What Are Hypercyanotic Spells?
Hypercyanotic spell is also known as hyperpneic, hypoxic, anoxic, blue, or tet. It occurs in cyanotic congenital heart diseases with reduced pulmonary blood flow. It is a pediatric emergency in which a young infant may develop deep blue skin, nails, and lips.
A rapid decrease in oxygen in the blood causes it. Peak incidence occurs between the age group of two to six months. Episodes occurring beyond the age of two years are rare. However, about 40 percent of patients with cyanotic congenital heart disease and decreased blood flow develop this spell.
A typical episode starts with a progressive increase in rate and depth of respiration, resulting in paroxysmal hyperpnoea, deepening cyanosis, limpness and syncope, convulsions, cerebrovascular accidents or stroke, and even death. The spells are usually self-limiting and last for about fifteen to thirty minutes. It tends to occur more often in the early morning but may occur at any time.
What Is Cyanosis?
Cyanosis is a bluish discoloration mostly noticeable on the lips and nail beds. During a cyanotic spell, the infant's skin and lips may suddenly turn blue, and their breathing pattern becomes more rapid and deeper. In addition, the infant may initially be very irritated and suddenly become grey, floppy, and unresponsive.
What Causes the Cyanotic Spell?
While the exact mechanism of a cyanotic spell remains unknown, several factors may cause an increase in the right to left shunting and, thereby, a decrease in arterial saturation. Cyanotic spells are caused by reduced pulmonary blood flow due to enhanced resistance in the pulmonary vessels leading to the right to left shunt across the ventricular septal defect (VSD).
Increased pulmonary vascular resistance (PVR) and a decrease in systemic vascular resistance (SVR) will cause right-to-left shunting, resulting in cyanosis. Potential precipitants include crying, which increases pulmonary resistance; defecation and high fever, which reduces systemic resistance; awakening from a deep sleep; feeding; tachycardia which usually reduces preload and angiotensin-converting enzyme inhibitors, such as candesartan, causing reduced afterload or systemic resistance. In addition, during a spell, the reduced oxygen saturation levels cause cerebral irritability leading to further crying; this, therefore, increases pulmonary vascular resistance, further exaggerating the problem.
What Is the Mechanism of Cyanotic Spell?
Multiple triggers stimulate the sympathetic nervous system and cause catecholamine release that leads to contraction of the right ventricular outflow tract (infundibulum). This causes an increased deoxygenated blood shunt into the systemic circulation. This is one of the most accepted mechanisms responsible for unfavorable hemodynamic changes.
Another mechanism thought to prevail is the presence of a vulnerable respiratory center, which after a prolonged deep sleep, responds by sudden increased demand of cardiac output triggered by crying, feeding, or straining.
The trigger starts with a series of physiological events leading to a vicious cycle. Increased catecholamine release causes tachycardia and cardiac output, increasing the deoxygenated systemic venous return to the right ventricle. In cases of severe obstruction to pulmonary outflow, more deoxygenated blood is shunted across the ventricular septal defect, causing a decreased systemic arterial oxygen content, acidosis, and hypercarbia. The respiratory centers in the medulla oblongata respond to the changes by gradually enhancing the rate and depth of respiration. This change in the respiratory pattern causes the increased venous return to the right ventricle, thus, perpetuating the vicious cycle.
What Are the Clinical Features of a Cyanotic Spell?
The clinical features of a cyanotic spell are:
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Bluish discoloration of the lips and nail beds.
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Unusual irritability.
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Difficulty in breathing.
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Reduced or no murmur.
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Limpness.
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Lethargy or weakness.
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Inconsolable cry.
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Tachycardia.
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Hyperpnea or increased and rapid breathing.
If the cyanotic spell worsens over time and is not corrected, then in the later stages, the spell may lead to anoxic seizures, gasping respiration, and apnoeas or no breathing.
What Are the Triggering Factors for Cyanotic Spells?
The following factors can trigger the cyanotic spell:
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Crying.
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Feeding.
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Dehydration.
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Bowel movement.
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Pain.
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High fever.
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Waking up from a deep sleep.
If a child has a cyanotic heart defect, parents should be extra cautious to keep the child hydrated throughout the hot climate.
What Is the Management of Cyanotic Spells?
Place the child in the knee-chest position, with the hips flexed and knees brought up to the chest. This helps increase systemic vascular resistance, reducing the right to left shunt and resulting in more blood flow to the lungs. High-flow oxygen should be administered with a non-breathe mask. This helps restore the oxygen content of the blood and reduces pulmonary vascular resistance. Cyanotic spells usually settle down with simple maneuvers. So, first, calm the child and avoid painful interventions. Then, if the hypercyanotic spell continues, administer intranasal fentanyl one mg per kg.
The correct underlying cause, if present, may exacerbate the episodes, such as cardiac arrhythmias, hypoglycemia, and hypothermia. If the spell continues, administer morphine sulfate 0.1 mg per kg subcutaneously unless intravenous access is present. Fentanyl and morphine suppress the respiratory centers, reducing the hyperpnea and the resultant systemic overload, which contributes to the right to left shunt.
Also, sedation helps in reducing the body's oxygen demands. Administration of beta-blockers such as propranolol may help reduce the heart rate and improve cardiac filling, preload, and systemic vascular resistance. Fluid bolus should be administered to increase the intravascular volume, as persistent hypoxia and shock may lead to acidosis, contributing to the vicious hemodynamic cycle of a hypercyanotic spell.
To prevent acidosis, intravenous sodium bicarbonate is recommended. If further interventions are required, intravenous access can be sited in the hand, foot, or scalp. This is sufficient to terminate the hypercyanotic spell. The oxygen saturation levels improve.
Conclusion
Hypercyanotic spell is a hallmark clinical manifestation of cyanotic heart diseases. Though it is self-limiting and managed with the alleviation of pain and anxiety, some severe cases may require immediate hospitalization and early intervention. Early intervention may help to prevent complications from prolonged hypoxia.
