Hyperbilirubinemia and phototherapy in newborns: Effects on cardiac autonomic control

• Hyperbilirubinemia in newborns is accompanied by subtle shift in cardiac autonomic control.
• Sympatho-vagal balance change occurs during and after phototherapy.
• Nonlinear heart rate variability measures were more sensitive to detect differences.

BackgroundNeonatal jaundice and its phototherapeutic treatment can lead to several side effects involving activation of autonomic control mechanisms.AimThe aims of this study are to investigate the autonomic nervous system changes in icteric neonates using heart rate variability (HRV) and to assess the effect of phototherapy on short-term heart rate dynamics as an indicator of autonomic nervous control of cardiovascular system.MethodsHRV recordings from 20 icteric full-term neonates before, during and after phototherapy and from 20 healthy controls were analyzed. In addition to traditional time and frequency domain measures, heart rate complexity parameters including normalized complexity index (NCI), normalized unpredictability index (NUPI), pattern classification indices (0 V%, 1 V%, 2LV%, 2UV%) and irreversibility index (P%) on four time scales were evaluated. All measures were derived from data segments of 1000 RR intervals.ResultsThe analysis revealed higher values of 1 V%, 2LV%, and lower P% in neonates with hyperbilirubinemia compared to controls. While HRV magnitude did not change, mean heart rate increased during and after the phototherapy. Nonlinear analysis showed a decrease of complexity, unpredictability and pattern classification measures 2LV% and 2UV%. In contrast, 0 V% and irreversibility index P% were increased during and at least 30 min after phototherapy.ConclusionThe results suggest a shifted autonomic balance in icteric neonates compared to the controls and its further alterations during phototherapy. As the nonlinear HRV parameters are independent of the linear methods, they can provide new information about the cardiac regulatory mechanisms and their changes in neonates.