Anesthesia for Cesarean Section

Anesthesia for Anesthesia for Cesarean SectionCesarean Section

Michelle Gros, FRCPCMichelle Gros, FRCPCFeb 13, 2008Feb 13, 2008

Cesarean SectionCesarean Section

Cesarean section rate in Canada in 2005 was 23.7% (CIH)Cesarean section rate in Canada in 2005 was 23.7% (CIH)

Cesarean section rate in US now exceeds 24%Cesarean section rate in US now exceeds 24%

Incidence of anesthesia-related maternal mortality is decliningIncidence of anesthesia-related maternal mortality is declining

Anesthesia remains responsible for ~ 3-12% of all maternal deathsAnesthesia remains responsible for ~ 3-12% of all maternal deaths

Majority during general anesthesia (failed intubation, failed Majority during general anesthesia (failed intubation, failed ventilation and oxygenation, and or aspiration)ventilation and oxygenation, and or aspiration)

Associated factors include obesity, hypertensive disorders of Associated factors include obesity, hypertensive disorders of pregnancy, and emergently performed procedurespregnancy, and emergently performed procedures

Cesarean SectionCesarean Section

Review of anesthetic technique used for all c-sections Review of anesthetic technique used for all c-sections performed at Brigham and Women’s hospital between performed at Brigham and Women’s hospital between 1990 and 19951990 and 1995

GA GA from 7.2% in 1990 to 3.6% in 1995 from 7.2% in 1990 to 3.6% in 1995

Are we getting enough experience in GA’s for c-Are we getting enough experience in GA’s for c-sections?sections?

Preparation for Anesthesia - MedsPreparation for Anesthesia - Meds

Minimize drugs prior to delivery of infantMinimize drugs prior to delivery of infantIf necessary, midazolam 0.5 – 1 mg or fentanyl 25-50 ug If necessary, midazolam 0.5 – 1 mg or fentanyl 25-50 ug IVIVSmall doses – minimal fetal and neonatal depressionSmall doses – minimal fetal and neonatal depressionDisadvantage of benzos – ?Disadvantage of benzos – ?Anticholinergics – decreases secretionsAnticholinergics – decreases secretions

Atropine – crosses placenta - Atropine – crosses placenta - FHR and FHR and variability variability Glycopyrrolate – does not cross placentaGlycopyrrolate – does not cross placenta

Aspiration prophylaxisAspiration prophylaxis

Preparation for Anesthesia - MedsPreparation for Anesthesia - Meds

CJA 2006; 53(1): 79-85.CJA 2006; 53(1): 79-85.RCT of 60 womenRCT of 60 women

Either 1 ug/kg fent and 0.02 mg/kg midaz IV, OR an equal Either 1 ug/kg fent and 0.02 mg/kg midaz IV, OR an equal volume IV NS at time of skin prep for spinalvolume IV NS at time of skin prep for spinal

No between group differences of neonatal outcome No between group differences of neonatal outcome variables (Apgar, neurobehavioural scores, continuous variables (Apgar, neurobehavioural scores, continuous oxygen saturation)oxygen saturation)

Mothers had no difference in recall of the birthMothers had no difference in recall of the birth

Preparation for Anesthesia – IV FluidsPreparation for Anesthesia – IV Fluids

Prior to regional – 15-20 mL/kg RL or NSPrior to regional – 15-20 mL/kg RL or NS30 mins prior30 mins priorRout et al. 1993 – incidence of hypotension Rout et al. 1993 – incidence of hypotension from 71% from 71% to 55% if prehydratedto 55% if prehydratedMessage:Message:

Additional means are necessaryAdditional means are necessary In urgent situation – not necessary to wait for fluid bolusIn urgent situation – not necessary to wait for fluid bolus

hypotension – means improved uteroplacental hypotension – means improved uteroplacental perfusionperfusion?crystalloid vs. colloid?crystalloid vs. colloid


CJA 2000; 47: 607-610.CJA 2000; 47: 607-610.Crystalloid preload no longer magic bulletCrystalloid preload no longer magic bulletStudy found 1 L crystalloid preload was of no value in Study found 1 L crystalloid preload was of no value in preventing hypotensionpreventing hypotensionBoth speed and volume of preloading unimportantBoth speed and volume of preloading unimportantStill reasonable to give modest preload prior to spinalStill reasonable to give modest preload prior to spinalPatients are often relatively dehydratedPatients are often relatively dehydratedBUT – no need to delay emergency surgery in order to BUT – no need to delay emergency surgery in order to preloadpreload


Siddik showed 500 mL pentaspan more effective than 1 Siddik showed 500 mL pentaspan more effective than 1 L NS in reducing hypotension (40% vs. 80%)L NS in reducing hypotension (40% vs. 80%)

N+V also reduced in colloid groupN+V also reduced in colloid group

Neonatal outcome unaffectedNeonatal outcome unaffected

Riley et al showed less hypotension in colloid group Riley et al showed less hypotension in colloid group (45% vs. 85%) but no difference in nausea scores or (45% vs. 85%) but no difference in nausea scores or neonatal outcomeneonatal outcome


French et al showed less hypotension in colloid group French et al showed less hypotension in colloid group (12.5% vs. 47.5%), again no differences in neonatal (12.5% vs. 47.5%), again no differences in neonatal outcomeoutcome

Karinen et al failed to find any differences in hypotension Karinen et al failed to find any differences in hypotension when colloid was usedwhen colloid was used


Disadvantages to Colloid?Disadvantages to Colloid?

ExpensiveExpensive

Anaphylactoid reactionsAnaphylactoid reactions

Coagulation effectsCoagulation effects


Is type, amount, timing of fluids that important?Is type, amount, timing of fluids that important?

Also consider:Also consider:

Effective LUD - 15Effective LUD - 15 often not enough often not enough

Aggressive use of vasopressorsAggressive use of vasopressors

Low dose spinal anesthesiaLow dose spinal anesthesia

Preparation for Anesthesia – Maternal Preparation for Anesthesia – Maternal PositionPosition

Avoid aortocaval compressionAvoid aortocaval compression

Results in Results in uteroplacental perfusion by 3 mechanisms: uteroplacental perfusion by 3 mechanisms:

1)1) venous return venous return C.O. and BP C.O. and BP

2)2) Obstruction of uterine venous drainage Obstruction of uterine venous drainage ’s uterine venous ’s uterine venous pressure and pressure and uterine artery perfusion pressure uterine artery perfusion pressure

3)3) Compression of aorta or common iliac arteries Compression of aorta or common iliac arteries uterine uterine artery perfusion pressureartery perfusion pressure

Preparation for Anesthesia – MonitorsPreparation for Anesthesia – Monitors

Standard monitorsStandard monitors

+/- art, CVP+/- art, CVP

FHR FHR Before, during, after administration of anesthesiaBefore, during, after administration of anesthesia Evaluates effects of maternal position, anesthesia, Evaluates effects of maternal position, anesthesia,

hypotension, and other drugs on the fetushypotension, and other drugs on the fetus

General ConsiderationsGeneral Considerations• ? Support person? Support person

• ? Oxygen? Oxygen

General Considerations - OxygenGeneral Considerations - Oxygen• For elective c-section, current evidence suggests For elective c-section, current evidence suggests

that supplementary oxygen is unnecessarythat supplementary oxygen is unnecessary

• For emergency section – further data are requiredFor emergency section – further data are required

• Improvement of fetal oxygenation should be primary Improvement of fetal oxygenation should be primary objective – this achieved in short-term by using very objective – this achieved in short-term by using very high FiO2high FiO2

• BUT, possibility of reperfusion injury with free BUT, possibility of reperfusion injury with free radicalsradicals

Prevention of Maternal Complications - Prevention of Maternal Complications - AspirationAspiration

ALLALL patients should receive aspiration prophylaxis, patients should receive aspiration prophylaxis, regardless of planned anesthetic for c-sectionregardless of planned anesthetic for c-section

Large survey from SwedenLarge survey from Sweden Incidence of aspiration ~ 15 per 10,000 cases of GA for c-sxnIncidence of aspiration ~ 15 per 10,000 cases of GA for c-sxn 3X greater than in nonobstetric surgery3X greater than in nonobstetric surgery

Preventing Aspiration – Pharmacologic Preventing Aspiration – Pharmacologic TxTx

1)1) Non-particulate antacid eg. 0.3 M sodium citrateNon-particulate antacid eg. 0.3 M sodium citrate

2)2) H2-receptor antagonistH2-receptor antagonist1)1) gastric pH, BUT does NOT alter pH of existing gastric gastric pH, BUT does NOT alter pH of existing gastric

contentscontents2)2) Rout et al 1993– IV ranitidine 50 mg + po Na citrate Rout et al 1993– IV ranitidine 50 mg + po Na citrate resulted resulted

in greater in greater in gastric pH than Na citrate alone (provided >30 in gastric pH than Na citrate alone (provided >30 mins from time of administration to intubation)mins from time of administration to intubation)

Preventing Aspiration – Pharmacologic Preventing Aspiration – Pharmacologic TxTx

3)3) Proton pump inhibitor eg. losecProton pump inhibitor eg. losec1)1) gastric aciditygastric acidity2)2) One study found it less effective than ranitidineOne study found it less effective than ranitidine

4)4) MetoclopramideMetoclopramide1)1) Accelerates gastric emptyingAccelerates gastric emptying2)2) ? Reliability of emptying stomach before c-sxn? Reliability of emptying stomach before c-sxn3)3) lower esophageal sphincter tonelower esophageal sphincter tone4)4) Antiemetic effectAntiemetic effect

Prevention of Maternal Complications - Prevention of Maternal Complications - HypotensionHypotension

In obstetric patients - In obstetric patients - in SBP > 25% OR, any SBP < in SBP > 25% OR, any SBP < 100 mmHg100 mmHg

Measures of prevention:Measures of prevention:1)1) FluidsFluids2)2) LUDLUD3)3) Prophylactic vasopressors (ephedrine, phenylephrine)Prophylactic vasopressors (ephedrine, phenylephrine)


Lee et al., CJA 2002 – systematic review of RCT’s of Lee et al., CJA 2002 – systematic review of RCT’s of ephedrine vs. phenylephrine for tx of hypotension ephedrine vs. phenylephrine for tx of hypotension during spinal for c-sxnduring spinal for c-sxn

No difference for prevention and treatment of maternal No difference for prevention and treatment of maternal hypotensionhypotension

Maternal bradycardia more likely to occur with phenylephrine Maternal bradycardia more likely to occur with phenylephrine than with ephedrinethan with ephedrine

No difference in the incidence of fetal acidosis (umbilical artery No difference in the incidence of fetal acidosis (umbilical artery pH < 7.2)pH < 7.2)


Chestnut says:Chestnut says: They still mostly use ephedrineThey still mostly use ephedrine Phenylephrine preferred in patients who may not Phenylephrine preferred in patients who may not

tolerate tachycardia eg. MS tolerate tachycardia eg. MS


Varying reports of efficacy of prophylactic ephedrineVarying reports of efficacy of prophylactic ephedrine

Some advocate 25 – 50 mg IM before spinal, or 5-10 Some advocate 25 – 50 mg IM before spinal, or 5-10 mg IV immediately after intrathecal injectionmg IV immediately after intrathecal injection

Chestnut – don’t give prophylactic ephedrine unless pt Chestnut – don’t give prophylactic ephedrine unless pt has a low baseline BP (ie. SBP <105 mmHg before has a low baseline BP (ie. SBP <105 mmHg before spinal)spinal)

Prevention of Maternal Complications - Prevention of Maternal Complications - FailuresFailures

1)1) Failed spinalFailed spinal• ~ 1% of cases~ 1% of cases


1)1) Failed spinalFailed spinal• ~ 1% of cases~ 1% of cases• If delivery not urgent – 2If delivery not urgent – 2ndnd spinal spinal



2)2) Failed epiduralFailed epidural• ~ 2-6% of cases~ 2-6% of cases



2)2) Failed epiduralFailed epidural• ~ 2-6% of cases~ 2-6% of cases• Repeat epiduralRepeat epidural

Watch for local toxicityWatch for local toxicityPt impatientPt impatient



2)2) Failed epiduralFailed epidural• ~ 2-6% of cases~ 2-6% of cases• Repeat epiduralRepeat epidural

Watch for local toxicityWatch for local toxicityPt impatientPt impatient

• SpinalSpinalCollection of local – falsely think this is CSFCollection of local – falsely think this is CSFHigh spinalHigh spinal


• Chestnut:Chestnut:~ 5% planned epidurals converted to spinals~ 5% planned epidurals converted to spinalsHigh spinals in 3 of 27 (11%)High spinals in 3 of 27 (11%)

Indications for Cesarean SectionIndications for Cesarean Section

RepeatRepeat ScheduledScheduled Failed attempt at vaginal Failed attempt at vaginal

deliverydelivery

DystociaDystociaAbnormal presentationAbnormal presentation

Transverse lieTransverse lie BreechBreech Multiple gestationMultiple gestation

Fetal stress/distressFetal stress/distressDeteriorating maternal Deteriorating maternal medical illnessmedical illness PreeclampsiaPreeclampsia Heart diseaseHeart disease Pulmonary diseasePulmonary disease

HemorrhageHemorrhage Placenta previaPlacenta previa Placental abruptionPlacental abruption

Choice of TechniqueChoice of Technique

Choice of TechniqueChoice of Technique1)1) Indication for c-sxnIndication for c-sxn2)2) Urgency of procedureUrgency of procedure3)3) Health of mother and fetusHealth of mother and fetus4)4) Desires of motherDesires of mother

SpinalSpinal

Pros:Pros:SimpleSimpleRapid onsetRapid onsetDense blockadeDense blockadeNegligible maternal risk of systemic local toxicityNegligible maternal risk of systemic local toxicityMinimal transfer of drug to infantMinimal transfer of drug to infantNegligible risk of local anesthetic depression of Negligible risk of local anesthetic depression of infantinfant

SpinalSpinal

Cons:Cons:Rapid onset of sympathetic blockade – abrupt, Rapid onset of sympathetic blockade – abrupt, severe hypotensionsevere hypotensionLimited durationLimited durationRecovery time may be prolonged (if procedure Recovery time may be prolonged (if procedure shorter than anticipated)shorter than anticipated)

EpiduralEpidural• Popularity increasingPopularity increasing

• LA LA nerve roots (dural cuffs) by absorption through nerve roots (dural cuffs) by absorption through arachnoid villi that penetrate duraarachnoid villi that penetrate dura

spread of anesthesia is volume dependentspread of anesthesia is volume dependent

EpiduralEpiduralPros:Pros:

Titrated dosing and slower onset Titrated dosing and slower onset risk of risk of severe hypotension and reduced uteroplacental severe hypotension and reduced uteroplacental perfusionperfusionDuration of surgery not an issueDuration of surgery not an issueLess intense motor blockade Less intense motor blockade good for pts with good for pts with multiple gestation or pulmonary diseasemultiple gestation or pulmonary diseaseLower extremity “muscle pump” may remain Lower extremity “muscle pump” may remain intact intact may may incidence of thromboembolic incidence of thromboembolic diseasedisease

EpiduralEpidural

Cons:Cons:

Slower onset Slower onset Risk of systemic local toxicityRisk of systemic local toxicityGreater placental transfer of drug than with spinalGreater placental transfer of drug than with spinal• BUT – does not affect neonatal BUT – does not affect neonatal

neurobehaviour and of little clinical neurobehaviour and of little clinical significance when appropriate doses usedsignificance when appropriate doses used

Risk of high spinalRisk of high spinal

Combined Spinal – Epidural (CSE)Combined Spinal – Epidural (CSE)• Initially described in 1981 (epidural catheter at L1-2 Initially described in 1981 (epidural catheter at L1-2

and spinal at L3-4)and spinal at L3-4)

Combined Spinal – Epidural (CSE)Combined Spinal – Epidural (CSE)

Pros:Pros:Rapid onset and density of spinal anesthesia Rapid onset and density of spinal anesthesia combined with versatility of epidural anesthesiacombined with versatility of epidural anesthesia

Cons:Cons:Potential for high spinalPotential for high spinalInability to test epidural catheterInability to test epidural catheterOnly 1 published report of presumed Only 1 published report of presumed unintentional insertion of epidural catheter unintentional insertion of epidural catheter through dural puncture sitethrough dural puncture site

Spinal Anesthesia for C - SectionSpinal Anesthesia for C - SectionMetoclopramide 10 mg IVMetoclopramide 10 mg IVClear antacid orallyClear antacid orallyIntravascular volume expansion with RL or NS Intravascular volume expansion with RL or NS (15-20 mL/kg)(15-20 mL/kg)Application of monitorsApplication of monitorsSupplemental oxygen by face mask or nasal Supplemental oxygen by face mask or nasal prongsprongsProphylactic intramuscular ephedrine (25-50 mg) Prophylactic intramuscular ephedrine (25-50 mg) in patients with a baseline SBP < 105 mmHgin patients with a baseline SBP < 105 mmHg

Spinal Anesthesia for C - SectionSpinal Anesthesia for C - SectionLumbar puncture at L3-4Lumbar puncture at L3-4

Right lateral or sitting positionRight lateral or sitting position25-gauge Sprotte or Whitacre needle25-gauge Sprotte or Whitacre needleBupivacaine 12 mg (heavy)Bupivacaine 12 mg (heavy)Morphine 0.1-0.25 mg for postoperative analgesiaMorphine 0.1-0.25 mg for postoperative analgesiaLeft uterine displacementLeft uterine displacementAggressive treatment of hypotensionAggressive treatment of hypotension

Exaggerated LUDExaggerated LUD IV fluidsIV fluids Ephedrine and/or low dose phenylephrineEphedrine and/or low dose phenylephrine

Drugs Used for Spinal Anesthesia for Drugs Used for Spinal Anesthesia for Cesarean SectionCesarean Section

DrugDrug Dosage (mg)Dosage (mg) Duration Duration (min)(min)

LidocaineLidocaine 60-7560-75 45-7545-75BupivacaineBupivacaine 7.5-15.07.5-15.0 60-12060-120TetracaineTetracaine 7.0-10.07.0-10.0 120-180120-180ProcaineProcaine 100-150100-150 30-6030-60Adjuvant drugsAdjuvant drugs EpinephrineEpinephrine 0.1-0.20.1-0.2 ---------- MorphineMorphine 0.1-0.250.1-0.25 360-1080360-1080 FentanylFentanyl 0.010-0.0250.010-0.025 180-240180-240

Epidural Anesthesia for C-SectionEpidural Anesthesia for C-SectionMaxeran 10 mg IVMaxeran 10 mg IVClear antacid poClear antacid poIV expansion with RL or IV expansion with RL or NS (15-20 mL/kg)NS (15-20 mL/kg)Application of monitorsApplication of monitorsSupplemental oxygenSupplemental oxygenEpidural catheter at Epidural catheter at L2-3 or L3-4L2-3 or L3-4LUDLUDTest doseTest dose

Therapeutic doseTherapeutic dose 5 ml boluses of 2% lido 5 ml boluses of 2% lido

with epiwith epi 5ml boluses of 0.5% 5ml boluses of 0.5%

bupivacaine, 0.5% bupivacaine, 0.5% ropivacaine, or 3% 2-ropivacaine, or 3% 2-chloroprocaine chloroprocaine (lidocaine or 2-(lidocaine or 2-chloroprocaine q 1-2 chloroprocaine q 1-2 mins, bupiv or ropiv q mins, bupiv or ropiv q 2-5 mins)2-5 mins)

Aggressive tx of Aggressive tx of hypotensionhypotension

Drugs Used for Epidural Anesthesia for Drugs Used for Epidural Anesthesia for Cesarean SectionCesarean Section

DrugDrug Dosage (mg)Dosage (mg) Duration Duration (min)(min)

2% lido with epi2% lido with epi 300-500300-500 75-10075-1002-2-chloroprocainechloroprocaine

450-750450-750 40-5040-50

0.5% 0.5% Bupivacaine Bupivacaine

75-12575-125 120-180120-180

0.5% 0.5% RopivacaineRopivacaine

75-12575-125 120-180120-180

Adjuvant DrugsAdjuvant Drugs MorphineMorphine 3-43-4 720-1440720-1440 FentanylFentanyl 0.05-0.100.05-0.10 120-240120-240 MeperidineMeperidine 50-7550-75 240-720240-720

Aids with RegionalAids with Regional40-50% N2O40-50% N2OLow-dose ketamine (0.25 mg/kg)Low-dose ketamine (0.25 mg/kg)Fentanyl 50-100 ug IVFentanyl 50-100 ug IVRemifentanilRemifentanilMetoclopramide, ondansetron, or droperidol may Metoclopramide, ondansetron, or droperidol may be given to treat nauseabe given to treat nauseaSmall dose of a benzodiazepine to treat anxiety Small dose of a benzodiazepine to treat anxiety and/or restlessnessand/or restlessness

Local Anesthetic?Local Anesthetic?Int. J Ob Anesth. 2006; 15: 106-114.Int. J Ob Anesth. 2006; 15: 106-114.

Prospective, single blind studyProspective, single blind study

Compared plain 0.5% bupivacaine (20 mL) with Compared plain 0.5% bupivacaine (20 mL) with 2% lidocaine (20 mL) + 100 ug epi + 100 ug 2% lidocaine (20 mL) + 100 ug epi + 100 ug fentanyl for extending previous low-dose epidural fentanyl for extending previous low-dose epidural analgesia for emergency c-sxn in 68 ptsanalgesia for emergency c-sxn in 68 pts

Local Anesthetic?Local Anesthetic?Sig. longer prep time for mixture (3.0 vs. 1.25 min)Sig. longer prep time for mixture (3.0 vs. 1.25 min)

Median onset time for block to T7 was 13.8 min for Median onset time for block to T7 was 13.8 min for mixture and 17.5 min for plain bupivacainemixture and 17.5 min for plain bupivacaine

Difference not statistically different, and was offset Difference not statistically different, and was offset by the longer prep timeby the longer prep time

Need for other intra-op supplementation was not Need for other intra-op supplementation was not significantly different between the groupssignificantly different between the groups

Lidocaine is cheaper and less toxic than Lidocaine is cheaper and less toxic than alternativesalternatives

Local Dose – How Low Can We Go?Local Dose – How Low Can We Go?Int J Ob Anesth, 2006; 15: 273-278.Int J Ob Anesth, 2006; 15: 273-278.

Randomized to receive either intrathecal hyperbaric Randomized to receive either intrathecal hyperbaric bupivacaine 3.75 mg or 9 mg, plus 25 ug fentanyl, bupivacaine 3.75 mg or 9 mg, plus 25 ug fentanyl, 100 ug morphine, and 1.5% lidocaine epidurally 3 mL100 ug morphine, and 1.5% lidocaine epidurally 3 mL

Max sensory block achieved in low-dose group was Max sensory block achieved in low-dose group was significantly lower than that in conventional group significantly lower than that in conventional group (T4 vs. T2)(T4 vs. T2)

Longer time to reach maximum sensory level in low Longer time to reach maximum sensory level in low dose group (8.6 min vs. 6.8 min)dose group (8.6 min vs. 6.8 min)

Local Dose – How Low Can We Go?Local Dose – How Low Can We Go?Low-dose group had less motor block, faster Low-dose group had less motor block, faster sensory regression to T10 and faster motor sensory regression to T10 and faster motor recoveryrecovery

No significant difference in need for epidural No significant difference in need for epidural supplementation before or after delivery of babysupplementation before or after delivery of baby

Low-dose group – less hypotension (14% vs. 73%) Low-dose group – less hypotension (14% vs. 73%) with less ephedrine usagewith less ephedrine usage

Spinal Bupivacaine Dosed Spinal Bupivacaine Dosed According to Patient HeightAccording to Patient Height

Barash p 1149Barash p 1149

Spinal bupivacaine 0.75% dosed according to Spinal bupivacaine 0.75% dosed according to patient height:patient height:

150-160 cm – 8 mg150-160 cm – 8 mg 160-182 cm – 10 mg160-182 cm – 10 mg >182 cm – 12 mg>182 cm – 12 mg

Onset of action: 2-4 minsOnset of action: 2-4 mins

Duration of action: 120-180 minsDuration of action: 120-180 mins

Addition of Fentanyl to SpinalAddition of Fentanyl to SpinalActa Anesth Scand, 2006; 50: 364-367.Acta Anesth Scand, 2006; 50: 364-367.

Tested effect of intrathecal fentanyl added to Tested effect of intrathecal fentanyl added to hyperbaric bupivacaine on maternal spirometry in hyperbaric bupivacaine on maternal spirometry in 40 pts40 pts

2 groups:2 groups:1)1) 2 mL hyperbaric bupivacaine 0.5% + 0.4 mL saline2 mL hyperbaric bupivacaine 0.5% + 0.4 mL saline2)2) 2 mL hyperbaric bupivacaine 0.5% + 0.4 mL fentanyl (20 ug)2 mL hyperbaric bupivacaine 0.5% + 0.4 mL fentanyl (20 ug)

Performed spirometry on arrival to OR and 15 mins Performed spirometry on arrival to OR and 15 mins after subarachnoid blockadeafter subarachnoid blockade

Addition of Fentanyl to SpinalAddition of Fentanyl to SpinalSubarachnoid block with bupivacaine – Subarachnoid block with bupivacaine – significantly significantly peak expiratory flow rates peak expiratory flow rates

No changes in VC or FVCNo changes in VC or FVC

Addition of intrathecal fentanyl:Addition of intrathecal fentanyl: Improved quality of blockade (T1.5 vs. T4)Improved quality of blockade (T1.5 vs. T4) Did not lead to a deterioration in resp function Did not lead to a deterioration in resp function

compared with intrathecal bupivacaine alonecompared with intrathecal bupivacaine alone

Addition of Fentanyl to SpinalAddition of Fentanyl to SpinalInt. J Ob. Anesth. 1997; 6: 43-48.Int. J Ob. Anesth. 1997; 6: 43-48.Double-blind placebo-controlled studyDouble-blind placebo-controlled studyCompared periop pain relief with fentanyl, Compared periop pain relief with fentanyl, morphine, or combinationmorphine, or combinationIn addition to bupivacaine – group A received 1 mL In addition to bupivacaine – group A received 1 mL NS, group B – 25 ug fent, group C – 100 ug morph, NS, group B – 25 ug fent, group C – 100 ug morph, group D – 25 ug fent + 100 ug morphgroup D – 25 ug fent + 100 ug morphQuality of intraop analgesia similar in all groups Quality of intraop analgesia similar in all groups receiving opioidreceiving opioidOpioid use increased side effectsOpioid use increased side effectsPostop analgesia with fentanyl inferior to morphinePostop analgesia with fentanyl inferior to morphine

Dose of Intrathecal Morphine?Dose of Intrathecal Morphine?No good conclusive studyNo good conclusive studyMany varied practicesMany varied practicesAnesth 1999; 90: 437-44.Anesth 1999; 90: 437-44.Dose-finding study for intrathecal morphineDose-finding study for intrathecal morphineNo difference in PCA morphine use between 0.1 No difference in PCA morphine use between 0.1 and 0.5 mg groupsand 0.5 mg groupsPruritis Pruritis in direct proportion to dose in direct proportion to doseNo difference in N+V between groupsNo difference in N+V between groupsConclusion: no need to use more than 0.1 mgConclusion: no need to use more than 0.1 mg

Epidural Morphine for Post-op Pain Epidural Morphine for Post-op Pain Control Control

Anesth Analg. 2007; 105(1): 176-83.Anesth Analg. 2007; 105(1): 176-83.

Compared 4 mg epidural morphine with 10 mg Compared 4 mg epidural morphine with 10 mg extended release epidural morphineextended release epidural morphine

Found superior and prolonged post-c-section Found superior and prolonged post-c-section analgesia (especially 24-48 hours post-op)analgesia (especially 24-48 hours post-op)

Risk Factors for Failure of Epidural Risk Factors for Failure of Epidural Analgesia for C-SectionAnalgesia for C-Section

Acta Anesth Scand, 2006; 50: 1014-1018.Acta Anesth Scand, 2006; 50: 1014-1018.Prospectively studied women undergoing c-sxn Prospectively studied women undergoing c-sxn with a functioning epidural in placewith a functioning epidural in placeAll pts received same epidural protocol All pts received same epidural protocol 16 mL 2% lido, 1 mL bicarb, and 100 ug 16 mL 2% lido, 1 mL bicarb, and 100 ug fentanyl given for c-sxnfentanyl given for c-sxnFailed epidural analgesia was defined as need Failed epidural analgesia was defined as need to convert to GAto convert to GA


Of 101 pts, 20 (19.8%) required conversion to Of 101 pts, 20 (19.8%) required conversion to GAGAFailed epidural inversely correlated with pt’s Failed epidural inversely correlated with pt’s ageageDirectly correlated with:Directly correlated with:

Pre-pregnancy weightPre-pregnancy weight Weight at end of pregnancyWeight at end of pregnancy BMIBMI Gestational weekGestational week Number of top-upsNumber of top-ups VAS 2 hour before c-sxnVAS 2 hour before c-sxn


Therefore, younger, more obese pts at a higher Therefore, younger, more obese pts at a higher gestational week, requiring more top-ups during gestational week, requiring more top-ups during labour, having a higher VAS in the 2 hours labour, having a higher VAS in the 2 hours before c-sxn – are at risk of inability to extend before c-sxn – are at risk of inability to extend labour epidural analgesia to epidural analgesia labour epidural analgesia to epidural analgesia for c-sxnfor c-sxn

Indications for General Anesthesia for Indications for General Anesthesia for Cesarean SectionCesarean Section

Indications for General Anesthesia for Indications for General Anesthesia for Cesarean SectionCesarean Section

Dire fetal distress in absence of pre-existing Dire fetal distress in absence of pre-existing epiduralepiduralAcute maternal hypovolemiaAcute maternal hypovolemiaSignificant coagulopathySignificant coagulopathyInadequate regional anesthesiaInadequate regional anesthesiaMaternal refusal of regional anesthesiaMaternal refusal of regional anesthesia

General Anesthesia for Cesarean General Anesthesia for Cesarean SectionSection

Ranitidine and/or metoclopramide IVRanitidine and/or metoclopramide IVClear antacid poClear antacid poLUDLUDApplication of monitorsApplication of monitorsDenitrogenation (100% O2)Denitrogenation (100% O2)Cricoid pressureCricoid pressureIV inductionIV induction

Pentothal, propofol, ketamine, or etomidatePentothal, propofol, ketamine, or etomidate Succinylcholine (roc if sux contraindicated)Succinylcholine (roc if sux contraindicated)

General Anesthesia for Cesarean General Anesthesia for Cesarean SectionSection

Intubation with 6.0-7.0 mm cuffed ETTIntubation with 6.0-7.0 mm cuffed ETT30-50% N2O in O2, and low conc of volatile (0.5 30-50% N2O in O2, and low conc of volatile (0.5 MAC)MAC)After delivery:After delivery: Increased conc of N2O with low conc. VolatileIncreased conc of N2O with low conc. Volatile OpioidOpioid IV hypnotic agent (eg. benzo, barbiturate, IV hypnotic agent (eg. benzo, barbiturate,

propofol) if neededpropofol) if needed Muscle relaxant (sux boluses or infusion, roc, Muscle relaxant (sux boluses or infusion, roc,

cisatracurium)cisatracurium)Extubation awake with intact airway reflexesExtubation awake with intact airway reflexes

General Anesthesia – Traditional RSI General Anesthesia – Traditional RSI Necessary?Necessary?

Int. J Ob Anesth. 2006; 15: 227-232Int. J Ob Anesth. 2006; 15: 227-232

The effects on the fetus of anesthetics and opioid analgesics are The effects on the fetus of anesthetics and opioid analgesics are “innocuous and reversible”“innocuous and reversible”

Dose-dependent neonatal respiratory depression is predictable and Dose-dependent neonatal respiratory depression is predictable and readily treatable by a neonatal pediatricianreadily treatable by a neonatal pediatrician

Choice of drug regimen for pt with cardiac or cerebrovascular Choice of drug regimen for pt with cardiac or cerebrovascular disease should not be restricted on account of concern for the fetusdisease should not be restricted on account of concern for the fetus

Opioids should not be withheld in hypertensive disorders, when Opioids should not be withheld in hypertensive disorders, when prevention of a dangerous hypertensive response to laryngoscopy prevention of a dangerous hypertensive response to laryngoscopy and tracheal intubation is paramountand tracheal intubation is paramount

General AnesthesiaGeneral AnesthesiaAdequate denitrogenation:Adequate denitrogenation:

FRCFRC O2 consumptionO2 consumption

Baraka – compared head-up and supine Baraka – compared head-up and supine positions for denitrogenation in pregnant and positions for denitrogenation in pregnant and non-pregnant ptsnon-pregnant pts

Head-up position prolonged interval between Head-up position prolonged interval between onset of apnea and desaturation (SpO2<95%) onset of apnea and desaturation (SpO2<95%) in non-pregnant pts, BUT NOT in pregnant ptsin non-pregnant pts, BUT NOT in pregnant pts

General Anesthesia – Induction AgentsGeneral Anesthesia – Induction Agents

Goals:Goals:

1)1) Preserve maternal BP, CO, and uterine blood Preserve maternal BP, CO, and uterine blood flowflow

2)2) Minimize fetal and neonatal depressionMinimize fetal and neonatal depression3)3) Ensure maternal hypnosis and amnesiaEnsure maternal hypnosis and amnesia

General Anesthesia – Induction AgentsGeneral Anesthesia – Induction Agents

ThiopentalThiopental Extensive published dataExtensive published data Safe in obstetric ptsSafe in obstetric pts 4 mg/kg4 mg/kg Rapidly crosses placentaRapidly crosses placenta Detected in umbilical venous blood within 30 Detected in umbilical venous blood within 30

secssecs Equilibration in fetus rapid and occurs by time Equilibration in fetus rapid and occurs by time

of deliveryof delivery With doses 4 mg/kg – peak concs in fetal brain With doses 4 mg/kg – peak concs in fetal brain

rarely exceed threshold for depressionrarely exceed threshold for depression

General Anesthesia – Unconscious General Anesthesia – Unconscious mother and awake neonate?mother and awake neonate?

1)1) Preferential uptake by fetal liver (1Preferential uptake by fetal liver (1stst organ perfused organ perfused by blood from umbilical vein)by blood from umbilical vein)

2)2) Higher relative water content of fetal brainHigher relative water content of fetal brain

3)3) Rapid redistribution of drug into maternal tissues Rapid redistribution of drug into maternal tissues rapid reduction in maternal – fetal conc gradientrapid reduction in maternal – fetal conc gradient

4)4) Non-homogeneity of blood flow to intervillous spaceNon-homogeneity of blood flow to intervillous space

5)5) Progressive dilution in fetal circulationProgressive dilution in fetal circulation

General Anesthesia – PropofolGeneral Anesthesia – PropofolRapid, smooth induction of anesthesiaRapid, smooth induction of anesthesiaAttenuates cardiovascular response to Attenuates cardiovascular response to laryngoscopy and intubation more effectively laryngoscopy and intubation more effectively than pentothalthan pentothalDoes not adversely affect umbilical cord blood Does not adversely affect umbilical cord blood gas measurements at deliverygas measurements at deliveryRapidly crosses placentaRapidly crosses placentaRapidly cleared from neonatal circulationRapidly cleared from neonatal circulationDetected low concs in breast milkDetected low concs in breast milkPropofol and pentothol Propofol and pentothol similar Apgar and similar Apgar and neurobehavioural scoresneurobehavioural scores

General Anesthesia – KetamineGeneral Anesthesia – Ketamine1 mg/kg1 mg/kgRapid onsetRapid onsetAnalgesia, hypnosis, and reliably provides Analgesia, hypnosis, and reliably provides amnesiaamnesiaGood in asthma or modest hypovolemiaGood in asthma or modest hypovolemia1 mg/kg does NOT 1 mg/kg does NOT uterine tone (larger doses uterine tone (larger doses do)do)Rapidly crosses placentaRapidly crosses placentaSimilar umbilical cord blood gas and Apgar Similar umbilical cord blood gas and Apgar scores with ketamine or pentothalscores with ketamine or pentothal

General Anesthesia – General Anesthesia – SuccinylcholineSuccinylcholine

1-1.5 mg/kg1-1.5 mg/kgMuscle relaxant of choice for most patientsMuscle relaxant of choice for most patientsHighly ionized and water soluble, Highly ionized and water soluble, only small only small amounts cross placentaamounts cross placentaMaternal administration rarely affects neonatal Maternal administration rarely affects neonatal neuromuscular functionneuromuscular functionOne study – only doses > 300 mg result in One study – only doses > 300 mg result in significant placental transfersignificant placental transferPseudocholinesterase activity Pseudocholinesterase activity 30% in 30% in pregnancy, BUT recovery is not prolongedpregnancy, BUT recovery is not prolonged volume of distribution offsets the effect of volume of distribution offsets the effect of activityactivity

General Anesthesia – RocuroniumGeneral Anesthesia – Rocuronium1 mg/kg1 mg/kgOnly very small amounts cross placentaOnly very small amounts cross placentaApgar and neurobehavioural scores not affectedApgar and neurobehavioural scores not affected

General Anesthesia – Maternal General Anesthesia – Maternal AwarenessAwareness

Desire to minimize neonatal depression must be Desire to minimize neonatal depression must be balanced against risk of awarenessbalanced against risk of awareness

If another agent not given If another agent not given incidence of incidence of awareness awareness in direct proportion to I-D interval in direct proportion to I-D interval

50% N2O/O2 alone 50% N2O/O2 alone 12-26% awareness 12-26% awareness

Awareness Awareness catecholamines catecholamines uterine artery uterine artery vasoconstriction and vasoconstriction and oxygen delivery to fetus oxygen delivery to fetus

General Anesthesia – Maternal General Anesthesia – Maternal AwarenessAwareness

Common Approaches:Common Approaches:50/50 N2O/O2 with 0.5 MAC inhalational agent50/50 N2O/O2 with 0.5 MAC inhalational agent awareness to <1%awareness to <1%Pregnancy Pregnancy anesthetic requirements by 30-40% anesthetic requirements by 30-40%No adverse affect on neonatal conditionNo adverse affect on neonatal conditionNo No maternal blood loss maternal blood lossDiscontinue volatile only if there is uterine Discontinue volatile only if there is uterine atony that is unresponsive to oxytocinatony that is unresponsive to oxytocin

General Anesthesia – OxygenGeneral Anesthesia – OxygenPiggott et al, BJA 1990 – 100% O2 Piggott et al, BJA 1990 – 100% O2 higher higher umbilical venous blood pO2 and higher 1 umbilical venous blood pO2 and higher 1 minute Apgar scores, compared to 50% O2minute Apgar scores, compared to 50% O2100% O2 100% O2 higher conc of iso, without maternal higher conc of iso, without maternal awareness or excessive bleedingawareness or excessive bleedingSupports 100% O2 and higher volatile in cases Supports 100% O2 and higher volatile in cases of fetal distressof fetal distressLawes et al, BJA 1988 – elective c-sxn – no Lawes et al, BJA 1988 – elective c-sxn – no difference in neonatal oxygenation or outcome difference in neonatal oxygenation or outcome between 33% and 50% O2between 33% and 50% O2

Cesarean Section Under LocalCesarean Section Under LocalPotential indications:Potential indications:

patient with severe coagulopathy, known patient with severe coagulopathy, known difficult airway and requires emergency c-sxndifficult airway and requires emergency c-sxn

No anesthesia provider immediately available No anesthesia provider immediately available and severe fetal distressand severe fetal distress

Can begin surgery and deliver infantCan begin surgery and deliver infant Temporary hemostasis achieved until anesthetist Temporary hemostasis achieved until anesthetist

arrives, then induce GA to complete the surgeryarrives, then induce GA to complete the surgery

Cesarean Section Under LocalCesarean Section Under LocalNeed:Need:

1)1) Midline abdominal incisionMidline abdominal incision2)2) Minimal use of retractorsMinimal use of retractors3)3) Do not exteriorize the uterusDo not exteriorize the uterus

Local Infiltration Anesthesia for Local Infiltration Anesthesia for Cesarean SectionCesarean Section

1)1) Professional support person with patientProfessional support person with patient2)2) Infiltration with lidocaine 0.5% (total dose < 500mg)Infiltration with lidocaine 0.5% (total dose < 500mg)3)3) Intracutaneous injection in midline from umbilicus to Intracutaneous injection in midline from umbilicus to

symphysis pubissymphysis pubis4)4) Subcutaneous injectionSubcutaneous injection5)5) Incision down to rectus fasciaIncision down to rectus fascia6)6) Rectus fascia blockadeRectus fascia blockade7)7) Parietal peritoneum infiltration and incisionParietal peritoneum infiltration and incision8)8) Visceral peritoneum infiltration and incisionVisceral peritoneum infiltration and incision9)9) Paracervical injectionParacervical injection10)10) Uterine incision and deliveryUterine incision and delivery11)11) GA with ETT for uterine repair and closure, if neededGA with ETT for uterine repair and closure, if needed

Cesarean Section Under LocalCesarean Section Under LocalDisadvantages:Disadvantages:1)1) Patient discomfortPatient discomfort2)2) Potential for systemic toxicity and anesthesia Potential for systemic toxicity and anesthesia

may not be available to assist with resuscitationmay not be available to assist with resuscitation3)3) Requires timeRequires time4)4) Does not provide satisfactory operating Does not provide satisfactory operating

conditions for complications, eg. uterine atony, conditions for complications, eg. uterine atony, uterine lacerationuterine laceration

Once Infant DeliveredOnce Infant DeliveredOnce umbilical cord clamped – oxytocin givenOnce umbilical cord clamped – oxytocin given10-20 U oxytocin in 1000 mL crystalloid and run 10-20 U oxytocin in 1000 mL crystalloid and run at 40-80 mU/minat 40-80 mU/minBolus IV oxytocin may cause maternal Bolus IV oxytocin may cause maternal hypotension and tachycardia and should be hypotension and tachycardia and should be avoidedavoided

Once Infant DeliveredOnce Infant DeliveredIf atony does not repond to oxytocin:If atony does not repond to oxytocin:

Methylergonovine 0.2 mg IMMethylergonovine 0.2 mg IM 15-methylprostaglandin F2-alpha 250 ug IM or IMM15-methylprostaglandin F2-alpha 250 ug IM or IMM

Ergots:Ergots: Severe hypertensionSevere hypertension

PGF2PGF2αα:: N+V, diarrhea, fever, tachypnea, tachycardia, N+V, diarrhea, fever, tachypnea, tachycardia,

hypertension, bronchoconstrictionhypertension, bronchoconstriction Avoid in asthmaticsAvoid in asthmatics

Once Infant DeliveredOnce Infant DeliveredExteriorize Uterus – What to watch for:Exteriorize Uterus – What to watch for:

PainPain NauseaNausea Hemodynamic changesHemodynamic changes Risk of VAERisk of VAE

Effects of Anesthesia on Fetus and Effects of Anesthesia on Fetus and NeonateNeonate

No significant difference in umbilical cord blood No significant difference in umbilical cord blood gas between general or regional anesthesia for gas between general or regional anesthesia for elective or emergency c-sxnelective or emergency c-sxn

Goals:Goals: Effective LUDEffective LUD Ensure adequate maternal oxygenationEnsure adequate maternal oxygenation Avoid maternal hyperventilationAvoid maternal hyperventilation Avoid excessive doses of anesthetic agentsAvoid excessive doses of anesthetic agents Treat hypotension promptlyTreat hypotension promptly

Effects of Anesthesia on Fetus and Effects of Anesthesia on Fetus and NeonateNeonate

Crawford – found uterine incision to delivery (U-Crawford – found uterine incision to delivery (U-D) interval is more important than I-D intervalD) interval is more important than I-D interval

A U-D interval >3 mins associated with A U-D interval >3 mins associated with incidence of low umbilical cord blood pH and incidence of low umbilical cord blood pH and Apgar scores, Apgar scores, regardless of anesthetic regardless of anesthetic techniquetechnique

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Anesthesia for Cesarean Section

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