Effects of nonionic contrast media on platelet aggregation: assessment by particle counting with laser-light scattering

Similar inhibition of platelet adhesion, P-selectin expression and plasma coagulation by ioversol, iodixanol and ioxaglate

Contrast media (CM) are reported to possess both prothrombotic and anticoagulant properties. The mechanisms are not clearly understood, and early reports are contradictory. To study the effects of CM on haemostasis, we analysed the ex vivo effects of ioversol and iodixanol on platelet adhesion and P-selectin expression, and the in vitro effects of ioversol, iodixanol and ioxaglate on platelet adhesion, P-selectin expression and plasma coagulation. A novel enzymatic assay was used to measure platelet adhesion to protein surfaces, and an enzyme-linked immunosorbent assay was used to measure platelet P-selectin surface expression. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were used to measure plasma coagulation. The ex vivo study consisted of blood from 27 outpatients administered ioversol and 9 patients administered iodixanol intravenously. Samples were collected before and 5 min after CM administration. Healthy donors were used for the in vitro studies on the effects of CM. The ex vivo study showed significantly (p<0.05) decreased platelet adhesion and P-selectin expression after administration of ioversol and iodixanol. Adhesion was more affected than P-selectin expression. The in vitro study showed that ioversol, iodixanol and ioxaglate significantly (p<0.05) and dose-dependently (beginning at 3 mg ml(-1)) decreased platelet adhesion and P-selectin expression. APTT and PT were significantly (p<0.01) prolonged at concentrations of 10 mg ml(-1) and 30 mg ml(-1), respectively. In conclusion, ioversol, iodixanol and ioxaglate inhibit platelet adhesion and P-selectin expression, as well as plasma coagulation. Platelets are more sensitive in relation to the inhibiting effect on plasma coagulation.

The product: All intravenous immunoglobulins are not equivalent

The first intravenous formulation of intravenous immunoglobulin (IGIV) was introduced in the United States in the early 1980s. At that time, the only indication was for treatment of primary immunodeficiency. By the mid-1990s, IGIV was mainly used for indications approved by the United States Food and Drug Administration, but as new indications are found, use of IGIVs is increasing. In fact, today, IGIV is mostly used for off-label indications. The specific characteristics of individual IGIV products must be directly addressed in the manufacturing process, as clinical efficacy may be affected. In addition, the safety profile of the ideal IGIV should be maximized by ensuring inactivation of the widest spectrum of viruses and prions. Some IGIV products are more suitable than others for certain patients; the challenge is to understand the different characteristics among products and select the most appropriate IGIV product for each patient. Convenience factors must be considered, for both the health care provider and the patient, without jeopardizing the more important features of the IGIV, such as tolerability and safety.

Ethylenediaminetetraacetic acid plus citrate-theophylline-adenosine-dipyridamole (EDTA-CTAD): a novel anticoagulant for the flow cytometric assessment of platelet and neutrophil activation ex vivo in whole blood

Ethylenediaminetetraacetic acid (EDTA) is the anticoagulant recommended for full blood counts, citrate is recommended for coagulation and platelet studies, and citrate-theophylline-adenosine-dipyridamole (CTAD) inhibits platelet activation. Because the combination of EDTA and CTAD (E/C) is better than EDTA or CTAD alone for measuring platelet parameters on the ADVIA 120 Haematology System, we investigated whether it also offers advantages for the flow cytometric assessment of platelet and/or neutrophil activation and platelet-leucocyte aggregate formation ex vivo. Blood from healthy subjects was collected into E/C or citrate, kept at room temperature or at 4 degrees C, and analysed 0 to 360 min later in the ADVIA 120 and by immunofluorescent flow cytometry. Platelet count, mean platelet volume, number of platelet clumps, mean platelet component, numbers of CD62P(+) platelets and platelet-leucocyte aggregates, and expression of CD11b on neutrophils changed little over 360 min in blood with E/C kept at 4 degrees C. In contrast, one or more parameter changed when blood was kept with E/C at ambient temperature or with citrate at either temperature. The use of E/C in in vitro and in vivo studies is illustrated. Platelet and neutrophil activation status ex vivo can be reliably assessed if blood is collected into E/C, held at 4 degrees C, and analysed within 6 h.