Setting and Patients We conducted a double-blind randomized controlled trial of children aged 2 to 18 years hospitalized at Boston Children's Hospital between February 1, 2011, and January 15, 2012, who required antimicrobial therapy with vancomycin (Hospira, Inc., Lake Forest, IL, lot #896188EO-4) for a suspected or documented infection. We excluded patients with a body weight above 67 kg (to limit the maximum loading dose to 2 g), preexisting severe renal dysfunction, defined as creatinine clearance \<50 mL/min/1.73m2 using the original Schwartz equation,7 known hearing impairment, intravenous vancomycin treatment in the prior 7 days or undergoing a procedure with anticipated moderate to severe blood loss (eg, cardiac surgery or extensive orthopedic procedure).
For all participants enrolled in the study, relevant baseline demographic, medical history and safety data were recorded. Medical history data included primary and secondary diagnoses; other comorbidities such as obesity or cystic fibrosis; and presence of systemic inflammatory response syndrome, defined as 2 or more of the following: temperature \>38.5°C or \<36°C; mean heart rate \>2 standard deviations above normal for age; mean respiratory rate \>2 standard deviations above normal for age; or high or low white blood cell count for age.
Randomization and Concealment Participants were randomized in blocks of 2 and 4 to receive either a loading dose of 30 mg/kg of vancomycin as a single intravenous infusion over 2 hours (intervention group) or an initial vancomycin dose of 20 mg/kg intravenously over 2 hours (comparison group). The initial dose was administered over 2 hours in both groups to preserve allocation concealment. All patients subsequently received a 20 mg/kg dose every 8 hours as was the standard of care in our hospital for treatment of severe infections at the time of the study. Subsequent doses were administered over 1 hour, unless the patient developed red man syndrome (as identified by the clinical team), in which case the infusion time was increased to 2 hours. The investigators, family and primary care teams were blinded to group assignment, and the first dose of vancomycin for all participants was prepared so that the solution volumes were identical. The computer-generated randomization was concealed in a locked binder until the intervention was assigned.
Vancomycin Concentration Sampling and Analysis Trough serum vancomycin concentrations were obtained within 60 minutes before the second (8-hour) and third (16-hour) vancomycin doses. In order to increase the likelihood of having a cloud of sparse data for population pharmacokinetic analysis, 1 or 2 additional serum vancomycin samples were obtained from each participant within the first 32 hours of therapy at a time coinciding with blood collection for clinical care. These samples were obtained only from participants with an indwelling catheter whose family provided written consent for additional sampling.
Vancomycin concentrations were measured using a fluorescence polarization immunoassay (Roche Diagnostics, Indianapolis, IN) on the Roche Integra 800 instrument. The assay had a limit of quantitation of 0.74 mg/L and an interassay coefficient of variability of \<3%.
