New concepts in phototherapy: photoisomerization of bilirubin IX alpha and potential toxic effects of light.

New information is summarized, indicating that configurational photoisomerization of bilirubin at the 5 and 15 carbon bridges is the major mechanism of bilirubin photocatabolism in vivo, and that singlet oxygen photooxidation plays only a minor role. The literature is reviewed concerning potentially damaging photodynamic reactions that are observed in vitro with vitamins, proteins, lipids, and nucleic acids, and their possible relationships to the limited number of toxic side-effects that have been detected with clinical phototherapy of neonatal jaundice. Secondary toxic effects, mediated by bilirubin photoderivatives or by retina-neuroendocrine pathways are also considered. Areas requiring further investigations are delineated.

Postoperative Clostridium difficile pseudomembranous colitis in idiopathic scoliosis. A brief clinical report.

The authors report two healthy young patients with progressive idiopathic scoliosis, both without allergies or histories of gastrointestinal disorders, who received perioperative preventive cephalosporin antibiotics, and developed explosive diarrhea postoperatively, confirmed as Clostridium difficile pseudomembranous colitis by stool toxin assay. Both patients had initially recovered uneventfully after posterior fusion and Cotrel-Dubousset instrumentation. Their youth, health, diagnosis, and lack of nosocomial factors made colitis unexpected. The two cases were sporadic, occurring 2 years apart over a 12-year observation period. Symptoms and signs of colitis for the two patients were markedly varied as to time of onset, order of appearance, and severity. Unexplained fever before onset of diarrhea led to renewed cephalosporin administration, potentially exacerbating the colitis. Initial symptoms and signs were nonspecific; appropriate treatment had to begin before diagnosis could be confirmed by stool toxin asay, which requires 2 days.

Extranasopharyngeal angiofibroma.

Juvenile nasopharyngeal angiofibromas are vascular neoplasms, which originate characteristically in the posterior lateral wall of the nasopharynx. Although angiofibromas extend beyond the nasopharynx commonly, they rarely originate outside the nasopharynx. Reports of primary extranasopharyngeal angiofibromas have appeared sporadically in the literature. We present an unusual case of an angiofibroma arising from the middle turbinate. The clinical characteristics of extranasopharyngeal angiofibromas do not conform to that of nasopharyngeal angiofibromas. Therefore, they can present diagnostic challenges. A methodic evaluation and a high index of suspicion are essential in establishing the proper diagnosis and treatment.

Effect of combined treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin and phototherapy on bilirubin metabolism in the jaundiced Gunn rat.

2,3,7,8-Tetrachlorodibenzo-p-dioxin, a potent inducer of microsomal cytochrome P448-dependent monoxygenases, and phototherapy both accelerate bilirubin metabolism and decrease jaundice in Gunn rats. The effects of combined treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin and light were studied in these rats by applying phototherapy for 65 hr, beginning 5 days after induction with 2,3,7,8-tetrachlorodibenzo-p-dioxin. 2,3,7,8-Tetrachlorodibenzo-p-dioxin pretreatment caused a 75% decline in plasma bilirubin in 5 days, with no change thereafter, whether or not the rats were exposed subsequently to phototherapy. In the uninduced rats, plasma bilirubin levels declined by 55% after 40 hr of phototherapy. As determined by [14C]bilirubin kinetics, both 2,3,7,8-tetrachlorodibenzo-p-dioxin and phototherapy increased fractional bilirubin turnover and decreased the total bilirubin pool. In the 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced rats, the contracted bilirubin pool shifted from skin to liver, but these tissue pools did not change further during phototherapy. By contrast, in uninduced rats, phototherapy decreased the cutaneous bilirubin pool, which is the main target of phototherapy. 2,3,7,8-Tetrachlorodibenzo-p-dioxin was more effective than phototherapy in diminishing plasma bilirubin levels and the total bilirubin pool, but the combined treatment (2,3,7,8-tetrachlorodibenzo-p-dioxin followed by phototherapy) was no more effective than 2,3,7,8-tetrachlorodibenzo-p-dioxin alone.

Effects of phenobarbital on bilirubin metabolism and its response to phototherapy in the jaundiced Gunn rat.

Jaundiced Gunn rats, treated with phenobarbital (60 mg per kg i.p. for 7 to 10 days) showed 25 and 36% decreases in mean plasma bilirubin levels in two experiments (p less than 0.01). Kinetic studies with tracer 14C-bilirubin revealed that there was no change in bilirubin turnover or total pool size due to phenobarbital, but a 49% increase in the hepatic pool and a 27% decrease in the cutaneous pool of bilirubin. The increase in the hepatic pool accounted for over 90% of the bilirubin lost from the plasma. Such pretreatment with phenobarbital did not alter the decline in plasma bilirubin or total bilirubin pool due to subsequent phototherapy. Phenobarbital followed by phototherapy produced a significantly greater reduction in plasma bilirubin levels than either treatment alone. These studies demonstrate that phenobarbital does decrease plasma bilirubin in Gunn rats primarily by shifting the pigment to the liver, and suggests that combined treatment with phenobarbital and phototherapy might be of value in patients with congenital hyperbilirubinemia due to glucuronyl transferase deficiency.