A new approach to an old hypothesis; phototherapy does not affect ductal patency via PGE2 and PGI2

Effect of phototherapy on the ductus arteriosus diameter in extremely premature infants: A randomised controlled trial

Patent ductus arteriosus (PDA) is a common complication among preterm infants (especially birth weight < 1000 g) and is closely associated with mortality and morbidity. Phototherapy (PT) is frequently used in the treatment of jaundice in premature infants in the first week of life. The relationship between PT and PDA has been investigated in a small number of studies but has not been fully elucidated because the studies had varying results.

AIM

To examine the effect of PT on parameter (DA diameter, left atrial/aortic root ratio) in premature infants.

METHODS

The study was planned as a prospective, randomised, double-blind study. A total of 83 infants <1000 g and < 30 weeks of gestation were included, and they were divided into two groups: the non-shielded and shielded groups. The babies included in the study were evaluated with a Doppler echocardiogram before and after PT.

RESULTS

The hemodynamically significant PDA (hs-PDA) and left atrial/aortic root ratio significantly decreased in the shielded group, and the need for treatment due to PDA was significantly lower. The PT times of both groups were similar.

CONCLUSION

Shielding application decreases the rate and severity of hs-PDA in extremely premature babies receiving PT.

Mechanisms of Cardiovascular Changes of Phototherapy in Newborns with Hyperbilirubinemia

During phototherapy of jaundiced newborns, vasodilation occurs in the skin circulation compensated by vasoconstriction in the renal and mesenteric circulation. Furthermore, there is a slight decrease in cardiac systolic volume, and blood pressure, as well as an increase in heart rate and discrete changes in the heart rate variability (HRV). The primary change during phototherapy is the skin vasodilation mediated by multiple mechanisms: 1) Passive vasodilation induced by direct skin heating effect of the body surface and subcutaneous blood vessels, modified by myogenic autoregulation. 2) Active vasodilation mediated via the mechanism provided by axon reflexes through nerve C-fibers and humoral mechanism via nitric oxide (NO) and endothelin 1 (ET-1). During and after phototherapy is a rise in the NO:ET-1 ratio. 3) Regulation of the skin circulation through the sympathetic nerves is unique, but their role in skin vasodilation during phototherapy was not studied. 4) Special mechanism is a photorelaxation independent of the skin heating. Melanopsin (opsin 4) - is thought to play a major role in systemic vascular photorelaxation. Signalling cascade of the photorelaxation is specific, independent of endothelium and NO. The increased skin blood flow during phototherapy is enabled by the restriction of blood flow in the renal and mesenteric circulation. An increase in heart rate indicates activation of the sympathetic system as is seen in the measures of the HRV. High-pressure, as well as low-pressure baroreflexes, may play important role in these adaptation responses. The integrated complex and specific mechanism responsible for the hemodynamic changes during phototherapy confirm adequate and functioning regulation of the neonatal cardiovascular system, including baroreflexes.

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.

Turkish Neonatal Society guideline on the management of patent ductus arteriosus in preterm infants

Ductus arteriosus is a physiologic phenomenon in utero and it closes spontaneously in term babies. The closure is problematic in preterm infants due to the intrinsic properties of the preterm ductus arteriosus tissue. Although patent ductus arteriosus has been reported to be associated with many adverse outcomes in this population, treatment has not led to a decrease in outcomes such as bronchopulmonary dysplasia. Treatment modalities also have their own risks and restrictions. The aim of the "Turkish Neonatal Society guidelines for the management of patent ductus arteriosus in preterm babies" is to standardize the diagnosis and treatment of patent ductus arteriosus in preterm infants by combining the current scientific data and the resources of our country.