Obstetrical anesthesia

OBSTETRICAL ANESTHESIA

Dr. John Snow

born 15 March 1813 in York, England.Queen Victoria was given chloroform by John Snow for the birth of her eighth child and this did much to popularize the use of pain relief in labor.

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http://en.wikipedia.org/wiki/File:John_Snow.jpg

Does Labor Pain Need Analgesia?


Analgesia for Labor and Delivery

• Always controversial!

• “Birth is a natural process”

• Women should suffer!!

• Concerns for mother’s safety

• Concerns for baby

• Concerns for effects on labor


Why have a Caregiver dedicated to pain management during

labor and delivery?

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• Labor and delivery result in severe pain for most women.

• In an attempt to quantify this pain, parturients were asked to rate their pain during labor.

• These results were then compared to values obtained from patients in a general pain clinic and emergency department.

• The pain of childbirth was greater than a fractured arm and cancer pain.

• Only causalgia and amputation of a digit exceeded the pain of labor and delivery.

• Parturients described the pain as sharp, cramping, aching, throbbing, stabbing, hot, shooting, and tight.


What is the cause of labor pain in stage 1? What type of pain is it?

• The pain resulting from the first stage of labor is primarily due to dilatation of the cervix with consequent distention and stretching.

• As the uterus contracts, the fetal head pushes against the cervix and causes dilatation.

• Therefore, stage 1 pain generally occurs only during uterine contraction.


• While the majority of pain during this stage occurs from the fetal head pushing against the cervix, there is also pain from pressure and stretching of the uterine muscles, which activate the high-threshold mechanoreceptors.

• In the first stage of labor, the pain is visceral.• It is strong and dull, and occurs over the lower

abdomen between the umbilicus and the symphysis pubis, laterally over the iliac crest, and posteriorly in the skin and soft tissue over the lower lumbar spines.


The location of labor pain in stage 1?? • The location of this pain is explained by the

concept of referred pain. • The sensory nerves of the uterus and cervix

leave the cervix and join the sympathetic nerves as they pass through the hypogastric plexus to the sympathetic chain, synapsing within the dorsal horn of the spinal cord at T10, T11, T12, and L1.


• This area of the spinal cord receives not only these visceral high-threshold afferents, but also the low-threshold cutaneous afferents of the skin from T10, T11, T12, and L1.

• With the convergence of both somatic and visceral fibers within the same area of the spinal cord, the parturient interprets the uterine pain as originating from the cutaneous afferents of these spinal segments. The pain is referred to this area.

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What is the cause of labor pain in stage 2? What type of pain

is it?

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• Second-stage pain occurs as the fetus descends through the birth canal.

• This results in stretching and tearing of fascia, skin, and subcutaneous tissue.

• This somatic pain is transmitted primarily through the pudendal nerve.

• The pudendal nerve is derived from the anterior primary divisions of sacral nerves, S2 S3 and S4.

• Of note, the fetus often begins to descend during the first stage of labor.

• During the transitional stage of the first stage, it is not uncommon for the mother to experience both visceral and somatic pain

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Labor Pain at different Stages of LaborLabor Pain at different Stages of Labor

Eltzschig, Leiberman, Camann, NEJM 348; 319:2003Eltzschig, Leiberman, Camann, NEJM 348; 319:20039/3/2013 13BITEW(IESO)

The Physiology of Pain in Labor11stst stage of labor stage of labor – mostly visceral

◦ Dilation of the cervix and distention of the lower uterine segment

◦ Dull, aching and poorly localized◦ Slow conducting, visceral C fibers, enter spinal cord at

T10 to L122ndnd stage of labor stage of labor – mostly somatic

◦ Distention of the pelvic floor, vagina and perineum◦ Sharp, severe and well localized◦ Rapidly conducting A-delta fibers, enter spinal cord

at S2 to S4


Pain Pathways of LaborPain Pathways of Labor


LaborLabor

CardiovascularCardiovascular

UrinaryUrinary

Neuro-endocrine Neuro-endocrine

post-traumatic stress syndromepost-traumatic

stress syndrome

RespiratoryRespiratoryGastro-intestinalGastro-intestinal


Potential effects of maternal hyperventilation and subsequent hypocarbia on oxygen delivery to the fetus


Pathways of labor painPathways of labor pain9/3/2013 18BITEW(IESO)

How do psychological factors influence labor pain?

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While labor is a physiologic process, psychological factors also affect the pain.

Anxiety is a particularly powerful factor in reducing pain tolerance.HOW??

Attention, the selective orientation of the receptor system to one source or pattern of stimulation to the exclusion of other sources, either enhances or diminishes the painful experience.

Motivation is another psychodynamic mechanism that can have a marked influence on the physiologic, behavioral, and affective aspects of pain.

Breathing exercises divert the mother's attention from the pain of contractions.

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IntroductionPain relief in labor presents unique problems. Labor begins without warning, and obstetrical

anesthesia may be required within minutes of a full meal.

Vomiting with aspiration of gastric contents is a constant threat that poses serious maternal morbidity and mortality.

Moreover, a host of disorders unique to pregnancy, such as preeclampsia, placental abruption, and chorioamnionitis, all superimposed on unique physiological adaptations of pregnancy, are directly affected by the choice of analgesia and anesthesia selected.


Introduction

Anesthesia complications caused 1.6 percent of pregnancy-related maternal deaths

Several factors likely have contributed to improved safety of obstetrical anesthesia;

the recent trend toward increased use of regional analgesia, rather than general anesthesia, may be the most significant factor.

The increased availability of in-house anesthesia coverage almost certainly is another important reason


GENERAL PRINCIPLES a woman’s request for labor pain relief is sufficient

medical indication for its provision. it is the responsibility of the obstetrician or certified

nurse-midwife, in consultation with an anesthesiologist, if appropriate, to formulate a suitable plan for pain relief.

Identification of any of the risk factors, should prompt consultation with anesthesia personnel to permit a joint management plan.

This plan should include strategies to minimize the need for emergency anesthesia in women for whom such anesthesia would be especially hazardous.



Maternal Risk Factors That Should Prompt Anesthesia Consultation

Marked obesity Severe edema or anatomical abnormalities of face, neck, or

spine, including trauma or surgery Abnormal dentition, small mandible, or difficulty opening

mouth Extremely short stature, short neck, or arthritis of the neck Goiter Serious maternal medical problems, such as cardiac,

pulmonary, or neurological disease Bleeding disorders Severe preeclampsia Previous history of anesthetic complications Obstetrical complications likely to lead to operative delivery—

e.g., placenta previa or higher-order multiple gestation9/3/2013 25BITEW(IESO)

Goals for optimizing obstetrical anesthesia services

1. Availability of a licensed practitioner who is credentialed to administer an appropriate anesthetic whenever necessary and to maintain support of vital functions in an obstetrical emergency.

2. Availability of anesthesia personnel to permit the start of a cesarean delivery within 30 minutes of the decision to perform the procedure.

3. Anesthesia personnel immediately available to perform an emergency cesarean delivery during the active labor of a woman attempting vaginal birth after cesarean (Candidates for a Trial of Labor).

4. Appointment of a qualified anesthesiologist to be responsible for all anesthetics administered.

5. Availability of a qualified physician with obstetrical privileges to perform operative vaginal or cesarean delivery during administration of anesthesia.

6. Availability of equipment, facilities, and support personnel equal to that provided in the surgical suite.

7. Immediate availability of personnel, other than the surgical team, to assume responsibility for resuscitation of the depressed newborn (see Chap. 28, Newborn Resuscitation).


Role of Obstetrician

Every obstetrician should be proficient in local and pudendal analgesia.

Regional analgesia may be administered by the properly trained obstetrician in appropriately selected circumstances.

In general, however, it is preferable for an anesthesiologist or anesthetist to provide this care so that the obstetrician can focus attention on the concerns for the laboring woman and her fetus.

General anesthesia should be administered only by those with special training.


Principles of Pain Relief

the experience of labor pain is a highly individual reflection of variable stimuli that are uniquely received and interpreted by each woman individually.

These stimuli are modified by emotional, motivational, cognitive, social, and cultural circumstances.

The complexity and individuality of the experience suggest that a woman and her caregivers may have a limited ability to anticipate her pain experience prior to labor.

Thus, choice among a variety of methods and individualization of pain relief is desirable.


Goals of Labour Analgesia

• Dramatically reduce pain of labor• Should allow parturient to participate in

birthing experience• Minimal motor block to allow ambulation• Minimal effects on fetus• Minimal effects on progress of labor


What Are the Types of Labor Analgesia?

What analgesic options are available for labor?


Types of Labor Analgesia

1. Non-pharmacological analgesia2. Pharmacological3. Regional Anesthesia/Analgesia4. General Anesthesia


NONPHARMACOLOGICAL METHODS OF PAIN CONTROL

Fear and the unknown potentiate pain. Make a woman who is free from fear, and develop confidence

in the obstetrical staff that cares for her Avoid emotional tension Lamaze teaching pregnant women relaxed breathing and their labor

partners psychological support techniques. Motivatation the presence of a supportive spouse


ANALGESIA AND SEDATION DURING LABOR


ANALGESIA AND SEDATION DURING LABOR

• When uterine contractions and cervical dilatation cause discomfort, pain relief with a narcotic such as meperidine, plus one of the tranquilizer drugs such as promethazine, is usually appropriate.

• With a successful program of analgesia and sedation, the mother should rest quietly between contractions.

• In this circumstance, discomfort usually is felt at the acme of an effective uterine contraction, but the pain is generally not unbearable. 9/3/2013 34BITEW(IESO)

Neuraxial Opioids

The following opioids have been used:Morphine, fentanyl, sufentanil, meperidine,

diamorphine.


Parenteral Agents for Labor PainAgent Usual Dose Frequency Onset Neonatal Half-

Life

Meperidine 25–50 mg (IV) 1–2 hr 5 min 13–22.4 hr

50–100 mg (IM) 2–4 hr 30–45 min 63 hr for active metabolites

Fentanyl 50–100 g (IV) 1 hr 1 min 5.3 hr

Nalbuphine 10 mg (IV or IM)

3 hr 2–3 min (IV) 4.1 hr

15 min (IM)

Butorphanol 1–2 mg (IV or IM)

4 hr 1–2 min (IV) Not known

10–30 min (IM) Similar to nalbuphine in adults

Morphine 2–5 mg (IV) 4 hr 5 min 7.1 hr

10 mg (IM) 30–40 min 9/3/2013 36BITEW(IESO)

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NEW DRUGS:

• Clonidine • Neostigmine• Midazolam


Parenteral AgentsMeperidine and Promethazine

Meperidine, 50 to 100 mg, with promethazine, 25 mg, may be administered intramuscularly at intervals of 2 to 4 hours.

A more rapid effect is achieved by giving meperidine intravenously in doses of 25 to 50 mg every 1 to 2 hours.

Whereas analgesia is maximal about 30 to 45 minutes after an intramuscular injection, it develops almost immediately following intravenous administration.

Meperidine readily crosses the placenta, and the half-life is approximately 13 hours or longer in the newborn


Butorphanol (Stadol)

This synthetic narcotic, given in 1- to 2-mg doses, compares favorably with 40 to 60 mg of meperidine.

The major side effects are somnolence, dizziness, and dysphoria.

Neonatal respiratory depression is reported to be less than with meperidine, but care must be taken that the two drugs are not given contiguously because butorphanol antagonizes the narcotic effects of meperidine

a sinusoidal fetal heart rate pattern following butorphanol administration


FentanylThis short-acting and potent synthetic opioid

may be given in doses of 50 to 100mcg intravenously every hour.

Its main disadantage is a short duration of action, which requires frequent dosing or the use of a patient-controlled intravenous pump.


Efficacy and Safety of Parenteral Agents

• Meperidine is the most common opioid used worldwide for pain relief in labor.

• There is no convincing evidence demonstrating that alternative opioids are better.

• There is no evidence that parenteral opioids influence the length of labor or need for obstetrical intervention.

• Epidural analgesia provides superior pain relief.• Intravenous and intramuscular sedation are not without

risks. maternal anesthetic-related deaths were from such sedation-

aspiration, inadequate ventilation, and overdosage. Moreover, meperidine or other narcotics used during labor may cause

newborn respiratory depression.


Narcotic Antagonists Naloxone is a narcotic antagonist capable of reversing

respiratory depression induced by opioid narcotics. It acts by displacing the narcotic from specific receptors

in the central nervous system. Withdrawal symptoms may be precipitated in recipients

who are physically dependent on narcotics. For this reason, naloxone is contraindicated in a

newborn of a narcotic-addicted mother. Naloxone, along with proper ventilation, may be given

to reverse respiratory depression in a newborn infant whose mother received narcotics.


Nitrous OxideA self-administered mixture of 50-percent

nitrous oxide (N2O) and oxygen provides satisfactory analgesia during labor for many women.

Some preparations are premixed in a single cylinder (Entonox), and in others, a blender mixes the two gases from separate tanks (Nitronox).

The gases are connected to a breathing circuit through a valve that opens only when the patient inspires. 9/3/2013 44BITEW(IESO)

Nitrous Oxide The use of intermittent nitrous oxide for labor pain ,the following

technique suggested:1) Instruct the woman to take slow deep breaths and to begin inhaling 30

seconds before the next anticipated contraction and to cease when the contraction starts to recede.

2) Remove the mask between contractions and encourage her to breathe normally. No one but the patient or knowledgeable personnel should hold the mask.

3) Instruct a caregiver to remain in verbal contact with the patient.4) Provide the expectation that the pain will likely not be eliminated, but

that the gas should provide some relief.5) Ensure intravenous access, pulse oximetry, and adequate scavenging of

exhaled gases.6) Use with additional caution after previous opioid administration

because the combination can more easily render a woman unconscious and unable to protect her airway.


Regional Analgesia


Regional anesthetic techniques, were introduced to obstetrics in 1900, when Oskar Kreis described the use of spinal anesthesia. Unfortunately he was an obstetrtian


Regional Analgesia

Various nerve blocks have been developed over the years to provide pain relief during labor and delivery.

They are correctly referred to as regional analgesics.


Regional Anesthesia/Analgesia

• Epidural • Spinal• Combined Spinal Epidural (CSE)• Continuous spinal analgesia • Paracervical block• Lumbar sympathetic block• Pudendal block• Perineal infiltration


Sensory Innervation of the Genital TractUterine Innervation

Pain during the first stage of labor is generated largely from the uterus.

Visceral sensory fibers from the uterus, cervix, and upper vagina traverse through the Frankenhäuser ganglion, which lies just lateral to the cervix, into the pelvic plexus, and then to the middle and superior internal iliac plexuses.

From there, the fibers travel in the lumbar and lower thoracic sympathetic chains to enter the spinal cord through the white rami communicantes associated with the T10 through T12 and L1 nerves.

Early in labor, the pain of uterine contractions is transmitted predominantly through the T11 and T12 nerves.


Pathways of labor painPathways of labor pain9/3/2013 51BITEW(IESO)

Uterine Innervation

The motor pathways to the uterus leave the spinal cord at the level of the T7 and T8 vertebrae.

Theoretically, any method of sensory block that does not also block the motor pathways to the uterus can be used for analgesia during labor.


Lower Genital Tract InnervationPain with vaginal delivery arises from stimuli from the

lower genital tract. These are transmitted primarily through the pudendal

nerve, the peripheral branches of which provide sensory innervation to the perineum, anus, and the more medial and inferior parts of the vulva and clitoris.

The pudendal nerve passes beneath the posterior surface of the sacrospinous ligament just as the ligament attaches to the ischial spine.

The sensory nerve fibers of the pudendal nerve are derived from the ventral branches of the S2 through S4 nerves.


Anesthetic Agents• Some preparations that contain dilute epinephrine to prolong

the action of the anesthetic will also cause symptoms when a test dose is inadvertently given intravenously.

• The dose of each agent varies widely and is dependent on the particular nerve block and physical status of the woman.

• The onset, duration, and quality of analgesia can be enhanced by increasing the dose.

• This can be done safely by only incrementally administering small-volume boluses of the agent and by carefully monitoring for early warning signs of toxicity.

• Administration of these agents must be followed by appropriate monitoring for adverse reactions, and equipment and personnel to manage these reactions must be immediately available.


Most often, serious toxicity follows inadvertent intravenous injection. For this reason, when epidural analgesia is initiated, dilute epinephrine is sometimes added and given as a test dose.

A sudden significant rise in the maternal heart rate or blood pressure immediately after administration suggests intravenous catheter placement.

Personnel using these agents must be cognizant that these agents are manufactured in more than one concentration and ampule size, which increases the potential for dosing errors.


Some Local Anesthetic Agents Used in Obstetrics

Plain Solutions

Anesthetic Agent

Usual Concentration (%)

Usual Volume (mL)

Usual Dose (mg)

Onset Average Duration (min)

Clinical Use

Amino-esters

2-Chloroprocaine

1–2 20–30 400–600 Rapid 15–30 Local or pudendal block

2–3 15–25 300–750 30–60 Epidural (not subarachnoid) for cesarean delivery

Tetracaine

0.2 — 4 Slow 75–150 Low spinal block/6%glucose

0.5 — 7–10 75–150 Spinal for cesarean delivery/5%glucose9/3/2013 57BITEW(IESO)

Amino-amides

Lidocaine 1 20–30 200–300 Rapid 30–60 Local or pudendal block

2 15–30 300–450 60–90 Epidural for cesarean delivery

5 1–1.5 50–75 45–60 Spinal for cesarean delivery or puerperal tubal ligation/7.5%glucose

5 0.5–1 25–50 30–60 Spinal for vaginal delivery/7.5%glucose


Bupivacaine 0.5 15–20 50–100 Slow 90–150 Epidural for cesarean delivery

0.25 8–10 20–25 60–90 Epidural for labor

0.75 1–1.5 7.5–11 60–120 Spinal for cesarean delivery/8.25%glucose

Ropivacaine

0.5 15–20 75–100 Slow 90–150 Epidural for cesarean delivery

0.25 8–10 20–25 60–90 Epidural for labor


• Addition of glucose to local anesthetics creates a hyperbaric solution, which is heavier and denser than cerebrospinal fluid.


Toxicity

• Systemic toxicity from local anesthetics typically manifests in the central nervous and cardiovascular systems.


Central Nervous System ToxicityEarly symptoms are those of stimulation but, as

serum levels increase, depression follows.Symptoms may include light-headedness,

dizziness, tinnitus, metallic taste, and numbness of the tongue and mouth.

Patients may show bizarre behavior, slurred speech, muscle fasciculation and excitation, and ultimately, generalized convulsions, followed by loss of consciousness.

The convulsions should be controlled, an airway established, and oxygen delivered.


Central Nervous System ToxicitySuccinylcholine abolishes the peripheral

manifestations of the convulsions and allows tracheal intubation.

Thiopental or diazepam act centrally to inhibit convulsions.

Magnesium sulfate, administered according to the regimen for eclampsia, also controls convulsions.


Central Nervous System Toxicity Abnormal fetal heart rate patterns, such as late

decelerations or persistent bradycardia, may develop from maternal hypoxia and lactic acidosis induced by convulsions.

With arrest of the convulsions, administration of oxygen, and application of other supportive measures, the fetus usually recovers more quickly in utero than following immediate cesarean delivery.

Moreover, maternal well-being is usually better served by waiting until the intensity of the hypoxia and the metabolic acidosis have diminished.


Cardiovascular Toxicity

• These manifestations generally develop later than those from cerebral toxicity.

• They do not always follow central nervous system involvement, because they are induced by higher drug levels.

• The notable exception is bupivacaine, which is associated with the development of neurotoxicity and cardiotoxicity at virtually identical serum drug levels.

• Because of this risk of systemic toxicity, use of 0.75-percent solution of bupivacaine for epidural injection was proscribed .


Cardiovascular Toxicity Similar to neurotoxicity, cardiovascular toxicity is characterized

first by stimulation and then by depression. Accordingly, there is hypertension and tachycardia, which soon

is followed by hypotension and cardiac arrhythmias. The latter contribute appreciably to impaired uteroplacental

perfusion and fetal distress. Hypotension is managed initially by turning the woman onto

either side to avoid aortocaval compression. A crystalloid solution is infused rapidly along with intravenously

administered ephedrine. Emergency cesarean delivery should be considered if maternal

vital signs have not been restored within 5 minutes of cardiac arrest.

As with convulsions, however, the fetus is likely to recover more quickly in utero once maternal cardiac output is reestablished.9/3/2013 66BITEW(IESO)

Pudendal Block• This block is a relatively safe and simple method of

providing analgesia for spontaneous delivery. • The end of the introducer is placed against the vaginal

mucosa just beneath the tip of the ischial spine. • The needle is pushed beyond the tip of the director into

the mucosa and a mucosal wheal is made with 1 mL of 1-percent lidocaine solution or an equivalent dose of another local anesthetic.

• To guard against intravascular infusion, aspiration is attempted before this and all subsequent injections.


Pudendal BlockThe needle is then advanced until it touches the

sacrospinous ligament, which is infiltrated with 3 mL of lidocaine.

The needle is advanced farther through the ligament, and as it pierces the loose areolar tissue behind the ligament, the resistance of the plunger decreases. Another 3 mL of the anesthetic solution is injected into this region.

Next, the needle is withdrawn into the introducer, which is moved to just above the ischial spine. The needle is inserted through the mucosa and the rest of 10 mL of solution is deposited. The procedure is then repeated on the other side.



Pudendal Block Within 3 to 4 minutes of the time of injection, the successful

pudendal block will allow pinching of the lower vagina and posterior vulva bilaterally without pain.

It is often of benefit before pudendal block to infiltrate the fourchette, perineum, and adjacent vagina with 5 to 10 mL of 1-percent lidocaine solution directly at the site where the episiotomy is to be made.

Then, if delivery occurs before pudendal block becomes effective, an episiotomy can be made without pain.

By the time of the repair, the pudendal block usually has become effective.

Pudendal block usually does not provide adequate analgesia when delivery requires extensive obstetrical manipulation.

Moreover, such analgesia is usually inadequate for women in whom complete visualization of the cervix and upper vagina, or manual exploration of the uterine cavity, are indicated.


Complications of Pudendal Block

Central Nervous System Toxicity , intravascular injection of a local anesthetic agent may cause serious systemic toxicity.

Hematoma formation Rarely, severe infection may originate at the

injection site. The infection may spread posterior to the hip joint, into the gluteal musculature, or into the retropsoas space.


Paracervical BlockThis block usually provides satisfactory pain relief during

the first stage of labor. Because the pudendal nerves are not blocked, however,

additional analgesia is required for delivery.Usually lidocaine or chloroprocaine, 5 to 10 mL of a 1-

percent solution, is injected into the cervix laterally at 3 and 9 o'clock.

Bupivacaine is contraindicated because of an increased risk of cardiotoxicity.

Because these anesthetics are relatively short acting, paracervical block may have to be repeated during labor.


Complications Of Paracervical Block

Fetal bradycardia(15%) Bradycardia usually develops within 10 minutes

and may last up to 30 minutes.The effect may be the consequence of

transplacental transfer of the anesthetic agent or its metabolites and in turn, a depressant effect on the fetal heart.

For these reasons, paracervical block should not be used in situations of potential fetal compromise.


Spinal (Subarachnoid) Block


Spinal Anesthesia/Analgesia• Used mainly for very

late in labor because it has limited duration of action

• Faster onset than Epidural

• Amount of local anesthetic used is much smaller


Spinal (Subarachnoid) Block• Introduction of a local anesthetic into the

subarachnoid space to effect analgesia has long been used for delivery.

• Advantages include a short procedure time, rapid onset of the block, and high success rate.

• Because of the smaller subarachnoid space during pregnancy, likely the consequence of engorgement of the internal vertebral venous plexus, the same amount of anesthetic agent in the same volume of solution produces a much higher blockade in parturients than in nonpregnant women.


Vaginal Delivery

Low spinal block is a popular form of analgesia for forceps or vacuum delivery.

The level of analgesia should extend to the T10 dermatome, which corresponds to the level of the umbilicus.

Blockade to this level provides excellent relief from the pain of uterine contractions.


Vaginal Delivery

• Several local anesthetic agents have been used for spinal analgesia.

• Addition of glucose to any of these agents creates a hyperbaric solution, which is heavier and denser than cerebrospinal fluid.

• A sitting position causes a hyperbaric solution to settle caudally, whereas a lateral position will have a greater effect on the dependent side.

• Lidocaine given in a hyperbaric solution produces excellent analgesia and has the advantage of a rapid onset and relatively short duration.


Vaginal Delivery

• Bupivacaine in an 8.25-percent dextrose solution provides satisfactory anesthesia to the lower vagina and the perineum for more than 1 hour.

• Neither is administered until the cervix is fully dilated and all other criteria for safe forceps delivery have been fulfilled.

• Preanalgesic intravenous hydration with 1 L of crystalloid solution will prevent or minimize hypotension in many cases.


Cesarean Delivery

• A level of sensory blockade extending to the T4 dermatome is desired for cesarean delivery.

• Depending on maternal size, 10 to 12 mg of hyperbaric bupivacaine or 50 to 75 mg of hyperbaric lidocaine are administered.

• The addition of 20 to 25 g of fentanyl increases the rapidity of the onset of the block and reduces shivering.

• The addition of 0.2 mg of morphine improves pain control during delivery and postoperatively.


Complications

• Hypotension• Postdural puncture headache• Pruritus• Failed regional block (need for general

endotracheal anesthesia)• High spinal block• Chemical meningitis or epidural abscess or

hematoma• obese women have significantly impaired

ventilation


Incidence (%) from ACOGa

Incidence (%) from MFMUb

Complication Spinal (n = N/A)

Epidural (n = N/A)

Combinedc (n = N/A)

Spinal (n = 27,319)

Epidural (n = 18,697)

Combinedc (n = 5,666)

Hypotensiond

25–67 28–31 — — — —

Postdural puncture headache

1.5–3 2 1–2.8 0.4 0.3 0.4

Pruritus 41–85 1.3–26 41–85 — — —

Failed regional block (need for GETA)

— — — 1.7 4.0 1.5

High spinal block — — — 0.05 0.08 0.07

Chemical meningitis or epidural abscess or hematoma

— — — 0 0 0


HypotensionHypotension may develop soon after injection of the local anesthetic agent

and is the consequence of vasodilatation from sympathetic blockade compounded by obstructed venous return from uterine compression of the vena cava and adjacent large veins.

In the supine position, even in the absence of maternal hypotension measured in the brachial artery, placental blood flow may still be significantly reduced.

Treatment of spinal block hypotension includes uterine displacement, intravenous hydration, and intravenous bolus injections of ephedrine or phenylephrine


HypotensionHypotension

The predominant action of ephedrine is to raise blood pressure by increasing cardiac output rather than vasoconstriction. Phenylephrine is a pure -agonist which, at least until recently, we have generally avoided because of concerns about potential adverse effects on uterine blood flow.


High Spinal Blockade

• Most often, complete spinal blockade is the consequence of administration of an excessive dose of local anesthetic agent.

• This is certainly not always the case, because accidental total spinal block has even occurred following an epidural test dose.

• In complete spinal block, hypotension and apnea promptly develop and must be immediately treated to prevent cardiac arrest.

• In the undelivered woman, (1) the uterus is immediately displaced laterally to minimize aortocaval compression; (2) effective ventilation is established, preferably with tracheal intubation; and (3) intravenous fluids and ephedrine are given to correct hypotension.


Spinal (Postdural Puncture) Headache

• Leakage of cerebrospinal fluid from the site of puncture of the meninges is thought to be the major factor in the genesis of spinal headache.

• Presumably, when the woman sits or stands, the diminished volume of cerebrospinal fluid allows traction on pain-sensitive central nervous system structures.

• With severe headache, an epidural blood patch is effective. A few milliliters of autologous blood are obtained aseptically by venipuncture without anticoagulant. This is injected into the epidural space at the site of the dural puncture. Relief is immediate and complications uncommon.


Convulsions

• In rare instances, postdural puncture cephalgia is associated with blindness and convulsions.


Bladder Dysfunction

• With spinal analgesia, bladder sensation is likely to be obtunded and bladder emptying impaired for the first few hours after delivery.

• As a consequence, bladder distention is a frequent postpartum complication, especially if appreciable volumes of intravenous fluid are given.


Oxytocics and Hypertension

• Paradoxically, hypertension from ergonovine or methylergonovine injected following delivery is more common in women who have received a spinal or epidural block.


Arachnoiditis and Meningitis

• Local anesthetics are no longer preserved in alcohol, formalin, or other toxic solutes, and disposable equipment is used by most. These practices, coupled with aseptic technique, have made meningitis and arachnoiditis rarities

• Still, these complications are occasionally occur.


Contraindications to Spinal Analgesia

• Obstetrical complications that are associated with maternal hypovolemia and hypotension—such as severe hemorrhage—are contraindications to the use of spinal block.


Absolute Contraindications to Absolute Contraindications to Regional AnalgesiaRegional Analgesia

Refractory maternal hypotension Maternal coagulopathy Treatment with once-daily dose of low-

molecular-weight heparin within 12 hrUntreated bacteremia Skin infection over site of needle placementIncreased intracranial pressure caused by mass

lesion9/3/2013 92BITEW(IESO)

In addition to refractory maternal hypotension, disorders of coagulation and defective hemostasis also preclude the use of spinal analgesia.

Similarly, subarachnoid puncture is contraindicated when the skin or underlying tissue at the site of needle entry is infected.

Neurological disorders are considered by many to be a contraindication, if for no other reason than that exacerbation of the neurological disease might be attributed without cause to the anesthetic agent.

Other maternal conditions, such as significant aortic stenosis or pulmonary hypertension, are also relative contraindications to the use of spinal analgesia


PreeclampsiaAs with significant hemorrhage, severe

preeclampsia is another complication in which markedly decreased blood pressure can be predicted when subarachnoid analgesia is used.

It has inherent risks of difficult intubation due to airway edema and cerebrovascular accidents due to increased blood pressure.

it to be quite controversial, they concluded that with severe preeclampsia, epidural analgesia is preferable to a subarachnoid block and especially preferable to a general anesthetic.9/3/2013 94BITEW(IESO)

Epidural Analgesia

Provides excellent pain relief reducing maternal catecholamines

Ability to extend the duration of block to match the duration of labor

Blunts hemodynamic effects of uterine contractions: beneficial for patients with preeclampsia.


Indications for LEA

PAIN EXPERIENCED BY A WOMAN IN LABORPAIN EXPERIENCED BY A WOMAN IN LABORWhen medically beneficial to reduce the stress of

laborACOG and ASA stated

“ “ in the absence of a medical contraindication, in the absence of a medical contraindication, maternal request is a sufficient medical indication for maternal request is a sufficient medical indication for pain relief…”pain relief…”


Obstetric conditions where epidural analgesia is more likely to be

indicated: • Pre eclampsia/hypertensive disease • Prolonged labour • Two or more babies inutero • Anticipated instrumental delivery • Diabetes Mellitus • Breech presentation for vaginal delivery • Significant respiratory disease

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Contraindications for LEAABSOLUTEABSOLUTE

Patients refusal Inability to cooperateIncreased intracranial

pressureInfectionSevere coagulopathySevere hypovolemiaInadequate training

RELATIVERELATIVESystemic maternal

infectionPreexisting

neurological deficiencyMild or isolated

coagulation abnormalities

Relative (and correctable) hypovolemia

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We are All Ready…Now What? - Last Check

• Obstetrician is consulted and confirmed LEA

• Preanesthetic evaluation is performed/verified

• Pt’s (and only patient’s) desire to have LEA is reconfirmed

• Pt’s understanding of risks of LEA is reconfirmed

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• Fetal well-being is assessed and reassured

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• Supporting personal is available and present

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• Resuscitation equipment and drugs are immediately available in the area where LEA placed

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Epidural Analgesia• Relief from the pain of labor and childbirth, including

cesarean delivery, can be accomplished by injection of a local anesthetic agent into the epidural or peridural space.

• This potential space contains areolar tissue, fat, lymphatics, and the internal venous plexus.

• These latter vessels become engorged during pregnancy such that the volume of the epidural space is appreciably reduced.

• Entry for obstetrical analgesia is usually through a lumbar intervertebral space, and less often through the sacral hiatus and sacral canal for caudal epidural analgesia.

• Although one injection may be used, these usually are repeated through an indwelling catheter, or they are given by continuous infusion using a volumetric pump.

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Standard Technique of LEA

1. Pre epidural check list is completed2. Aspiration prophylaxis 3. Intravenous hydration (what? When? How?)4. Monitoring– BP every 1 to 2 min for 20 min after injection of drugs– Continuous maternal HR during induction ( e.g., pulse

oximetry)– Continuous FHR monitoring– Continual verbal communication

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Standard Technique of LEA

4. Maternal position ( sitting or lateral?)

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Comparison of Sitting and Lateral Positions for Performing Spinal or Epidural Procedures

Sitting Lying (left lateral)

Advantages• Midline easier to identify in obese women• Obese patients may find this position more comfortable

• Can be left unattended without risk of fainting.• No orthostatic hypotension• Uteroplacental blood flow not reduced (particularly important in the stressed fetus)

Disadvantages• Uteroplacental blood flow decreased• Orthostatic hypotension may occur• Increased risk of orthostatic hypotension if Entonox and pethidine have been administered• Assistant (or partner) needed to support patient

• May he more difficult to find the midline in obese patient

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Influence of epidural analgesia on maternal plasma concentrations of catecholamines during labor. Modified from Shnider SM et al. Maternal catecholamines decrease during labor after lumbar epidural analgesia. Am J Obstet Gynecol 1983;147:13-5.

Continuous Lumbar Epidural Block

Complete analgesia for the pain of labor and vaginal delivery necessitates a block from the T10 to the S5 dermatomes.

For cesarean delivery, a block extending from the T4 to the S1 dermatomes is desired.

The spread of the anesthetic depends upon the location of the catheter tip; the dose, concentration, and volume of anesthetic agent used; and whether the mother is head-down, horizontal, or head-up.

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Individual variations in the epidural space anatomy also will affect the block, and in some cases, synechiae may preclude a completely satisfactory block.

It also should be recognized that the catheter tip might move from its original location during the course of labor.

• Appropriate resuscitation equipment and drugs must be available during administration of epidural analgesia.

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Technique for Labor Epidural Analgesia

1. Informed consent is obtained, and the obstetrician consulted.2. Monitoring includes the following: Blood pressure every 1–2

min for 15 min after giving a bolus of local anesthetic. Continuous maternal heart rate monitoring during analgesia

induction. Continuous fetal heart rate monitoring. Continual verbal communication. 3. Hydration with 500 to 1000 mL of lactated Ringer solution.4. The woman assumes a lateral decubitus or sitting position.

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5. The epidural space is identified with a loss-of-resistance technique. 6. The epidural catheter is threaded 3–5 cm into the epidural space. 7. A test dose of 3 mL of 1.5%lidocaine with 1:200,000 epinephrine or 3 mL of

0.25%bupivacaine with 1:200,000 epinephrine is injected after careful aspiration and after a uterine contraction—this minimizes the chance of confusing tachycardia that results from labor pain with tachycardia from intravenous injection of the test dose.

8. If the test dose is negative, one or two 5-mL doses of 0.25%bupivacaine are injected to achieve a cephalad sensory T10 level.

9. After 15–20 min, the block is assessed using loss of sensation to cold or pinprick. If no block is evident, the catheter is replaced. If the block is asymmetrical, the epidural catheter is withdrawn 0.5–1.0 cm and an additional 3–5 mL of 0.25%bupivacaine is injected. If the block remains inadequate, the catheter is replaced. 10. The woman is positioned in the lateral or semilateral position to avoid aortocaval compression.

11. Subsequently, maternal blood pressure is recorded every 5–15 min. The fetal heart rate is monitored continuously.

12. The level of analgesia and intensity of motor block are assessed at least hourly

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Complications of epidural analgesia

• Total Spinal Blockade• Ineffective Analgesia• Hypotension• Central Nervous Stimulation• Maternal Pyrexia• Back Pain9/3/2013 117BITEW(IESO)

Effect on Labor

• report that epidural analgesia prolongs labor and increases the need for oxytocin stimulation.

• increase the need for instrumental delivery due to prolonged second-stage labor

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Fetal Heart Rate

• Compared with intravenous meperidine, no deleterious effects were identified.

• In fact, reduced beat-to-beat variability and fewer accelerations were more common in fetuses whose mothers received

• Based on their systematic review of eight studies, Reynolds and co-workers (2002) found that epidural analgesia was associated with improved neonatal acid–base status compared with that with meperidine.

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Cesarean Delivery

• These results are consistent with the belief of many investigators that the epidural administration of dilute solutions of local anesthetic is less likely to increase cesarean delivery rates than concentrated solutions.

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Contraindications

• actual or anticipated serious maternal hemorrhage, actual or anticipated serious maternal hemorrhage, infection at or near the sites for puncture, and suspicion infection at or near the sites for puncture, and suspicion of neurological diseaseof neurological disease

• Rolbin and colleagues (1988) advise against epidural analgesia if the platelet count is below 100,000/L. Conversely, Rasmus and associates (1989) found no cases in which bleeding was caused by regional analgesia in thrombocytopenic women.

• They recommended consideration of this method if the patient might be difficult to intubate or ventilate. The American College of Obstetricians and Gynecologists (2002b) has concluded that women with platelet counts of 50,000 to 100,000/L may be considered potential candidates for regional analgesia.

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Anticoagulation

• Women receiving anticoagulation therapy who are given regional analgesia are at increased risk for spinal cord hematoma and compression.

• The American College of Obstetricians and Gynecologists (2002b) has recommended the following for women taking anticoagulants:

• Women receiving unfractionated heparin therapy should be able to receive regional analgesia if they have a normal activated partial thromboplastin time (aPTT).

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Cont…• Women receiving prophylactic doses of unfractionated

heparin or low-dose aspirin are not at increased risk and can be offered regional analgesia.

• For women receiving once-daily low-dose low-molecular-weight heparin, regional analgesia should not be placed until 12 hours after the last injection.

• Low-molecular-weight heparin should be withheld for at least 2 hours after the removal of an epidural catheter.

• The safety of regional analgesia in women receiving twice-daily low-molecular-weight heparin has not been studied sufficiently.

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Severe Preeclampsia–Eclampsia

• As previously discussed, ideal labor analgesia for women with severe preeclampsia is controversial.

• Obstetrical concerns include hypotension induced by sympathetic blockade, dangers from pressor agents given to correct hypotension, and potential for pulmonary edema following infusion of large volumes of crystalloid.

• Conversely, general anesthesia with tracheal intubation may result in severe, sudden hypertension further complicated by pulmonary or cerebral edema or intracranial hemorrhage.

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• Over the past two to three decades, most obstetrical anesthesiologists have come to favor epidural blockade for labor and delivery in women with severe preeclampsia.

• There seems to be no argument that epidural analgesia for women with severe preeclampsia–eclampsia can be safely used when specially trained anesthesiologists and obstetricians are responsible for the woman and her fetus (ACOG)

• Epidural analgesia provided superior pain relief without a significant increase in maternal or neonatal complications.

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Intravenous Fluid Preload

• Women with severe preeclampsia have remarkably diminished intravascular volume compared with normal pregnancy.

• And also aggressive volume replacement increases the risk for pulmonary edema, especially in the first 72 hours postpartum

• Importantly, this risk can be reduced or obviated with judicious prehydration—usually with 500 to 1000 mL of crystalloid solution.

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• Moreover, vasodilation produced by epidural blockade is less abrupt if the analgesia level is achieved slowly with dilute solutions of local anesthetic agents.

• This allows maintenance of blood pressure while simultaneously avoiding infusion of large volumes of crystalloid.

• With vigorous intravenous crystalloid therapy, there is also concern about development of cerebral edema.

• the majority of cases of pharyngolaryngeal edema were related to aggressive volume therapy.

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Epidural Opiate Analgesia

• Their mechanism of action derives from interaction with specific receptors in the dorsal horn and dorsal roots.

• Apparently both cerebral and spinal opioid receptors are stimulated by these narcotics.

• Opiates alone usually will not provide adequate analgesia, and they most often are given with a local anesthetic agent such as bupivacaine.

• The major advantages of using such a combination are the rapid onset of pain relief, a decrease in shivering, and less dense motor blockade.

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Continuous Infusion of Dilute Local Anesthetic Plus Opioid

• Better pain relief while producing less motor block.

• Maternal and neonatal drug concentrations safe.

Regimen Regimen 0.0625% - 0.08% bupivacaine with 2-3 0.0625% - 0.08% bupivacaine with 2-3

mcg /ml fentanyl, with or without mcg /ml fentanyl, with or without epinephrine, infusing at 10-12 ml/hourepinephrine, infusing at 10-12 ml/hour

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Searching For Balanced Labor Searching For Balanced Labor AnalgesiaAnalgesia

Ambulatory Labor AnalgesiaAmbulatory Labor Analgesia(CSE)(CSE)

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Combined Spinal–epidural Techniques

• may provide rapid and effective analgesia for labor as well as for cesarean delivery.

• an introducer needle is first placed in the epidural space. A small-gauge spinal needle is then introduced through the epidural needle into the subarachnoid space—this is called the needle-through-needle technique.

• A single bolus of an opioid, sometimes in combination with a local anesthetic, is injected into the subarachnoid space, the spinal needle is withdrawn, and an epidural catheter is then placed. The use of a subarachnoid opioid bolus results in the rapid onset of profound pain relief with virtually no motor blockade.

• The epidural catheter permits repeated dosing of analgesia.

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Combined spinal epidural (CSE)

Initial reports: two interspace technique-epidural followed by spinal

Later evolution of CSE in the direction of needle through needle technique

Postdural puncture headache: 1% or less incidence for CSE with small bore atraumatic needles.

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• combined method produced excellent immediate pain relief.

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Advantages of CSE 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”)

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Combined Spinal epidural

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Espocan CSE Needle (B. Braun)Espocan CSE Needle (B. Braun)

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Espocan CSE Needle (B. Braun)Espocan CSE Needle (B. Braun)

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Eldor needle Combined Spinal Epidural for Obstetric Anesthesia.flv

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Maintenance of epidural analgesia can be Maintenance of epidural analgesia can be achieved by:achieved by:regular top-upsan epidural infusionpatient-controlled epidural analgesia (PCEA).

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Intermittent bolus injections:

Bupivacaine: 0.125%-0.375%, 5-10 ml, duration:1-2 hr

Ropivacaine: 0.125%-0.25%, 5-10 ml, duration: 1-2 hr

Lidocaine: 0.75%-1.5%, 5-10 ml, duration: 1-1.5 hr

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Neuraxial Labor Techniques

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Does epidural analgesia affect the course of labor?

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Local Infiltration for Cesarean Delivery

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Local Infiltration for Cesarean Delivery

• Local block is occasionally useful to augment an inadequate or "patchy" regional block that was given in an emergency.

• On more rare occasions, local infiltration may be used to perform an emergency cesarean to save the life of the fetus in the absence of any anesthesia support.

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Local anesthetic block for cesarean delivery.Local anesthetic block for cesarean delivery.9/3/2013 147BITEW(IESO)

Local Infiltration for Cesarean Delivery:Technique

• READING ASSIGNMENT

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General Anesthesia

• The increased safety of regional analgesia has increased the relative risk of general anesthesia.

• The case-fatality rate of general anesthesia for cesarean delivery is estimated to be approximately 32 per million live births compared with 1.9 per million for regional anesthesia

• Failed intubation occurs in approximately 1 of every 250 general anesthetics administered to pregnant women, a 10-fold higher rate than the nonpregnant population.

• The American College of Obstetricians and Gynecologists The American College of Obstetricians and Gynecologists (2002b) has concluded that this relative increased morbidity (2002b) has concluded that this relative increased morbidity and mortality suggest that regional analgesia is the preferred and mortality suggest that regional analgesia is the preferred method of pain control and should be used unless method of pain control and should be used unless contraindicatedcontraindicated9/3/2013 149BITEW(IESO)

Patient Preparation

• Prior to anesthesia induction, several steps should be taken to help minimize the risk of complications for the mother and fetus. These include the

use of antacids, lateral uterine displacement, andpreoxygenation.

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Induction of Anesthesia

ThiopentalKetamine

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Thiopental

• This thiobarbiturate given intravenously is widely used and offers the advantages of ease and extreme rapidity of induction as well as prompt recovery with minimal risk of vomiting.

• Thiopental and similar compounds are poor analgesic agents, and the administration of sufficient drug given alone to maintain anesthesia may cause appreciable newborn depression.

• Thus, thiopental is not used as the sole anesthetic agent, but rather is administered in a dose that induces sleep.

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Ketamine

• This agent also may be used to render the patient unconscious.

• Given intravenously in low doses of 0.2 to 0.3 mg/kg, ketamine may be used to produce analgesia and sedation just prior to vaginal delivery.

• Doses of 1 mg/kg induce general anesthesia.• Ketamine may prove useful in women with acute

hemorrhage because, unlike thiopental, it is not associated with hypotension.

• Conversely, it usually causes a rise in blood pressure, and thus it generally should be avoided in women who are already hypertensive.

• Unpleasant delirium and hallucinations are commonly induced by this agent.

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Intubation

• Immediately after the patient is rendered unconscious, a muscle relaxant is given to facilitate intubation.

• Succinylcholine, a rapid-onset and short-acting agent, commonly is used.

• Cricoid pressure—the Sellick maneuver—is used to occlude the esophagus from induction until intubation is completed by a trained assistant.

• Before the operation begins, proper placement of the endotracheal tube must be confirmed.

• Such confirmation includes auscultation of bilateral breath sounds and end-tidal carbon dioxide analysis.

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Failed IntubationAlthough 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.

Even in cases where the initial assessment of the airway was uneventful, edema may develop intrapartum and present considerable difficulties.

Morbid obesity is also a major risk factor for failed or difficult intubation.

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Management of failed intubation

start the operative procedure only after it has been ascertained that tracheal intubation has been successful and that adequate ventilation can be accomplished.

Even with an abnormal fetal heart rate pattern, initiation of cesarean delivery will only serve to complicate matters if there is difficult or failed intubation.

Frequently, the woman must be allowed to awaken and a different technique used, such as an awake intubation or regional analgesia.

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• Following failed intubation, the woman is ventilated by mask and cricoid pressure is applied to reduce the chance of aspiration.

• Surgery may proceed with mask ventilation or the woman may be allowed to awaken.

• In those cases where the woman has been paralyzed, and where ventilation cannot be reestablished by insertion of an oral airway, laryngeal mask airway, or use of a fiberoptic laryngoscope to intubate the trachea, a life-threatening emergency exists.

• To restore ventilation, percutaneous or even open cricothyrotomy is performed, and jet ventilation begun.

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Gas Anesthetics

Once the endotracheal tube is secured, a 50:50 mixture of nitrous oxide and oxygen is administered to provide analgesia.

Usually, a volatile halogenated agent is added to provide amnesia and additional analgesia.

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Volatile Anesthetics The most commonly used volatile anesthetic in the United States is

isoflurane. Both isoflurane and halothane are potent, nonexplosive agents that

produce remarkable uterine relaxation when given in high, inhaled concentrations.

Their use in high concentrations is restricted to those uncommon situations in which uterine relaxation is a requisite rather than a hazard.

They are used for internal podalic version of the second twin, breech decomposition and replacement of the acutely inverted uterus.

As soon as the maneuver has been completed, anesthetic administration should be stopped and immediate efforts begun to promote myometrial contraction to minimize hemorrhage.

Because of cardiodepressant and hypotensive effects, these agents may intensify the adverse effects of maternal hypovolemia.

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Anesthesia Gas Exposure and Pregnancy Outcome

• Without exception, all anesthetic agents that depress the maternal central nervous system cross the placenta and depress the fetal central nervous system. As a result, personnel responsible for the care of the newborn immediately following delivery with a general anesthetic should be prepared to provide respiratory support.

• Ideally, induction-to-delivery time should be minimized when general anesthesia is used.

• In one study, Datta and colleagues (1981) concluded that fetal exposure of more than 8 minutes was associated with increased neonatal depression. Kavak and co-workers (2001) randomly assigned 84 women scheduled for elective cesarean delivery to either spinal analgesia or general anesthesia.

• There were no significant differences in short-term measures of neonatal outcome, including Apgar scores, umbilical artery blood gas determinations, or length of stay.

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Extubation

• The tracheal tube may be safely removed only if the woman is conscious to a degree that enables her to follow commands and is capable of maintaining oxygen saturation with spontaneous respiration.

• Typically, the stomach is emptied via a nasogastric tube prior to extubation.

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Aspiration

• Massive gastric acidic inhalation causing pulmonary insufficiency from aspiration pneumonitis.

• Such pneumonitis has in the past been the most common cause of anesthetic deaths in obstetrics and therefore deserves special attention.

• Procedures mentioned previously that are important to effective prophylaxis include use of antacids, skillful intubation accompanied by cricoid pressure, emptying of the stomach with a nasogastric tube, and use of regional analgesia when possible.

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Fasting

• Clear liquids such as water, clear tea, black coffee, carbonated beverages, and fruit juices without pulp may be allowed in uncomplicated laboring women.

• Obvious solid foods should be avoided. • "a fasting period of 8 hours or more is preferable

for uncomplicated parturients undergoing elective cesarean delivery."

• Despite these precautions, it should be assumed that any woman in labor has both gastric particulate matter as well as acidic contents.

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Pathophysiology

• if the pH of aspirated fluid was below 2.5, severe chemical pneumonitis developed.

• 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.

• In severe cases, there is bilateral widespread involvement.

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• The woman who aspirates may develop evidence of respiratory distress immediately or as long as several hours after aspiration, depending in part on the material aspirated and the severity of the process.

• Aspiration of a large amount of solid material causes obvious signs of airway obstruction.

• Smaller particles without acidic liquid may lead to patchy atelectasis and later to bronchopneumonia.

• When highly acidic liquid is inspired, decreased oxygen saturation along with tachypnea, bronchospasm, rhonchi, rales, atelectasis, cyanosis, tachycardia, and hypotension are likely to develop. At the sites of injury, pulmonary capillary leakage results in protein-rich fluid containing numerous erythrocytes exuding from capillaries into the lung interstitium and alveoli to cause decreased pulmonary compliance, shunting of blood, and severe hypoxemia. Radiographic changes may not appear immediately and they may be quite variable, although the right lobe most often is affected. Therefore, chest radiographs alone should not be used to exclude aspiration.

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Treatment

Respiratory rate and oxygen saturation as measured by pulse oximetry are the most sensitive and earliest indicators of injury.

• As much of the inhaled fluid as possible should be immediately wiped out of the mouth and removed from the pharynx and trachea by suction.

• If large particulate matter is inspired, bronchoscopy may be indicated to relieve airway obstruction.

• If clinical evidence of infection develops, however, then vigorous treatment is given.

• When acute respiratory distress syndrome develops, mechanical ventilation with positive end-expiratory pressure may prove lifesaving.

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What anesthetic options are available for cesarean delivery?

What options are available for pain control following cesarean delivery?

What anesthetic risks accompany preeclampsia?

Is fetal outcome any different between regional and general anesthesia?

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THANK YOU!!

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Anesthesia for Cesarean Section

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The choice of anesthesia depend on:• The indication for the CS• The urgency of the procedure• The medical condition of the mother and the

fetus• The desire of the mother

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• GA associated with higher risk of airway problems .• Incidence of failed tracheal intubation in pregnant

women is 1 in 200 to 1 in 300 cases Anesthesia2000;55:690-4

• Maternal death due to anesthesia is the sixth leading cause of pregnancy related death in USA

Obstet Gynecol 1996;88:161-7

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• The risk of maternal death from complications of GA is 17 times as high as that associated with Regional anesthesia

• In USA the shift from GA to RA for CS resulted in

decrease in anesthesia related maternal mortality from 4.3 to 1.7 per 1 million live birth Anesthsiology 1997;86:277-84

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Epidural anesthesia • AdvantageAdvantage– Titration (volume dependent, not gravity

dependent), decreased likelihood of hypotension

– Incremental dose (for longer operation)• DisadvantageDisadvantage– Dural puncture :1/200-1/500 in experienced

hands, higher in training institution– If unintentional dural puncture, PDPH

incidence is 50-85%– Slower onset

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Spinal anaesthesia• Hyperbaric bupivacaine 0.5% is the drug

most commonly used for spinal anaesthesia for Caesarean section.

• Pregnant patients require a smaller dose than the nonpregnant population (why?)

• The dose used via a standard lumbar approach is typically 2.0–2.75 ml.

no significant correlation between age, height, weight, body mass index and length of vertebral column and the final

block height achievedAnesthesiology1990; 72: 478–482.

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Combined spinal epidural(CSE)

Combines the rapid onset and efficacy of the spinal technique with the ability to:Extend anaesthesia if surgery is prolongedProvide excellent postoperative epidural analgesia.Combined Spinal Epidural for Obstetric Anesthesia.flv

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Medication Spinal Epidural

Local anesthetic Bupivacaine 12 mg(range 9–15)

Lidocaine 2%;

Fentanyl 15–35 ug 50–100 ug

Morphine 0.1 mg 3.75 mg

Optimal Neuraxial Medication Combinations for Cesarean Delivery

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Complications of Regional Anesthesia

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Complications of regional anesthesia

Post Dural Puncture Headache (PDPH)Post Dural Puncture Headache (PDPH)severe, disabling fronto-occipital headache

with radiation to the neck and shoulders.present 12 hours or more after the dural

punctureworsens on sitting and standingrelieved by lying down and abdominal

compression.

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PDPH syndromePDPH syndrome1. Photophobia2. Nausea3. Vomiting4. Neck stiffness5. Tinnitus6. Diplopia7. Dizziness

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Differential diagnosis of post-dural punctureDifferential diagnosis of post-dural punctureheadache in the obstetric patient:headache in the obstetric patient:11. Non-specific headache2. Caffeine-withdrawal headache3. Migraine4. Meningitis5. Sinus headache6. Pre-eclampsia7. Drugs (amphetamine, cocaine)8. Pneumocephalus-related headache9. Intracranial pathology (hemorrhage, venous thrombosis)

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Management of PDPHManagement of PDPHConservative:Conservative:Bed restEncourage oral fluids and/or intravenous

hydrationCaffeine - either i.v. (e.g. 500mg caffeine in 1litre

of saline) or orallyRegular AnalgesiaReassurance

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Management of PDPHManagement of PDPHOthersOthers1. Theophylline3. Sumatriptan4. Epidural saline5. Epidural dextran6. Subarachnoid catheter7. Epidural blood patch

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Complications of regional anesthesiaThe new method of prevention of post-dura The new method of prevention of post-dura

puncture headache (maintaining CSF volume):puncture headache (maintaining CSF volume):

1. Injecting the CSF in the glass syringe back into thesubarachnoid space through the epidural needle2. Passing the epidural catheter through the dural holeinto the subarachnoid space3. Injecting of 3-5 ml of preservative free saline into thesubarachnoid space through the intrathecal catheter4. Administering bolus and then continuous intrathecallabor analgesia through the intrathecal catheter5. Leaving the subarachnoid catheter in-situ for a totalof 12-20 h

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Cardiovascular complicationsCardiovascular complicationsHypotension (can lead to cord ischaemia)Bradycardia

Effects on the course of labour and on the fetusEffects on the course of labour and on the fetus

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Effect of epidural analgesia on the progress and outcome of labour

The recently published guidelines on intrapartum care by the UK national institute of health and clinical excellence indicate that epidural analgesia is:

Not associated with a longer first stage of labour or an increased chance of a caesarean birth

Associated with a longer second stage of labour and an increased chance of an instrumental birth.

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Effect of epidural analgesia on the progress and outcome of labour

The most important factors determining The most important factors determining labour outcome are:labour outcome are:

• Low concentrations of local anaesthetics• Oxytocin• Maternal pushing in the second stage of

labour should, if possible be delayed!

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Neurological complicationsNeurological complicationsNeedle damage to spinal cord, cauda equina

or nerve roots.Spinal haematomaSpinal abscessMeningitis and ArachnoiditisNeurotoxicity

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MiscellaneousMiscellaneousVenous puncture e.g. of dural veinsCatheter breakageExtensive block (including unplanned blocks)ShiveringBackache - Long-term backache is not a

complication of neuraxial techniques although there will always be some local bruising.

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Drug side effectsDrug side effectsNausea and vomiting (opiates)Respiratory depression (opiates)AnaphylaxisToxicity (including intravascular injection of

local anaesthetics)

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Toxicity of local anaesthetics:

Causes: Causes: An overdose of local anaesthetic is given, Large dose of local anaesthetic is inadvertently given intravenously.

The recommended protocol isThe recommended protocol is• Take a 500 ml bag of intralipid 20% and immediately give a 100 ml bolus over 1 minute

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Toxicity of local anaesthetics

• Infuse at a rate of 400 ml over 20 minutes• Give two further boluses of 100 ml at 5-minute

intervals if Circulation is not restored• Continue infusion at a rate of 400 ml over 10 minutes

until stable circulation is restored.

Airway, ventilatory and cardiovascular Airway, ventilatory and cardiovascular support should be maintained via support should be maintained via

standard protocols. It may be >1 hour standard protocols. It may be >1 hour before recoverybefore recovery

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Is There Still Place For General Anesthesia?

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Conclusion

“The delivery of the infant into the arms of a The delivery of the infant into the arms of a conscious and pain-free mother is one of the conscious and pain-free mother is one of the

most exciting and rewarding moments in most exciting and rewarding moments in medicine.”medicine.”

Moir DD. Extradural analgesia for caesarean section. Br Moir DD. Extradural analgesia for caesarean section. Br J Anaesth 1979; 51: 1093. J Anaesth 1979; 51: 1093.

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Health & Medicine

Obstetrical anesthesia