Thrombosis Research 127 (2011) 492

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Thrombosis Research

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Letter to the Editors-in-Chief

Do sick preterm babies need adult levels of AntiXa unitsfor thrombolysis?

Dear Editors,

We read a recent review on the use of Enoxaprin in neonatalthrombosis byMalowany et al. [1] with great interest and would like toreport our observation with a question regarding future research.

We recently treateda490 g, 24 weekbaby for anocclusivedistal aorticthrombus measuring 0.6×0.1 cm with 2 mg/kg Q12 hr Enoxaparin. Wewere unable to achieve the therapeutic level of Anti-Xa units despiteincreasing the dose to 2.5 mg/kgQ12 on day 3 of therapy. The therapeuticlevel (0.68 U/ml)wasachievedafter6 daysof therapy. Since the thrombuswas a limb threatening occlusion we were following it with frequentDoppler ultrasounds.Whatwas interestingwas the fact that the thrombushad significant resolution at day 6 andwas completely resolved by day 12despite the “sub-therapeutic levels”.

There have been many case reports of spontaneous resolution ofthrombus in this population and close observation has been suggestedas one of the therapeutic options in non emergent situations. It is easyto imagine that the haemostatic and thrombolytic ability of the sickbabies would be different depending on the severity of illness andtheir gestational age.

The observation raises the following questions-Is the extrapolationof the adult data for achieving the “ideal” therapeutic levels in thisvulnerable population a good idea or should we look at other markersof the inherent thrombolytic ability of these sick preterm babies andadjust the therapy accordingly.

(A) Ultrasonographic image of an occlusive thrombus measuring 6×1 mm, visualized iarterial catheterization. (B) Repeat sonogram showing a significant resolution in throm

0049-3848/$ – see front matter © 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.thromres.2010.12.007

Reference

[1] Malowany JI, Monagle P, Knoppert DC, Lee DS, Wu J, McCusker P, et al. Enoxaparin forneonatal thrombosis: a call for a higher dose for neonates. Thromb Res 2008;122(6):826–30.

Vishal Pandey⁎Krishna Dummula

Prabhu ParimiKansas University Medical Center

⁎Corresponding author. Tel.: +1 91 216 315 5882;fax: +1 91 913 588 6317.

E-mail address: vpandey@kumc.edu (V. Pandey).

n the distal aorta in a 10 day old-24 week premature infant secondary to umbilicalbus size after 6 days of enoxaparin therapy.