NEW YORK (Reuters Health) – Thrombosis occurs in about one in 10 children undergoing cardiac surgery cases, with serious complications in over a quarter of those cases, a Canadian group has shown.

“This study establishes thrombosis in the context of pediatric cardiac surgery as an important clinical problem and will, we hope, form the basis of further research aimed at better prevention, diagnosis, and treatment of those complications,” the authors conclude in their report in Circulation published online September 12.

Dr. Brian W. McCrindle, with The Hospital for Sick Children in Toronto, Ontario, and colleagues say thrombosis in pediatric cardiac surgery is recognized as a serious entity but is considered somewhat rare – even though children are a high-risk group in theory because of their immature coagulation system and the need for shunts in many types of congenital heart lesions.

To examine the risk and outcomes of thrombosis associated with pediatric cardiac surgery, the team conducted a retrospective study of 1542 such operations performed in 1361 children over a 40-month period.

Thrombi occurred after 171 of the surgeries involving 155 patients (11%), the researchers report. They found that the median time from surgery to detection of thrombosis was 11 days for extrathoracic venous thrombi, 7 days for extrathoracic arterial thrombi, and 16 days for intrathoracic thrombi.

Serious complications, ranging from ischemic stroke to pulmonary embolism to death, occurred with 64 thrombi involving 47 patients, the report indicates.

On multivariate analysis, thrombosis was significantly associated with increased length of ICU stay (11 vs 3 days) and total hospital stay (25 vs 7 days), increased odds of cardiac arrest (odds ratio 4.9), early catheter reintervention (OR 3.3), early reoperation (OR 2.5), and in-hospital mortality (OR 5.1).

Dr. McCrindle and colleagues identified several factors associated with the risk of thrombosis, including younger age, oxygen saturation <85%, and use of deep hypothermic circulatory arrest.

“Future research,” they conclude, “is necessary to determine the mechanisms by which these factors are associated with thrombosis by focusing on pathways of coagulation and platelet activation that are stimulated in response to those risk factors.”

Circulation 2011;124.