Heparin is frequently used in central venous catheters (CVCs) in post-operative cardiac patients. It remains unclear if a heparin infusion, compared to a normal saline infusion, prevents thrombosis of CVCs after surgery. This study will answer the question: does a low-dose heparin infusion (10 units/kg/h) prevent thrombosis, compared to a normal saline infusion, in patients less than one year of age after cardiac surgery?

Patients are contacted pre-operatively and their parents consented. The following criteria apply:

Inclusion criteria:

All infants < 1 year of age undergoing cardiac surgery at Lucile Packard Children's Hospital

Exclusion Criteria:

Known coagulopathy History of clinically significant bleeding (GI, cranial, pulmonary) Need for therapeutic heparinization ECMO

Randomization and blinding are performed in the Pharmacy. The intervention is initiated at the intensive care unit physician's discretion, generally within the 1st 24 hours post-operatively. The study is terminated when all catheters have been discontinued or at POD #14, whichever occurs first.

Thrombosis is demonstrated by echocardiogram or ultrasound performed at

1 - 3 days, 5 - 7 days, and 10 - 14 days after initiation of the study drug.

The following are calculations for statistical analysis:

Sample size determination - Using 2 - sided alpha = 0.05 and Beta = 0.2, and assuming a baseline thrombosis incidence of 20%, 160 patients are required to detect an effect size of 15%.

Inclusion Criteria:

• All infants < 1 year of age undergoing cardiac surgery at Lucile Packard Children's Hospital & #xA

Exclusion Criteria:

• Known coagulopathy
• History of clinically significant bleeding (GI, cranial, pulmonary)
• Need for therapeutic heparinization
• ECMO