CSC Review Course: Session 1

1
CSC Review CourseSession 1

• Myra F Ellis, RN, MSN, CCRN-CSC
• Duke Heart Center
• Duke University Hospital

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Preoperative Evaluation

• Coronary anatomy review
• Indications for cardiac surgery
• Risks of cardiac surgery
• Factors increasing mortality
• Factors increasing morbidity

3
Intraoperative Management

• Myocardial protection cardioplegia
• Conduct of cardiopulmonary bypass
• Deep hypothermic circulatory arrest
• Cerebral perfusion
• Consequences of CPB

4
Coronary Circulation

• At rest, myocardium extracts most of the
  available O2 (70)
• Flow determined by pressure and resistance
  (CPPDBP-LVEDP)
• Increase in demand must be met by an increase in
  flow
• LV circulation

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Right Coronary Artery

• Arises from aorta and courses AV groove
• Bifurcates at junction of right and left atria
• SA node (55)
• AV node (90)
• Bundle of HIS
• RA and RV
• Inferior surface of LV
• Posterior 1/3 of septum
• Posterior/inferior division of left bundle

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Left Main Coronary Artery

• 2-5 cm in length
• Bifurcates into LAD and Circumflex
• Carries worst prognosis in terms of survival
• Not grafted directly
• Inaccessible without dividing PA and aorta

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Left Anterior Descending

• 50 of total LV blood flow
• Diagonal branches pass over LV
• Anterior wall of LV
• Anterior 2/3 of septum
• Posterior/inferior division of left bundle
• Bundle of HIS
• Right bundle branch
• Anterior/superior division of left bundle
• Apex of LV

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Circumflex Artery

• Courses AV groove beneath L atrial appendage
• Obtuse marginal branches
• SA node (45)
• AV node (10)
• Inferior surface of LV
• Lateral wall of LV
• LA
• Posterior/inferior division of left bundle branch

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Tertiary Left Main

• Between LAD and Cx - Ramus artery
• Can be large vessel
• Usually subepicardial for only a few cm

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Summary

• Vessels grafted determine optimal ECG leads for
  postoperative monitoring
• ST segment monitoring is recommended
• AACN Practice Alert ST Segment Monitoring

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Indications for Revascularization

• Chronic stable angina
• Unresponsive to treatment
• Degree of symptoms
• Left main disease
• Stenosis gt 50
• Widow-maker
• CASS study

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Indications (continued)

• Triple vessel disease
• 2 lesions or more
• CASS - improved survival with surgery
• Unstable angina
• Increasing symptoms
• Indicates imbalance between O2 supply and demand
• Pt at risk for ischemic events

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Indications (continued)

• Acute MI
• Controversial
• Best outcomes
• Intractable ventricular irritability
• Complications from MI
• Refractory to medical treatment

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Indications (continued)

• LV failure
• Data inconsistent
• VSD repair
• Cardiogenic shock
• High mortality with medical management
• Results of CABG based on LV damage

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Indications (continued)

• PTCA failure
• Less than 2 of patients develop complications
• Emergent CABG within 24 hours increases mortality
• Restenosis rate is high

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Summary

• Patients that benefit the most from surgery are
  the sickest
• Patients with less severe disease and preserved
  LV function have less admissions and procedures
  with CABG

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Contraindications

• Small, narrow vessels
• Diffuse disease
• Lack of conduit
• Severe aortic sclerosis
• Severe LV dysfunction

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Increased Risk

• Age gt 65
• Female gender
• Previous heart surgery
• Urgency of operation

• Low EF
• Percent stenosis of LMCA
• Number of arteries greater than 70
• STS website risk calculation

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Less Important Factors

• PTCA during index admission
• MI within 1 week
• History of angina
• Ventricular dysrrhythmias
• CHF
• Mitral regurgitation
• Presence of comorbidities DM, CVA, PVD, COPD,
  CRI

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Myocardial Preservation

• Prevent heart damage during surgery
• Based on principles of myocardial function
• Blood flow regulation
• Ischemia is more damaging than hypoxia
• LV subendocardium is most vulnerable
• Hypothermia diminishes the effects of ischemia

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Techniques of Myocardial Preservation

• Traditional use of cardioplegia and aortic
  cross-clamp
• Allows still, bloodless field for surgeon
• Combination approach
• Cardioplegia - induction and maintenance of the
  heart in an arrested state

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Hypothermia

• Systemic cooling
• Bathing the heart
• Cold cardioplegia
• Medications

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Cardioplegia Ingredients

• Depolarizing agent
• Temperature of 4 8 degrees Celsius
• Substrate for energy
• Buffering agent
• Membrane stabilizing agent
• High osmolarity

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Autologous Blood Cardioplegia

• Improves O2 delivery
• Hypothermia causes left shift of oxyhemoglobin
  curve

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Administration of Cardioplegia

• Antegrade
• Catheter proximal to cross clamp
• Initial volume 1.5 L
• Global arrest in 30 seconds
• Reinfuse periodically
• Retrograde
• Catheter inserted transatrially
• Often combined with antegrade

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Cardiopulmonary Bypass

• First CPB in 1950s
• Primed with whole blood
• Crystalloid prime
• Prophylactic blood products
• 1980s lower HCT
• Recent improvements

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Anticoagulation

• Heparin
• Natural substance
• Has an antidote
• ACT (activated clotting time) allows close
  titration

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Components of CPB

• Arterial and venous cannulae
• Oxygenator
• Reservoir
• Pumps
• Filters
• Heat exchanger
• Hemoconcentrator

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Initiation of CPB

• CPB circuit primed
• Heparin at 300 u/kg
• Surgeon inserts cannulae
• Cardiac operations performed with cardioplegia
  and aortic x-clamp
• Pt connected to tubing of CPB circuit

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Initiation (continued)

• Initiate venous drainage, then arterial pump
• Blood cooled slowly
• Hemodilution
• Maintenance of CPB

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Weaning from CPB

• Rewarming
• Air removed from aorta
• Aortic cross-clamp off
• Establish sinus rhythm
• Ventilate lungs
• Retard venous drainage

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Weaning (continued)

• Atrial cannula out
• Protamine
• Remove arterial cannula
• Additional oxygenator blood given
• Failure to wean

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Deep Hypothermic Circulatory Arrest (DHCA)

• Operations of the Aorta
• Patient placed on CPB temp ? to 18 degrees
  Celsius
• Complete suppression of cerebral activity
• ? O2 consumption
• Monitor temperature at multiple sites

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DHCA (continued)

• Safe duration unknown
• Alpha-stat pH management
• Rewarm slowly
• Maintain euglycemia

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Cerebral Perfusion

• Adjunct to DHCA for ? cerebral protection
• Hypothermia ? O2 consumption
• Antegrade
• Offers best cerebral protection and maintains
  cerebral hypothermia
• Retrograde
• Flow through SVC
• Clamp IVC

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Other Adjuncts

• Ice-packing of the head
• Wait for electrical silence
• Monitor jugular SvO2
• Hematocrit greater than 20
• ??? pulsatile flow

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Physiologic Effects of CPB

• Complement activation
• Blood- extracorporeal circuit
• Anaphalaxatoxin c3a
• Chemotoxin c5a
• Initiates coagulation and fibrinolytic cascades

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Physiologic Effects of CPB

• Endocrine - altered hormone production
• Altered hormone degradation by lungs
• Altered release of hormones
• Lowered concentrations of hormones
• Increased catecholamine production
• Hyperglycemia

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Physiologic Effects of CPB

• Cerebral
• High degree of dysfunction
• Strokes
• Autoregulation
• Microembolization
• Pulmonary
• Complement activation
• O2 free radicals

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Physiologic Effects of CPB

• Hematologic
• Platelet dysfunction - bind procoagulants
• Coagulation factors
• Red blood cells

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Physiologic Effects of CPB

• Renal
• Hemodilution preserves RBF
• Hemolysis may cause ATN
• Vulnerable to low flow

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Complications of CPB

• Air embolus
• Malfunction of CPB
• Protamine reaction
• Vasodilation and hypotension
• Systemic inflammatory response
• Post-perfusion syndrome
• Rare complications