Clinical Presentation

Between 1990 and 2006, 104 children have been reported with HIT. Fourteen (13.4%) were newborns, 43 (41.3%) were children aged 1 mo to 3 yr, 20 (19.2%) were between 4 and 11 yr of age, and 27 (25.9%) ranged in age from 12 to 18 yr (Fig. 1). In most newborns and young children (under 4 yr of age) HIT occurred after cardiac surgery (40/57 = 70.1%). In contrast, among 27 children aged 12 yr or older, HIT complicated the use of UFH given because of preceding thrombosis

■ heart surgery □ treatment of DVT □ prophylaxis □ other

FIGURE 1 Reasons for preceding heparin therapy in children with HIT. Among the various age groups, the reasons for heparin therapy that led to HIT varied considerably: whereas newborns and infants usually developed HIT after cardiac surgery, among teenagers, HIT more often complicated the use of heparin during treatment of thrombosis.

■ heart surgery □ treatment of DVT □ prophylaxis □ other

FIGURE 1 Reasons for preceding heparin therapy in children with HIT. Among the various age groups, the reasons for heparin therapy that led to HIT varied considerably: whereas newborns and infants usually developed HIT after cardiac surgery, among teenagers, HIT more often complicated the use of heparin during treatment of thrombosis.

in 13 (48.1%) patients, and following use of antithrombotic prophylaxis in eight (29.6%); only two of the older children had undergone cardiac surgery.

Five patients developed HIT during low-dose UFH given for catheter patency (4.8%). Hemodialysis or hemofiltration accounted for UFH use in eight (7.6%) patients. In 23 (22.1%) of the 104 patients, the laboratory test for HIT was negative or not performed.

The most frequent manifestation of HIT in children was a decrease in platelet count (83/104, 79.8%). HIT was associated with thromboembolic complications in about two-thirds of the patients, most commonly involving iliac and femoral veins, the inferior vena cava, and pulmonary embolism (Table 1). Less commonly, intracardiac thrombi or neurological events occurred, or clotting of the dialyzer. Only about 9% (9/104) of patients developed arterial thrombosis. Thus, there is a strong preponderance of venous thrombosis in pediatric HIT.

Thirteen (12.5%) of the 104 children died (Butler et al., 1997; Weigel et al., 1999; Deitcher et al., 2002; Boshkov et al., 2003a; Klenner et al., 2003a; Newall et al., 2003; Porcelli et al., 2003; Alsoufi et al., 2004; Mejak et al., 2004; Martchenke and Boshkov, 2005; Bidlingmaier et al., 2006), and three required amputations. In four children, only partial recanalization of thrombosed veins occurred.

This summary does not include the 14 newborns reported by Spadone and colleagues (1992). These workers primarily observed arterial thrombosis, with at least 11 (78.6%) developing aortic thrombosis (one infant died without imaging studies). Two newborns with thrombosis had normal platelet counts. Eleven (78.6%) survived, the remaining three developing mesenteric ischemia. Arterial thrombosis likely was related to umbilical artery catheters (used in all but one of the 14 neonates). In adults, intravascular catheters are a risk factor for HIT-associated thrombosis (Hong et al., 2003), but whether the arterial thrombi observed by Spadone et al. (1992) indeed were HIT-related is unclear.

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