Effects of Cardiopulmonary Bypass - PowerPoint
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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!