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

Heme Catabolism and Bilirubin Production in Readmitted Jaundiced Newborns

We measured end-tidal CO levels in 50 jaundiced newborns readmitted for phototherapy at age 54-244 hours. The median end-tidal CO level was 1.55 ppm, suggesting that hemolysis is not the primary contributor to the hyperbilirubinemia in many readmitted newborns.

Phototherapy to prevent severe neonatal hyperbilirubinemia in the newborn infant 35 or more weeks of gestation

OBJECTIVE

To standardize the use of phototherapy consistent with the American Academy of Pediatrics clinical practice guideline for the management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation.

METHODS

Relevant literature was reviewed. Phototherapy devices currently marketed in the United States that incorporate fluorescent, halogen, fiber-optic, or blue light-emitting diode light sources were assessed in the laboratory.

RESULTS

The efficacy of phototherapy units varies widely because of differences in light source and configuration. The following characteristics of a device contribute to its effectiveness: (1) emission of light in the blue-to-green range that overlaps the in vivo plasma bilirubin absorption spectrum (~460-490 nm); (2) irradiance of at least 30 μW · cm(-2) · nm(-1) (confirmed with an appropriate irradiance meter calibrated over the appropriate wavelength range); (3) illumination of maximal body surface; and (4) demonstration of a decrease in total bilirubin concentrations during the first 4 to 6 hours of exposure. RECOMMENDATIONS (SEE APPENDIX FOR GRADING DEFINITION): The intensity and spectral output of phototherapy devices is useful in predicting potential effectiveness in treating hyperbilirubinemia (group B recommendation). Clinical effectiveness should be evaluated before and monitored during use (group B recommendation). Blocking the light source or reducing exposed body surface should be avoided (group B recommendation). Standardization of irradiance meters, improvements in device design, and lower-upper limits of light intensity for phototherapy units merit further study. Comparing the in vivo performance of devices is not practical, in general, and alternative procedures need to be explored.

Controversies in bilirubin biochemistry and their clinical relevance

Despite a century of research, several clinically relevant areas of bilirubin biochemistry remain controversial, poorly understood, or unrecognized. These include: (i) The structure and molecularity of bilirubin under physiological environments such as membranes, brain tissue and when bound to proteins. Related to this is the large number of structurally different bilirubin species that may occur in blood under pathological conditions and their potential effects on measurements of bilirubin and free bilirubin. (ii) The mechanism of phototherapy, the neurotoxicity of the photoisomers produced and their influence on measurements of bilirubin and free bilirubin. (iii) The role of membrane transporters in the passage of unconjugated bilirubin across the placenta, intestine, vascular epithelium, blood-brain barrier, and into the liver. (iv) Biochemical mechanisms of bilirubin toxicity, pharmacologic prevention of kernicterus, the contribution of bilirubin to antioxidant defenses, and the practical value of free bilirubin measurements for identifying infants at most risk of kernicterus.