Elevated catecholamine levels and abnormal hypoxic arousal in apnea of infancy

Arousal from quiet sleep in response to a hypoxic challenge fails to occur in many patients with apnea of infancy. It was hypothesized that catecholamine-mediated responses might be involved in the depressed hypoxic arousal response in apnea of infancy and that these differences would be reflected in serum catecholamine concentrations. Fifteen infants with a median age of 5.5 months and a history of unexplained apnea during sleep were studied. Two hypoxic challenges (PiO2 80 mm Hg) were given for three minutes or until arousal from quiet sleep occurred. Of the 15 patients with apnea of infancy 11 (73%) did not arouse to hypoxia. These infants had serum epinephrine levels that were elevated 4.1-fold while awake (P less than .05), 3.4-fold during quiet sleep (P less than .02), and 3.5-fold during hypoxia (P less than .05). They also had serum norepinephrine levels that were elevated threefold while awake (P less than .05), 5.3-fold during quiet sleep (P less than .001), 3.2-fold during hypoxia (P less than .02), and 12-fold during recovery from hypoxia (P less than .001) in comparison with the corresponding levels in the four (23%) infants who aroused normally to hypoxia. It is speculated that elevated circulating catecholamines are associated with abnormal hypoxic arousal responses in children with apnea of infancy.