Anesthesia for Cardiac Surgery

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Author:
ariadne9
ID:
260873
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Anesthesia for Cardiac Surgery
Updated:
2014-02-08 14:28:20
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BC Nurse Anesthesia
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Anesthesia for Cardiac Surgery
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  1. What 2 drugs classes comprise the mainstay of medical management for ischemic HD pts?
    BB and nitrates
  2. Syndrome X
    • angina with normal coronaries and lack of extra cardiac etiology of angina
    • ? due to coronary microvascular flow
  3. Stunning
    • ischemic symptom
    • brief period of myocardial ischemia leads to cardiac dysfunction for several hours
    • occurs during reperfusion phase
    • in CT surg pts often occurs after CPB when heart is reperfused
    • generally transient
  4. Hibernation
    • Symptom of ischemia
    • Adjacent to an area of infarction in an area of myocardium with impaired function
    • Occurs in setting of impaired myocardial blood flow
    • Transient
  5. Preconditioning
    Brief intermittent period of ischemia confers protection against subsequent larger ischemic insult
  6. LCA 2 branches
    LAD (anterior) and Lcx (lateral)
  7. RCA 3 branches
    • conus
    • PDA
    • R marginal
  8. What factor can cause a 200% increase in cardiac oxygen demand?
    contractility
  9. After contractility, what factor causes the next greatest increase in O2 demand?
    HR
  10. What factors affect O2 demand?
    HR, wall tension (diastolic volume and after load), contractility
  11. What factors affect O2 supply?
    arterial O2 content (anemia, hypoxia), O2 extraction (left shift on oxyHbg dissoc curve), coronary blood flow
  12. Papillary muscles
    • Pull valve cusps downward and together at onset of ventricular contraction
    • Prevent back flow of blood into the atria
  13. systolic anterior motion
    • form of papillary muscle dysfunction
    • valve leaflets move back into the atria during systole
    • regurg results
  14. 2 AV valves
    • tricuspid (3 cusps)- right side
    • mitral  (2 cusps)- left side
  15. Semiluminar valves
    • Pulmonary (right side)
    • Aortic (left side)
    • both have 3 cusps normally
  16. Most common congenital heart issue
    Valve disease
  17. Most common valve issue
    AS
  18. What is considered severe AS?
    • valve area < 0.8 cm2
    • or
    • systolic gradient > 50 mmHg
  19. Major principles in management of AS
    • Maintain NSR to allow for adequate filling
    • Avoid hypotension and hypertension
    • Maintain adequate volume
  20. Issues associated with AS (changes to the heart)
    • LVH (to try to maintain LV output)
    • Increased dependence on atrial kick for filling
  21. Hypertrophic CMP
    • Ventricular hypertrophy without an obvious cause such as AS or HTN
    • Genetic- AD
    • Manage like AS
  22. General principles for management of regurg pts
    • fast full forward flow
    • afterload reduction is beneficial
    • Avoid bradycardia and hypovolemia
  23. Most common cause of AR and MS
    rheumatic heart disease
  24. Normal MV area
    4 cm2
  25. Severe MS area
    < 1 cm2
  26. Management of MS
    • Maintain NSR
    • Avoid tachycardia
    • Maintain euvolemia
  27. Why is PH often associated with MS?
    Blood backs up into LA which causes pressure build up in pulm vein
  28. things to check prior to induction
    • availability of blood
    • surgeon present
    • defibrillator in room
  29. Pts at high risk for ischemia during induction
    • AS, MS
    • LM disease or LM equivalent disease
  30. LM equivalent disease
    High grade stenosis of both LAD and LCx
  31. Preferred opioid and dose used for induction
    • fentanyl due to bradycardia SE, little effect on contractility
    • 3-10 mcg/ kg
  32. How does induction for cardiac surgery differ from regular induction
    Usually use higher dose opioid (3-10 mcg/ kg fentanyl) and lower dose hypnotic (1-2 mg prop)
  33. How does the dose of volatiles used in cardiac surgery differ from standard dosing?
    • Lower volatile doses to avoid tachycardia and hypotension
    • Usually iso is used
  34. Why is N20 not used in cardiac anesthesia?
    Avoid expansion of air bubbles in bypass machine
  35. When using the US machine to insert a CL, is the artery or vein compressible?
    Vein
  36. Fast track cardiac anesthesia
    • extubation 8 hours post-op
    • most cardiac surgery these days
    • lower dose narcs are used, limit fent to 10-15 mcg/ kg
  37. Preincision
    -level of stimulation
    -anesthetist duties
    • low stim
    • check PPP
    • drop OGT and decompress stomach
    • TEE probe is inserted
    • obtain baseline labs (ACT and lytes)
    • start antibiotics
  38. Anesthetist duties during incision
    • Ensure adequate level of anesthesia- sternal split is very stimulating
    • Avoid HTN
    • Deflate lungs (detach from vent)
    • Once chest open switch to internal paddles
    • Ensure blood is available
  39. Amps used for internal defib
    10 milliamps
  40. What occurs after incision?
    • IMA and radial artery dissection
    • then sympathetic nerve dissection (can be very stimulating)
  41. How do we prepare for bypass?
    • Heparinize
    • Check ACT
  42. How does heparin work?
    binds to antithrombin 3
  43. heparin half life
    2.5 hours
  44. goal ACT prior to bypass
    > 300 sec
  45. Normal ACT
    105-167 seconds
  46. Sling placement
    • Goes behind heart to allow it to be lifted 
    • Can cause extreme HD changes (flat line)
    • Not treated if due to manipulation
  47. Goal BP during arterial (aortic) cannulation- why?
    • Goal SBP <= 90 mmHg
    • Risk of aortic dissection
  48. Goal BP during venous cannulation
    SBP <= 90 mmHg
  49. How would know you aortic dissection occurred during cannulation?
    • There's a pressure sensor on the aortic cannula (goes to perfusionist)
    • If aortic pressure reads 20 mmHg but radial reads 60 mmHg that could mean possible dissection
  50. Risks associated with venous cannulation
    • Atrial dysrhythmias- not treated as about to go on bypass
    • Occur as cannula is placed in or close to atria
  51. Communication during cardiac surgery
    Closed loop!!
  52. Prebypass checklist
    • Adequate anticoagulation
    • Adequate anesthesia
    • Cannulation proper and patent
    • Infusions off
    • Monitors in place
    • Foley in
    • Check pupils (check for eye swelling 2/2 misplaced venous cannula)
  53. How does bypass affect the concentrations of our drugs?
    CPB solution dilutes our drugs, may need to give more
  54. CPB checklist
    • Face- color, temp, symmetry (potential misplaced venous cannula)
    • Eyes- pupils equal and symmetric
    • Pump lines- visible color difference btw arterial and venous blood
    • Art and pulm BP
    • Stop ventilation once aortic ejection ceases
  55. Normal arterial BP on bypass
    • Will see mean only
    • 30-60 mmHg
  56. Normal PA pressures on bypass (if monitored)
    < 15 mmHg
  57. What happens once on CPB
    • stop ventilation
    • induce mild to moderate hypothermia
    • aorta is cross clamped (note on anesthesia record)
    • cardioplegia is infused
  58. cardioplegia solution
    • differs by inst
    • high K sol'n that stops the heart
  59. Distal vs. proximal anastamoses
    • Distal- on heart, not aorta
    • Proximal- on aorta
  60. What occurs after the distal anastamoses are completed
    Start to rewarm pt, need normothermia prior to coming off of bypass
  61. why do we tend to see hyperglycemia while on CPB?  How do we manage it?
    • D/t cardioplegia solution
    • Check BS q 20 mins
    • Insulin gtt
    • Goal BS < 150
  62. Why is checking UO q 30 minutes important?
    Ensure adequate renal perfusion
  63. CPB termination
    • Rewarm pt
    • Remove air PRN (more likely to occur with valve surgery as the heart is open)
    • Optimize metabolic condition
  64. Partial bypass
    • Occurs when weaning pt off of CPB
    • Some of venous blood flows into bypass, some into heart
  65. When do you start reventilating the pt
    Once blood is again flowing directly to the heart and lungs
  66. When is CPB terminated
    SBP > = 90 mmHg or < 1L pump flow
  67. In terminating CPB, the key factor is optimal ____.
    Preload
  68. How can we assess preload
    Via echo
  69. The pt no long requires bypass, now what?
    • Venous cannula is removed first, then arterial
    • Protamine is given
  70. Protamine administration
    • 1st give test dose of 5-10 mg
    • Perfusionist calculates dose
    • Surgeon will tell you when to give
    • Administer slowly
    • Tell surgeon progress of administration (33%, 50%, etc)
  71. Protamine complications
    PH, systemic hypotension
  72. Pump lung
    • Severe ARDS
    • Occurs 2/2 CPB
    • Rarely occurs nowadays
  73. Differential dx of LV failure after CPB
    • Ischemia
    • Inadequate coronary flow
    • Valve failure
    • Gas exchange issues
    • Preload- excessive or inadequate
    • Reperfusion injury
  74. 1st line agents for inotropic support once off CPB
    • epi or milrinone
    • varies by institution
  75. What pts are at risk for RV failure?
    PH, MV dz, RV infarct or ischemia, RV outflow obstruction, TR
  76. RV failure treatment
    • Hyperventilate to lower CO2 and thus lower PVR
    • Avoid hypoxemia, acidosis, and N20
    • NTG
    • optimize preload
    • inotropic support with milrinone or dobutamine
  77. MIDCAB
    • minimally invasive CPB
    • no bypass

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