Evaluation of weight-based dosing of unfractionated heparin in obese children.

OBJECTIVE: To determine whether pediatric patients with obesity receiving weight-based dosages of unfractionated heparin (UFH) exhibit an enhanced response when dosed by actual body weight compared with nonobese patients as assessed primarily by the frequency of supratherapeutic anticoagulation. Secondary measures included UFH doses associated with therapeutic anticoagulation. STUDY DESIGN: This single-institution retrospective case-matched study included children with and without obesity, matched on a 1:1 basis, who received a weight-based continuous infusion of UFH. Therapeutic monitoring values were defined for activated partial thromboplastin time (aPTT) level (70-101 seconds) and anti-activated factor X (Xa) level (0.35-0.7 U/mL). RESULTS: The study included 50 children. The percentage of patients with supratherapeutic anticoagulation at any point in the study, as measured by either aPTT or anti-Xa level, was similar in the obese and nonobese groups (76% vs 72%; P = 1.0). However, compared with patients without obesity, those with obesity received a lower mean starting dose (17.4 vs 20.2 U/kg/hour; P = .013) and a lower mean maintenance dose (19.1 vs 24.3 U/kg/hour; P = .033) to achieve stable therapeutic monitoring test values. There was no difference in mean initial post-UFH aPTT between the 2 groups, but the mean initial anti-Xa level was higher in the obese group (0.45 vs 0.29 U/mL; P = .045). CONCLUSION: Compared with children without obesity, those with obesity who received actual body weight-based continuous UFH infusions did not exhibit a higher frequency of supratherapeutic anticoagulation, but did require lower dosages to achieve comparable anticoagulation. Our results highlight recognized discrepancies between aPTT and anti-Xa monitoring assays.

Gentamicin dosing for pediatric patients with congenital heart disease.

Pediatric patients with congenital heart disease can have physiologies that alter the pharmacokinetics of certain medications, such as aminoglycosides. Currently, no literature describes the appropriate dosing of aminoglycoside antibiotics for infants and children with congenital heart disease. Patients were identified through the pharmacy and laboratory computer systems. Patients were included in the study if they were younger than 18 years, received gentamicin on the acute-care (nonintensive care) cardiology floor at the authors' institution, had structural congenital heart disease, and had a peak and trough level obtained at about the third dose or later. Cohort achievement of therapeutic peak and trough concentrations based on standard dosing guidelines was evaluated. The inclusion criteria were met by 48 patients (31 boys). Eight patients (17%) had baseline cyanosis. Cardiac surgery was performed for 23 patients (48%) during the same admission at which aminoglycoside therapy was initiated. A total of 27 patients (56%) received at least one other nephrotoxic medication at the time of aminoglycoside therapy. Six patients had undetectable serum trough levels. A therapeutic peak concentration was not achieved by 16.7% of the cohort, and 7.1% of the cohort did not achieve a therapeutic trough concentration. Pediatric patients with congenital heart disease may require alterations in gentamicin dosing. Close pharmacokinetic monitoring of aminoglycoside therapy for these patients is warranted to ensure attainment of goal concentrations.