1821 ELEVATED CATECHOLAMINES AND ABNORMAL HYPOXIC AROUSAL IN APNEA OF INFANCY

Abstract

Arousal from quiet sleep (QS) in response to a hypoxic challenge (HC) does not occur in many apnea of infancy (AOI) patients [Ped. Res., 16:363A, 1982]. Since catecholamines (C) stimulate respiration, abnormal C metabolism might be involved in the depressed arousal response to HC in AOI. We studied 14 AOI infants [age 12.4±3.3 (SE) months; with a history of apnea, cyanosis and limpness, requiring at least vigorous shaking for resuscitation; no identified treatable cause of apnea; and still having apnea]. When in QS by EOG and behavioral criteria, HC (PIO2 80 mmHg) was given for 3 minutes or until arousal (eye opening, agitation, movement, crying) occurred. Through an indwelling venous line, blood samples were obtained for epinephrine (E), norepinephrine (NE), and dopamine (D) levels [by REA] while awake, after 10-min of QS, and 1 min after the start and completion of each HC. Of the 14 AOI patients, 11 (79%) did not arouse to 2 consecutive HC 10 min apart. In infants who did not arouse, E was 2.5 × greater during QS (p < 0.025), NE was 2.7× greater while awake (p < 0.02), 6.4× grater in QS (p < 0.001), and 12× greater post-HC (P <0.001) than in those who did arouse. There were no differences in D. We conclude that E and NE are increased in AOI patients with abnormal hyposic arousal reponses: decreased C reponsiveness might contribute to the abnormal arousal response to HC.

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