The effect of hematocrit on in vitro bilirubin photoalteration

Abstract

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.

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

“…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. This was strongest at the wavelength 400-460 nm, also found in vitro by Linfield et al (5) in 2016. On the basis of these results, it was predicted that a high hematocrit would reduce the therapeutic efficacy of phototherapy in vivo.…”

“…Whether the biochemical processes during phototherapy occur predominantly intravascularly or extravascularly has long been debated, although recent evidence strongly supports the idea that the biochemical processes during phototherapy predominantly take place intravascularly. In these in vitro studies, it has also been found that hemoglobin is a major competitor with bilirubin for the absorption of light during light exposure (4,5). The authors predicted that a high hematocrit would reduce the therapeutic efficacy of phototherapy; however, this has never been confirmed in vivo (4,5).…”

“…In these in vitro studies, it has also been found that hemoglobin is a major competitor with bilirubin for the absorption of light during light exposure (4,5). The authors predicted that a high hematocrit would reduce the therapeutic efficacy of phototherapy; however, this has never been confirmed in vivo (4,5). Confirming this hypothesis in a clinical setting is an important step in understanding the basic mechanisms of phototherapy, and could have implications for the treatment strategy for neonates with hyperbilirubinemia.…”

Efficient Photocatalytic Bilirubin Removal over the Biocompatible Core/Shell P25/g-C3N4 Heterojunctions with Metal-free Exposed Surfaces under Moderate Green Light Irradiation

“…Previous animal experiments showed that skin bilirubin of jaundiced rats under blue or green light irradiation was converted to metastable geometric isomers, which were then transported in the blood and excreted in the bile3334. The same reaction probably occurred in light-exposed jaundiced babies, particularly during phototherapy.…”

Update on phototherapy in jaundiced neonates

“…As the transformation of Z,Z-bilirubin predominantly takes place intravascularly, hemoglobin will compete with bilirubin for the absorption of light [38,39]. An increase in hemoglobin concentration decreased the percentage of Z,E-bilirubin in plasma in the first hour of PT but this effect disappeared later [19].…”