Pediatric Anesthesiology
Congenital Heart Disease - 3
IV. Pathophysiology of selected lesions
A. Basic definitions
- Physiologic L->R shunt = lungs -> lungs shunt; i.e., blood returning from the lungs is
recirculated directly back to the lungs without going to the body (body = everything but lungs)
- Physiologic R->L shunt = body -> body shunt; i.e., blood returning from the body is
recirculated directly back to the body without going to the lungs to be oxygenated
- Effective pulmonary blood flow = blood returning from the body that is actually directed
to the lungs to be oxygenated
- Nonrestrictive VSD = VSD large enough so that pressure equalizes in the two ventricles; no
pressure gradient can be maintained; RV pressure = LV pressure
B. Left ventricluar volume overload (LVVO): VSD, PDA
VSD:
- Most common CHD lesion
- 2/3rds close spontaneously
- Newborn VSD:
- Small: murmur present
- Large:
- No murmur
- Home with Mom without problems until
- Gradual onset of CHF by 4-8 weeks
- Shunt calculation (Fick)
Pulmonary:Systemic flow ratio, Qp:Qs,
= (SaO2 - SvO2) / (SpvO2 - SpaO2)
- Shunt depends on size of small VSD's only
- Shunt depends on SVR/PVR ratio for nonrestrictive VSD's
C. Right ventricular volume overload (RVVO): ASD
- Ostrium primum defect
- Part of spectrum of endocardial cushion defect (ECD)
- Often associated with cleft mitral valve and LV->RA shunt
- Ostium secundum defect
- Most common isolated ASD
- Shunt depends on RV:LV compliance
- Pulmonary vascular obstructive disease (PVOD) rare regardless of shunt
D. Right ventricular outflow tract (RVOT) obstruction with R->L shunt: tetralogy of Fallot (TOF)
- Most common cyanotic lesion
- Newborn
- Cyanosis
- "Quiet" precordium
- Diminished pulmonary blood flow
- Ao ejection click
- Tet "spells"
- tachypnea
- pallor
- loss of consciousness
- less murmur
- Treatment of tet spell
- 100% O2
- knee-chest position (compression of femoral arteries)
- morphine 0.05-0.1 mg/kg IM, IV
- crystalloid 15-30 ml/kg (increase heart size)
- phenylephrine 5-10 mcg/kg IV bolus or 2-5 mcg/kg/min to increase systolic BP 20-40 mmHg
- propranolol 0.1 mg/kg or esmolol 0.5 mg/kg and 50-300 mcg/kg/min
- ABG -> NaHCO3 1-2 mEq/kg if necessary
- ECMO in refractory cases
- Surgery
- (CONTRAINDICATED: beta-adrenergic agonists)
E. Cyanosis with increased pulmonary blood flow: transposition of the great arteries (TGA)
Newborn:
- Cyanosis
- No more than moderate respiratory distress
- Hyperactive precordium
- CxR: increased pulmonary blood flow, narrow superior mediastinum
- PGE1 0.05 - 0.1 microgram/kg/min to maintain PDA
- Balloon atrial septostomy
- Mustard or Senning procedure (or arterial "switch" procedure)