title: Reduction of the red blood cell mass of horses: toxic effect of heparin anticoagulant therapy.
abstract: This study was designed to test the efficacy of heparin anticoagulant therapy in the horse and its effect on the formed elements of blood. Nine clinically normal, nontraumatized adult horses were subjected to 4 different heparin maintenance regimens (dosages of 320, 240, 160, and 40 U/kg of body weight). Porcine intestinal mucosa heparin (20,000 U/ml) was injected subcutaneously every 12 hours for 96 hours (total 9 times). A loading dose of one-third the maintenance dose was given IV just before the first heparin injection. Three control horses were given an equivalent volume of 0.9% saline solution. The 2 large doses of heparin (320, 240 U/kg) resulted in an extension of the therapeutic range for heparin anticoagulant therapy (1.5 to 2.5 X data base-line prolongation of the activated partial thromboplastin time [APTT]). The 160-U/kg dose maintained the APTT in the therapeutic range, and the 40-U/kg dose had no effect on the APTT. Heparin was shown to exert a profound influence on the RBC mass of the horse. Three of the heparin regimens (320, 240, and 160 U/kg) resulted in a significant decrease in RBC numbers, PCV, and total hemoglobin content. Platelet count also was reduced in the horses when given the 320 and 240 U/kg doses. The observed increase in the mean corpuscular volume was associated with decreasing RBC numbers. Plasma proteins, serum bilirubin, free hemoglobin (plasma), haptoglobin (plasma), and urine and fecal hemoglobin values remained unchanged in all groups. Heparin anticoagulation therapy with the smallest dose (40 U/kg) had no detectable effects on the measured values, nor did the saline solution.
mesh_terms: D000818:Animals; D004837:Epinephrine / Q000494:pharmacology; D004906:Erythrocyte Count / Q000662:veterinary; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects*; D006400:Hematocrit / Q000662:veterinary; D006493:Heparin / Q000008:administration & dosage / Q000009:adverse effects*; D006736:Horses / Q000097:blood*; D007279:Injections, Subcutaneous / Q000662:veterinary; D010314:Partial Thromboplastin Time / Q000662:veterinary; D010953:Plasma Volume / Q000187:drug effects; D010976:Platelet Count / Q000662:veterinary; D011517:Prothrombin Time / Q000662:veterinary
chemical_list: D006493:Heparin; D004837:Epinephrine