Hazards of small amounts of heparin in a patient with subclinical vitamin K deficiency

The use of small amounts of a dilute solution of heparin (≤ 100 IU) to keep indwelling intravenous needles or catheters patent for intermittent venous access either for intravenous therapy or timed blood sampling is a common clinical practice. It is considered safe since the amount of heparin required is much less than that required for heparinization. Herein, we describe a 13-yr-old patient with malabsorption who developed clinically significant bleeding shortly after a diagnostic test which required multiple small injections of heparin for intermittent venous access (total amount of heparin administered was 600 units over 5 hr). The coagulopathy was corrected by a single dose (10 mg) of parenteral vitamin K. As our patient had multiple risk factors for the development of vitamin K deficiency including malabsorption, decreased food intake, and antibiotic use, we postulate that the small amount of heparin precipitated the coagulopathy by increasing the anti-protease activity of antithrombin III on abnormal factors X and II formed in the vitamin K deficient state. We would therefore recommend administration of vitamin K to patients who are at risk of developing vitamin K deficiency before using even small amounts of heparin.