title: Heparin-induced thrombocytopenia-associated thrombosis in pediatric intensive care patients.
abstract: BACKGROUND
  Heparin-induced thrombocytopenia (HIT), a well-known side effect of heparin therapy, occurs in 1% to 5% of adults exposed to heparin. Of those, about 29% to 88% develop thrombosis. Most data on HIT-associated thrombosis in children are confined to anecdotal reports.
  
  
  OBJECTIVE
  To determine the incidence of HIT-associated thrombosis in heparin-exposed children.
  
  
  METHODS
  We performed a retrospective cohort study on all patients admitted to our pediatric intensive care unit between August 1996 and January 1999. Patients who received heparin for >/=5 days were eligible. Within these patients, we identified all cases of radiologically confirmed thrombosis. Cases of thrombosis were reviewed for fulfillment of clinical HIT criteria. HIT-associated thrombosis was confirmed serologically by determination of levels of antibodies against heparin/platelet factor 4 complexes.
  
  
  RESULTS
  Of 1950 children admitted during the study period, 612 were exposed to heparin for >/=5 days. Thrombosis occurred in 57 patients (9.3%). Plasma samples were available for 38 cases, of which 14 satisfied clinical HIT-criteria. Calculated incidence rate for HIT-associated thrombosis: 2.3%, (95% confidence interval: 1.3%-3.9%, for patients exposed to heparin >/=5 days). Nine patients suffered from venous, 2 patients from arterial, and 3 had combined arterial and venous thrombosis. None of the 14 patients died or underwent amputation. Six patients had heparin and platelet factor 4-complex antibody levels above the cutoff level for adults. The remaining 8 patients had significantly higher antibody levels than a matched control group.
  
  
  CONCLUSIONS
  Compared with that reported for adults, HIT-associated thrombosis in pediatric intensive care unit patients has a similar incidence but a less severe outcome.
authors.affiliation: Division of Hematology/Oncology, Hospital for Sick Children, Toronto, Ontario, Canada. m.schmugge@freesurf.ch
authors.forename: Markus
authors.initials: M
authors.lastname: Schmugge
authors.forename: Lorenz
authors.initials: L
authors.lastname: Risch
authors.forename: Andreas R
authors.initials: AR
authors.lastname: Huber
authors.forename: Anne
authors.initials: A
authors.lastname: Benn
authors.forename: Joachim E
authors.initials: JE
authors.lastname: Fischer
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D007223:Infant; D015278:Intensive Care Units, Pediatric / Q000706:statistics & numerical data; D008297:Male; D012189:Retrospective Studies; D013557:Switzerland / Q000453:epidemiology; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000453:epidemiology*; D013927:Thrombosis / Q000139:chemically induced* / Q000453:epidemiology*
chemical_list: D006493:Heparin