Age is a determinant factor for measures of concentration and effect in children requiring unfractionated heparin

Area of Science:

• Pediatric Pharmacology
• Hematology
• Pharmacokinetics

Background:

• Previous research indicates age-related variations in unfractionated heparin (UFH) response in pediatric patients using continuous infusions.
• Understanding these age-dependent responses is crucial for optimizing anticoagulant therapy in children.

Purpose of the Study:

• To investigate the age-related pharmacokinetic and pharmacodynamic response to a single bolus of unfractionated heparin (UFH) in pediatric patients.
• To determine how UFH concentration and its anticoagulant effects (anti-Xa and anti-IIa activity) vary with age following a standardized UFH dose.

Main Methods:

• A single bolus of unfractionated heparin (UFH) at 75-100 IU/kg was administered to 56 children.
• Blood samples were collected at multiple time points (15, 30, 45, and 120 minutes) post-UFH administration.
• Assays performed included anti-Xa, anti-IIa, activated partial thromboplastin time (APTT), thrombin time (TCT), and protamine titration.

Main Results:

• Significant age-dependent differences were observed in UFH's effect and concentration for anti-Xa, anti-IIa, and protamine titration assays.
• A trend indicated a proportional increase in both anti-Xa and anti-IIa-mediated UFH effect with increasing age.
• Logistic regression revealed a 0.6 IU/ml increase in protamine titration per year of age at 15 minutes post-UFH. The anti-Xa to anti-IIa ratio increased with age, particularly in younger children.

Conclusions:

• The age-dependent response to UFH in children is associated with age-dependent serum concentrations of UFH.
• Increased UFH concentration and anticoagulant activity with age may stem from transient differences in UFH binding to plasma proteins.
• These findings highlight the importance of considering age in UFH dosing and monitoring in pediatric populations.