Sites of Action of Light during Phototherapy

Granati, B; Felice, Michele; Fortunato, Antonio; Giancola, G.; Rubaltelli, Firmino F.

doi:10.1159/000241630

Cited by 7 publications

(7 citation statements)

References 10 publications

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“…Furthermore, they found photoisomers in only two of their samples, and then only in small quantities. Nonetheless, both early studies (3,6) still demonstrated that the presence of Hb does indeed impact bilirubin photochemistry. In our study, we exposed our samples to a much lower dose (~10 times lower than used in the aforementioned studies) and used the loss of diazo-reactive bilirubin as a measure of bilirubin photoalteration, which is considered indicative of lumirubin formation (1,7).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, Granati et al (6) used the loss of bilirubin absorbance, which reflects the destruction of the bilirubin chromophore, as their measure of bilirubin photoalteration. Furthermore, they found photoisomers in only two of their samples, and then only in small quantities.…”

Section: Discussionmentioning

confidence: 99%

“…Granati et al (6) compared the reduction in serum bilirubin levels in nonhemolytic infants with similar prephototherapy total bilirubin levels (13.5 mg/ dl) with mean Hcts of 67 ± 5% (n = 30) and 50 ± 5% (n = 27) in the in vivo phase of their study. After 24 h of phototherapy (425-475 nm, 22 μW/cm 2 /nm) using blue broad-band fluorescent tubes (which includes UV and IR wavelengths), they observed that infants in the lower Hct group had a higher mean reduction (8%) of total bilirubin than those in the higher Hct group but was deemed not statistically significant.…”

Section: Discussionmentioning

confidence: 99%

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The effect of hematocrit on in vitro bilirubin photoalteration

et al. 2015

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Background: Phototherapy using light in the spectral range of 410-500 nm, which overlaps the absorption of bilirubin, is the common treatment for neonatal hyperbilirubinemia. Hemoglobin (Hb) absorbs light strongly throughout this same range and thus can compete with bilirubin for this light and consequently reduce the efficacy of phototherapy. Here, we determined the effect of hematocrit (Hct) on in vitro bilirubin photoalteration using narrow-band blue (450 nm) lightemitting diodes (LEDs). Methods: Suspensions with Hcts from 0 to 80% and 16 ± 1 mg/dl bilirubin were prepared by mixing red blood cells (RBCs), bilirubin (30 mg/dl) in 4% human serum albumin, and normal saline. Aliquots of each suspension were exposed to blue light at equal irradiances. Before and after 60 min of exposure, bilirubin levels in supernatants (n = 46) were measured using a diazo-dye method. results: Bilirubin photoalteration steeply decreased by ~60% as Hct increased from 0 to 10%. Over the clinically relevant range of 30-70% Hct, the decrease was significant, but less drastic, exhibiting a quasi-linear dependence on Hct. conclusion: Bilirubin photoalteration under blue light in vitro is significantly reduced as Hct increases. Clinical studies are warranted to confirm these in vitro observations that Hct can affect the efficacy of phototherapy.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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The effect of hematocrit on in vitro bilirubin photoalteration

et al. 2015

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“…They observed in in vitro irradiation studies that changes in the Hct affect diazo-reactive bilirubin disappearance in blood. Almost a decade elapsed before a clinical study (8) showed a modest decrease in phototherapy efficacy with an increase in Hct, and this was deemed statistically insignificant on the basis of limited data. No further investigations of the question have appeared since then.…”

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confidence: 99%

The effect of hematocrit on the efficacy of phototherapy for neonatal jaundice

et al. 2013

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Background:The therapeutic phototherapy action spectrum ranges from 420 to 500 nm. However, a recent report of improved efficacy of fluorescent "turquoise" light (~490 nm) as compared with blue light (~450 nm) underscores the need to define an optimal action spectrum for precision-targeted phototherapy using very narrow wavelength ranges. Methods: We used a current semi-empirical model of the optical properties of skin for robust calculations of the fraction of light absorbed by bilirubin at various wavelengths that could be confounded by hemoglobin (Hb), melanin, and skin thickness. Applying assumptions regarding the wavelength dependence of bilirubin photochemistry, "action spectra" were assembled from the calculated values. results: All the calculated action spectra displayed a peak between 472 and 480 nm (most at 476 nm), which is a significant shift from the well-reported 460 nm absorption peak of bilirubin. Of note, the relative amplitudes of the action spectra showed an inverse relationship with hematocrit (Hct). conclusion: We speculate that a narrow range of light at 476 nm would be 60% more effective than blue (broadband) fluorescent lamps. Because Hb serves as a major competitor of bilirubin for light absorption, the calculations also predict that the efficacy of phototherapy is dependent on the Hct. A high Hct could reduce therapeutic efficiency. a n in vivo model to better define the optimal wavelength range for precision-targeted phototherapy has been elusive. Advances in understanding of skin optical properties have provided an optical model of neonatal skin in the therapeutic range (400-520 nm) that allows facile calculation of the influences of skin structure, melanin pigmentation, and cutaneous hemoglobin (Hb) on the action spectrum for phototherapy. Of these, Hb absorbs most of the visible light in the skin (1,2). As a result, competition from Hb with bilirubin for light should strongly affect the wavelength region of light that is most effective for phototherapy of neonatal jaundice. Although Hb competition has been recognized and used, in part, to predict the action spectrum for phototherapy (3,4), explicit reference to Hb competition appears to be absent from the recent literature. The reports of clinical studies showing that blue-green or green light may be more effective than blue light (5,6) generally rationalize these observations on the general notion that the longer wavelengths "penetrate deeper into the skin" without specific reference to Hb absorbance.Furthermore, significant competition for light by skin Hb also implies that the hematocrit (Hct) may in turn affect the efficacy of phototherapy. This possibility was recognized in 1974 by Lucey and Hewitt (7), who conjectured that the Hct "may be a contributing factor to the differences in response of serum bilirubin to light that one observes in different infants. " They observed in in vitro irradiation studies that changes in the Hct affect diazo-reactive bilirubin disappearance in blood. Almost a decade elapsed before a clinical st...

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“…In 1983, Granati et al (9) showed in vitro that, as hematocrit declined, bilirubin photodegradation increased; however, the correlation was not confirmed in vivo. In another in vitro study, by Lamola et al (4), using a semiempirical skin model, it was confirmed that hemoglobin in the skin competes with bilirubin for absorption of light during phototherapy.…”

Section: Discussionmentioning

confidence: 99%

The impact of hemoglobin on the efficacy of phototherapy in hyperbilirubinemic infants

et al. 2017

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BackgroundPhototherapy is the routine treatment for neonatal hyperbilirubinemia. Absorption of light in the skin transforms the native Z,Z-bilirubin to photobilirubins. This study investigates whether the hemoglobin concentration has an impact on efficacy of phototherapy, expressed by the decline of total serum bilirubin concentration (TsB).MethodsA trial was conducted on 93 infants, gestational age ≥33 weeks, with uncomplicated hyperbilirubinemia. The infants were treated with conventional phototherapy using LED light for 24 h. The median light irradiance was 66.8 μW/cm/nm.ResultsThe median decrease in TsB after 24 h was 121 (57-199) μmol/l; the median hemoglobin was 12.0 (7.0-14.7) mmol/l. There was a significant effect of hemoglobin concentration on the decrease in TsB of -3.61 μmol/mmol hemoglobin (P=0.022), after adjusting for initial TsB and postnatal age. That is, assuming the same initial TsB and postnatal age, for each mmol/l increase in hemoglobin, the decrease in TsB was 3.61 μmol/l smaller. In our hemoglobin range, the decrease in TsB is reduced by 28 μmol/l (23%).ConclusionIncreasing hemoglobin levels led to a decrease in the efficacy of phototherapy. Our data provide additional support for the conclusion that the transformation of bilirubin to photobilirubins takes place mainly in the superficial capillaries of the skin.

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Sites of Action of Light during Phototherapy

Cited by 7 publications

References 10 publications

The effect of hematocrit on in vitro bilirubin photoalteration

The effect of hematocrit on in vitro bilirubin photoalteration

The effect of hematocrit on the efficacy of phototherapy for neonatal jaundice

The impact of hemoglobin on the efficacy of phototherapy in hyperbilirubinemic infants

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