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Aortic Stenosis and Neuraxial Anesthesia

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    Aortic Stenosis and Neuraxial Anesthesia Aortic Stenosis and Neuraxial Anesthesia Presentation Transcript

    • 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
    • PBLD #8 Aortic Stenosis and Neuraxial 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
      • 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 cm 2
        • Severe concentric left ventricular hypertrophy (septum is 1.5 cm thick)
    • What are the indications for aortic valve replacement in patients with aortic stenosis?
    • Indications for AVR in Patients with AS
      • Symptoms
        • Angina
        • Dyspnea
        • Arrhythmias
      • Gradient increasing and >50 mmHg
      • Moderate AS in patient requiring other cardiac surgery (e.g. CAB or MVR)
    • What are the Anesthetic Goals for a Patient Undergoing AVR?
    • 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.
    • 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
      • 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
    • What would be the benefits of regional anesthesia in this patient?
    • Benefits of regional anesthesia in this patient
      • Simple anesthetic
      • Reduced postoperative delirium
      • Potential for:
        • Reduced bleeding
        • Reduced DVT
        • Reduced pulmonary emboli
        • Better outcome
    • 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
    • What would be the benefits of general anesthesia in this patient?
    • 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
    • What are the cardiovascular effects of spinal and epidural anesthesia?
    • Cardiovascular physiology of spinal anesthesia
      • Sympathetic nervous system
        • Age effects
        • Venous pooling
        • Reduced peripheral resistance
        • Indirect myocardial effect = bradycardia
      • Treatment of hypotension
    • Age effects on systolic blood pressure Increasing age associates with an increasing incidence of hypotension Dohi et al. Anesthesiology 1979;50:319-23
    • Lidocaine spinal causes blood pooling in abdomen and legs % Rooke et al. Anesth Analg 1997;85:99-105
    • 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
    • Bradycardia and hypotension complications after SPA
      • 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 Odds Ratios
    • 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
      •  -, but not  -adrenergic agonists reverse venous pooling during spinal anesthesia
      • Butterworth. Anesth Analg 1986;65:612-6
      μ g/kg/min mg/kg μ g/kg/min
    • 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
    • Brooker et al Anesthesiology 1997; 86:797-805
    • Brooker et al Anesthesiology 1997; 86:797-805
    • 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
    • Pooling of blood in legs after lumbar epidural anesthesia % Arndt. Anesthesiology 1985;63:616-23
    • Effect of level of epidural anesthesia on CV responses
      • 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 % change from baseline Bonica. Anesthesiology 1970;33:619-26
    • TEA vs LEA CV effects ARM BF LEG BF CARD OUTPT MAP -12% -1% +47% +21% -9% +7% -35% +510% TEA vs. LEA: differing effects on regional blood flow
    • Do either the baricity or the specific the local anesthetic make a difference during spinal anesthesia?
    • 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
      • 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 μ g
    • Local anesthetic baricity and spinal anesthesia
      • 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
    • Hyperbaric Isobaric Hypobaric Sensory dermatome Time (min) Greater dermatomal spread with hyperbaric than hypobaric or isobaric bupivacaine in supine patients Van Gessel EF. Anesth Analg 1991;72:779-84
    • Effects of local anesthetic dose on spinal anesthesia
      • Dose of hyperbaric LA has almost no influence on dermatomal spread, even in pregnancy (tetracaine 10 or 15 mg blocks comparable dermatomes)
      •  dose =  onset,  duration, and  &quot;quality&quot; of block (hyperbaric, hypobaric, and isobaric)
    • 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
    • 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?)
    • 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?
    • How case was managed
      • You have got to be kidding!