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TABLE 1 Clinical Complications of HIT in Children (n = 104)

Complication Absolute Percentage

Venous thrombosis Iliac vein Femoral vein Inferior vena cava Pulmonary embolism Progression of venous thrombosis Superior vena cava Calf vein Subclavian vein Jugular vein

Rare: innominate vein, pulmonary vein, arm veins, renal vein, dural sinus veins

Arterial thrombosis Femoral artery Iliac artery Foot arteries

Rare: renal artery, arterial embolism Others

Clotted lines (ECMO, hemodialyzer, catheters) Bleeding

Intracardiac thrombi Neurological deficits Clotted shunt

Decreased ventricular function Reoperation Skin necrosis

Note: Patients may have had more than one complication.

Abbreviations: ECMO, extracorporeal membrane oxygenation; HIT, heparin-induced thrombocytopenia.

were detected by platelet aggregation assay (incidence 14/930 = 1.5%). However, this study has several limitations. It is an observational study without a defined protocol. As differentiation of HIT from other causes of thrombocytopenia or thrombosis is difficult and the specificity of the applied platelet aggregation test for HIT antibodies may be low in ICU patients (see Chapter 10), the incidence of HIT might have been overestimated.

In a retrospective cohort study in a pediatric ICU, 57 patients developed arterial and/or venous thrombosis among 612 children treated with UFH for more than 5 days (Schmugge et al., 2002). In 14 children (2.3%), HIT was suspected based on thrombosis and a platelet count below 150 X 109/L (or platelet fall exceeding 50%) occurring after 5 or more days of UFH use. In six patients (1.0%), HIT antibodies were demonstrated by platelet factor 4 (PF4)-dependent enzyme immunoassay (EIA), using adult cutoff values in determining a positive assay result. The eight other patients with clinically suspected HIT had antibody levels below adult cutoff. Eleven of the 14 patients had received UFH following cardiac surgery. Four were newborns and five others were also under 1 yr of age (mean age, 6.5 mo).

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