PBLD #8Aortic Stenosis and

Neuraxial Anesthesia

Until 30 June 2005:John Butterworth, MDDepartment of AnesthesiologyWake Forest University School of MedicineWinston-Salem, North CarolinaSee: http://www1.wfubmc.edu/

anesthesiology/research/faculty_presentations.htm

PBLD #8Aortic Stenosis and

Neuraxial Anesthesia

After 1 July 2005:John Butterworth, MDDepartment of AnesthesiologyIndiana University School of MedicineIndianapolis, Indiana

See: http://www1.wfubmc.edu/anesthesiology/research/faculty_presentations.htm

Clinical CaseClinical Case• 78 year old woman with known aortic valvular 78 year old woman with known aortic valvular

stenosis requires hemiarthroplasty of left hip stenosis requires hemiarthroplasty of left hip for avascular necrosisfor avascular necrosis

• Mild dementiaMild dementia• Mild chronic renal insufficiency (CrCl <50 Mild chronic renal insufficiency (CrCl <50

ml/min)ml/min)• Preoperative echocardiogram showsPreoperative echocardiogram shows

– Calcified aortic valve– Peak gradient 60 mm Hg– Valve area 0.5 cm2

– Severe concentric left ventricular hypertrophy (septum is 1.5 cm thick)

What are the indications for What are the indications for aortic valve replacement in aortic valve replacement in

patients with aortic patients with aortic stenosis?stenosis?

Indications for AVR inIndications for AVR inPatients with ASPatients with AS

• SymptomsSymptoms– Angina– Dyspnea– Arrhythmias

• Gradient increasing and >50 mmHgGradient increasing and >50 mmHg

• Moderate AS in patient requiring other Moderate AS in patient requiring other cardiac surgery (e.g. CAB or MVR)cardiac surgery (e.g. CAB or MVR)

What are the Anesthetic What are the Anesthetic Goals for a Patient Goals for a Patient Undergoing AVR?Undergoing AVR?

Anesthetic Goals for a Anesthetic Goals for a Patient Undergoing AVRPatient Undergoing AVR

• Avoid hypotensionAvoid hypotension– Critical importance of coronary perfusion

perfusion pressure– Potential for difficult resuscitation

• Avoid tachycardiaAvoid tachycardia

• Lack of awareness, analgesia, Lack of awareness, analgesia, immobility, etc.immobility, etc.

What Would be Appropriate What Would be Appropriate Monitoring During Monitoring During

Anesthesia for AVR in a Anesthesia for AVR in a Patient with AS?Patient with AS?

Appropriate Monitoring Appropriate Monitoring During Anesthesia for AVR During Anesthesia for AVR

in a Patient with ASin a Patient with AS• Arterial line before inductionArterial line before induction

• Large bore intravenous lineLarge bore intravenous line

• Vasopressor infusion ready for use Vasopressor infusion ready for use (some will initiate the infusion before (some will initiate the infusion before induction)induction)

• Central line vs. PA lineCentral line vs. PA line

• TEETEE

What would be the benefits What would be the benefits of regional anesthesia in of regional anesthesia in

this patient?this patient?

Benefits of regional Benefits of regional anesthesia in this patientanesthesia in this patient

• Simple anestheticSimple anesthetic

• Reduced postoperative deliriumReduced postoperative delirium

• PotentialPotential for: for:– Reduced bleeding– Reduced DVT– Reduced pulmonary emboli– Better outcome

Reduction of morbidity and Reduction of morbidity and mortality with epidural or spinal mortality with epidural or spinal

anesthesia: meta analysisanesthesia: meta analysis• 141 trials, n=9559141 trials, n=9559• Neuraxial block Neuraxial block

significantly significantly reduced risk of reduced risk of death (0.7), DVT death (0.7), DVT (0.56), PE (0.45), (0.56), PE (0.45), pneumonia (0.61), pneumonia (0.61), incidence of incidence of transfusion of 2 or transfusion of 2 or more units (0.5)more units (0.5)

0

1

2

3

4

5

6

Die DVT PE 2+U

RA

GA

% incidence

Rodgers. BMJ 2000;321:1-12

What would be the benefits What would be the benefits of general anesthesia in this of general anesthesia in this

patient?patient?

Benefits of general Benefits of general anesthesia in this patientanesthesia in this patient

• Control of airwayControl of airway• No need for sedation of demented patientNo need for sedation of demented patient• Can (theoretically) avoid vasodilating Can (theoretically) avoid vasodilating

anesthetic drugsanesthetic drugs• Can perform intraoperative TEE to reassess Can perform intraoperative TEE to reassess

valve and ventricular filling/functionvalve and ventricular filling/function• No need to explain to fellow anesthesiologists No need to explain to fellow anesthesiologists

why you chose regionalwhy you chose regional

What are the cardiovascular What are the cardiovascular effects of spinal and effects of spinal and epidural anesthesia?epidural anesthesia?

Cardiovascular physiology of Cardiovascular physiology of spinal anesthesiaspinal anesthesia

• Sympathetic nervous systemSympathetic nervous system– Age effects– Venous pooling– Reduced peripheral resistance– Indirect myocardial effect = bradycardia

• Treatment of hypotensionTreatment of hypotension

Age effects on systolic blood Age effects on systolic blood pressurepressureIncreasing age associates with an

increasing incidence of hypotensionDohi et al. Anesthesiology 1979;50:319-23

Lidocaine spinal causes blood Lidocaine spinal causes blood pooling in abdomen and legspooling in abdomen and legs

-20

-15

-10

-5

0

5

10

LVEDV LVR SPLN KID MES LEGS

%

Rooke et al. Anesth Analg 1997;85:99-105

Spinal anesthesia increases venous Spinal anesthesia increases venous pooling and reduces arterial resistance pooling and reduces arterial resistance during canine cardiopulmonary bypassduring canine cardiopulmonary bypass

• Total spinal anesthesia with 20 mg tetracaine Total spinal anesthesia with 20 mg tetracaine in cisterna magnain cisterna magna

• Cardiac output (CPB flow) held constantCardiac output (CPB flow) held constant• Volume of CPB venous reservoir declines 5.6 Volume of CPB venous reservoir declines 5.6

0.9 ml/kg (venous pooling) 0.9 ml/kg (venous pooling)• Mean arterial pressure declines 31 Mean arterial pressure declines 31 5% 5%

(reduced systemic vascular resistance)(reduced systemic vascular resistance)

Butterworth. Anesth Analg 1986;65:612-6;Butterworth. Anesth Analg 1987;66:209-14

Bradycardia and hypotension Bradycardia and hypotension complications after SPAcomplications after SPA

• In non-OB pts, risk of In non-OB pts, risk of hypotension 33%; hypotension 33%; bradycardia 13%bradycardia 13%

• Odds ratios for Odds ratios for hypotension: >T5: 3.8, hypotension: >T5: 3.8, >40 yrs old: 2.5, baseline >40 yrs old: 2.5, baseline SAP <120 mm Hg: 2.4, SAP <120 mm Hg: 2.4, LP above L3-4: 1.8LP above L3-4: 1.8

• ORs for bradycardia: ORs for bradycardia: ARBs: 2.9 , >T5: 1.7, ARBs: 2.9 , >T5: 1.7, baseline HR <60: 4.9, baseline HR <60: 4.9, prolonged PR: 3.2prolonged PR: 3.2

0

1

2

3

4

5

>T5 <60 PR

HypoBrady

Carpenter. Anesthesiology 1992;76:906-16Liu. Reg Anesth 1995;20:41-4

Odds Ratios

Failure to prevent SPA hypotension: Failure to prevent SPA hypotension: crystalloid (n=29), colloid (n=28), or no crystalloid (n=29), colloid (n=28), or no

prehydration (n=28)prehydration (n=28)

Failure to prevent SPA hypotension: Failure to prevent SPA hypotension: crystalloid (n=29), colloid (n=28), or no crystalloid (n=29), colloid (n=28), or no

prehydration (n=28)prehydration (n=28)

0

1020

3040

5060

70

Hypot Ephed N or V

Cry 0.5 LCol 0.5 LNil

%

Buggy et al Anesth Analg 1997;84:106-10

-, but not -, but not -adrenergic agonists reverse -adrenergic agonists reverse venous pooling during spinal venous pooling during spinal

anesthesiaanesthesiaButterworth. Anesth Analg 1986;65:612-6Butterworth. Anesth Analg 1986;65:612-6

μg/kg/min mg/kgμg/kg/min

Epinephrine preferable to Epinephrine preferable to phenylephrine for hypotension after phenylephrine for hypotension after

hyperbaric tetracaine spinal anesthesiahyperbaric tetracaine spinal anesthesia

Epinephrine preferable to Epinephrine preferable to phenylephrine for hypotension after phenylephrine for hypotension after

hyperbaric tetracaine spinal anesthesiahyperbaric tetracaine spinal anesthesia• 14 patients: 10 mg hyperbaric tetracaine14 patients: 10 mg hyperbaric tetracaine• Transthoracic echo estimation of SVTransthoracic echo estimation of SV• Treatment when SAP decreased 15%Treatment when SAP decreased 15%• Epi (4 µg + 50 ng/kg/min) & Phenyl (40 µg + Epi (4 µg + 50 ng/kg/min) & Phenyl (40 µg +

0.5 µg/kg/min), randomized, double-blind, 0.5 µg/kg/min), randomized, double-blind, cross-over designcross-over design

• Epi increases stroke volume and maintains Epi increases stroke volume and maintains HR; Phenyl decreases HRHR; Phenyl decreases HR

Brooker et al Anesthesiology 1997;86:797-805

Brooker et al Anesthesiology 1997;86:797-805

Brooker et al Anesthesiology 1997;86:797-805

Effects of epidural anesthesia Effects of epidural anesthesia on the cardiovascular systemon the cardiovascular system

• Sympathetic blockSympathetic block– Venous pooling = ↓apparent blood volume– ↓Peripheral resistance

• Effects of epinephrine in LA solutionsEffects of epinephrine in LA solutions

• Dermatomal level of anesthesia Dermatomal level of anesthesia determines hemodynamic effectsdetermines hemodynamic effects

• Differing hemodynamic effects of thoracic Differing hemodynamic effects of thoracic vs. lumbar epidural anesthesiavs. lumbar epidural anesthesia

Pooling of blood in legs after Pooling of blood in legs after lumbar epidural anesthesialumbar epidural anesthesia

-10

-5

0

5

10

Thorax Abd Arms Legs

%

Arndt. Anesthesiology 1985;63:616-23

Effect of level of epidural Effect of level of epidural anesthesia on CV responsesanesthesia on CV responses

• Volunteers (n=10) Volunteers (n=10) received 2% lido LEA received 2% lido LEA (11-20 mg/kg) to (11-20 mg/kg) to produce increasing produce increasing dermatomal levels of dermatomal levels of anesthesiaanesthesia

• Increased arm blood Increased arm blood flow (cervical flow (cervical sympathectomy) only sympathectomy) only when block >T2when block >T2 -20

-15

-10

-5

0

5

10

8 6 4 >2

MAP

ABF

LBF

Thoracic dermatome

% change from baseline

Bonica. Anesthesiology 1970;33:619-26

TEA vs LEA CV effectsTEA vs LEA CV effects

ARMBF

LEGBF

CARDOUTPT

MAP

-12% -1% +47% +21%

-9% +7% -35% +510%

TEA vs. LEA: differing effects onregional blood flow

Do either the baricity or the Do either the baricity or the specific the local anesthetic specific the local anesthetic

make a difference during make a difference during spinal anesthesia?spinal anesthesia?

Choices in spinal anesthesiaChoices in spinal anesthesia

• Needle size and styleNeedle size and style• Puncture sitePuncture site• Local anesthetic species and doseLocal anesthetic species and dose• Baricity of local anesthetic solution Baricity of local anesthetic solution • Patient position after injectionPatient position after injection• Additives (opioids, vasoconstrictors, clonidine, Additives (opioids, vasoconstrictors, clonidine,

neostigmine)neostigmine)• Continuous spinal or combined spinal-epiduralContinuous spinal or combined spinal-epidural

Local anesthetic choices for Local anesthetic choices for spinal anesthesiaspinal anesthesia

• Hyperbaric solutionsHyperbaric solutions– Procaine 5% (<45 min)– Lidocaine 1.5-5% (<1 h)– Tetracaine 0.5% (<3 h)– Tetracaine 0.5% + epi

(<4 h)– Bupivacaine 0.75%

(<3 h)

• Isobaric solutionsIsobaric solutions– Bupivacaine 0.5% (<3 h)– Lidocaine 2% (<2 h)– Tetracaine 0.5% (<3 h)– Meperidine 2.5% (<2 h)– Mepivacaine 1-2%

• Hypobaric solutionsHypobaric solutions– Tetracaine 0.1-0.2% (<3 h)– Bupivacaine 0.5% +

fentanyl 20 μg

Local anesthetic baricity and Local anesthetic baricity and spinal anesthesiaspinal anesthesia

• Hyperbaric solutionsHyperbaric solutions– Density > CSF

– Flows to dependent sites

– Sitting”Saddle” block’

– Supinethoracic level

• Isobaric solutionsIsobaric solutions– Density CSF

– No effect of position

– Long duration

• Hypobaric solutionsHypobaric solutions– Density < CSF

– Flows from dependent sites

– Sitting ?total spinal

– Supine inconsistent spread

– Jack-knife (Buie) sacral block

– Lateral block of superior side

Hyperbaric

Isobaric

HypobaricSen

sory

der

mat

om

e

Time (min)

Greater dermatomal spread with hyperbaricthan hypobaric or isobaric bupivacaine in

supine patients

Van Gessel EF. Anesth Analg 1991;72:779-84

Effects of local anesthetic Effects of local anesthetic dose on spinal anesthesiadose on spinal anesthesiaEffects of local anesthetic Effects of local anesthetic dose on spinal anesthesiadose on spinal anesthesia

• Dose of hyperbaric LA has almost Dose of hyperbaric LA has almost nono influenceinfluence on dermatomal spread, even in on dermatomal spread, even in pregnancy (tetracaine 10 or 15 mg blocks pregnancy (tetracaine 10 or 15 mg blocks comparable dermatomes)comparable dermatomes)

dose = dose = onset, onset, duration, and duration, and "quality" "quality" of block (hyperbaric, hypobaric, and of block (hyperbaric, hypobaric, and isobaric)isobaric)

Combined spinal-epidural (CSE)Combined spinal-epidural (CSE)• Rapidly increasing popularityRapidly increasing popularity

• AdvantagesAdvantages: rapid onset, ability to titrate : rapid onset, ability to titrate or prolong block, or prolong block, spinal drug dosagespinal drug dosage

• DisadvantagesDisadvantages: catheter migration, : catheter migration, reliability of test dosing, ↑failure rate (?)reliability of test dosing, ↑failure rate (?)

• Needle through needle vs double segmentNeedle through needle vs double segment

• Useful forUseful for::– OB analgesia– Ambulatory anesthesia– Postop pain management after spinal anesthetic

Continuous spinal Continuous spinal anesthesiaanesthesia

• Analogous to continuous epidural anesthesiaAnalogous to continuous epidural anesthesia• Permits long duration spinal anesthesiaPermits long duration spinal anesthesia• No special safety problems No special safety problems providedprovided that there that there

is free flow of CSF through catheter and the is free flow of CSF through catheter and the catheter tip is not misplaced in a root sleevecatheter tip is not misplaced in a root sleeve

• Requirement for larger needle Requirement for larger needle PDPH riskPDPH risk• 27g catheters formerly available associated 27g catheters formerly available associated

with neurological deficits (maldistribution or with neurological deficits (maldistribution or restricted distribution of 5% lidocaine?)restricted distribution of 5% lidocaine?)

How case was managedHow case was managed

• Arterial line placedArterial line placed• CSE techniqueCSE technique• Hyperbaric bupivacaine 5 mg + 20 Hyperbaric bupivacaine 5 mg + 20 µg µg

fentanylfentanyl• Lateral positionLateral position• Phenylephrine dripPhenylephrine drip• Patient now in PACU, will you start PCEA Patient now in PACU, will you start PCEA

infusion with bupivacaine-morphine?infusion with bupivacaine-morphine?

How case was managedHow case was managed

• You have got to be kidding!You have got to be kidding!