Background: The principal sites of neonatal phototherapy (NNPT) action may localize not only in the skin but also in capillary circulation under the skin. Thus, the safety of phototherapy particularly in relation to hemodynamic control must be investigated. Since regional blood flow is affected by Endothelin-1 (ET) and nitric oxide (NO), it is important to study the effect of phototherapy on circulating levels of both of them and to use the changes of vital signs as markers for hemodynamic stability.
Aim: This study aimed to evaluate the effect of phototherapy on blood ET and NO in hyperbilirubinemic newborn infants of different gestational ages with stable vital signs and to observe changes in vital signs in those newborn infants after 24 hours of phototherapy.
Methods: This study included 50 newborn infants (29 < 37 weeks [preterm]; 21 ≥ 37 weeks [full term]) with stable vital signs who received phototherapy for high unconjugated bilirubin levels. Heart rate (HR), respiration rate (RR), mean arterial blood pressure (MABP), serum ET and NO levels were detected before phototherapy and subsequently monitored after 24 hours under phototherapy.
Results: The present study revealed that after 24 hours of phototherapy there is a significant increase in NO and ET serum levels, NO:ET ratio, and HR and a significant decrease in MABP in both full term and preterm newborns. There is no significant change in RR in either preterm or full term newborns.
Conclusions: Phototherapy can disturb the dynamic balance between NO and ET, leading to a more prominent effect of NO. This effect may be not harmful in newborns with stable vital signs, but harmful effect may occur in newborns with septicemia or decompensated vital signs. Careful observation of vital signs should be done in all newborns under the effect of phototherapy. Also the safety of continuous phototherapy for more than 24 hours in newborn infants with different gestational ages and different birth weights should be verified.