Dear Editor

It was a pleasure to go through the article “Use of low molecular mass heparin (Enoxaparin) in newborn infants: a prospective cohort study of 62 patients” by W. Streif et al.[1]

In present setting in which increasingly preterms and extremely low birth weight babies are being salvaged, the degree of intervention in form of peripherally inserted central catheters and other modalities of interventions have increased. The iatrogenic factors and various inherent defects predispose these neonates to thromboembolic phenomenon, which are increasingly being diagnosed with Doppler facilities. In view of such a scenario, the endeavour to use enoxaparin is highly appreciable and opens gate for newer agents with antithrombotic activity in neonates.

However, in context of above mentioned article we have a few observations:
1. The study does not compare enoxaparin to efficacy of unfractionated heparin which is the standard drug being used for therapeutic and prophylactic purpose in neonatal thromboembolism. Hence, a parallel control group receiving unfractionated heparin & then comparing their therapeutic effects & side effects would have added a new dimension to this study.
2. The neonates with congenital heart diseases form a major fraction of this study. These congenital heart diseases have not been classified into cyanotic & acyanotic. Cyanotic heart diseases by coexistence of polycythemia are more predisposed to thromboembolism & hence may have different pharmacokinetics for LMWH.
3. The observers, while doing imaging for thromboembolism prior to initiation of therapy, could have assessed the degree of thrombotic occlusion (i.e. occlusive/non occlusive thrombus). This would have added a meaningful dimension to efficacy of treatment in terms of clot resolution/ extension. Also an observation in respect of type of vessel (vein/ artery) involved by thrombus & its response to LMW heparin in terms of dosage and time of onset resolution since first dose of LMW heparin would have been interesting.
4. An earlier study has shown that decreased concentrations of heparinoids are required to inhibit thrombin generation in plasma from newborns and children compared to adults due to low thrombin potential.[2] However, in the present study evidence with respect to preterms is controversial. Hence an evaluation of thrombin potential of preterms would have been meaningful to assess as to why they require higher and prolonged dosages for desired effects.

We solicit opinion of workers on remarks.

References

1. Streif W, Goebel G, Chan A K C, Massicote M P Use of low molecular mass heparin (enoxaparin) in newborn infants: a prospective cohort study of 62 patients. Archive Dis child Fetal Neonatal Ed 2003; 88F365-F370

2. Chan AK, Berry LR, Monagle PT, Andrew M Decreased concentrations of heparinoids are required to inhibit thrombin generation in plasma from newborns and children compared to plasma from adults due to reduced thrombin potential. Thromb Haemost. 2002 Apr;87(4):606-13.