Adverse Effects of Intravenous Vancomycin-Based Prophylaxis during Therapy for Pediatric Acute Myeloid Leukemia.

Children and adolescents with acute myeloid leukemia (AML) are at risk of life-threatening bacterial infections, especially with viridans group streptococci. Primary antibacterial prophylaxis with vancomycin-based regimens reduces this risk but might increase the risks of renal or liver toxicity or Clostridium difficile infection (CDI). A retrospective review of data for patients treated for newly diagnosed AML at St. Jude Children's Research Hospital between 2002 and 2008 was conducted. Nephrotoxicity was classified according to pediatric risk, injury, failure, loss, and end-stage renal disease (pRIFLE) criteria and hepatotoxicity according to Common Terminology Criteria for Adverse Events (CTCAE) criteria. The risks of nephrotoxicity, hepatotoxicity, and CDI were compared between patients receiving vancomycin-based prophylaxis, no intravenous prophylaxis, or other prophylaxis. Generalized linear mixed models were used to address potential confounding. A total of 392 chemotherapy courses (108 with no intravenous prophylaxis, 218 with vancomycin-based prophylaxis, and 66 with other prophylaxis) for 111 patients were included. Development of pRIFLE risk, injury, and failure occurred in 190, 44, and 2 courses, respectively. Increases of at least one, two, and three grades for hepatotoxicity occurred in 189, 52, and 19 courses, respectively. After adjustment for confounders, vancomycin-based prophylaxis was not associated with nephrotoxicity or hepatotoxicity and reduced the risk of CDI, compared to no intravenous prophylaxis (0.9% versus 6.5%; P = 0.007) or other prophylactic regimens (0.9% versus 3.0%; P = 0.23). Despite concerns about vancomycin toxicity, vancomycin-based prophylaxis in pediatric patients with AML did not increase the risk of nephrotoxicity or hepatotoxicity and reduced the risk of CDI. Caution is advised to avoid contributing to antibiotic resistance.

Effect of temperature, pH and heme ligands on the reduction of Cygb(Fe(3+)) by ascorbate.

Cytoglobin (Cygb) plays a role in regulating vasodilation in response to changes in local oxygen concentration by altering the rate of nitric oxide (NO) metabolism. Because the reduction of Cygb(Fe(3+)) by a reductant is the control step for Cygb-mediated NO metabolism, we examined the effects of temperature, pH, and heme ligands on the Cygb(Fe(3+)) reduction by ascorbate (Asc) under anaerobic conditions. The standard enthalpy of Cygb(Fe(3+)) reduction by Asc was determined to be 42.4 ± 3.1 kJ/mol. The rate of Cygb(Fe(3+)) reduction increased ~6% per °C when temperature varied from 35°C to 40°C. The yield and the rate of Cygb(Fe(3+)) reduction significantly increases with pH (2-3 times per pH unit), paralleling the formation of the Asc ion (A(2-)) and the increased stability of reduced state of heme iron at high pH values. Heme ligand cyanide (CN(-)) decreased the yield and the rate of Cygb(Fe(3+)) reduction, but ligands CO and NO allowed the process of Cygb(Fe(3+)) reduction to continue to completion. Critical information is provided for modeling and prediction of the process of Cygb-mediated NO metabolism in vessels in a range of temperature and pH values.