AKA Paroxysmal hypercyanotic attacks, hypoxic spells, blue spells, or anoxic spells.
Acute emergency requiring prompt recognition and intervention.
Peak incidence between 2 and 6 months of age.
Frequent occurrence before 2 years of age.
Higher susceptibility in infants with mild resting cyanosis lacking homeostatic compensatory mechanisms (e.g., polycythemia).
Triggers and Precipitating Factors
Spontaneous and unpredictable onset.
Early morning occurrence immediately after awakening.
Vigorous crying, agitation, or exertion.
Feeding.
Dehydration, fever, or pain.
Pathophysiology
graph TD
A[Triggers: Crying, Feeding, Fever, Dehydration] --> B[Increased Catecholamines / Peripheral Vasodilatation]
B --> C[Infundibular Spasm]
B --> D[Decreased Systemic Vascular Resistance]
C --> E[Decreased Pulmonary Blood Flow]
D --> F[Increased Right-to-Left Shunt via VSD]
E --> F
F --> G[Severe Systemic Hypoxemia]
G --> H[Metabolic Acidosis]
H --> I[Stimulation of Respiratory Center]
I --> J[Hyperpnea / Increased Venous Return]
J --> F
Acute decrease in pulmonary blood flow.
Increased right-to-left shunting across ventricular septal defect.
Infundibular spasm from increased circulating catecholamines.
Activation of right ventricular mechanoreceptors secondary to decreased systemic venous return.
Activation of left ventricular mechanoreceptors secondary to decreased pulmonary blood flow.
Peripheral vasodilatation causing severe fall in systemic vascular resistance.
Systemic hypoxia inducing severe metabolic acidosis.
Acidosis stimulating respiratory center causing hyperpnea.
Increased venous return from hyperpnea worsening right-to-left shunt (vicious cycle).
Clinical Features
Inconsolable crying, restlessness, and severe irritability.
Hyperpnea with deep and rapid breathing.
Absence of significant subcostal recession despite hyperpnea.
Progressive, deepening cyanosis.
Gasping respirations.
Disappearance or marked reduction of right ventricular outflow tract systolic ejection murmur.
Episode duration ranging from a few minutes to several hours.
Generalized weakness and sleep following brief episodes.
Differential Diagnosis of Cyanotic Episodes
Cyanotic breath-holding spells (forced expiration during crying, age 6 months to 5 years).
Pallid breath-holding spells (associated severe bradycardia, first 1-2 years of life).
Acrocyanosis (peripheral cyanosis with cold exposure, normal pink mucous membranes).
Respiratory disorders (variable partial pressure of oxygen, responsive to mechanical ventilation).
Central nervous system disorders (hypoxia reversed with artificial ventilation).
Persistent pulmonary hypertension of the newborn (improved hypoxia with hyperventilation).
Complications
Syncope or loss of consciousness.
Convulsions and seizures.
Cerebral thrombosis, central nervous system infarction, hemiplegia.
Intractable metabolic acidosis, shock, and respiratory failure.
Death.
Management
Immediate Interventions
Reduce SVR and oxygen
Knee-chest position on abdomen (increases systemic vascular resistance, increases systemic venous return).
Loosening of constrictive clothing.
Oxygen delivery via face mask or nasal cannula.
Calming the child
Calming and holding the infant.
Subcutaneous morphine (0.2 mg/kg).
Intramuscular ketamine (3-5 mg/kg).
Intranasal fentanyl or midazolam.
ACIDOSIS/dehydration correction
Intravenous fluid bolus (10 mL/kg dextrose normal saline).
Avoidance of premature, agitating blood draws.
Transcutaneous oxygen saturation monitoring.
Intravenous sodium bicarbonate (1-2 mEq/kg diluted 1:1 or in 10 mL/kg N/5 in 5% dextrose) for rapid metabolic acidosis correction.
Pharmacological Interventions (Refractory Spells)
BETA blockers
Intravenous beta-blockade for infundibular spasm reduction and heart rate control.
Intravenous propranolol (0.15-0.25 mg/kg given slowly, repeatable once in 15 minutes).
Intravenous metoprolol (0.1 mg/kg slowly over 5 minutes, maximum 3 doses, followed by 1-2 mcg/kg/min infusion).
Intravenous esmolol infusion.
VASOPRESSORS
Vasopressor administration for systemic vascular resistance augmentation and forced pulmonary blood flow.