regional anesthesia for cs

8/6/2019 Regional Anesthesia for Cs

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HARRY SINGH, MDDEPT. OF ANESTHESIOLOGY

UTMB


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INCIDENCEy CS rate exceeds 24% in US

y 3-12% maternal deaths related to anesthesia

y

Anesthesia sixth leading cause of maternal mortalityy Risk of maternal death 16.7 times greater with GETA

y Majority of anesthesia deaths result from failedintubation, failed ventilation and oxygenation and/or

pulmonary aspirationyAssociated factors include obesity, hypertensive

disorders and emergently performed procedures

y GETA should be used only when absolutely necessary


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INCIDENCEy 1992 Hawkins Study-17% CS under GETA

y 1992 UCSD-7.6 % CS under GETA

y Brigham and Women:

y 1990-7.2% under GETA

y 1995-3.6% under GETA

y Now concern about limited experience of GETA forCS due to inadequate numbers


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Anesthetic techniques administered for cesarean section in the United States in 1981 and

1992 and at the University ofCalifornia San Diego (UCSD) in 1992. (The 1981 United States

data were obtained from Gibbs CP, Krischer J.,Peckman BM, et al. Obstetric anesthesia work

force survey, 1981 versus 1992. Anesthesiology1997;87:135-43.)

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5

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4045

50

General Spinal Epidural

USA 1981

USA 1992

UCSD 1992


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ASPIRATIONy Incidence: 1:700

y 3 times greater than for patients receiving GETA

for nonobstetric surgeryyAspiration cause of 1/3rd of 67 maternal deaths in

US from GETA between 1979 to 1990.

y

Aspiration also possible under regional anesthesiayAspiration prophylaxis mandatory in these

patients


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AORTOCAVAL COMPRESSIONy Results from: Decreased venous return by compression

of inferior vena cava

y

Increased uterine venous pressure from obstruction ofuterine venous drainage decreasing uterine arteryperfusion pressure

y Compression of aorta or common iliac artery resultingin decreased uterine artery pressure

y Prevention: Left lateral tilt/placement of wedge underbuttock

yAdequacy can be assessed by monitoring BP or SaO2of lower extremity


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PRELOADINGy Large volumes of crystalloids may exacerbate

postpartum decrease of colloid osmotic pressure

y

Use caution in patients with preeclampsia orcardiovascular disease

y Other countries: Some use dextran or hespan forpreloading

y Stays in circulation longer

y Expensive

yAlters blood rheology and platelet function

y Dextran-Small but definite risk of anaphylaxis


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Efficacy of hypotension prophylaxis during administration of spinal anesthesia for cesarean section.

LUD, Left uterine displacement. (Modified from Clark RB, Thompson CH. Prevention of spinal

hypotension associated with cesarean section. Anesthesiology 1976; 45:670-4; Modified from

Gutsche B. Prophylactic ephedrine preceding spinal analgesia for cesarean section. Anesthesiology

1976; 45:462-5.)

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Percent

hypotension

None Fluids Fluids + LUD Fluids + LUD

+IM ephederin

*

*

*

**


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HYPOTENSIONy Treat by preloading, left lateral tilt, vasopressors and O2y Maintenance of normal BP during regional results in better

umbilical cord blood gases and acid base balance

y Laboratory evidence in animals suggest ephedrine betterthan phenylephrine for uteroplacental perfusion

y One review of controlled trials of phenylephrine vs.ephedrine found increased umbilical artery pH withphenylephrine with no difference in true fetal acidosis

(pH


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MONITORINGy Standard ASA monitors unless invasive monitors

indicatedy EKG: Studies report as much as 25-60% ST depression

in lateral leads in these patientsy Common after delivery of infanty Could be due to acute hypervolemia, tachycardia,

venous air embolism, coronary vasospasm, vasopressoradministration and/or amniotic fluid embolism

y Mostly benign, no wall motion abnormality or elevatedenzymes

y Possibly rate related transient subendocardialischemiay Baseline maternal heart rate may be predictive of

hypotension in patients receiving spinal anesthesia


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HIGH OR TOTAL SPINALy May result from unintentional intrathecal injection of

epidural dose through epidural catheter or extensiverostral spread of subarachnoid block

y

Incidence of high spinal: 1:50,000 from epidural dosey May also result from subarachnoid or epiarachnoid

placement of epidural cathetery Presents as complete sensory and motor blockade,

hypotension, bradycardia, unconciousness, loss ofprotective reflexes and respiratory arrest

y Medical management includes endotrachealintubation, IPPV with 100% O2, f luids, vasopressors(ephedrine, epinephrine), left uterine tilt, lifting up ofthe legs to facilitate venous return, emergencyCS insome instances


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LOCAL ANESTHETIC TOXICITYy Results from accidental injection of local anestheticinto epidural vein or from overdosage

y Convulsions, unconciousness, arrythmias (polymorphicventricular tachycardia), cardiovascular collapse

y Treatment similar as total spinal but more potentcardiac stimulation with epinephrine as well as chestcompressions and defibrillation may be required

y Resuscitation difficult if bupivacaine local anestheticdue to enhanced cardiovascular toxicity during

pregnancyy Rule out intravenous injection by test dose

(epinephrine/isoproterenol) and by negative aspirationfor incremental dosing of epidural

y 0.75% bupivacaine preparation withdrawn from market


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FAILED SPINALy Incidence: 1%; can result from either of the following:y Omission of local anesthetic from drug mixtureyAdministration of inadequate dosey Placement of drug in space other than subarachnoidspacey Pooling of hyperbaric drug in the sacral region

(maldistribution)-sacral analgesiay Injection in dural root sleeve

yA low potency loty One can consider performing second spinal if delivery

not urgenty Look for evidence of sacral blockade before

performing second spinal


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FAILEDEPIDURALy Incidence 2-6%; can result from either of the

following:

y C

atheter may not be in epidural space in the firstplace/

y Displacement of the catheter from the epidural space

y Malposition of the catheter

yAnatomic barriers to diffusion of local anesthetic inepidural space

yAdministration of inadequate concentration/volumeof local anesthetic


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F

AILEDEPIDURALy Options:

y Second epidural-be cautious about local anesthetic

toxicityy GETA

y Spinal: two issues to be considered

y Spinal needle will encounter local anesthetic fromepidural space

y Expect high spinal due to decompression ofintrathecal sac

y Therefore, reduce dose for subarachnoid block


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PERSISTENT NEUROLOGICDEF

ICITy Rare these daysy Previous reports due to unintentional subarachnoid

injection of large dose of 2-chloroprocaine

yAntioxidant sodium metabisulfite and low pH ofpreviously marketed solutions may have beenresponsible

y Current Preparation-Higher pH, no antioxidant orpreservative

y C

auda Equina Syndrome: Reports after continuousspinal with hyperbaric lidocainey Spinal microcatheters for continuous spinal

withdrawn by FDA in 1992 following six cases ofCaudaEquina Syndrome, probably resulted frommaldistribution of 5% lidocaine in sacral region.


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SPINAL ANESTHESIAyAdvantages: Rapid onset, dense block, negligible

risk of maternal or fetal local anesthetic toxicity

y

Disadvantages: Rapid onset

rapid sympatheticblockade, abrupt severe hypotension

y Dosage range of local anesthetics for spinal:7.5-15 mg bupivacaine

60-75 mg lidocaine7-10 mg tetracaine10-25 mg ropivacaine100-150 mg procaine


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SPINAL ANESTHESIAy Procaine: duration 30-60 min

y Lidocaine: Rapid onset, duration 45-75 min

y Hyperbaric lidocaine-TNS, dilute 5% lidocainewith CSF or saline

y Tetracaine: Onset 5-10 min, duration 120-180 min,prolonged sensory block than motor block

y Bupivacaine: Duration intermediate betweentetracaine and lidocaine, duration of sensory andmotor block about same

y Etidocaine: More pronounced motor block


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EPIDURAL ANESTHESIAy Incremental dosingy Total dose can be titrated to desired sensory levelyAllows maternal cardiovascular system to compensate

for occurrence of sympathetic blockadey Decreased risk of severe maternal hypotension or

reduced placental perfusionyAnesthetic of choice in preeclampsia or cardiovascular

diseasey Less intense motor blockade than spinal:

advantageous for patients with multiple gestation,macrosomia or pulmonary disease

y Lower extremity pump may remain intact decreasingrisk of thromboembolism

yAnesthesia can be extended for prolonged surgery


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EPIDURAL ANESTHESIAy Slow onsety Higher failure ratey Unintentional dural tap: 1:200-1:500 in experienced

handsy PDPH: 50-85% with 16 or 18-G Touhys needley Risk of maternal local anesthetic toxicityy Risk of subarachnoid or intravascular migration of

cathetery Drugs for epidural: 3% 2-chloroprocaine, 1.5-2%

lidocaine epinephrine, 0.5% bupivacaine, 0.5%ropivacaine (less motor block, similar concentrationsless cardiotoxic than bupivacaine)


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EPIDURAL ANESTHESIAy Duration: 40-50 min for chloroprocaine, 75-100 min

for lidocaine with epinephrine, 120-180 min forbupivacaine or ropivacaine

y Chloroprocaine requires continuous infusion or

repeated dosingy Blocks and receptors-duramorph less effectiveyAddition of bicarbonate to lidocaine hydrochloride

(1 mEq to 10 ml)-hastens onsety

Onset of alkalinized lidocaine similar tochloroprocaineyAlkalinized lidocaine activity similar to lidocaine

hydrocarbonate available in some other countries


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COMBINED SPINAL-EPIDURAL

y First described in 1981 by Brownridge for CSy Rapid onset and ability to prolong blockade if

necessaryy Initially-two interspace technique in early eightiesy Later on needle through needle techniquey Eldor modification: small separate conduit for

spinal needle with epidural needley Espocan needle: Different exit points for epidural

catheter and spinal needle through epidural needley Intrathecal placement of catheter rare; one case

report of unintentional intrathecal catheterplacementy Distance from tip of Tuohy to wall of postdural sac:

3 -15 mmy Protrusion of spinal needle beyond tip of epidural:

10-16 mm


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LOCAL INFILTRATIONy Primary anesthetic technique if no anesthesia

personnel available or patient in extremis

y

One would need approx. 100 ml of 0.5% lidocainey Bonica described six steps for local infiltration

y Infiltration from umbilicus to symphysis pubis

y Intracutaneous, subcutaneous, intrarectus,

parietal peritoneum, visceral peritoneum,paracervical


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POSTOPERATIVE ANALGESIAy Intrathecal preservative free morphine:y Dose 0.1-0.25 mg, onset 30 min, peak effect 45-60

min, duration 12-24 hrsy

Advantageous for parturients concerned aboutexcretion of opioids in breast milky Epidural preservative free morphine: Dose 2-4 mg,

onset 45-60 min, peak effect 60-120 min, duration12-24 hrs

y

DepoDur: Liposomal extended release preparation,dose 10-15 mg, duration approx. 48 hours.y Decreased side effects (delayed respiratory

depression, pruritus and nausea and vomiting)with lower doses


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SUGGESTEDREADINGy Kuczkowski KM, Reisner LS, Lin D. Anesthesia forCesarean Section in Principles and Practice of

Obstetric Anesthesia, Ed David Chestnut, ElsevierMosby, PA.


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Juneau, Alaska


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Jasper National Park,Canada

regional anesthesia for cs

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