7obstetricanalgesia10-100609041939-phpapp01

Obstetric analgesia Obstetric analgesia and anesthesiaand anesthesia

The Third Affiliated Hospital of Sun Yat-sen UniversityThe Third Affiliated Hospital of Sun Yat-sen University

GUJIANGUJIAN

theses must be concerned about during theses must be concerned about during performing anesthesia for a parturient :performing anesthesia for a parturient :

• safety of the mothersafety of the mother• The effects on the uterine The effects on the uterine

contractioncontraction• the effects of maternal-fetal the effects of maternal-fetal

barrier on drugsbarrier on drugs• The side effects on the fetusThe side effects on the fetus…………

Main pointsMain points

1.Charateristics of obstetric 1.Charateristics of obstetric analgesia and anesthesiaanalgesia and anesthesia

2.The techniques in obstetric 2.The techniques in obstetric analgesia and anesthesiaanalgesia and anesthesia

3. Analgesia and anesthesia for 3. Analgesia and anesthesia for abnormal obstetricsabnormal obstetrics

Charateristics of obstetric Charateristics of obstetric analgesia and anesthesiaanalgesia and anesthesia

definitiondefinition• Analgesia:Analgesia: The loss or modulation of The loss or modulation of pain pain

perceptionperception. (local, systemic). (local, systemic)• Anesthesia:Anesthesia: the the total loss of sensorytotal loss of sensory

perceptionperception (light tough, pain, (light tough, pain, temperature, and her capacity for temperature, and her capacity for vasomotor control)vasomotor control) , and may , and may include loss of consciousness.include loss of consciousness.

Physical and chemical Physical and chemical characteristics of anestheticscharacteristics of anesthetics

Local anesthetics components:Local anesthetics components: aromatic ring : aromatic ring : lipid solublelipid soluble amine radical : amine radical : exists partly asexists partly as base base (un-ionized form)(un-ionized form) resposible for penetration and resposible for penetration and

diffusiondiffusion cation:cation: (ionized form)(ionized form) resposible for analgesiaresposible for analgesia

Passing through the lipid membranePassing through the lipid membrane

Henderson-Hasselbalch equationHenderson-Hasselbalch equation

Ph=pKPh=pKaa+log+log

pKpKa a ↓↓ ,, ph↑ : base form ↑ph↑ : base form ↑ penetration ↑penetration ↑pKpKa a ↑↑ ,, ph↓ : base form ↓ph↓ : base form ↓ penetration ↓penetration ↓

cationbase

Drugs pKDrugs pKa a pene- efficacypene- efficacy trationtration

Procaine 9.0Procaine 9.0Bupivacaine 8.1Bupivacaine 8.1Ropivacaine 8.0Ropivacaine 8.0Lidocaine 7.9 Lidocaine 7.9 Etidocaine 7.7Etidocaine 7.7

Passing through the maternal-Passing through the maternal-fetal barrierfetal barrier

• Drugs with molecular weighs 600 cross ﹤Drugs with molecular weighs 600 cross ﹤the placenta easilythe placenta easily

• By simple diffusionBy simple diffusion according to the according to the principles of Fick’s law:principles of Fick’s law:

Q/T=K[ ]Q/T=K[ ]

Q/T: rate of diffusionQ/T: rate of diffusionA: A: the surface area available for drug transferthe surface area available for drug transferCCMM: maternal drug concentration: maternal drug concentrationCCFF: fetal drug concentration: fetal drug concentrationD: D: membrane thicknessmembrane thicknessK : the diffusion constant of the drugK : the diffusion constant of the drug

At term, transfer of drugs across the placenta↑At term, transfer of drugs across the placenta↑

D)CA(C FM

The pH of the blood on the fetal side of the The pH of the blood on the fetal side of the placenta is 0.1~0.2U lower than that of the placenta is 0.1~0.2U lower than that of the maternal side.maternal side.

ph↓, pKph↓, pKa a ↑↑ : base form (un-ionized) ↓: base form (un-ionized) ↓ cation form (ionized) ↑cation form (ionized) ↑ ph↓ph↓

Maternal placenta fetalMaternal placenta fetal

un-ionizedun-ionized

Total drugs (ionized+unionized)

the pKa values of local anesthetic=maternal blood the pKa values of local anesthetic=maternal blood PH, these agent tend to accumulate on fetal sidePH, these agent tend to accumulate on fetal side

Acidic drug (thiopental): opposite directionAcidic drug (thiopental): opposite direction

ph↓, pKph↓, pKa a ↑↑ : base form (un-ionized) ↓: base form (un-ionized) ↓ cation form (ionized) ↑cation form (ionized) ↑ ph↓ph↓

Maternal placenta fetalMaternal placenta fetal

un-ionizedun-ionized

Total drugs

Fetal distributionFetal distribution• The distribution of drugs in The distribution of drugs in

fetus is just the same as fetus is just the same as fetal fetal circulationcirculation

Distribution of drugs between maternal Distribution of drugs between maternal and fetal compartmentsand fetal compartments

The techniques in obstetric The techniques in obstetric analgesia and anesthesiaanalgesia and anesthesia


1.1. Systemic Systemic

2.2. RegionalRegional

Systemic analgesics and Systemic analgesics and anestheticsanesthetics

• Sedatives and hypnoticsSedatives and hypnotics Produce drowsinessProduce drowsiness Reduce anxietyReduce anxietyeg. eg. diazepamdiazepamCan be used in latent phase of Can be used in latent phase of

the first stage of laborthe first stage of laborIt should be avoided during labor It should be avoided during labor

(long chemical half-time), and in (long chemical half-time), and in preterm neonate (kernicterus)preterm neonate (kernicterus)


• TranquilizersTranquilizersUsed to relieve anxietyUsed to relieve anxietyHydroxyzine, diazepanHydroxyzine, diazepan


Narcotic analgesicsNarcotic analgesics• MeperidingMeperiding

• Morphine: Morphine: not used in active not used in active laboring patientslaboring patients (excessive (excessive respiratory depression in the neonate)respiratory depression in the neonate)

• Fentanyl: Fentanyl: also used in the epidural also used in the epidural analgesiaanalgesia


ThiobarbituratesThiobarbituratesThiopentalThiopentalThiamylalThiamylalThe mother will lose consciousness and The mother will lose consciousness and

airway protective reflexairway protective reflexOnly used in association with general Only used in association with general

endotracheal anesthesiaendotracheal anesthesia


KetamineKetamine Useful in maternal hypotension Useful in maternal hypotension

and hemorrhageand hemorrhage (Stimulates the cardiovascular (Stimulates the cardiovascular

system to maintain HR, BP, cardiac system to maintain HR, BP, cardiac output) output)

• ≥≥2mg/kg: respiratory suppress 2mg/kg: respiratory suppress effect on neonateeffect on neonate


Inhalation anestheticsInhalation anestheticsNitrous oxide: Nitrous oxide: use subanesthetic concentration to use subanesthetic concentration to

treat contraction paintreat contraction painHalothane:Halothane:Isoflurane:Isoflurane:Sevoflurane:Sevoflurane:• Must prepare endotracheal Must prepare endotracheal

intubationintubation• Halothane and isoflurane: uterine Halothane and isoflurane: uterine

relaxation relaxation

Local anesthetic agentsLocal anesthetic agents

Lipid Lipid solubilitysolubility

Protein Protein combina-combina-tiontion

Duration Duration of actionof action efficacyefficacy

ProcaineProcaine

Lidocaine:Lidocaine:Epidural Epidural anesthesiaanesthesiaBupivacaineBupivacaineSpinal Spinal anestheisiaanestheisia


1.1. Regional Regional Local infiltration analgesiaLocal infiltration analgesiaLumbar epidural blockLumbar epidural blockCaudal blockCaudal blockSpinal anesthesiaSpinal anesthesiaCCombined ombined SSpinal-pinal-EEpidural pidural AAnesthesianesthesia22. Systemic. Systemic


1.1. Regional Regional Local infiltration analgesiaLocal infiltration analgesiaLumbar epidural blockLumbar epidural blockCaudal blockCaudal blockSpinal anesthesiaSpinal anesthesiaCCombined ombined SSpinal-pinal-EEpidural pidural AAnesthesianesthesia

2. Systemic2. Systemic

Local infiltration analgesiaLocal infiltration analgesia

Local tissue infiltration of dilute Local tissue infiltration of dilute solutions of anesthetic drugs yields solutions of anesthetic drugs yields unsatisfactory resultsunsatisfactory results

The total dosage must keep below the The total dosage must keep below the accepted toxic doseaccepted toxic dose

0.25~2% lidocaine ( 400mg)﹤0.25~2% lidocaine ( 400mg)﹤ Infiltration in or near an area of Infiltration in or near an area of

inflammation is contraindicatedinflammation is contraindicated Pudendal block : often used in second Pudendal block : often used in second

stage pain relief (stage pain relief (lateral episiotomy)lateral episiotomy) Occasionally used in emergency Occasionally used in emergency

cesarean section (eg. umbilical cord cesarean section (eg. umbilical cord prolapse) prolapse)


1.1. Regional Regional Local infiltration analgesiaLocal infiltration analgesiaLumbar epidural blockLumbar epidural blockCaudal blockCaudal blockSpinal anesthesiaSpinal anesthesiaCCombined ombined SSpinal-pinal-EEpidural pidural AAnesthesianesthesia2. Systemic2. Systemic

Lumbar epidural blockLumbar epidural block

• Become more popularBecome more popular• Satisfactory results of analgesia, Satisfactory results of analgesia,

muscle relaxationmuscle relaxation• The catheter can be used for The catheter can be used for

surgery and postoperative surgery and postoperative analgesia analgesia

• The fetal outcome is not adversely The fetal outcome is not adversely affected affected

• Well suited to obstetric anesthesia: Well suited to obstetric anesthesia: vaginal delivery, or cesarean vaginal delivery, or cesarean surgerysurgery

puncture sites:L2~3, L3~4puncture sites:L2~3, L3~4

Puncture with the epidural Puncture with the epidural needle and place the catheterneedle and place the catheter

Lumbar epidural blockLumbar epidural block• Procedure :Procedure :Inject 3ml of a Inject 3ml of a

1.5% lidocaine 1.5% lidocaine as a as a test dosetest dose. If . If spinal anesthesia spinal anesthesia dose not result dose not result after 5~10min, after 5~10min, inject an inject an additional additional 5 ml 5 ml



Caudal blockCaudal block• An epidural block approached An epidural block approached

through the caudal spacethrough the caudal space• Seldom usedSeldom usedHard to perform (the landmarks Hard to perform (the landmarks

of the sacral hiatus is obscured of the sacral hiatus is obscured , and the fetus is injured by the , and the fetus is injured by the needle )needle )



Spinal anesthesiaSpinal anesthesia

• Is currently used to alleviate the Is currently used to alleviate the pain of delivery and cesarean pain of delivery and cesarean deliverydelivery

• 0.25~0.5% bupivacaine 2-5mg, with 0.25~0.5% bupivacaine 2-5mg, with narcotic (fentanyl 25narcotic (fentanyl 25μμg) are usedg) are used

• Good relaxation of pelvic floor , Good relaxation of pelvic floor , lower birth canal and abdominal lower birth canal and abdominal musclemuscle

• Short onset timeShort onset time duration time 50~70minsduration time 50~70mins• The dosage is smallThe dosage is small• the complications (hypotension) the complications (hypotension)

are fewerare fewer



CCombined ombined SSpinal-pinal-EEpidural pidural AAnesthesianesthesia

• Immediate onsetImmediate onset of analgesia by of analgesia by spinal anesthesiaspinal anesthesia

• After spinal anesthesia complete, After spinal anesthesia complete, an epidural catheter can be an epidural catheter can be placed immediately prior the placed immediately prior the surgerysurgery

• Drug can be re-injectedDrug can be re-injected according according to the duration of the surgery to the duration of the surgery

• Most common usedMost common used in cesarean in cesarean section deliverysection delivery

Place the catheter

Inject 1.5%lidocaine

Puncture the spinal needle, fluid from the subarachnoid space

Inject 0.5%bupivacaine

side effects of epidural and spinal side effects of epidural and spinal anesthesiaanesthesia

The block of Sympathetic nerve fibers

arterial resistance ↓arterial resistance ↓

1. Blood pressure ↓

venous pooling ↑venous pooling ↑

Venous return ↓Venous return ↓

Compression of inferior Compression of inferior vena cava by uterusvena cava by uterus

Treatment for hypotensionTreatment for hypotension1.1. Left lateral Left lateral

positionposition2. The mother 2. The mother

receive oxygen by receive oxygen by mask mask

3. Ringer’s lactate 3. Ringer’s lactate is givenis given

4. 4. Ephedrine Ephedrine 5~10mg iv to 5~10mg iv to sustain a mild sustain a mild vasopressor effectvasopressor effect

↑↑BP: Effective BP: Effective


2. Nausea and vomiting2. Nausea and vomiting Due to rapid onset of Due to rapid onset of

hypotensionhypotension and and parasympathetic stimulationparasympathetic stimulation of the gastrointestinal tract of the gastrointestinal tract (block of sympathetic nerve)(block of sympathetic nerve)

Atropine, Antiemetics, etc can Atropine, Antiemetics, etc can be used be used


3. Postdural puncture headache3. Postdural puncture headache due to leakage of cerebrospinal fluid due to leakage of cerebrospinal fluid

through the needle hole in the durathrough the needle hole in the dura

Use a small-caliber needles (25F) Use a small-caliber needles (25F) Recumbent position (bed sore)Recumbent position (bed sore)HydrationHydrationsedationsedation


4.Cardiopulmonary arrest4.Cardiopulmonary arrest Inadvertent intravascular injection of local Inadvertent intravascular injection of local

anesthetic (toxic reaction) or intrathecal anesthetic (toxic reaction) or intrathecal injection of anesthetic (total spinal) injection of anesthetic (total spinal)

Full cardiopulmonary resuscitation (CRR) is Full cardiopulmonary resuscitation (CRR) is indicatedindicated

(establish a patent airway, intubate the trachea, (establish a patent airway, intubate the trachea, OO22supply,give vasoprssors, treat arrhythmias, supply,give vasoprssors, treat arrhythmias, provide external cardiac massage)provide external cardiac massage)

Then, immediate cesarean section delivery to Then, immediate cesarean section delivery to savage fetussavage fetus

• The pregnant patient is more likely to The pregnant patient is more likely to have an intravascular drug injection have an intravascular drug injection because of the venous distention in because of the venous distention in the epidural space the epidural space

• Injection of the drug into a highly Injection of the drug into a highly vascularized area will result in rapid vascularized area will result in rapid systemic absorptionsystemic absorption

Prevention and treatment of Prevention and treatment of local anesthetic overdoselocal anesthetic overdose

• Toxic doses of local anesthetics used Toxic doses of local anesthetics used in obstetricsin obstetrics

Lidocaine: 5 mg/kgLidocaine: 5 mg/kgBupivacaine: 1.5 mg/kgBupivacaine: 1.5 mg/kgRopivacaine: 3.0 mg/kgRopivacaine: 3.0 mg/kg

• Add epinephrine (1:200,000) to Add epinephrine (1:200,000) to produce local vasoconstriction: produce local vasoconstriction: prevent too-rapid absorption and prevent too-rapid absorption and prolong the anestheticprolong the anesthetic

Prevention and treatment of Prevention and treatment of local anesthetic overdoselocal anesthetic overdose

• If manifested by central nerve If manifested by central nerve system toxicity (convulsion):system toxicity (convulsion):

Recognize the Recognize the prodromal sings:prodromal sings:ringing in the ears, diplopia, perioral ringing in the ears, diplopia, perioral

numbness, slurred speechnumbness, slurred speech Oxygen supplyOxygen supply protect the patient’s airwayprotect the patient’s airway Inject: thiopental 50mg, Inject: thiopental 50mg, midazolam 1~2mgmidazolam 1~2mg


1.1. Regional Regional Local infiltration analgesiaLocal infiltration analgesiaLumbar epidural blockLumbar epidural blockCaudal blockCaudal blockSpinal anesthesiaSpinal anesthesiaCCombined ombined SSpinal-pinal-EEpidural pidural AAnesthesianesthesia22. . SystemicSystemic

Systemic anesthesiaSystemic anesthesia IndicateIndicate for cesarean section delivery when for cesarean section delivery when

regional techniques cannot be used:regional techniques cannot be used: Coagulopathy, infection (spinal), Coagulopathy, infection (spinal),

hypovolemia, or urgency , moderate to hypovolemia, or urgency , moderate to severe vulvular stenosis, progressive severe vulvular stenosis, progressive neurologic diseaseneurologic disease

… ….. Mother :unconscious, no pain, unpleasant Mother :unconscious, no pain, unpleasant

memories memories Fetus: should not be injured with minimal Fetus: should not be injured with minimal

depression and intact reflex irritabilitydepression and intact reflex irritability

Systemic anesthesiaSystemic anesthesiaProcedure:Procedure:1. Be prepared with antacid 1. Be prepared with antacid 2. Give 100% oxygen with a close-fitting mask for 2. Give 100% oxygen with a close-fitting mask for

3’3’3. Patient’s abdomen is surgical scrubbed 3. Patient’s abdomen is surgical scrubbed

(disinfection) and draped for surgery (disinfection) and draped for surgery (anesthetics act on the fetus ↓)(anesthetics act on the fetus ↓)

4. Thiopental, 2-5mg/kg iv4. Thiopental, 2-5mg/kg iv succinylcholing, 120~140mg ivsuccinylcholing, 120~140mg iv5. Endotracheal intubation5. Endotracheal intubation6.50% Nitrous oxide, 50% oxygen, 6.50% Nitrous oxide, 50% oxygen,

(0.5%)halothane or isofluran(0.5%)halothane or isofluranInduction to delivery time under 10 minsInduction to delivery time under 10 mins fast!!!fast!!!

ProcedureProcedure7. After delivery of the fetus ,the 7. After delivery of the fetus ,the

nitrous oxide concentration may nitrous oxide concentration may be increase to 70%, intravenous be increase to 70%, intravenous narcotics and benzodiazepines narcotics and benzodiazepines injected for supplemental injected for supplemental anesthesia anesthesia

Special side effects of general Special side effects of general anesthesia in obstetricsanesthesia in obstetrics

1.Aspiration of gastric contents into 1.Aspiration of gastric contents into the lungthe lung

Before endotracheal intubation ,Before endotracheal intubation ,apply cricoid pressure to prevent apply cricoid pressure to prevent aspiration.aspiration.

2.narcotics and barbiturates may 2.narcotics and barbiturates may cause neonatal depress after cause neonatal depress after delivery. delivery.

The use of a narcotic antogonist The use of a narcotic antogonist (naloxone) may reverse the effects(naloxone) may reverse the effects

Anesthesia apparatusAnesthesia apparatus

Sevoflurane:Sevoflurane: isoflurane:isoflurane:

Analgesia for intrapartum Analgesia for intrapartum obstetricobstetric

• Never promise a painless laborNever promise a painless labor• The management of labor The management of labor

analgesia can be determined analgesia can be determined during the first 2 stages of laborduring the first 2 stages of labor

(start from the first stage phase (start from the first stage phase Ⅱ:cervical dilatation ≥3cm)Ⅱ:cervical dilatation ≥3cm)

• Epidural block (common)Epidural block (common)• Spinal block Spinal block (last only 50~70mins)(last only 50~70mins)

Analgesia and anesthesia for Analgesia and anesthesia for abnormal obstetricsabnormal obstetrics

The trapped head in breech The trapped head in breech deliverydelivery

• If an epidural block is in If an epidural block is in place, no further analgesia place, no further analgesia will be required (forceps?)will be required (forceps?)

• General anesthesia is General anesthesia is acceptable acceptable

Fetal distressFetal distress• Fetus development of bradycardia Fetus development of bradycardia

and appearance of meconiumand appearance of meconium• Uterine perfusion is correlated with Uterine perfusion is correlated with

BP. Hypotension will aggravate fetal BP. Hypotension will aggravate fetal distressdistress

• The probable choice are no analgesia, The probable choice are no analgesia, minimal systemic analgesia (small minimal systemic analgesia (small dose), or segmental epidural blockdose), or segmental epidural block

• Neonatal resuscitation is needed Neonatal resuscitation is needed

Preeclmpsia-EclampsiaPreeclmpsia-Eclampsia• Composed of hypertension, Composed of hypertension,

generalized edema, and proteinuria.generalized edema, and proteinuria.• The primary pathologic characteristics The primary pathologic characteristics

is generalized arterial spasmis generalized arterial spasm• Regional and general anesthesia are Regional and general anesthesia are

used used • Contraindications to regional Contraindications to regional

anesthesia include coagulopathy, anesthesia include coagulopathy, urgercy for fetal distressurgercy for fetal distress

Hemorrhage and shockHemorrhage and shock• Placenta previa and aruptio Placenta previa and aruptio

placenta are accompanied by placenta are accompanied by serious maternal hemorrhage.serious maternal hemorrhage.

• Treatment of shock must be Treatment of shock must be formulated.formulated.

• Ketamine can support BP for Ketamine can support BP for inductioninduction

• Regional block is contraindicated Regional block is contraindicated in the presence of hypovolemiain the presence of hypovolemia

questionsquestions

1.1. Contraindications for epidural Contraindications for epidural anesthesia in cesarean section?anesthesia in cesarean section?

2.2. The mechanism of hypotension The mechanism of hypotension in epidural anesthesia ? How to in epidural anesthesia ? How to treat ittreat it

3.3. What kinds of anesthesia can What kinds of anesthesia can be use in cesarean sectionbe use in cesarean section

Thank you for your Thank you for your attentionattention

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