Antithrombin III Supplementation in a Premature Infant: Is There a Target Antithrombin Level?

Area of Science:

• Neonatal medicine
• Pharmacology
• Hematology

Background:

• Optimal antithrombin (AT) activity for low-molecular-weight heparin (LMWH) efficacy in neonates is not established.
• There is a lack of neonatal-specific guidelines for antithrombin III (ATIII) supplementation targets.
• Venous thromboembolism (VTE) is a serious concern in premature infants.

Purpose of the Study:

• To describe a case of VTE in a premature infant treated with enoxaparin and ATIII supplementation.
• To investigate the required ATIII levels and enoxaparin dosing to achieve therapeutic anti-Xa levels in this patient.
• To highlight the need for further research into optimal AT activity targets in critically ill premature infants.

Main Methods:

• Case report of a critically ill premature infant with inferior vena cava thrombus.
• Treatment involved enoxaparin and supplemental ATIII.
• Monitoring of anti-Xa levels to assess therapeutic efficacy.

Main Results:

• The patient did not achieve therapeutic anti-Xa levels despite escalating enoxaparin doses up to 3 mg/kg every 12 hours.
• ATIII supplementation to achieve >40% AT activity, combined with enoxaparin >2 mg/kg every 12 hours, was necessary for therapeutic anti-Xa levels.

Conclusions:

• Achieving therapeutic anti-Xa levels in premature infants with VTE may require higher enoxaparin doses and ATIII supplementation.
• A target AT activity of >40% may be necessary in conjunction with specific enoxaparin dosing.
• Further large-scale studies are essential to determine optimal AT activity targets for critically ill premature infants receiving LMWH therapy.