Influence of X-ray contrast media on blood viscoelasticity

Transcription

1 Influence of X-ray contrast media on blood viscoelasticity Poster No.: B-630 Congress: ECR 2009 Type: Topic: Authors: Keywords: DOI: Scientific Paper Contrast Media V. Ribitsch, C. Well; Graz/AT Blood viscoelasticity, X-ray contrast media, red blood cell aggregation, rigidity /ecr2009/B-630 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 8

2 Purpose Influence of X-Ray contrast media on Blood Viscoelasticity Camilla Well, Volker Ribitsch University Graz, Institute of Chemistry, Rheology & Colloid Science Department A Graz, Heinrichstrasse 28 To investigate if the influence of X-Ray Contrast Media (XR-CM) on blood viscoelasticity. From this data information is gained about changes in Red Blood Cell (RBC) aggregation and deformability and possible affects on the microcirculation. Methods and Materials The following nonionic contrast media of different iodine concentration were applied: Iopamiro 370 mg Iodine/mL,Ultravist 370 mg Iodine/mL, Optiray 350 mg Iodine/mL, Iomeron 350 mg Iodine/mL and Visipaque 320 mg Iodine/mL. The rheological properties were determined using the DCR - Dynamic Capillary Rheometer, manufactured by A. Paar GmbH Graz, Austria. The device creates an oscillating capillary flow and enablesthe fission of the complex viscosity into a viscose and an elastic component. The experiments were performed at a constant frequency of 1/s (6.28 rad) and variable amplitudes resulting in shear rates(the shear rate represents the flow rate (speed of liquid) in vessels). Blood was obtained from healthy donors, anti-coagulated by EDTA and adjusted to a hematocrit of 45%. 10 volume percent of X-ray contrast media XR-CM were added and homogenized for 10 minutes. Bloodviscoelasticity was measured at 37 C, the data presented are the mean values of at least 5 measurements. The symbol size represents the standard deviation. Results Elastic properties (elastic component) of blood represents the RBC membranes elasticity and the elasticity of RBC aggregates. The RBCaggregates exist at low shear rates and are separated with increasing shear forces into single RBC - in human circulation and also during the experiment as depicted in figure 1. Page 2 of 8

3 The single RBC s rigidity is important for the flow / penetration through capillary vessels. The elastic component shown in figure 2 decreases with increasing flow rate due to the separation of RBC aggregates into single RBC. At low shear rates properties of blood in large vessels (slowflow) are represented hereas at high shear rates microcirculation in small vessels is figured out (fast flow or deformation in micro vessels). Page 3 of 8

4 Table 1 shows the investigated XR-CM s viscosity which does not have an elastic component. One sample (Visipaque) is a dimmer XR-CM, all others aremonomer units. The dimmer sample has the highest viscosity values compared to similar XR-CM loadings. The viscosity value determines the stress on the vessel wall (wall shear stress) developed duringinfusion. Page 4 of 8

5 Figure 3 presents a comparison of the viscoelasticity of normal blood with blood containing 10% (v/v) of different XR-CM as well as buffer added for the base line. For comparisonreasons XR-CM with concentrations between 320 to 370 mg were selected. Total viscose component of XR-CM containing blood (upper curves) is almost similar to that of the pure blood. It decreases slightly over the entire shear rate range caused by the cell orientationduring flow. The elastic component (lower curves) shows significant differences to that of blood containing buffer. The reduced elasticity at low flow rates indicates a reduced RBC aggregation. This is seen atthe shear rate range between 4 to 40 1/s.The reason may be that XR-CM molecules are adsorbed on the RBC membrane and thus decrease their interaction capability and thus may explain rigidity of RBCmembranes. At high flow rates (above 60 1/s) the elasticity of XR-CM containing blood is highly increased compared to blood/buffer, i.e. a clear indication for increased RBC membrane rigidity. Page 5 of 8

6 Figure 4 shows the high shear region in detail in a semi-linear presentation. It is clearly visible, that different XR-CMs increase the RBC rigidity differently according theirchemical and physical properties. The non-ionic monomer XR-CM Iopamiro and Ultravist increased significantly (> 100%) the rigidity of the RBC membranes followed by Iomeron and Visipaque (50%) and Optiray (20%) which maintains the flexibility and deformability of the red cell membrane best. The results showed that e.g. Optiray 350 increase in elasticity is similar to blood/buffer and seems to have the least impact on rigidity of RBC. Page 6 of 8

7 The non-ionic monomer XR-CM Iopamiro and Ultravist increased significantly (> 100%) the rigidity of the RBC membranes followed by Iomeron and Visipaque (50%) andoptiray (20%) which maintains the flexibility and deformability of the red cell membrane best. The results showed that e.g. Optiray 350 increase in elasticity is similar to blood/buffer andseems to have the least impact on rigidity of RBC. Table 2 presents the wall shear stress - the force acting on the vessel wall during infusion. The wall shear stress was calculated under the assumption of an infusion rate of 2ml/s, 3 ml/s and 5 ml/s into a vessel of 7mm diameter. All XR-CM show wall shear stresses larger then blood (approx. 240 Pa if calculated as Newtonian fluid, assumed to be less due to a slip layer atthe wall) and create an increased mechanical stress on the blood vessel wall. For XR-CM s of 350 mg iodine concentration an increase of 80% are observed, whereas samples of higher concentrations up to 370 mg show an increase of 250%. I. e. just anincrease of 6% in iodine concentration results in a considerable increased vessel stress. Page 7 of 8

8 Conclusion XR-CM exposed blood shows a different behaviour compared to blood/buffer: Low deformation rates exhibit reduced elasticity values while high deformation rates exhibit increasedelasticity, i.e. dependent on the type XR-CM. These results show clearly that XR-CM molecules have an impact on the aggregation behaviour and rigidity, respectively, of the RBC membrane as they seem to reduce their flexibility to a differentdegree. This effect should be considered especially if applied to patients at risk, e.g. with diabetes, where erythrocyte deformability nonetheless is diminished. The mechanical stress developed at the vessel wall during XR-CM infusion depends on the viscosity level. The elevated XR-CM viscosity combined with high infusion rates causes a stress elevation onthe vessel walls of 80% to 250% compared to whole blood, i.e. also an increase of iodine concentration of XR-CM should be evaluated prior to use for patients at risk. Page 8 of 8