine

Ropivacaine

Lidocaine

2-Chloroprocaine
Bupivacaine
An amide local anesthetic
 Commonly used in spinal and epidural anesthesia and
analgesia in obstetric practice
 The placental transfer depends on two factors:
1) the degree of ionization at physiologic pH
2)
the extent of protein binding.
 pKa = 8.05 (highly ionized at physiologic pH) and is 95%
protein bound;
 Limited transfer to the placenta .

Bupivacaine

The UV/M ratio for bupivacaine ranges from 0.31to
0.44 and is much lower than that for lidocaine.

Due to Reports of several deaths related to the
cardiovascular or cardiac toxicity of bupivacaine, FDA
prohibited the use of a 0.75% epidural solution in
obstetric practice.
Bupivacaine

Bupivacaine consists of two stereoisomers, S− and R+,
and is marketed as a racemic mixture of these isomers.
When separated, the R component was found to
contribute to bupivacaine’s unwanted toxicity.
This finding led to develop the use of S isomers for
clinical practice:
 Ropivacaine
 Levobupivacaine

Ropivacaine

A homolog of mepivacaine and bupivacaine.

Was the first S isomer of a local anesthetic to be
marketed.

Less soluble than bupivacaine so less potent.

Minimum local anesthetic concentration (MLAC) studies
have found that the analgesic potency of ropivacaine was
0.60 (0.47 to 0.75) relative to bupivacaine.
Minimum local anesthetic concentration
(MLAC)

Definition: The potency of local anesthetics for
neuraxial labor analgesia

MLAC is the median effective concentration of local
anesthetic solution when administered as a 20-mL bolus.

It is lower both for women in early labor and when the
local anesthetic is combined with a lipid-soluble opioid.
Capogna G, Celleno D, Lyons G, et al. Minimum local analgesia concentration of
extradural bupivacaine increases with progression of labor. Br J Anaesth 1998; 80:11-3.
Levobupivacaine


Long-acting local anesthetic with a clinical profile similar
to that of bupivacaine.
The lethal dose of levobupivacaine was 1.3- to 1.6-fold
higher than other recemic bupivacaine in most animal
studies, thereby providing supportive evidence for the
greater safety of levobupivacaine should accidental
intravascular injection occur.
Levobupivacaine

Assesment of block with 0.5% bupivacaine and 0.5%
levobupivacaine in C/S demonstrated no difference in:
1)
Adequacy of the block
Time taken to reach a surgically adequate block.
Onset or duration of sensory block,
Fade-out of sensory and motor blockade,
The quality of anesthesia, and muscle relaxation
2)
3)
4)
5)
Levobupivacaine

Provide epidural analgesia for labor.

Levobupivacaine and bupivacaine have equivalent analgesic
efficacy. motor blockade was similar between the groups.

Fentanyl significantly reduces levobupivacaine requirements
for epidural analgesia in labor.

Levobupivacaine is not currently being marketed in the
United States but is available in many other countries.
Lidocaine

Used for many years in obstetrics.

Quick onset of action with an intermediate duration of
action.

UV/M ratios= 0.4 to 0.6

Not popular for labor analgesia because of motor block.
Lidocaine

Controversy in use of 5% hyperbaric lidocaine for SA
because of reports of transient neurologic
symptoms(TNS).

Recent data indicates that the 2.5% and 2% solutions may
still cause transient radicular irritation.
2-Chloroprocaine

An ester local anesthetic

Rapid onset time and short-lived duration of action.

Rapid metabolism by ester hydrolysis (half-life, 45
seconds) makes it a safe agent for use in obstetrics
because almost no drug crosses the placenta.
Disadvantage of chloroprocaine
Interfer with the action of epidural opioids. due to antagonism
at the µ- and κ-opioid receptors.
 May also interfere with the action of epidural bupivacaine.
 Previous preparations of 2-chloroprocaine were considered to
be neurotoxic( arachnoiditis after unintentional subarachnoid
injection )
 Replacement of metabisulfite and methylparaben has
eliminated the risk of neurotoxicity.
.

Chloroprocaine

Caution is advised because despite the availability of
preservative-free preparations marketed as MPF
(methylparaben free), formulations containing preservatives
are still commercially available.

Recent reports, advocate the use of spinal chloroprocaine.
Thank you for your attention