Heparin Information and Courses from MediaLab, Inc.

The specimen of choice for coagulation testing is plasma. Venous blood is drawn into a 3.2% buffered sodium citrate tube (blue top tube), yielding a whole blood sample with a 9:1 blood to anticoagulant ratio. Inadequate filling of the collection tube will decrease this ratio, and may affect test results. A blue top tube used for coagulation testing should be drawn before any other tubes containing additives. This includes tubes containing other anticoagulants and/or plastic serum tubes containing clot activators. A serum tube that does not contain an additive can be collected before the blue top tube. If a winged blood collection set is used in drawing a specimen for coagulation testing, a discard tube should be drawn first. The discard tube must be used to fill the blood collection tubing dead space to assure that the proper anticoagulant/blood ratio is maintained, but the discard tube does not need to be completely filled. The discard tube should be a nonadditive or a coagulation tube. If a blood specimen used for coagulation testing must be collected from an indwelling line that may contain heparin, the line should be flushed with 5 mL of saline, and the first 5 mL of blood or 6-times the line volume (dead space volume of the catheter) be drawn off and discarded before the coagulation tube is filled.

The use of heparin is prophylactic. It is used either to prevent thromboembolism (a condition in which a blood clot forms inside a vessel), or used to limit a previous thromboembolism. Heparin inhibits thrombin. The degree of inhibition is dosage dependant. Low doses of heparin inhibit initial thrombin formation in the coagulation cascade, and act to slow down overall thrombin generation. At higher doses, heparin can inhibit thrombin entirely, making blood coagulation impossible. Heparin is a potent anticoagulant. Accurate monitoring is essential. The activated partial thromboplastin time (APTT) and/or activated clotting time is used to monitor unfractionated heparin therapy.

Some global specimen collection and handling issues to consider include: Specimens that contain nucleated cells will be of interest in DNA methodologies while specimens lacking nucleated cells are more useful in RNA methodologies. rRNA is more stable than mRNA, which is labile and sensitive to contamination. DNA is relatively stable and can be obtained from nonviable sources. Serum or plasma obtained by standard routine venipuncture procedures can be used as long as proper site selection and decontamination occur. Standard anticoagulants such as Ethylenediaminetetraacetic Acid (EDTA) and Acid Citrate Dextrose (ACD) can be used; however avoid the use of heparin as an anticoagulant as it interferes with some polymerase chain reaction (PCR) methodologies. When using fluorescence, fasting serum or whole blood specimens should be used to decrease the interference by lipids.

Basophils serve as mediators of inflammatory responses, especially hypersensitivity reactions.IgE binds to the membrane receptors on basophils and degranulation is initiated.The enzymes released are vasoactive, bronchorestrictive and chemotactic (especially for eosinophils), so basophils seem to play a role in inducing and maintaining allergic reactions.The granules of basophils contain histamine, heparin and peroxidase.After degranulation occurs, basophils can synthesize more granules.The release of large numbers of these granules can cause anaphylactic shock and death.

Drug-binding proteins in serum can fluctuate in disease states. For example, if albumin levels fall, as can occur in liver failure or nephrotic syndrome, less albumin will be available for drug binding; a subsequent dose may produce a toxic concentration of free drug.The image on the right illustrates the loss of equilibrium between a protein-bound drug and a free drug when drug-binding proteins are diminished.Doses of drugs that are highly protein-bound may need to be adjusted in patients with lower drug-binding protein levels. Examples of some common drugs that are highly protein-bound include thyroxine, warfarin, diazepam, heparin, imipramine and phenytoin. �

Contain either sodium or lithium heparin.Used for tests requiring whole blood or plasma such as ammonia or whole blood potassium.

Another example of an echinocyte is seen in the center of this slide. In rare instances, echinocytes circulate in vivo in uremia, following heparin injection, in certain congenital anemias and in pyruvate kinase deficiency. Plastic slides must be used to verify the presence of in vivo echinocytes. Since echinocytes do not aid in the diagnosis of these conditions, their main importance lies in the fact that they are artifactual and reversible and must be distinguished from acanthocytes.

A basophil and a small lymphocyte are compared in the same field of the upper photograph, A single basophil is shown in the lower photograph.The cytoplasmic granules of the basophil are larger than the granules of toxic granulation.They contain chemical mediators of immediate hypersensitivity, and are found in the cytoplasm and overlying the nucleus (better seen in the lower photograph). Basophilic granules stain metachromatically with toluidine blue indicating the presence of acid mucopolysaccharide or proteoglycans, both thought to be heparin or heparin-like substances.Basophils are related to tissue mast cells, each involved in hypersensitivity responses and following anaphylactic episodes.Under the stimulation of complement components C3a and C5a, many mediators are released from the basophil granules, including histamine, heparin, and eosinophil chemotactic factors of anaphylaxis, or ECF-A.Basophils are the least common neutrophils in the peripheral blood, comprising 2% or less of the differential count.The presence of large granules of irregular size in basophils and the admixture of eosinophilic granules may indicate dysplastic changes associated with myelodysplastic disorders and leukemia.