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PBLD #8 Aortic Stenosis and Neuraxial Anesthesia Until 30 June 2005: John Butterworth, MD Department of Anesthesiology Wake Forest University School of Medicine Winston-Salem, North Carolina See: http://www1.wfubmc.edu/ anesthesiology/research/ faculty_presentations.htm

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PBLD #8 Aortic Stenosis and Neuraxial Anesthesia

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Pbld 8 aortic stenosis and neuraxial anesthesia l.jpg

PBLD #8Aortic Stenosis andNeuraxial Anesthesia

Until 30 June 2005:

John Butterworth, MD

Department of Anesthesiology

Wake Forest University School of Medicine

Winston-Salem, North Carolina

See: http://www1.wfubmc.edu/

anesthesiology/research/

faculty_presentations.htm


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PBLD #8Aortic Stenosis andNeuraxial Anesthesia

After 1 July 2005:

John Butterworth, MD

Department of Anesthesiology

Indiana University School of Medicine

Indianapolis, Indiana

See: http://www1.wfubmc.edu/

anesthesiology/research/

faculty_presentations.htm


Clinical case l.jpg

Clinical Case

  • 78 year old woman with known aortic valvular stenosis requires hemiarthroplasty of left hip for avascular necrosis

  • Mild dementia

  • Mild chronic renal insufficiency (CrCl <50 ml/min)

  • Preoperative 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)


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What are the indications for aortic valve replacement in patients with aortic stenosis?


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Indications for AVR inPatients with AS

  • Symptoms

    • Angina

    • Dyspnea

    • Arrhythmias

  • Gradient increasing and >50 mmHg

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


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What are the Anesthetic Goals for a Patient Undergoing AVR?


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Anesthetic Goals for a Patient Undergoing AVR

  • Avoid hypotension

    • Critical importance of coronary perfusion perfusion pressure

    • Potential for difficult resuscitation

  • Avoid tachycardia

  • Lack of awareness, analgesia, immobility, etc.


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What Would be Appropriate Monitoring During Anesthesia for AVR in a Patient with AS?


Appropriate monitoring during anesthesia for avr in a patient with as l.jpg

Appropriate Monitoring During Anesthesia for AVR in a Patient with AS

  • Arterial line before induction

  • Large bore intravenous line

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

  • Central line vs. PA line

  • TEE


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What would be the benefits of regional anesthesia in this patient?


Benefits of regional anesthesia in this patient l.jpg

Benefits of regional anesthesia in this patient

  • Simple anesthetic

  • Reduced postoperative delirium

  • Potential for:

    • Reduced bleeding

    • Reduced DVT

    • Reduced pulmonary emboli

    • Better outcome


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Reduction of morbidity and mortality with epidural or spinal anesthesia: meta analysis

  • 141 trials, n=9559

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

% incidence

Rodgers. BMJ 2000;321:1-12


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


Benefits of general anesthesia in this patient l.jpg

Benefits of general anesthesia in this patient

  • Control of airway

  • No need for sedation of demented patient

  • Can (theoretically) avoid vasodilating anesthetic drugs

  • Can perform intraoperative TEE to reassess valve and ventricular filling/function

  • No need to explain to fellow anesthesiologists why you chose regional


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What are the cardiovascular effects of spinal and epidural anesthesia?


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Cardiovascular physiology of spinal anesthesia

  • Sympathetic nervous system

    • Age effects

    • Venous pooling

    • Reduced peripheral resistance

    • Indirect myocardial effect = bradycardia

  • Treatment of hypotension


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Increasing age associates with an increasing incidence of hypotension

Dohi et al. Anesthesiology 1979;50:319-23

Age effects on systolic blood pressure


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Lidocaine spinal causes blood pooling in abdomen and legs

%

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


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

  • Total spinal anesthesia with 20 mg tetracaine in cisterna magna

  • Cardiac output (CPB flow) held constant

  • Volume of CPB venous reservoir declines 5.6  0.9 ml/kg (venous pooling)

  • Mean arterial pressure declines 31  5% (reduced systemic vascular resistance)

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

Butterworth. Anesth Analg 1987;66:209-14


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Bradycardia and hypotension complications after SPA

Odds Ratios

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

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

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

Carpenter. Anesthesiology 1992;76:906-16

Liu. Reg Anesth 1995;20:41-4


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

%

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


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-, but not -adrenergic agonists reverse venous pooling during spinal anesthesia

Butterworth. Anesth Analg 1986;65:612-6

μg/kg/min

mg/kg

μg/kg/min


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Epinephrine preferable to phenylephrine for hypotension after hyperbaric tetracaine spinal anesthesia

  • 14 patients: 10 mg hyperbaric tetracaine

  • Transthoracic echo estimation of SV

  • Treatment when SAP decreased 15%

  • Epi (4 µg + 50 ng/kg/min) & Phenyl (40 µg + 0.5 µg/kg/min), randomized, double-blind, cross-over design

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

Brooker et al Anesthesiology 1997;86:797-805


Slide24 l.jpg

Brooker et al

Anesthesiology 1997;

86:797-805


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Brooker et al

Anesthesiology 1997;

86:797-805


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Effects of epidural anesthesia on the cardiovascular system

  • Sympathetic block

    • Venous pooling = ↓apparent blood volume

    • ↓Peripheral resistance

  • Effects of epinephrine in LA solutions

  • Dermatomal level of anesthesia determines hemodynamic effects

  • Differing hemodynamic effects of thoracic vs. lumbar epidural anesthesia


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Pooling of blood in legs after lumbar epidural anesthesia

%

Arndt. Anesthesiology 1985;63:616-23


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Effect of level of epidural anesthesia on CV responses

% change from baseline

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

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

Thoracic dermatome

Bonica. Anesthesiology 1970;33:619-26


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TEA vs. LEA: differing effects on

regional blood flow

TEA vs LEA CV effects

ARM

BF

LEG

BF

CARD

OUTPT

MAP

-12%

-1%

+47%

+21%

+510%

-35%

-9%

+7%


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Do either the baricity or the specific the local anesthetic make a difference during spinal anesthesia?


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Choices in spinal anesthesia

  • Needle size and style

  • Puncture site

  • Local anesthetic species and dose

  • Baricity of local anesthetic solution

  • Patient position after injection

  • Additives (opioids, vasoconstrictors, clonidine, neostigmine)

  • Continuous spinal or combined spinal-epidural


Local anesthetic choices for spinal anesthesia l.jpg

Hyperbaric 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 solutions

Bupivacaine 0.5% (<3 h)

Lidocaine 2% (<2 h)

Tetracaine 0.5% (<3 h)

Meperidine 2.5% (<2 h)

Mepivacaine 1-2%

Hypobaric solutions

Tetracaine 0.1-0.2% (<3 h)

Bupivacaine 0.5% + fentanyl 20 μg

Local anesthetic choices for spinal anesthesia


Local anesthetic baricity and spinal anesthesia l.jpg

Hyperbaric solutions

Density > CSF

Flows to dependent sites

Sitting”Saddle” block’

Supinethoracic level

Isobaric solutions

Density  CSF

No effect of position

Long duration

Hypobaric solutions

Density < CSF

Flows from dependent sites

Sitting  ?total spinal

Supine  inconsistent spread

Jack-knife (Buie) sacral block

Lateral  block of superior side

Local anesthetic baricity and spinal anesthesia


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Greater dermatomal spread with hyperbaric

than hypobaric or isobaric bupivacaine in supine patients

Hyperbaric

Sensory dermatome

Isobaric

Hypobaric

Time (min)

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


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Effects of local anesthetic dose on spinal anesthesia

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

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


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Combined spinal-epidural (CSE)

  • Rapidly increasing popularity

  • Advantages: rapid onset, ability to titrate or prolong block, spinal drug dosage

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

  • Needle through needle vs double segment

  • Useful for:

    • OB analgesia

    • Ambulatory anesthesia

    • Postop pain management after spinal anesthetic


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Continuous spinal anesthesia

  • Analogous to continuous epidural anesthesia

  • Permits long duration spinal anesthesia

  • No special safety problems provided that there is free flow of CSF through catheter and the catheter tip is not misplaced in a root sleeve

  • Requirement for larger needle PDPH risk

  • 27g catheters formerly available associated with neurological deficits (maldistribution or restricted distribution of 5% lidocaine?)


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How case was managed

  • Arterial line placed

  • CSE technique

  • Hyperbaric bupivacaine 5 mg + 20 µg fentanyl

  • Lateral position

  • Phenylephrine drip

  • Patient now in PACU, will you start PCEA infusion with bupivacaine-morphine?


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How case was managed

  • You have got to be kidding!


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