Introduction

Heparin-induced thrombocytopenia (HIT) can occur in children, with the potential for severe venous and arterial thrombotic complications (Table 1). Unlike in adults, few data exist regarding pediatric HIT. Only 104 children have been reported with HIT between 1990 and 2006 (Martchenke and Boshkov, 2005; Oriot et al., 1990; Potter et al., 1992; Murdoch et al., 1993; Boon et al., 1994; Klement et al., 1996; Wilhelm et al., 1996; Butler et al., 1997; Schiffmann et al., 1997; Barth, 1998; Sauer et al., 1998; Scurr et al., 1998; Bocquet et al., 1999; Saxon et al., 1999; Weigel et al., 1999; Neuhaus et al., 2000; Ranze et al., 1999, 2001; Girisch et al., 2001, 2002; Severin and Sutor, 2001; Zohrer et al., 2001; Deitcher et al., 2002; Schmugge et al., 2002; Severin et al., 2002a; Boshkov et al., 2002, 2003a,b, 2004; Gatti et al., 2003; Schlegel and Hurtaud-Roux, 2003; Klenner et al., 2003a, 2004; Newall et al., 2003; Nguyen et al., 2003; Porcelli et al., 2003; Alsoufi et al., 2004; Dager and White, 2004; Lischetzki et al., 2004; Malherbe et al., 2004; Mejak et al., 2004; Rischewski et al., 2004; Tcheng and Wong, 2004; Verso et al., 2004; Frost et al., 2005; Grabowski et al., 2005; Iannoli et al., 2005; John and Hallisey, 2005; Bidlingmaier et al., 2006; Knoderer et al., 2006).

II. PATHOPHYSIOLOGY

Studies of the pathophysiology of HIT have been performed using adult blood. In our laboratory, pediatric and adult HIT sera react similarly in various in vitro assays. Therefore, it seems reasonable to infer that the pathophysiology of HIT in children resembles that in adults (see Chapters 4-9).

III. FREQUENCY

Eleven studies have addressed the frequency of HIT in children. A. Pediatric Intensive Care Unit Patients

Spadone and coworkers (1992) collected cases of suspected HIT in a neonatal intensive care unit (ICU) between 1988 and 1990. Of 1329 newborns enrolled, about 70% received unfractionated heparin (UFH), either 0.5-1.0 IU/mL added to central venous or peripheral/umbilical artery catheters or via flushing of peripheral venous catheters (10 IU/mL UFH-saline every 4 h). In 34 (3.7%) newborns, HIT was suspected because the platelet count fell to less than 70 x 109/L or because of new thromboembolic events. In 14 of these 34 infants, HIT antibodies

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