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A 2 year old child recently brought from a third world country with PMH of an unrepaired hole in the heart and mild cyanosis is brought in to the ED. The patient fed in the AM, then began to cry and became unconsolable, hyperpneic, and deeply cyanotic. On arrival, the patient has a temp of 37.6, HR 180, RR 60, BP unobtainable, O2 sat 40% on room air.
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December 5, 2017 at 10:13 am
The patient is having a hypercyanotic spell, which happens not only in Tetralogy of Fallot, but also in other cyanotic congenital heart lesions with VSD and decreased pulmonary blood flow. The pathophysiology is thought to involve a sudden obstruction of the RV outflow tract, possibly due to a spasm of the pulmonary infundibulum, resulting in decreased pulmonary blood flow. The increase in pulmonary vascular resistance (PVR) results in decreased left to right flow through the VSD, resulting in cyanosis and absence of the usual murmur. A vicious cycle occurs whereby hypoxemia further increases PVR. Common precipitants of spells include crying, defecation, feeding, first awakening in the AM, fever, dehydration, tachycardia, and certain medications. Treatment involves relaxing the infundibulum/lowering PVR (oxygen, morphine, propranolol or esmolol), and increasing systemic vascular resistance (SVR) to promote a return to left to right shunting (knee chest position, squatting, IV fluid bolus to increase preload, ketamine, phenylephrine). Epinephrine is not used as its effects on SVR are dose-dependent and moderate compared to phenylephrine. For more info: http://pedemmorsels.com/hypercyanotic-spells/ and https://first10em.com/2015/03/04/tet-spell/