The primary physiologic goal when managing a tetralogy spell (cyanosis following a sudden increase in PVR) is reducing the right-to-left shunt (through the VSD), i.e. re-directing blood through the lungs.
Pharmacologic management of tetralogy spells include β-blockade, alpha-agonism (increases both PVR and SVR, however if PVR is already elevated, does not have an additional effect), bicarbonate (acidosis can increase PVR), and morphine.
Non-pharmacologic strategies include administration of 100% oxygen (reduces PVR), knee-to-chest position (increases SVR and reduces the R-L shunt), and fluid administration (may increase the diameter of the RVOT).
Pharmacologic Treatment of Tetralogy Spell (Adapted from Smith)
- β-Blockade: esmolol or propranolol (increased contractility is bad)
- Phenylephrine: 5 to 10 mcg/kg IV
- Bicarbonate: 1-2 mEq/kg. Normalizes SVR, decreases MV
- Morphine: leads to sedation, decreases MV (increased PVR)