Platelets consumption

Thrombotic thrombocytopenic purpura (TTP) is a severe systemic disorder characterized by the thrombi formation within the circulation that result in the platelet consumption and subsequent thrombocytopenia. The inherited sub-type is chronic and relapsing and generally occurs in childhood. Acute idiopathic TTP, which occurs in adults, is more common and harder to treat. The estimated annual incidence of TTP is 3.7 cases per million.33... 

Casonato A, Steffan A, Pontara E, Zucchetto A, Rossi C, De Marco L, Girolami A. Post-DDAVP thrombocytopenia in type 2B von Willebrand disease is not associated with platelet consumption failure to demonstrate glycocalicin increase or platelet activation. Thromb Haemost 1999 81(2) 224-8. 

Figure 8. Platelet consumption of polyurethanes as a function of percent hydrocarbon component in the C-ls spectra (from Ref. 9)...

None of the smooth surfaces prepared by the depositing of plasma polymer on the smooth surface of Silastic tubing showed detectable thrombus formation by gamma camera imaging. Therefore, they were evaluated by measurement of relative rates of platelet consumption. Table 35.7 shows the results obtained using the plasma polymers described previously [5]. 

Table 35.7 Platelet Consumption Rates for Various Plasma Polymers...

Granegger S, Flores J, Widhalm K, Sinzinger H (1988) Increased low-density lipoproteins (LDL) negatively affect human labelling. Folia Haematol 115 451-453 Harker LA, Slichter SJ, Sauvage LR (1977) Platelet consumption by arterial prostheses the effects of endothelialization and pharmacologic inhibition of platelet function. Ann Surg 186 594-601 Hawker RJ, Hawker LM, Wilkinson AR (1987) Indium-labelled human platelets. Optimal method. Clin Sci 58 243-248... 

Measurements of Platelet Consumption. A baboon AV shunt model was used to assess quantitatively the effects of physicochemical properties associated with polyacrylamide grafted substrates. In this model, measurements of platelet consumption using 51Cr-labeled platelets were steady state, reproducible between test animals, and unaffected by the surgical procedure (8,10). The methodology involved in the use of AV baboon shunts has been described previously (8,10). We concluded that this primate model simulates arterial thrombotic processes in humans and is suitable for the in vivo evaluation of biomaterial thrombogenesis (10). 

Measurements of Platelet Consumption. When the extent of grafting of acrylamide on Silastic was varied, cannular platelet consumption increased... 

Table II shows the effect on platelet consumption of increasing lengths of the polyacrylamide-Silastic tubing. The acrylamide surface is much more destructive to platelets than is the Silastic surface. Table II also shows that platelet consumption increases linearly with shunt area for both the polyacrylamide-Silastic shunts.

A series of shunts with radiation and ceric ion-initiated grafts of polyacrylamide on the luminal Silastic surface, and having water contents varying between 51-83% were also studied. Table III shows these data. The platelet consumption increases linearly with the gel water, such that the ratio of platelet consumption to graft water content remains relatively constant. 

Figure 11. Platelet consumption vs. graft level of polyacrylamide-Silastic shunts (9). (Numbers in parentheses refer to the number of shunts tested for each value reported.)...

Table II. Effect of Cannula Composition and Area on Platelet Consumption (8)...

Exposed Area (cm2) Mean Platelet Survival Time (days) Cannula Platelet Consumption (platelets/day x 10 10) Polyacrylamide-grafted Silastic Cannula Platelet Consumption/ Unit Area (platelets/cm2 day x 10 H)... 

Table III. Platelet Consumption by Polyacrylamide-Grafted Substrates (9)...

Figure 12. Rates of production of thromboemboli volume ( 3Is) and equivalent platelet consumption by embolization (platelets/day) vs. surface area for two biomaterials Silastic (bottom) and polyacrylamide-Silastic (top). The equivalent steady-state platelet consumption is (3.0 0.2) x 108 (platelets day-cm2) for polyacrylamide-Silastic and (0.8 0.1) X 108 (platelets day-cm2) for Silastic.

Other concerns regarding the practicality of surface bound heparin for the preparation of materials with long-term thromboresistance remain. Because the interaction of heparin with platelets is unclear (31), whether the immobilized heparin causes greater thrombosis under conditions where platelet deposition is more important than fibrin formation remains to be shown. The passivating effect of antithrombin III on platelet consumption caused by surface-bound heparin is a significant observation in this context (32, 33). 

Figure 2 shows that similar adsorption phenomena are exhibited by lysozyme and albumin. Related work seems to suggest that polymers that contain a certain balance of hydrophobic and hydrophilic chemical groups show minimized biological interaction (for example, low protein adsorption, low thrombus deposition, and low platelet consumption) (6). The adsorption of radiolabeled IgG, however, was maximal at intermediate copolymers. This result has a number of implications with respect to both the fundamental adsorption mechanism and the biocompatibility of these materials. 

The finite life span of most mature blood cells requires their continuous replacement, a process termed hematopoiesis. New cell production must respond to basal needs and states of increased demand. Red blood cell production can increase >20-fold in response to anemia or hypoxemia, white blood cell production increases dramatically in response to a systemic infection, and platelet production can increase 10-20-fold when platelet consumption results in thrombocytopenia. 

More polar polymers had low initial adsorption in vitro which increased with time but in vi vo fibrinogen deposition on these polymers was characterized by a second stage of great increase, inhibitable by heparin. These polymers also caused enhanced platelet consumption. 

Defraigne J., Pincemail, J., Dekoster, G., Larbuisson, R., Dujaidin, M., Blaffart, F., David, J., and Limet, R., SMA circuits reduce platelet consumption and platelet factor release during cardiac surgery, Ann. Thorac. Surg., 2(X)0 70(6) 2075-2081. 

Polyurethanes, due in part to their flexibility and toughness, are perhaps the polymer of choice for ventricular assist devices and blood pumps. Consequently, they have received considerable interest as bloodcontacting materials. In nonhuman primates, those polyurethanes, such as Pellethane , which exhibit the most hydrophobic surface chemistry produce the least platelet consumption [12]. In dogs, early platelet interactions with polyurethanes vary considerably although relationships to polymer surface chemistry remain unclear [13]. Thus while polyurethanes are chemically versatile and possess many desirable mechanical properties, it is generally not possible to predict their biologic responses in humans. 

Skrzypchak, A.M., Lafayette, N.G., Bartlett, R.H., Zhou, Z., Frost, M.C., Meyerhoff, M.E., Reynolds, M.M., Annich, G.M., 2007. Effect of varying nitric oxide release to prevent platelet consumption and preserve platelet function in an in vivo model of extracorporeal circulation. Perfusion 22, 193-200. 

Rarely, arterial embolization is required to treat life-threatening hemorrhage, high-output cardiac failure, or platelet consumption (Kasabach-Merritt phenomenon) ([17], Fig. 1.3a-c). 

Fig. 44 Platelet consumption by polyurethanes, measured using an arteriovenous shunt inserted in a baboon, as a function of the concentration ratio of carbon in a hydrocarbon-type environment [C—(C,H)] to carbon in an ether-like environment [C—O] measured by XPS on these polyurethanes. Redrawn from Ref. 275 with permission from Elsevier...

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