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Anesthetic ConsiderationsAnesthetic Considerationsof Physiological Changesof Physiological Changes
During PregnancyDuring Pregnancy
Presented by:Mona Abdelsamie
Assistant lecturer of AnesthesiologyUnder Supervision of:Prof. Dr. Hoda Omar
Professor of Anesthesiology !ntensive careAnesthesiology Department
Ain Shams University
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OBJECTIVES OBJECTIVES
Maternal physiology duringMaternal physiology duringpregnancy.pregnancy.Uteroplacental circulation.Uteroplacental circulation.
Placental transfer of anestheticPlacental transfer of anestheticagents.agents."ffect of labor on maternal"ffect of labor on maternalphysiology.physiology.
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Anaesthesia for parturient
What is the difference?
Physiologicalchanges
Alter the usualresponse
to anaesthesia
2Patients are cared#or simultaneously
Mother #etus
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Maternal Physiology during PregnancyMaternal Ph
ysiology during Pregnancy
1) Progressive MAC.1) Progressive MAC. by 40% at termby 40% at term Returns to normal by 3Returns to normal by 3 rdrd dayday
postpartum.postpartum.
$%S
Progesterone increases20times normal
level at term
&' endorphin surge during labor delivery
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2( ↑Sensitivity to Local Anesthetics.LA requirements
during RA ↓ by 30%
Hormonally Mediated
"ngorged "pidural(enous Ple)us
↓ F Volume
↓olume o!"idural "ace
↑"idural s"ace#ressure
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*espiratorysystem
↑ygen consum"tion20–40%
↑inute Ventilation40–50%↑↑' ( ) RR
&↑*0 +30 mm,g- )a$ .
↓aCo. +./ 3. mm,g-Com"ensatory ↓ ,Co 3ˉ
#rogesterone↑$. #roduction
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!*(!*(
+,,,+,,,mlml
++5%5%
!$+- ,
ml+15%
($($/ ,,/ ,,
mlml%o%o
$hange$hange
01$01$2 ,2 ,
mlml--5%5%
(0(0 - ,ml- ,ml++45%45%
"*("*( 3 ,ml3 ,ml--25%25%
#*$#*$
45,,45,,mlml--20%20%
*(*( 4, ,4, ,mlml
--15%15%
(olumes $apacities
1ung volumes&capacities at termgestation in absolutevolumes as thepercentage changefrom non'pregnant(alues
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↓RC 1 )$ . Consum"tion
!Ra"id desaturation during
"eriods o a"nea
☼re o ygenation "rior to 2A is mandatory.☼arturient hould not lie lat ithout
su""lemental o ygen.
↓RC ( )&V ↑☼"ta5e o 6nhalational nesthetics.
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,ormonal ChangesCa"illary engorgement ores"iratory tract mucosa
1"↑ncidence o di icult intubation.2(rauma and bleeding during
endotracheal intubation.
☼se a small !'' +7 8 9 mm-during 2A
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,ematologicalChanges
! : ) :lood Volume + u" to ;0ml< =g-#by 4,,, 6 4 ,, ml at term
*eturns to normal 4 6 + 7ee8spostpartum
↑lasma Volume > ) R:C mass+
!
Dilutional anemia ↓ blood viscosity
#acilitates maternal fetale)change of respiratory gases$
nutrients metabolites
↓m"act o maternal bloodloss at delivery
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66 ? ,y"ercoagulable state
↑ibrinogen@ actors V66@ V666@ 6 @ ( 66
↓actor 6
666 ? $ther changes
9 1eucocytosis up to +4 ooo;
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$(S↑$# by E0% at term
↑R * 8 30% ↑V 30%Returns to normal 2 ee!s postpartum.
SVR ↓ S:# ( ↓↓ D:#@ the res"onse to adrenergic and vasoconstric
agents is decreased.
C"P# PAP# PA$P unchanged.
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u"ine ,y"otension syndrome
$OP ↓ in su"ine "osition a ter ./th
ee5 o gestation.$ccurs in .0% o omen at term
Com"ression o 6VC Com"ression o lo er aorta
Aortocaval com"ression
lood lo to 5idneys$
tero"lacental circulation&
o er e tremeties
↓R ↓ C$# by .E% at term.
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Com"ensatory mechanisms inunanaesthetised Gomen
Venous Collaterals
#aravertebral
Venous "le usAbdominal
all
↑VR ( ,R
Reduced during generalor regional anesthesia
evere ,y"otension
#ro ound Fetal ,y"o ia
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Ho oman in late "regnancy should lie su"ine ithout shi ting
the uterus o the great abdomino "elvic vessels.
Le t lateral decubitus
'ilting the tableLe t side do n
Rigid edge under'he right hi"
Fluid "reloading be ore neuroa ial anesthesia6t does not com"letely avoid maternal hy"otension but
it) maternal C$# "reserve utero"lacentalblood lo.
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>!0
☼p ard displa&ement o' t(e stoma&( by t(euterus 6ncom"etence o gastroeso"hageals"hincter 2astroeso"hageal re lu ( eso"hagitis.
'he "arturient should be considered a ull stomach "atient uring most o gestation
☼ ↑#rogesterone ↓ tone o gastroeso"hageal s"hincter.☼#lacental 2astrin ,y"ersecretion o gastric acid.
☼2astric em"tying Delayed ith labor.
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#harmacological "ro"hyla is against as"irationHo "ositive "ressure ventilation be ore intubation
Ra"id sequence induction ellic5Is maneouvre
For 2A
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Renal ystem
♦:F ( 2FR ) by *0% at st trimester but returns tonormal in 3 rd trimester.
♦↑enin ( Aldosterone Ha + retention.
♦rB Creatinine ( :4H may ↓ to 0B* 8 0B7mg
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,e"atic! ects
♦e"atic unction ( he"atic blood lo unchanged
♦inor ) in rB 'ransaminases ( LD, in 3 rd trimester.
♦↑rB Al5aline "hos"hatase +"lacental-.
♦ild ↓ in rB albumin +dilutional-.
♦25–30%↓n "seudocholine estrase activity.
#rogesterone levels inhibit release o cholecysto5inin incomem"tying o gall bladder altered bile acid com"osition ormo cholesterol stones.
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&etabolic! ects
#regnancy is Diabetogenic
,uman #lacental lactogen relative insulin resistance.
tarvation li5e state
↓lood 2lucose ( Amino Acid levels.↑ree Fatty Acids@ =etones ( triglycerides.
↑strogen levels 'hyroid gland hy"ertrohy ) ' 3 ( ' E
↑:2 Free '3@ '
E ( ' , remain normal
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4tero"lacental Circulation
At term? uterine bloodlo is 0% o C$#
'(00 )*00l
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ally dilated uterine vasculature ith absent autoregulation
4terine :lood Flo
Directly "ro"ortional to di erence bet een
uterine arterial and venous "ressure
6nversely "ro"ortional to uterine ascular resistance
Abundant K adrenergic ( some adrenergic rece"tors.
#reviously @ vasoconstrictor agents ith "redominant adrenergic actiBgB !"hedrine",ere of choice for hy otension during regnancy
Recent studies sho that K adrenengic drugs +eBgB#henyle"hrine- have etter e ects.
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.aMor actors ↓ uterine blood lo during "regnancy
ystemic,y"otension
4terineVasoconstriction Uterine$ontractions
♦ortocaval com"ression.
♦y"ovolemia.
♦ym"athetic bloc5ith regional anesthesia.
♦tress induced endogenousCatecholamines during labor.
♦adrenergic agonists.
♦ocal anesthetic agents.
♦y"ertensive disorders→eneraliNed vasoconstriction.
♦abor.
♦ytocin in usions.
♦treme hy"oca"nia#aC$. J .0 mmhg.
♦arbiturates&#ro"o ol.
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#lacental trans er o anesthetic agents
#lacental trans er o drugs de"ends on
1olecular eight ? J *00 Da cross easily
2rotein binding
Li"id solubility? ,ighly ioniNed substances have "oor li"id sol
4aternal ( etal ", ? a ect ioniNation o the drug
5aternal drug concentration? a ected by dose givenand route o administration
(iming o administration
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6nhalational Agents
Cross "lacentareely
Limited e ects i J&AC ( delivery ithin0 minB o inductionntravenous Agents
'hi"ental@ 5etamine( "ro"o ol
Limited etal e ectsin usual inductiondoses
rug distribution@metabolism ( "lacentalu"ta5e"
Opioids Cross "lacentareely
Variable e ects
&orhine&ost signi icant res"iratory de"ressant
e ects&e"eridinee"eridine igni icant res"iratory de"ression "ea5ing
3 h a ter administration
Fentanyl &inimal e ect i J Og
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Local anesthetics #lacental trans er de"ends on:
1=a
2aternal ( etal ", ? Fetal acidosis higher etal to
maternal
drug ratios B :inding o hydrogen ions to the nonioniNed orm
tra""ing
o local anesthetic in etal circulation.egree o "rotein binding ? highly "rotein bound agents
di use "oorly across the "lacentaChloro"rocaine has the least "lacental trans er as it is ra"idlbro5en do n by "lasma cholinestrase in the maternal circulatio
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Most of anesthetic agents sho7 significant placental transfer
#etal effects of drugs administered to parturient depend on
1Maturity of fetal organs substantial fetal hepaticupta8e of many drugs
2Dilution of the umbilical venous blood by venous blood from lo7er half of fetal body modify fetal
drug distribution.
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! ect o labor on maternal "hysiology
tages o labor
st stage . nd stage 3rd stage
tarts ith true labor"ains@ ends by ullcervical dilation
tarts ith ull cervical ilation@ etal descent
ccurs@ ends ith com"letedelivery o etus
! tends rom birth o tbaby to delivery o the"lacenta
Latent "hase Active "hase
#rogressive cervical e acement&inor dilataton +. 8 E cm-
#rogressive cervical dilatationu" to 0 cm
/ 8 . h in nulli"arous* 8 / h in multi"arousB
Contractions are B* . mina"art@ last 8 B* min
15 )120in
15 ).0in
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6ntense "ain ul contractions
&aternalhy"erventilation&V ) u" to 300%
↑. consum"tion 70%
above 3rd
trimester values
#Co. J .0 mm,g
4terine VC Fetal acidosis
+#eriods o hy"oventilation transientmaternal ( etal hy"o emia in bet eenContractions.
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!ach contraction
Dis"laces 300 8 *00ml blood rom
terus to central circulation
C$# ) E*% above 3 rd trimesteric value.
&a imum strain on the heart occurs immediatelya ter delivery
4terine intense involution sudden relieve o 6VC
→ ↑$# /0% above "relabor values.
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Discussioniscussion
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Puestions
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Fetal blood concentrations o lidocaineetal blood concentrations o lidocaineollo ing maternal administration ould beollo ing maternal administration ould be
higher than e "ected?igher than e "ected?BB 6 administered during uterine contractionB administered during uterine contractionB
.BB 6n the "resence o umbilical cordn the "resence o umbilical cordcom"ressionBom"ressionB
3BB 6n the "resence o maternal acidosisBn the "resence o maternal acidosisB
EBB 6n the "resence o etal acidosisBn the "resence o etal acidosisB
*BB 6n the "resence o increased maternaln the "resence o increased maternalmetabolismBetabolismB
√
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B 'otal "eri"heral resistance decreasesB.B ,b concentration decreasesB3B #lasma cholinestrase concentration increasesBEB :lood glucose concentration increasesB*B Functional residual ca"acity increasesB
During "regnancyuring "regnancy
√√
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'he dose o bu"ivacaine required or s"inalhe dose o bu"ivacaine required or s"inalanesthesia is reduced in the "regnant "atient atnesthesia is reduced in the "regnant "atient at
term because o decreasederm because o decreased
B C F volumeB.B "inal cord blood lo B3B &etabolism o bu"ivacaineB
EB C F "ressureB*B 'urnover o C FB
√
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B &aternal arterial ",B.B Fetal cerebral blood lo B3B &aternal cerebral blood lo BEB &aternal uterine artery lo B*B Fetal arterial #$ .B
ternal hy"erventilation "roduces a decrease inernal hy"erventilation "roduces a decrease in
√
√
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'he ollo ing substances trans er reely acrosshe ollo ing substances trans er reely acrossthe "lacenta?he "lacenta?
BB HeostigmineBeostigmineB.BB 6nsulinBnsulinB3BB #ancuroniumBancuroniumBEBB Atro"ineBtro"ineB
*BB glyco"yrolateBlyco"yrolateB
√
√
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'han5 you