Cyanotic Spell

Cyanotic Spell

dr. Shirley L A, Sp. A12 April 2011Cyanotic spell= hypoxic spell, tet spell or hypercyanotic spell

occurs in young infants with TOF

It consists of hyperpnea, worsening cyanosis, & disappearance of the heart murmur

Any event such as crying, defecation, or increased physical activity that suddenly lowers the SVR or produces a large right-to-left ventricular shunt may initiate the spell and, if not corrected, establishes a vicious circle of hypoxic spells Fall in arterial Po2, increase in Pco2and a fall in pH, stimulates the respiratory center and produces hyperpnea

The hyperpnea, in turn, makes the negative thoracic pump more efficient and results in an increase in the systemic venous return to the RV

In the presence of fixed resistance at the RVOT (i.e., pulmonary resistance) or decreased SVR, the increased systemic venous return to the RV must go out the aorta

This leads to a further decrease in the arterial oxygen saturation, which establishes a vicious circle of hypoxic spells

Treatment of hypoxic spells

1.knee-chest position traps systemic venous blood in the legs temporarily systemic venous return & helping to calm the baby The knee-chest position may also SVR by reducing arterial blood flow to the lower extremities

2.Morphine sulfate suppresses the respiratory center & abolishes hyperpnea

7.Propranolol has been used successfully in some cases of hypoxic spell, both acute and chronic Mechanism of action ? - may slow HR and perhaps reduce the spasm of the RVOT - may increase SVR by antagonizing the vasodilating effects of -adrenergic stimulation

The successful use of propranolol in the prevention of hypoxic spell is more likely the result of the drug's peripheral action

The drug may stabilize vascular reactivity of the systemic arteries, thereby preventing a sudden decrease in SVR.

SquattingWhat is the mechanism of recovery from these symptoms during squatting? same as the knee-chest position

3 mechanisms may be involved : 1. reduction of the systemic venous return by trapping venous blood in the lower extremities reduces RL shunt at the ventricular level 2. reduced arterial blood flow to the legs reduces venous washout from leg muscles 3. may also increase SVR, a known mechanism to reduce R L ventricular shunt