[Acenocoumarol (Sintrom) and fluinidione (Previscan) in pediatrics after cardiac surgical procedures]. / Acénocoumarol (Sintrom) et fluindione (Previscan) en pédiatrie après intervention de chirurgie cardiaque.

PATIENTS AND METHODS: Between 1997 and 2001, 150 children (one month to 16 years of age) were treated with oral anticoagulants after cardiac surgery (Fontan's operations and congenital heart diseases without valvulopathy: 62%, valvular prosthesis: 20%, arrhythmia: 4.6%, thrombosis: 4%, other: 9.4%). They were first treated by either unfractionated heparin (49%) or nadroparin (51%), then by acenocoumarol (n1 = 114) or fluindione (n2 = 36) until steady state. RESULTS: The retrospective analysis of data (age, body weight, international normalized ratio, loading and maintenance doses, time to achieve the steady state) led to the building of a dosage nomogram usable in pediatrics. CONCLUSION: We demonstrated that the mean maintenance dose depended on age and weight. After three years, that dose (mg/kg) was getting close to adult values; it was higher before three years of age, especially before 12 months (p < 0.01), and very variable from a child to another. The recommended loading dose should be as close as possible to the effective maintenance dose: within that cohort, about 0.14 and 0.05 (acenocoumarol) or 1.1 and 0.40 mg kg-1 day-1 (fluindione), before 12 months and after three years respectively.

Population pharmacokinetic of nadroparin calcium (Fraxiparine) in children hospitalised for open heart surgery.

Administration of low molecular weight heparin following heart surgery in paediatric patients in order to prevent thromboembolic events results in a large variation in anti-Xa activities. A population study was undertaken to determine pharmacokinetic parameters after nadroparin calcium (Fraxiparine) administration and the effects of potential covariates; this study included 154 children divided into two groups: a model group (124 patients) and a validation group (30 patients). The 432 anti-Xa activities were analysed using NONMEM on the basis of a one-compartment model with three parameters: apparent clearance, apparent volume of distribution and absorption rate. The influence of body weight, age, sex and dose regimen (once or twice daily) were investigated. The best fit corresponds to the formula: apparent clearance (l/min)=0. 541 x weight1.51/(6.151.51 + weight1.51) and apparent volume (l)=0.355 x weight. The inter-individual variability (expressed in coefficient of variation) of these parameters are high, especially with regard to the apparent volume (92%), but no other available covariate was found to explain this variability.

Ex vivo lung model of pig-to-human hyperacute xenograft rejection.

OBJECTIVE: Our objective was to study lung hyperacute rejection in the pig-to-human xenotransplantation combination. METHODS: Pig lungs were harvested and continuously ventilated and perfused ex vivo, using a neonatal oxygenating system, with either xenogeneic unmodified human blood (n = 6) or autogeneic pig blood (n = 6). RESULTS: Autoperfused lungs displayed normal hemodynamics, oxygen extraction (arteriovenous oxygen difference), and histologic characteristics throughout the 3-hour study period. By contrast, xenoperfused lungs displayed, within 30 minutes, severe pulmonary hypertension and abolishment of arteriovenous oxygen difference culminating in massive pulmonary edema, hemorrhage, and lung failure after 115 +/- 44.2 minutes of reperfusion. Within 30 minutes, the human blood showed a significant drop of anti-alpha Gal immunoglobulin M and G xenoreactive antibodies (enzyme-linked immunosorbent assay) and complement activity, consumption of clotting factors, and hemolysis; total circulating human immunoglobulins remained substantially normal. Histologically, lungs perfused with human blood were congestive and showed alveolar edema and hemorrhage and multiple fibrin and platelet thrombi obstructing the small pulmonary vessels (arterioles, capillaries, and venules) but not large (segmental or lobar) pulmonary vessels. On immunohistologic examination, deposits of human immunoglobulin M and complement (C1q and C3) proteins were observed on the alveolar capillaries. CONCLUSIONS: This pig-to-human xenograft model suggests that the pig lung perfused with human blood has an early and violent hyperacute rejection that results in irreversible pulmonary dysfunction and failure within approximately 150 minutes of reperfusion.