Impact of phototherapy on vasoactive mediators: NO and VEGF in the newborn

Cardiovascular changes during phototherapy in newborns

Phototherapy is the most effective non-invasive method of neonatal hyperbilirubinemia treatment. Application of this method can be associated with side effects including changes in the cardiovascular system. During phototherapy, the primary effects in the cardiovascular system include cutaneous vasodilation leading to skin hyperperfusion and subsequent redistribution of blood. The increased blood flow through the skin is associated with increased transepidermal water loss. Further effects include an increase in cerebral blood flow. Redistribution of blood to the cutaneous bed is compensated by hypoperfusion in the splanchnic area (mostly postprandial) and a significant reduction of the renal blood flow. Regarding closure/reopening of the ductus arteriosus, the results suggest that that phototherapy does not affect ductal patency. During phototherapy the cardiac output can be slightly reduced due to a decreased stroke volume, especially in preterm newborns. Systemic blood pressure is decreased and heart rate is elevated in both preterm and term newborns during phototherapy. The heart rate variability is slightly reduced. Symbolic dynamics analysis of the short-term HRV showed that during phototherapy the activity of the ANS regulating the heart rate is shifted towards the dominancy of the sympathetic activity. The responses in the cardiovascular system of premature/mature newborns without other pathology confirm a well physiologically functioning control of this system, even under specific conditions of phototherapy.

Phototherapy and its effect on some physiological functions in newborns

Phototherapy represents the most common therapeutic intervention at neonatology departments in the first days of life. The beneficial effects of light on the decrease of the serum bilirubin level were first described by Cremer et al. in 1950’s (1). Since then phototherapy has been successfully used to treat severe hyperbilirubinaemia and has almost completely replaced exchange transfusion. Phototherapy is a relatively non-invasive method. However, along with decreasing bilirubin level, it can also influence some other functions: perfusion of organs, predominantly skin; peripheral vascular resistance; distribution of blood flow; heart activity and, thus, also systemic blood pressure along with breathing. A side component of applied light is a certain amount of heat which warms the body surface up and, therefore, the risk of exogenous overheating and increased water loss through the skin arise. Maternal-infant separation, modification of calcium homeostasis, disturbed circadian rhythm, or changes of the hemodynamics of various organ systems are only a few of the undesired effects which prove phototherapy not to be a treatment without any side effects. Careful indication of phototherapy is essential, particularly in premature infants.

Treatment of congenital generalized lymphangiectasia with propranolol in a preterm infant

Generalized lymphangiectasia is a rare congenital disorder characterized by dilated lymphatic vessels with a fatal prognosis, especially in cases with thoracic involvement. We describe the use of propranolol in the therapy of generalized lymphangiectasia in a preterm infant with hydrops fetalis. Propranolol was well tolerated and effective within the first months. It remains to be shown whether propranolol is a treatment option for infants with generalized lymphangiectasia.

Effect of phototherapy on growth factor levels in neonatal rat skin

AIM

Neonates undergoing surgery may receive phototherapy (PT) for the treatment of hyperbilirubinemia. Although the effects of PT on neonatal structures are well documented, the effect of PT on wound healing has not been previously evaluated. An experimental study was performed to evaluate the effect of PT on growth factor levels responsible for wound healing in neonatal rat skin.

MATERIALS AND METHODS

Eighteen Wistar newborn rats (7 ± 2 g) were included in the study. Rats were randomized into 3 groups: control (CG), PT, and sham (SG) (n = 6). Both groups had 1-cm median dorsal skin incision. In CG, 1 × 1 cm of dorsal skin was sampled including the incised skin. The PT group received 5 banks of blue light (wave density, 30-40 μw/cm(2) per nanometer; exposure distance, 45 cm). Phototherapy was started 24 hours after birth and exposed during light period (mean duration, 21 hours to 15 minutes ± 2 hour to 1.5 minutes). Sham group consisted of animals that received a bank of white light with same exposure distance and a total duration of 26 hours to 18 minutes ± 3 hours to 9.1 minutes. After exposure, 1 × 1 cm dorsal skin samples were obtained from both PT and SG groups, including the median incision. The effect of PT was evaluated with the expressions of vascular endothelial growth factor (VEGF), its receptor (VEGF receptor), and transforming growth factor β (TGF-β) in endothelial vessels and fibroblasts of neonatal skin samples.

RESULTS

There was no significant difference between groups in VEGF receptor and transforming growth factor β expressions. The VEGF levels in endothelial vessels were significantly decreased in PT and SG when compared with CG (P < .05).

CONCLUSION

Vascular endothelial growth factor is a mediator of angiogenesis and may decrease in neonatal rat skin after light exposure. It can be suggested that decreased levels of VEGF after PT application may alter angiogenesis and also may adversely affect the healing features of neonatal skin.

Effect of phototherapy on blood endothelin and nitric oxide levels: clinical significance in preterm infants

BACKGROUND

Phototherapy may have an adverse effect on the hemodynamics of preterm infants, and endothelin (ET) and nitric oxide (NO) are both the powerful vasoactive substances. This study was designed to observe the effect of phototherapy on blood levels of ET and NO in preterm infants.

METHODS

Sixty-four preterm infants with hyperbilirubinemia requiring phototherapy were studied. Among them, 31 patients were born at 32-36 weeks' gestational age (GA), and 33 patients were < or =32 weeks GA. Control group included 26 full-term infants with hyperbilirubinemia requiring phototherapy. All patients were treated with continuous phototherapy for 24 hours. Blood samples were collected before and after phototherapy. The amount of ET in the blood samples was determined by radioimmunoassay, and NO levels were determined using nitrate reductase. Heart rate, respiratory rate, apnea, and mean arterial blood pressure (MABP) were monitored regularly (defined interval: hourly, 4 hours, etc) during phototherapy.

RESULTS

Blood ET levels measured after 24 hours of phototherapy were higher than the pretreatment values, as were blood NO levels measured after 12 hours and 24 hours of phototherapy. Both increases were statistically significant (P<0.05) in the GA< or =32 weeks group. In the GA>32 weeks group, blood NO levels measured after 24 hours of phototherapy were higher than the pretreatment values; these changes were also statistically significant (P<0.05). In the GA<32 weeks group, heart rate increased and the MABP decreased during phototherapy. The changes after 24 hours of phototherapy compared to the pretreatment values were statistically significant. A few episodes of apnea occurred during phototherapy in the GA< or =32 weeks group. This was significantly higher than that in the other two groups.

CONCLUSIONS

Under phototherapy, blood levels of ET and NO were significantly higher in preterm infants, especially in preterm infants of < or =32 weeks GA.