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Carbon dioxide (CO(2)) plays important roles in regulating both respiratory drive and cerebral blood flow. These effects are mediated, in part, by activity of the sympathetic nervous system. We hypothesized that the presence of acute life-threatening events or apnea in term or preterm infants, respectively, would serve as a marker for immaturity of cerebral autonomic innervation and that such infants would display a reduced cerebral vascular response to elevated pCO(2). Therefore, we evaluated the cerebral vascular response during CO(2) challenge tests in groups of term and preterm infants with primary apnea. In term infants (39 +/- 2 weeks gestation) with acute life-threatening events, elevated pCO(2) was accompanied by decreasing pulsatility index and increasing mean anterior cerebral blood flow velocity. However, in preterm infants (29 +/- 2 weeks' gestation) with apnea, pulsatility index and anterior cerebral artery flow velocity did not significantly change in response to CO(2) supplementation. We conclude that preterm, but not term, infants with apnea exhibit impaired vascular responses to hypercarbia., (Copyright 2003 S. Karger AG, Basel)

Objective: To analyze the effects of apnea duration on changes in heart rate and oxygen saturation and to examine the temporal relationships among these variables., Study Design: An event analysis sheet was designed to analyze numerous variables reflecting changes in heart rate and oxygen saturation associated with infant apnea. From July 1, 1991 through June 30, 1992 we identified 32 infants enrolled in The Infant Apnea Program at St. Peter's Medical Center, New Brunswick, NJ who had apnea > or = 15 seconds in duration on consecutive 12-hour multichannel recordings of heart rate, thoracic impedance, nasal thermistry, and oxygen saturation. The apnea epochs of these patients were subdivided into apnea of short (10 to 14 seconds), medium (15 to 19 seconds), and long (> or = 20 seconds) duration, and a total of 236 apnea epochs were analyzed. The significance of differences was assessed by analysis of variance and Newman-Keuls multiple comparisons., Results: We found that the duration of apnea has significant effects on perturbations in both heart rate and oxygen saturation, however, the degree of oxygen desaturation can not be predicted by the perturbation in heart rate. Analysis of the temporal relationship of apnea, bradycardia, and oxygen desaturation reveals that, although apnea precedes both heart rate and oxygen saturation drops in most infants as the length of apneic interval increases, the interval between apnea onset and associated drops in heart rate and/or oxygen saturation also increases., Conclusion: Oxygen saturation monitoring may provide important physiologic data that can not be assessed by cardiorespiratory monitoring alone.

Purpose: To examine the ventilatory response to inspired carbon dioxide in infants considered to be at risk for sudden infant death syndrome or apnea., Design: Clinical data measurement., Setting: Infant apnea evaluation program of a university division of neonatology., Patients: Fifty nine infants were full term characterized by the following diagnoses; siblings of infants who had died from sudden infant death syndrome (SIDS) (n = 7), apparent life threatening event (ALTE) (n = 24), apnea/cyanosis in the newborn nursery (n = 21), and controls. Sixty-nine infants were preterm and consisted of patients suffering from idiopathic apnea (n = 61), and bronchopulmonary dysplasia (n = 8)., Measurements: The ventilatory response to carbon dioxide was measured with a computerized waveform analyzer., Main Results: Among full term infants no significant differences in the ventilatory slope in response to CO2 was seen. The range of mean slope was 19.4 +/- 7.6 in siblings of SIDS and 36 +/- 17 in control infants. Greater number of sibling of SIDS had slopes less than 20 ml/kg/min/mmHg in comparison to control infants. Sibling of SIDS had less increase in minute ventilation and inspiratory flow in response to CO2 administration in comparison to control infants. Preterm infants had similar slopes with a mean of 33 ml/kg/min/mmHg in infants with idiopathic apnea and 28 ml/kg/min/mmHg in infants with bronchopulmonary dysplasia., Conclusions: The large intragroup variability in the ventilatory response to inspired CO2, confirming previously reported data, comprises the benefit of this test. Thus, ventilatory response to CO2 administration is not useful in unselected patients at risk of SIDS or apnea.

The neurodevelopmental outcome of premature infants with persistent apnea of prematurity (AOP) is reported. Sixty premature infants (birthweight [BW], 1469 +/- 533 gm; gestational age [GA , 31 +/- 3 weeks) with AOP were compared to 47 control infants (BW, 1586 +/- 581 gm; GA, 31 +/- 3 weeks) matched for gestational age and degree of neonatal illness. The infants were enrolled in a multidisciplinary follow-up program, and outcome data between 12 and 24 months are reported. Assessments included the Bayley Scores of Infant Development, neurologic examinations, speech and hearing examinations. There were no significant differences in the cognitive outcome between the premature infants with AOP and the premature control group. In 50 of 60 infants the Bayley Mental Developmental Index was in the normal range (112 +/- 18) as was 39 of 47 of the control group (112 +/- 13). Delays in motor development were seen in both premature groups, although a greater percentage of premature infants with persistent apnea had mild motor delays than did control infants. There was a comparable incidence of cerebral palsy (8% vs 11%), speech delays (20% vs 23%), retinopathy (8% vs 13%), and esotropia (7% vs 4%) between the infants with AOP and the premature control infants. The presence of persistent neonatal apnea without additional adverse perinatal events did not appear to be associated with a higher incidence of significant developmental problems.

We studied the efficacy of caffeine in improving pneumogram abnormalities and relieving clinically important apnoea of infancy in 23 infants. After obtaining a 12 hour pneumogram we administered caffeine citrate in a loading dose of 20 mg/kg followed by 5 mg/kg once daily. This dose achieved a trough caffeine blood concentration of 9.6 (SD 2.0) micrograms/ml. A repeat pneumogram performed seven to 10 days after the first pneumogram showed a significant reduction in the number of short and prolonged attacks of apnoea as well as in the per cent periodic breathing and apnoea density. Episodes of prolonged apnoea disappeared in all infants after administration of caffeine and in 11 infants all pneumogram abnormalities resolved. This improvement in the results of pneumograms was associated with resolution of clinically important apnoea requiring intervention. Caffeine was administered for 3.4 (SD 1.3) months and was well tolerated by all except two infants. We conclude that treatment with caffeine is helpful in preventing attacks of apnoea that require intervention, and improvement in the results of pneumograms after administration of caffeine predicts this favourable response.