[Effect of hyperbilirubinemia on biologic rhythms in healthy full-term neonates]. / Efecto de la hiperbilirrubinemia sobre los ritmos biológicos en recién nacidos a término sanos.

OBJECTIVE: The toxicity of bilirubin (BP) on the brain presents unknown aspects. Therefore, the treatment for neonatal hyperbilirubinemia is controversial. The aim of this study was to establish if moderate levels of BP produce toxicity in brain nuclei that regulate the biological rhythms (BR) of healthy full-term newborns. PATIENTS AND METHODS: We studied 17 jaundiced (BP 12.8-18.1 mg/dl) and 36 non jaundiced newborns. Heart and respiratory rate, temperature and systolic blood pressure were recorded during 24 hours at 30 minute intervals. Cosinor analysis was used to calculate the incidence of BR. The Fisher exact test was carried out to compare both groups and the relative risks to determine the association between hyperbilirubinemia and the absence of BR. RESULTS: Differences in the BR parameters did not reach statistical significance. Differences in heart rate 12-h BR (p = 0.071) and systolic blood pressure 8-h BR (p = 0.076) approached a statistical significance. The 95% confidence intervals of the relative risks were all close to 1 and the lower limits in respiratory rate (0.40) and systolic blood pressure (0.35) 24-h BR indicate a negative association. CONCLUSIONS: The aim was to verify the relationship between moderate neonatal hyperbilirubinemia and the decrease in the incidence of BR. The results do not show the sought after relationship and provide evidence against neurotoxicity from moderate levels of bilirubin. The limited evidence for developing long term mental alterations permits us to make an optimistic prognosis for full-term newborns with moderately elevated levels of bilirubin.

[Biologic rhythm of respiratory rate in the first trimester of life]. / Ritmo biológico de la frecuencia respiratoria en el primer trimestre de la vida.

This study was designed to address the following objectives: 1) To record the respiratory rate in a population of newborns and infants. 2) To verify the existence of a rhythm in each population group, as well as the organization and maturing process of these rhythms. 3) To determine the possible influence of environmental factors on these rhythms. The study population consisted of the following groups and ages: A) 1 day (21 cases); B) 7 (15 cases); C) 15 (10 cases); D) 30 (17 cases); E) 60 (17 cases); F) 90 (18 cases). Respiratory rate was continuously monitored and recorded, as well as environmental light, noise and temperature. Rhythmometric analysis of the data was done by simple Cosinor test and analysis of variance. The zero amplitude test showed statistically significant differences in the circadian rhythm of groups E and F (p < 0.005). An ultradian rhythm of 3 hours was detected in groups D and F. Environmental factors also showed a circadian rhythm. The appearance of an ultradian rhythm suggest the maturation in a rhythm. To evaluate physiological parameters, reference to time series must be considered.