BACKGROUND: Unfractionated heparin (UFH) is one of the most frequently prescribed drugs in paediatric tertiary care centres and is used in a diverse group of disorders including cardiopulmonary bypass, extra corporeal membrane oxygenation, dialyses and maintenance of both venous and arterial catheter patency. Dosing of UFH in children is extrapolated from adults and is assessed by either a chromogenic Anti-Xa assay or a clot-based activated partial thromboplastin time (aPTT). The overall objective of the study was to assess safety of current standard of practice in the use of therapeutic UFH in children.

Objective #1: The primary objective was to determine the incidence of bleeding and the incidence of recurrent thrombosis in children receiving UFH.

Objective #2: To assess the monitoring UFH by assessing the relationship of the aPTT and Anti-Xa heparin levels to heparin dose.

STUDY DESIGN: A prospective cohort study in nonselected children in a intensive care setting. The primary outcomes were major bleeding events and recurrent thrombosis. The secondary outcomes were assessing the APTT and Anti-Xa levels. Inclusion Criteria: Patients 〉 36 weeks gestation and 〈18 years of age requiring therapeutic doses of UFH. Exclusion Criteria: patients who received UFH for less than 1 day. Major bleeding was defined aprior as any of the following: CNS bleeding, retroperitoneal bleeding, and/or bleeding that results in stopping UFH infusion.

RESULTS: Patient Population 39 patients were enrolled, 22 (56%) male, 32 (82%) < 1 year of age and 90% of which where cardiac patients. Major Bleeding events: 11/39 patients had a major bleeding event 28.2% (95% CI 15.0–44.9%). No patient had recurrent thrombosis. Relationship of aPPT and Anti-Xa to heparin dose; A total of 188 paired aPTTs and anti-Xa levels were performed. There was little correlation between aPTT and anti-Xa levels (r2=0.205) and APTT and UFH dose (r2=0.054). There was no relationship between anti-Xa levels and UFH dose (r2=0.0089). (Figure 1 and 2)

CONCLUSIONS:. There is an unacceptably high rate of bleeding in children receiving UFH for clinical care. There is little or no relationship of aPPT and Anti-Xa to heparin dose. Clinical trials are needed to assess the appropriate use of UFH therapy in children.

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