Study sheds light on risk of life-threatening blood clots in hospitalized children

Life-threatening blood clots occur so rarely in children that the condition, known as venous thromboembolism (VTE), is often not on pediatricians' mental radar screens - an absence that can lead to woefully delayed recognition and treatment.

Now findings of a Johns Hopkins Children's Center study, published online Dec. 12 in The Journal of Pediatrics, may help clinicians determine which hospitalized children are at greatest risk of VTE and require vigilant monitoring or preemptive treatment with anticlotting medications.

The investigators say that in the absence of much-needed pediatric guidelines on VTE prophylaxis in children, the study findings can help guide clinical decision-making for certain categories of hospitalized patients who are at a disproportionately high risk for developing clots.

Such categories include older teens and young adults, those with multiple medical conditions, patients with central venous catheters and those with cardiac and renal disease.

The study, which analyzed 15 years' worth of medical records of thousands of children treated at the Johns Hopkins Children's Center between 1994 and 2009, found 270 cases of VTE in more than 90,000 pediatric admissions. Despite the miniscule overall VTE rate, clotting risk loomed large in several groups, with older age and the presence of multiple medical conditions carrying the highest risk of VTE. Young adults between the ages of 18 and 21 were eight times more likely to develop a clot than younger children between the ages of 2 and 9. Teens, ages 14 to 17, had a four-fold rate of VTEs, compared with younger children. In addition, teenage girls and young women were nearly two times as likely to develop a clot as males the same age. Children with four or more medical conditions were four times more likely to develop VTE than others.

Other factors that appeared to fuel clotting risk were the presence of central venous catheters, recent surgery and traumatic injuries. Half of the 238 children who developed clots had a central venous catheter, and 40 percent of clots developed in children who'd undergone recent surgeries. When clots developed in infants, they did so predominantly in patients with congenital heart defects. By contrast, clots in trauma patients tended to develop mostly in older teens and young adults.

The research team says that children who fall into more than one category should be monitored extra vigilantly for signs suggestive of a clot.

"Are we saying that every kid with more than one risk factor should be on prophylactic treatment? Absolutely not," says study lead investigator Cliff Takemoto, M.D., a pediatric hematologist at the Johns Hopkins Children's Center. "What we are saying, however, is that we, as clinicians, should take a closer look at each and every patient with multiple risk factors and gauge cumulative risk - if the chance of clotting appears high enough, then treatment is certainly reasonable."