C HIT in Children and Neonates

There are anecdotal reports of HIT occurring in children, some as young as 3 mo of age (Laster et al., 1987; Oriot et al., 1990; Potter et al., 1992; Murdoch et al., 1993; Klement et al., 1996; Butler et al., 1997; Ranze et al., 1999, 2001; Klenner et al., 2004) (see Chapter 20). However, not all of these patients underwent confirmatory testing with specific diagnostic assays. HIT in children has a similar, often dramatic clinical course, as is seen in adults. The frequency of HIT in the pediatric population is unknown.

The frequency and clinical import of HIT in neonates receiving heparin in intensive care settings is controversial. Spadone and colleagues (1992) investigated 34 newborn infants (average gestational age, 29 wk) who developed thrombocyto-penia or thrombosis, beginning an average of 22 days after starting heparin therapy. Platelet aggregation studies suggested the presence of HIT antibodies in 41% of these neonates. Aortic thrombosis complicating umbilical artery catheter use was the most common complication. Another group (Butler et al., 1997), also using platelet aggregation studies, reported a neonate who may have developed fatal HIT shortly after birth. More specific activation or antigen assays were not performed in either study, however. A recent study of 108 neonates who received UFH flushes found no HIT antibodies using a sensitive antigen assay (Klenner et al., 2003).

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