Hyperbilirubinemia and phototherapy in newborns: Effects on cardiac autonomic control.
BACKGROUND
Neonatal jaundice and its phototherapeutic treatment can lead to several side effects involving activation of autonomic control mechanisms.


OBJECTIVE
The 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.


METHODS
HRV 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 (0V%, 1V%, 2LV%, 2UV%) and irreversibility index (P%) on four time scales were evaluated. All measures were derived from data segments of 1000 RR intervals.


RESULTS
The analysis revealed higher values of 1V%, 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, 0V% and irreversibility index P% were increased during and at least 30min after phototherapy.


CONCLUSIONS
The 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.
Clinic of Neonatology, Comenius University, Jessenius Faculty of Medicine and University Hospital, Kollarova 2, 03601 Martin, Slovakia. Electronic address: bukovinska.zuzana@gmail.com.
Zuzana
Z
Uhrikova
Clinic of Neonatology, Comenius University, Jessenius Faculty of Medicine and University Hospital, Kollarova 2, 03601 Martin, Slovakia. Electronic address: zibolen.mirko.sen@gmail.com.
Mirko
M
Zibolen
Department of Physiology, Comenius University, Jessenius Faculty of Medicine, Mala Hora 4, 03601 Martin, Slovakia. Electronic address: Javorka@jfmed.uniba.sk.
Kamil
K
Javorka
Department of Physiology, Comenius University, Jessenius Faculty of Medicine, Mala Hora 4, 03601 Martin, Slovakia.
Lenka
L
Chladekova
Department of Physiology, Comenius University, Jessenius Faculty of Medicine, Mala Hora 4, 03601 Martin, Slovakia. Electronic address: mjavorka@jfmed.uniba.sk.
Michal
M
Javorka
D017776:Autonomic Pathways / Q000502:physiology*; D016022:Case-Control Studies; D005260:Female; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology* / Q000528:radiation effects; D006801:Humans; D006932:Hyperbilirubinemia / Q000503:physiopathology* / Q000628:therapy*; D007231:Infant, Newborn; D016014:Linear Models; D008297:Male; D017711:Nonlinear Dynamics; D010789:Phototherapy / Q000009:adverse effects / Q000379:methods*; D018709:Statistics, Nonparametric; D013997:Time Factors
Heart rate variability; Hyperbilirubinemia; Neonates; Nonlinear analysis; Phototherapy; Sympatho-vagal balance