o. anesthesia

7/31/2019 o. Anesthesia

1/59

Far Eastern UniversityDr. Nicanor Reyes Medical Foundation

Department of Obstetrics and Gynecology


2/59

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


3/59

Goals for Optimizing ObstetricalAnesthesia Services


4/59

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


5/59

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


6/59

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


7/59

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


8/59

Nonpharmacological Methods of

Pain Control


9/59

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


10/59

PARENTERAL AGENTS


11/59


12/59

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


13/59

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


14/59

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


15/59

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


16/59

REGIONAL ANALGESIA


17/59

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


18/59


19/59

Motor:T7 & T8

Early

labor:T11

T12


20/59

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


21/59


22/59

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


23/59

Cardiovascular Toxicity

Generally develop later than those from

cerebral toxicity

Hypertension and tachycardia, which is

soon followed by hypotension and cardiacarrhythmias


24/59

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


25/59


26/59

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


27/59

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


28/59


29/59

Hypotension

High spinal blockade

Spinal (Postural puncture) headache

Convulsions

Bladder dysfunction

Oxytocics and hypertension

Arachnoiditis and meningitis


30/59

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


31/59

EPIDURAL ANESTHESIA

Continuous Lumbar Epidural Block

VAGINAL DELIVERY - Block from T10 to S5dermatomes

CESAREAN DELIVERY - Block extending fromthe T4 to S1

dermatomes is desired


32/59

Total spinal blockade

Ineffective analgesia

Hypotension

Central nervous stimulation

Maternal pyrexia

Back pain


33/59

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


34/59

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


35/59

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


36/59

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


37/59

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.


38/59

LOCAL INFILTRATION FOR CESAREAN DELIVERY


39/59

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


40/59

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.


41/59

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


42/59

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


43/59

INDUCTION OF ANESTHESIA


44/59

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.


45/59

INTUBATION

Succinylcholine

Rapid-onset and short-acting muscle

relaxant

Sellick maneuverCricoid pressure is

used to occlude the esophagus frominduction until intubation


46/59

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.


47/59

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.


48/59

GAS ANESTHETICS


49/59

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


50/59


51/59

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.


52/59

FASTING

A fasting period of 8 hours or more

is preferable for uncomplicatedparturients undergoing electivecesarean delivery.


53/59

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.


54/59

Types of Analgesic and Sedation


55/59

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


56/59

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


57/59

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


58/59

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


59/59

o. anesthesia

Documents