Effects of Cardiopulmonary Bypass - PowerPoint

							 Post-Operative Care of
Congenital Heart Disease
       Patients
 A brief pediatrics perspective
                 Electrolytes
• Severe electrolyte abnormalities
  – Cause: Pump solutions, saline solutions, fluid
    shifts.
  – Most important are those with effects on heart
     • Potassium (arrhythmogenic)
     • Calcium (affects contractility and arrhythmias)
     • Magnesium (same as Ca)
  – Also, but less important
     • Sodium and phosphate
                   Glucose
• Hyperglycemia (outside of neonatal period)
• Causes:
  – Stress response
     • Endogenous steroids
     • Epinephrine
  – Steroids given for bypass
• Tx: Incr sedation & pain control
                   Renal Effects
• All due to decr MAP and non-pulsatile flow.
• Release of
   – Angiotensin
      • Causes HTN
   – ADH
      • Causes retention of free water leading to hyponatremia
   – Catecholamines
      • Causes HTN and faster heart rate.
• Tx: Antihypertensives, Lasix.
            Renal Effects, cont.
• Acute Renal Insufficiency (incidence 8%)
  – Oliguria
  – Incr creatinine
  – Fluid retention
• Tx:
  – MUF
  – Lasix
             Pulmonary Effects
• Causes
  – Leukocyte & complement activation
  – Surfactant loss
• Results:
  – Capillary leak… pulmonary edema.
  – Atelectasis
• Tx: ventilation with increased PEEP
                Pulmonary, cont.
• Pulmonary Hypertension
   –   Constriction of pulm vascular bed
   –   Leads to poor oxygenation
   –   Caused by acidosis & high CO2
   –   Tx: Hyperventilation.
• Reperfusion injury
   – Unique to Pulmonary Stenosis
        • Very common in pediatric CHD (esp. ToF)
        • Related to procedure itself, not bypass.
        • Presents as pulmonary edema
   – Tx: Diuretics.
                Coagulopathy
• Causes:
  –   Activation of clotting factors in tubing
  –   Real clotting to stop surgical bleeding
  –   Hemodilution
  –   Heparin in pump
• Tx:
  – FFP
  – Protamine
        Hemodynamic Effects
• Tissue ischemia, capillary sludging due to
  low MAP and non-pulsatile flow.
• Leads to Lactic Acidosis.
  – May exacerbate electrolyte disturbances
     • Potassium driven into cells with acidosis
  – Worse with longer bypass duration.
• Tx: shorten bypass time, bicarb, vent.
        Hemodynamics, cont.
• Hemodilution from pump priming
  solutions, iv fluids & renal insufficiency.
• Result worsens HCT than just surgical
  blood loss.
• Tx:
  – Modified Ultrafiltration (MUF)
  – Lasix
  – PRBC
        Hemodynamics, cont.
• Myocardial dysfunction
  – Usually Right Ventricle in children (unlike
    adults)
  – Increased CVP, decreased Bp and UOP
• Tx:
  – Dopamine
  – Epinephrine
  – Dobutamine
        Hemodynamics, Cont.
• Capillary leak… diffuse edema
  – Caused by inflammatory mediators activated
    against tubing of bypass.
  – Worse in children than adults
     • Length of tubing is longer in relation to the length of
       the child’s vascular system.
  – Tx: Lasix, limiting of IV fluids.
             Conclusions
• Overall the pathophysiology of bypass is
  similar to Systemic Inflammatory Response
  Syndrome seen in patients with sepsis.
• Similar derangements in coags, capillary
  permeability and tissue ischemia occur in
  both.
• Bottom line: minimize the pump time!