[Effect of hyperbilirubinemia on biologic rhythms in healthy full-term neonates]

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.

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.

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.

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.