Low-molecular-weight heparin dosage in newborn foals.

BACKGROUND: Heparin is used in humans as prophylaxis of hypercoagulable states and disseminated intravascular coagulation (DIC). However, babies need a higher heparin dose than do adults. Septic neonate foals are at high risk of hypercoagulable state and DIC, and there is limited objective information about heparin dose for equine neonates. OBJECTIVE: To assess whether neonate foals require higher dosages of low-molecular-weight heparin (LMWH) than adults. ANIMALS: Eighteen healthy and 11 septic neonate foals. METHODS: Experimental and clinical studies. Firstly, healthy foals were randomly distributed in 2 groups, 1 receiving 50 IU/kg SC of dalteparin and the 2nd group receiving 100 IU/kg SC of dalteparin, once daily for 3 days. Blood samples were collected before and 3, 6, 27, and 51 hours after the 1st LMWH administration. Plasma antifactor-Xa activity was measured, together with hemostatic and hematologic parameters used to assess the risk of bleeding. Subsequently, septic foals were treated blindly either with placebo (saline) or 100 IU/kg of dalteparin for 3 days. Plasma antifactor-Xa activity and other hemostatic parameters were determined before and after treatment. RESULTS: Plasma antifactor-Xa activity in healthy foals was below prophylactic activity when using the adult dosage (50 IU/kg), whereas prophylactic activities were achieved when using the double dosage (100 IU/kg). No hemorrhagic events and erythrocyte-related complications were observed with either dosage. In the clinical study, only 4/6 septic foals had plasma antifactor-Xa activity adequate for prophylaxis. CONCLUSIONS AND CLINICAL IMPORTANCE: Equine neonates require higher dosages of LMWH compared with adults to reach prophylactic heparinemia.