Variability in measures of mineral metabolism in children on hemodialysis: impact on clinical decision-making.

BACKGROUND: Variability in measures of mineral metabolism has not been studied in pediatric end stage kidney disease. We sought to determine the intra-individual variability in measures of mineral metabolism in children on hemodialysis (HD) and its impact on clinical decision-making. METHODS: We conducted a prospective single-center study of children (3.6-17.3 years old) on chronic HD. Serial twice weekly measures of serum calcium, phosphate and intact parathyroid hormone (PTH), as well as weekly measures of fibroblast growth factor 23 (FGF23) and vitamin D metabolites, were obtained over a 12-week period in 10 children. Samples (n = 226) were assayed in a single batch at the end of the study. RESULTS: The median intra-individual coefficient of variation (CV) calculated by 4-week blocks was 5.1-6.5% for calcium, 9.5-14.9% for phosphate and 32.7-33.4% for PTH. The median overall CV for FGF23 was 44.4%. Using the first value of each block as a reference, subsequent values would dictate a discrepant management decision 33-56%, 19-28%, and 30-33% of the time for calcium, phosphate, and PTH, respectively. Adjusting for sex and age, most of the variability in phosphate and PTH was attributable to within-participant variability. For calcium, 49% of the variability was attributable to day of blood collection (Monday vs. Friday). The median (range) of an individual participant's values within clinical target ranges was 55% (26-86%) for calcium, 58% (0-96%) for phosphate, and 21% (0-64%) for PTH. CONCLUSIONS: There is considerable intra-individual variability in measures of mineral metabolism that serve as surrogate markers for bone health in children on HD. Within a 4-week period, at least 20-30% of measures would dictate a discrepant decision from the referent measure of that month. These findings have important implications for clinical decision-making and underscore the need to base therapeutic decisions on trends rather than single measurements.

The bioavailability of oral methotrexate in children with inflammatory bowel disease.

OBJECTIVES: Methotrexate is used to treat patients with inflammatory bowel disease. Although no available pharmacologic data support the assumption that the bioavailability of methotrexate is diminished in patients with inflammatory bowel disease, most such patients receive methotrexate parenterally. METHODS: The oral bioavailability of methotrexate was determined in 11 pediatric patients being treated with methotrexate for inflammatory bowel disease. Serial plasma methotrexate concentrations were determined after equal subcutaneous and oral doses of methotrexate. RESULTS: The mean bioavailability of methotrexate in patients with inflammatory bowel disease was 84% +/- 38%. Interpatient variability in drug exposure was similar after oral and subcutaneous administration. CONCLUSIONS: The bioavailability of methotrexate in patients with inflammatory bowel disease is no different from that observed in other disease states. Subcutaneous administration of methotrexate does not appear to decrease the interpatient variability in drug exposure. There is no sound pharmacologic basis for favoring administration of methotrexate via the subcutaneous route for patients with inflammatory bowel disease.

Laparoscopic-assisted bowel resection offers advantages over open surgery for treatment of segmental Crohn's disease in children.

BACKGROUND/PURPOSE: Minimally invasive approaches have been shown to decrease hospital length of stay (LOS), decrease postoperative pain, and speed return to normal activity for a number of intraabdominal procedures. In this study, laparoscopic (LAP)-assisted bowel resection is compared with an open technique for patients undergoing an initial bowel resection. METHODS: A retrospective review was conducted of 28 patients (12 LAP, 16 open) undergoing initial bowel resection for segmental Crohn's disease. RESULTS: Patients in the LAP group had decrease LOS (5.5 days v 11.5 days) decreased days of parenteral narcotics (3 days v 5 days) and more rapid return to regular diet (3 days v 5 days). CONCLUSIONS: The data suggest that the laparoscopic approach may offer advantages to pediatric patients undergoing an initial bowel resection for segmental Crohn's disease.