Phototherapy and Photo-Oxidation in Premature Neonates

Abstract

Objective: The potential for photo-oxidation during phototherapy in premature neonates was assessed by measuring parameters reflective of photo-oxidation. Methods: Blood was sampled from premature neonates prior to, and after 4 and 24 h of phototherapy, respectively. Total plasma bilirubin (TPB), blood carboxyhemoglobin corrected for inspired carbon monoxide (COHbc) (a sensitive index of heme catabolism), blood thiobarbituric acid reacting substances (TBARS) (a measure of lipid peroxidation), and plasma protein carbonyls (representative of protein oxidation) were determined. Study measurements were compared with baseline values both for the entire study group, and also individually for subgroups < and ≧1.5 kg birthweight, respectively. The percentage difference (%δ) between baseline and the 24-hour measurement was calculated for each parameter. Results: Forty-one premature neonates (mean [± SD] gestational age 30.5 ± 2.7 weeks and birthweight 1,499 ± 448 g) were studied. Mean TPB values decreased from a baseline of 9.1 ± 2.3 to one of 7.2 ± 2.8 mg/dl, p < 0.01, during the first 24 h of phototherapy. For the entire patient sample, neither COHbc, TBARS or protein carbonyl values increased significantly over baseline measurements: COHbc: 0.90 ± 0.26% vs. 0.92 ± 0.32%; TBARS: 19.0 ± 5.6 vs. 18.0 ± 4.5 nmol/ml, and protein carbonyls 7.73 ± 3.78 vs. 7.63 ± 3.56 U/ml (baseline and 24-hour samples only are shown in the abstract). Similarly, for the entire group, %δ (mean, interquartile range) were not significantly different between COHbc [–3.77 (–15.89–17.65)%], TBARS [–7.47 (–17.37–7.38)%], and protein carbonyls [–1.47 (–28.51–43.48)%], respectively. For subgroup analysis of neonates < or ≧ 1.5 kg birthweight, respectively, no significant increases in COHbc, TBARS or protein carbonyls were documented. A significant increase in %δ for COHbc in the <1.5 kg birthweight subgroup compared with those ≧1.5 kg, possibly indicative of hemolysis, was not matched by similar changes in %δ for TBARS or protein carbonyls, and may therefore not be a result of photo-oxidation. Conclusions: Except for changes in %δ in COHbc alone and in the smallest babies only, overall, short term phototherapy in premature infants was effective in reducing TPB concentrations without associated evidence reflective of photo-oxidation.

Optical properties of neonatal skin measured in vivo as a function of age and skin pigmentation

“…3 Knowledge of the optical properties of the tissue is essential when predicting or modeling light-tissue interactions, which in turn is invaluable for the development and improvement of these procedures. Although the majority of optical techniques at the neonatal intensive care depend on the interaction of light with skin, very little information can be found in literature about the optical properties (e.g., absorption and scattering coefficients) of neonatal skin.…”

Does intensive phototherapy produce hemolysis in newborns of 35 or more weeks gestation?

“…In one study of preterm neonates, 8 96 hour of phototherapy (irradiance not stated) produced a significant increase in blood thiobarbituric acidreacting substances (TBARS, a measure of lipid peroxidation), suggesting that phototherapy induces oxidative stress. On the other hand, Kaplan et al 9 found no increase in TBARS or plasma protein carbonyls (representative of protein oxidation) in 41 preterm infants, p35 weeks gestation, during the first 24 hours of phototherapy (average irradiance 18 mW/cm 2 /nm). They did, however, find an increase in the percentage change in blood carboxyhemoglobin levels in infants <1.5 kg birthweight when compared with those X1.5 kg, suggesting the possibility of some hemolysis in this very low birthweight subgroup.…”

Carboxyhemoglobin – the forgotten parameter of neonatal hyperbilirubinemia

“…First, by measuring end tidal CO (ETCO) or ETCO corrected for inspired CO (ETCO c ), as has been demonstrated repeatedly in neonates [22][23][24]. Second, by gas chromatographic analysis of COHb or COHb corrected for inspired CO (COHb c ), as has been described by Kaplan et al repeatedly [25,26]. ETCO c has been validated as an index for the rate of bilirubin production due to hemolysis [22,25] and has gained clinical importance with newly developed screening devices.…”

“…Second, by gas chromatographic analysis of COHb or COHb corrected for inspired CO (COHb c ), as has been described by Kaplan et al repeatedly [25,26]. ETCO c has been validated as an index for the rate of bilirubin production due to hemolysis [22,25] and has gained clinical importance with newly developed screening devices. As yet COHb has not been studied extensively.…”