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pbld 8 aortic stenosis and neuraxial anesthesia

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pbld 8 aortic stenosis and neuraxial anesthesia

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    1. PBLD #8Aortic Stenosis andNeuraxial Anesthesia

    2. PBLD #8Aortic Stenosis andNeuraxial Anesthesia

    3. 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)

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

    5. 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)

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

    7. 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.

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

    9. 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

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

    11. Benefits of regional anesthesia in this patient Simple anesthetic Reduced postoperative delirium Potential for: Reduced bleeding Reduced DVT Reduced pulmonary emboli Better outcome

    12. 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)

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

    14. 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

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

    16. Cardiovascular physiology of spinal anesthesia Sympathetic nervous system Age effects Venous pooling Reduced peripheral resistance Indirect myocardial effect = bradycardia Treatment of hypotension

    17. Age effects on systolic blood pressure

    18. Lidocaine spinal causes blood pooling in abdomen and legs

    19. 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)

    20. 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

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

    22. ?-, but not ?-adrenergic agonists reverse venous pooling during spinal anesthesia Butterworth. Anesth Analg 1986;65:612-6

    23. 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 g + 50 ng/kg/min) & Phenyl (40 g + 0.5 g/kg/min), randomized, double-blind, cross-over design Epi increases stroke volume and maintains HR; Phenyl decreases HR

    26. 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

    27. Pooling of blood in legs after lumbar epidural anesthesia

    28. 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

    29. TEA vs LEA CV effects

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

    31. 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

    32. 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 g

    33. 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

    35. 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 ?"quality" of block (hyperbaric, hypobaric, and isobaric)

    36. 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

    37. 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?)

    38. How case was managed Arterial line placed CSE technique Hyperbaric bupivacaine 5 mg + 20 g fentanyl Lateral position Phenylephrine drip Patient now in PACU, will you start PCEA infusion with bupivacaine-morphine?

    39. How case was managed You have got to be kidding!

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