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Far Eastern UniversityDr. Nicanor Reyes Medical Foundation
Department of Obstetrics and Gynecology
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MATERNAL RISK FACTORS THAT SHOULD PROMPT
ANESTHESIA CONSULTATION:
1. Marked Obesity
2. Severe edema or anatomical abnormalities of face, neck, or
spine,
including trauma or surgery
3. Abnormal dentition, small mandible, or difficulty opening
mouth
4. Extremely short stature , short neck, or arthritis of the neck
5. Goiter
6. Serious maternal medical problems, such as cardiac,pulmonary or
neurological disease
7. Bleeding disorders
8. Severe preeclampsia9. Previous histor of anesthetic com lications
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Goals for Optimizing ObstetricalAnesthesia Services
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Availability of a licensed practitioner who is credentialed
to administer an appropriate anesthetic whenevernecessary and to maintain support of vital functions in
an obstetrical emergency
Availability of anesthesia personnel to permit the start of
a cesarean delivery within 30 minutes of the decision toperform the procedure
Anesthesia personnel immediately available to perform
an emergency cesarean delivery during the active laborof a woman attempting vaginal birth after cesarean
Appointment of a qualified anesthesiologist to be
responsible for all anesthetics administered
Goals for Optimizing Obstetrical AnesthesiaServices
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Availability of a qualified physician with
obstetrical privileges to perform operative
vaginal or cesarean delivery during
administration of anesthesia
Availability of equipment, facilities, and
support personnel equal to that provided in the
surgical suite
Immediate availability of personnel, other than
the surgical team, to assume responsibility for
resuscitation of the depressed newborn
Goals for Optimizing Obstetrical AnesthesiaServices
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ROLE OF AN OBSTETRICIAN
Every obstetrician should be
proficient in local and pudendal
analgesia that may be administeredin appropriately selected
circumstances
General anesthesia should beadministered only by those with
special training
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Principles of Pain Relief
Labor pain is a highly individual reflection of variablestimuli.
These stimuli are modified by emotional, motivational,cognitive, social, and cultural circumstances
Choice among a variety of methods and individualizationof pain relief is desirable
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Nonpharmacological Methods of
Pain Control
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1.LAMAZEPain often can be lessened by teaching pregnant women
relaxed breathing and their labor partners psychological
support techniques.
The presence of a supportive spouse or other family member,
of conscientious labor attendants, and of a considerate
obstetrician who instills confidence, have all been found to be
of considerable benefit.
2. CLINICAL HYPNOSIS power of the mind to heal thebody; increases of beta endorphins in the peripheral blood
3. ACUPUNCTURE
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PARENTERAL AGENTS
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1. Meperidine and Promethazine
Meperidine 50-100mg and Promethazine 25 mg administered intramuscularly at intervals of 2 to 4
hours
More rapid effect if given intravenously in doses of 25
to 50mg every 1 to 2 hours
Meperidine - readily crosses the placenta
Half-life: 13 hours or longer in the newborn
PARENTERAL AGENTS
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2. Butorphanol (Stadol)
Synthetic narcotic
1-2mg doses Major side effects: somnolence, dizziness anddysphoria
Neonatal respiratory depression is less than withMeperidine
Antagonizes the narcotic effects of Meperidine
3. Fentanyl
Short-acting, very potent synthetic opioid
50-100 g intravenously every hour
Main disadvantage: short duration of action
PARENTERAL AGENTS
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1. Meperidineis the most common opioid used worldwide for painrelief in labor.
2. There is no convincing evidence demonstrating that alternative
opioids are better.
3. There is no evidence that parenteral opioids influence the length
of labor or need for obstetrical intervention.
4. Epidural analgesia provides superior pain relief.
Meperidine or other narcotics cause newborn respiratorydepression
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Naloxone
Capable of reversing respiratory depression induced by
opioid narcotics Withdrawal symptoms may be precipitated in recipients
who are physically dependent on narcotics
Contraindicated in newborn of narcotic-addicted mother
NITROUS OXIDE
Self-administered mixture of 50% nitrous oxide and oxygen
provides satisfactory analgesia during labor
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REGIONAL ANALGESIA
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Uterine Innervation
Pain during 1st stage of labor generated largely from the
uterus
Visceral sensory fibers from the uterus, cervix, and uppervagina traverse through the Frankenhuser ganglion, which lies
just lateral to the cervix, into the pelvic plexus, and then to the
middle and superior internal iliac plexuses.
Early in labor pain of uterine contractions transmitted throughthe T11 and T12 nerves
Motor pathways leave the spinal cord at the level of the T7
and T8 vertebrae
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Motor:T7 & T8
Early
labor:T11
T12
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Lower Genital Tract Innervation
Pain with vaginal delivery arises from stimuli from
the lower genital tract.
Transmitted primarily through the pudendal nerve
Pudendal nerve sensory nerve fibers derived
from the ventral branches of the S2 through S4nerves
Passes beneath the posterior surface of the
sacrospinous ligament just as the ligament
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ANESTHETIC AGENTS(Table 19-3. Some Local Anesthetic Agents used in Obstetrics)
Central Nervous System Toxicity
Early symptoms are those of stimulation but as serum
levels increase depression follows
Light-headedness, dizziness, tinnitus, metallic taste and
numbness of the tongue and mouth
Bizarre behavior, slurred speech, muscle fasciculation and
excitation and generalized convulsions, followed by loss of
consciousness
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Cardiovascular Toxicity
Generally develop later than those from
cerebral toxicity
Hypertension and tachycardia, which is
soon followed by hypotension and cardiacarrhythmias
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PUDENDAL BLOCK
Relatively safe and simple
A tubular introducer that allows 1.0 to 1.5 cm
of a 15-cm 22-gauge needle is used to guide
the needle into position over the pudendal
nerve
Complications: may cause serious systemictoxicity, hematoma formation from perforation
of a blood vessel
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Provides satisfactory pain relief during the firststage of labor
Lidocaine or Chloroprocaine 5-10mL isinjected into the cervix laterally at 3 and 9
oclock
Complication: fetal bradycardia usuallydevelops within 10 minutes and may last up to
30 minutes
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Advantages: short procedure time, rapid onset ofblock, high success rate
Vaginal Delivery
Popular form of analgesia for forceps or vacuumdelivery
Should extend to the T10 dermatome
LidocaineorBupivacaine
Cesarean Delivery Level of sensory blockade extending to the T4
dermatome
10-12 mg of hyperbaric bupivacaineor50-75mg
of hyperbaric Lidocaine
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Hypotension
High spinal blockade
Spinal (Postural puncture) headache
Convulsions
Bladder dysfunction
Oxytocics and hypertension
Arachnoiditis and meningitis
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ABSOLUTE CONTRAINDICATIONS
Refractory maternal hypotension Maternal coagulopathy
Treatment with once-daily dose of low-molecular-
weight heparin within 12 hours
Untreated bacteremia Skin infection over site of needle placement
Increased intracranial pressure caused by mass lesion
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EPIDURAL ANESTHESIA
Continuous Lumbar Epidural Block
VAGINAL DELIVERY - Block from T10 to S5dermatomes
CESAREAN DELIVERY - Block extending fromthe T4 to S1
dermatomes is desired
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Total spinal blockade
Ineffective analgesia
Hypotension
Central nervous stimulation
Maternal pyrexia
Back pain
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Effect on LaborProlongs active phase of labor by 1 hour
Increases the need for instrumental delivery due to prolonged
second-stage labor
Fetal Heart Rate associated with improved neonatal acid-
base status compared with meperidine
Cesarean Delivery Epidural administration of dilute
solutions of local anesthetic is less likely to increase cesareandelivery rates than concentrated solutions.
Timing of epidural placement women in labor should not be
required to reach 4-5cm of cervical dilatation before receiving
epidural analgesia
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Safety
No maternal deathsVery low incidence of complications
Contraindications
Maternal hemorrhage
Infection at or near the sites of puncture
Suspicion of neurological disease
Anticoagulation women receiving anticoagulation therapyare at increased risk for spinal cord hematoma a
compression
EPIDURAL ANESTHESIA
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EPIDURAL ANESTHESIA
Severe Preeclampsia-Eclampsia
Most have come to favor epidural blockade for labor and deliveryin women with severe preeclampsia
Labor epidural analgesia is to be considered in women withhypertensive disorders, but it is not to be considered as therapy.
Provided superior pain relief without significant increase inmaternal or neonatal complications
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Epidural Opiate Analgesia
Most often given with a local anesthetic agent such asbupivacaine
ADVANTAGES
Rapid onset of pain reliefDecrease in shivering
Less dense motor blockade
SIDE EFFECTSPruritusUrinary retention
Immediate or delayed respiratory depression
EPIDURAL ANESTHESIA
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COMBINED SPINAL-EPIDURALTECHNIQUES
May provide rapid and effective analgesia for labor as well as
for cesarean delivery
Needle-through-needle technique
An introducer needleis first placed in the epidural space, then a small-gauge spinalneedle is introduced through the epidural needle into the
subarachnoid space.
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LOCAL INFILTRATION FOR CESAREAN DELIVERY
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LOCAL INFILTRATION FOR CESAREAN DELIVERYTo augment an inadequate or patchy regional block that
was given in an emergency
1st - halfway between the
costal margin and iliac crest
in midaxillary line to block
the 10th, 11th, and 12th
intercostal nerves.
2nd - along the line ofproposed skin incision.
3rd - at the external inguinal
blocks the genitofemoral and
ilioinguinal nerves.
12
3
G S S
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GENERAL ANESTHESIA
PATIENT PREPARATION
ANTACIDS
Administered shortly before induction of anesthesia
Sodium citrate with citric acid (Bacitra) 30mL given 45minutes before surgery
UTERINE DISPLACEMENT
With lateral uterine displacement, the duration of
general anesthesia has less effect on neonatal condition
than when the woman remains supine.
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Severe Preeclampsia-Eclampsia
Most have come to favor epidural blockade for
labor and delivery in women with severe
preeclampsia
Labor epidural analgesia is to be considered in
women with hypertensive disorders, but it is not to
be considered as therapy.
Provided superior pain relief without significant
increase in maternal or neonatal complications
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Preoxygenation
Because functional reserve capacity is reduced,
pregnant women become hypoxemic more rapidly
during periods of apnea than do nonpregnant
patients.
100% oxygen via face mask for 2-3 minutes prior
to anesthesia induction to replace nitrogen in the
lungs with oxygen
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INDUCTION OF ANESTHESIA
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Thiopental
Ease and rapid, with minimal risk of vomitingPoor analgesic agents
May cause appreciable newborn depression if given alone
Ketamine
Used to render patient unconscious
Given intravenously in low doses of0.2 to 0.3 mg/kg
Not associated with hypotensionUsually causes a rise in blood pressure
Unpleasant delirium and hallucinations are commonly induced
by this agent.
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INTUBATION
Succinylcholine
Rapid-onset and short-acting muscle
relaxant
Sellick maneuverCricoid pressure is
used to occlude the esophagus frominduction until intubation
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Although uncommon, failed intubation is a major cause
of anesthesia-related maternal mortality.
A history of previous difficulties with intubation as well as
a careful assessment of anatomical features of the neck,
maxillofacial, pharyngeal, and laryngeal structures may
help predict a difficult intubation.
Edema of the airway may develop intrapartum and
present considerable difficulties.
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Morbid obesity is also a major risk factor for failed or difficult
intubation.
An important principle is to start the operative procedure only
after it has been ascertained that tracheal intubation has been
successful and that adequate ventilation can be accomplished.
Following failed intubation, the woman is ventilated by mask
and cricoid pressure is applied to reduce the chance ofaspiration.
Surgery may proceed with mask ventilation or the woman
may be allowed to awaken.
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GAS ANESTHETICS
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Volatile Anesthetics
Most commonly used is isoflurane.Potent nonexplosive agent that produce remarkable
uterine relaxation when given in high, inhaled concentration
USES:
Internal podalic version of the second twin
Breech decomposition
Replacement of acutely inverted uterus
Occasionally associated with hepatitis and massive
hepatic necrosis
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EXTUBATION
The tracheal tube may be safely removed only if the
woman is conscious to a degree that enables her tofollow commands and is capable of maintaining
oxygen saturation with spontaneous respiration.
ASPIRATION
Aspiration pneumonitis has been the most common
cause of anesthetic deaths in obstetrics.
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FASTING
A fasting period of 8 hours or more
is preferable for uncomplicatedparturients undergoing electivecesarean delivery.
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The right mainstem bronchus usually offers the
simplest pathway for aspirated material to reach
the lung parenchyma, and therefore the right
lower lobe is most often involved.
The woman who aspirates may develop
evidence of respiratory distress immediately oras long as several hours after aspiration,
depending in part on the material
aspirated and the severity of the process.
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Types of Analgesic and Sedation
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Effects Side EffectsMeperidine 50-100mg
with Promethazine
25mg IM every 3 to 4
hours
Does not lead to
prolongation of labor,
rather an increase in
uterine activity
Depressant effect in
the fetus follows peak
analgesic affect in
mother
Butorphanol 1-2mg Compares with 40-60mg of MeperidineLess respiratory
depression
Not givencontiguously with
Meperidine,
antagonizes the
narcotic effect of
MeperidineFentanyl 50-100ug/hr Safe, without effect on
active phase of labor
Nalbuphine 15-20mg No neonatal
yp g
R t f M h i f Ad t Di d tGeneral Anesthesia
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Route of
AdministrationMechanism of
ActionAdvantages Disadvantages
Nitrous
Oxide
Inhalation Alter the functionof receptors for
neurotransmitters,nonselectively,
controlling the
overall state of
consciousness and
response to
sensory stimuli
Low potency,
therefore must be
combined withother agents;
Rapid induction and
recovery;
Good analgesic
properties;
Does not prolonglabor or interfere
with uterine
contractions
Produces
analgesia and
alteredconsciousness;
Risk of bone
marrow
depression due to
inhibition of
Methioninesynthase with
prolonged
administration
Enflura
neInhalation Same Halogenated
anaesthetic similar
to halothane;
Less metabolism
than halothane,
therefore less risk
of toxicity;
Fast induction and
recovery than
Some risk of
epilepsy-like
seizures
Route of Mechanism of Advantages Disadvantages
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Administration ActionIsoflurane Inhalation Same Similar to Enflurane,
but lacks
epileptogenic
property;May precipitate
myocardial ischaemia
in patients with
coronary disease
Unconsciousness;Potential for
aspiration in an
unprotected airway;Crosses the placenta
produce narcosis in
the fetus;Produces uterine
relaxation in high
dosesHalothane Inhalation Same Widely used agent Potential for
aspiration in an
unprotected airway;Crosses the placenta
produce narcosis inthe fetus;
Produces uterine
relaxation in high
doses;
Risk of liver damage
if used repeatedly
Indication Complications and theirManagement
Precautions
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ManagementPudendal block Provide analgesia for
spontaneous deliveryCan be used with epidural
analgesia given during
labor
Intravascular injection may
cause serious toxicity
characterizedMay not provide
adequate analgesia for
other than outlet delivery
or when delivery requires
extensive manipulationParacervical block Provide good to excellent
pain relief during the first
stage of laborFetal bradycardia, as a
consequence of
transplacental transfer of
the anesthetic agent
Relatively short acting,
may have to be repeated
during labor
Spinal(subarachnoid)block
For forceps and vacuum
deliveryHypotensionTotal spinal blockageSpinal headacheConvulsionsBladder dysfunction
Disorder of coagulation
and defective hemostasis
preclude the use of spinal
analgesiaEpidural block Relief of pain of uterine
contractions and delivery,
vaginal or abdominalHypotensionUrinary retentionCardiorespiratory arrestMaternal pyrexiaBack pain
Before any injection of
the local anesthetic agent,
a test dose is given and
the women observed for
features of toxicity from
intravascular injection
and signs of spinal
blockade form
subarachnoid injection
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Recommended