Anticoagulant activity of heparin in intravenous fluids.

The anticoagulant activity of heparin dissolved in intravenous solutions was measured by two different methods of heparin assay. Both procedures showed markedly reduced anticoagulant activity within four hours after the addition of heparin to the solutions. When measured according to the procedure of Yin, heparin in the intravenous solutions fully regained its lost anticoagulant activity after 24 hours at room temperature. When measured by the thrombin time, however, the heparin anticoagulant activity reamained reduced. The source of heparin, from either the lung or intestine, does not explain the reduction in anticoagulant activity. Although its cause is unknown, the erratic behaviour of heparin in intravenous solutions stresses the importance of a laboratory monitor of heparin therapy.