Specific Therapies

1. Methemoglobinemia. Infuse 1-2 mg/kg of methylene blue as a 1% solution in normal saline over 5 minutes.

2. Tet spell. In an infant with known or suspected tetralogy of Fallot, hypercyanotic episodes (tet spells) should be managed by increasing preload and systemic vascular resistance to overcome right ventricular outflow obstruction and increase pulmonary blood flow. Treatment typically consists of IV fluid bolus, knee-to-chest positioning, and oxygen (may or may not be useful). In addition, sodium bicarbonate (0.51.0 mEq/kg IV) should be administered for metabolic acidosis and morphine sulfate (0.05-0.1 mg/kg IV or SQ) for sedation. Phenylephrine (5-10 mcg/kg) can be administered IV to increase systemic vascular resistance and increase pulmonary blood flow.

VI. Problem Case Diagnosis. Results of the hyperoxia test in the 1-week-old infant suggested a diagnosis of cyanotic congenital heart disease, which became symptomatic after PDA closed. Prostaglandin E was infused to reopen the ductus. An echocardiogram confirmed transposition of the great arteries.

■ VII. Teaching Pearl: Question. Why is cyanosis not apparent in a newborn at the same arterial oxygen saturation that causes cyanosis in a 1-year-old child?

VIII. Teaching Pearl: Answer. Fetal hemoglobin has a higher affinity for oxygen than does hemoglobin A.

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