Book of Abstracts - New Frontiers 2022

Abstracts of oral presentations

MECHANISMS OF CARDIOVASCULAR CHANGES OF PHOTOTHERAPY IN NEWBORNS WITH HYPERBILIRUBINEMIA

K. Javorka 1 , M. Javorka 1 , K. Maťašová 2 , M. Zibolen 2

1 Department of Physiology, Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia; 1 Neonatology Clinic of Jessenius Faculty of Medicine CU and University Hospital, Martin, Slovakia During phototherapy (PT) of newborns, vasodilation occurs in the skin circulation compensated by vasoconstriction in the mesenteric and renal circulation, without significantly affecting the coronary and cerebral circulation. Furthermore, there is a slight decrease in cardiac systolic volume, blood pressure, an increase in heart rate and discrete changes in the heart rate variability (HRV). Mechanisms of the skin vasodilatation: The primary change during phototherapy is vasodilatation mediated by multiple mechanisms: Heat effect: One of the components of the light is the thermal influx. At higher irradiance intensities, body temperature increases, which promotes cutaneous vasodilation. Photorelaxation: In both in vitro and in vivo animal experiments, light elicits a maximal response of the vessel diameter at the wavelength of ∼ 430-460 nm, also used in PT ( ∼ 450 ± 20 nm). The mechanisms of smooth muscle photorelaxation are being intensively studied. "Atypical opsins" have been found in the eye, but also in arteries of the systemic and pulmonary circulation. Of these, opsin4 (Opn4) - melanopsin is thought to play a major role in vascular photorelaxation. The signaling cascade of the photorelaxation via Opn4 is specific, independent of endothelium and NO (1). Humoral regulation: Blood vessel diameter is influenced by endothelin 1 (ET-1) and nitric oxide (NO), among other substances. Abu Faddan et al. (2) found a rise in serum levels of NO but also ET-1 after phototherapy. The NO:ET-1 ratio increased, which may lead to a predominant effect of NO. Neural regulation: A decrease in tonic sympathetic activity to the skin vessels during PT is expected. Mechanisms of changes in cardiac function and blood redistribution: Cardiac systolic output is slightly reduced from the beginning of phototherapy (3), which may be due to reduced venous return associated with skin vasodilation and decreased motor activity of the newborns. Heart rate increases during PT. This response can arise through baroreflexes, the action of NO as well as the effect of increased body temperature on cardiac pacemaker. Changes in HRV assessed by methods of symbolic dynamics confirm increase in sympathetic activity. Redistribution of blood into the skin circulation during PT is ensured by restriction of blood flow in the mesenteric and renal circulations. The presumed dominant regulator here are baroreflexes, which, when the systemic blood pressure decreases, increase vasoconstriction in the above mentioned regional circulations (3). Conclusion: During neonatal phototherapy, cardiovascular changes occur which are important for maintaining vital functions as well as for improving the effect of PT by increasing skin blood flow. Complex and specific mechanisms of the hemodynamic changes during PT confirm the functioning regulation of the neonatal cardiovascular system, including baroreflexes. 1.Sikka et al. 2014; 2. Abu Faddan, et al. 2014; 3.Benders et al. 1999.

Keywords: Phototherapy, cardiovascular changes, photorelaxation, skin vasodilation, newborns

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