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!