Potential thrombogenicity of angiographic contrast agents

Thromboelastographic Changes Following Nonionic Contrast Medium Injection During Transfemoral Angiography in Patients with Peripheral Arterial Occlusive Disease

BACKGROUND/PURPOSE

Patients with peripheral arterial occlusive disease (PAOD) are known to be systemically hypercoagulable and there is concern that exposing them to contrast media during angiography may exacerbate that thrombotic tendency. Many in vitro studies in which blood is exposed to contrast media suggest that nonionic contrast medium (NICM) has a weaker anticoagulant effect than ionic contrast medium (ICM) and some studies suggest that NICM can lead to activation of coagulation thus increasing the risk of thrombotic events where it is employed. We have looked at the changes in coagulation adjacent to the site of contrast injection/potential angioplasty to determine the magnitude of change locally.

METHODS

We measured changes in the coagulability of aortic blood samples immediately before and within 2 min after injection of the last bolus of iohexol (NICM) prior to any intervention procedure in 30 patients with PAOD. Samples were analyzed using thromboelastography (TEG) to identify changes in the coagulability of the aortic blood samples.

RESULTS

TEG tracings of samples taken from the aorta after injection of NICM showed a significant increase in R time (time to fibrin formation) (p = 0.036) and in k time (dynamics of clot formation) (p = 0.028) and a reduction in Angle (decreased acceleration of fibrin build-up) (p = 0.013), Maximal amplitude (MA) (reduced ultimate clot strength) (p = 0.018) and Coagulation Index (CI) (p = 0.032).

CONCLUSION

These changes in TEG parameters show that the local effect of NICM is a reduction in coagulation activity rather than the activation suggested by some previous studies.

Changes in the fibrinolytic system during angiography with ionic and with nonionic contrast media

RATIONALE AND OBJECTIVES

The purpose of the study was to evaluate and compare changes in some parameters of the fibrinolytic system caused by the use of ionic and nonionic contrast media during angiography in certain groups of patients.

MATERIALS AND METHODS

Angiographic diagnostic procedures were performed in 126 patients (male and female) clinically suspected of having kidney cancer (38 patients), arteriosclerotic occlusive disease of lower extremities (44 patients), or dissection of cerebral artery (44 patients). The control group included 12 patients with clinical symptoms of the disease in whom angiographic examination excluded the presence of cerebral artery dissection or kidney cancer. Patients were randomly assigned to receive either an ionic (diatrizoate sodium) or a nonionic (iopromide) contrast medium. Immediately before and 30 minutes after administration, venous blood samples were obtained to determine select parameters of the hemostatic system.

RESULTS

There were no significant differences in the fibrinolytic parameters within the control group after contrast medium administration. The nonionic contrast medium (iopromide) caused a decrease in fibrinolytic activity in the patients, unlike the controls, which was particularly pronounced among the patients undergoing renal angiography.

CONCLUSION

The use of contrast media in some groups of patients led to transient changes in the fibrinolytic system. These results indicate that ionic contrast media should be used during angiographic procedures in patients at increased risk for thrombotic complications.

Haemostatic effects of low osmolar non-ionic and ionic contrast media: a double-blind comparative study

In this prospective, double-blind, randomized study the effects of a non-ionic contrast medium (Iopromide) on the haemostatic system were compared with those of a low osmolar ionic medium (Ioxaglate). The aim was to investigate in vivo whether a non-ionic contrast agent is less anticoagulant or more pro-thrombotic than an ionic medium. A large number of haemostatic parameters, including activation markers, were measured. Either Iopromide (n = 16; median volume 102 ml; 95% confidence interval 90-108 ml) or Ioxaglate (n = 15; median 105 ml; 95% confidence interval 95-114 ml) was given to 31 patients scheduled for abdominal and femoral arteriography. Blood for laboratory investigations was collected before, and 5 and 30 min after, administering the contrast medium. Indications for activation of coagulation and platelets were already found in nearly 50% of the patients before any contrast medium was given. Both Iopromide and Ioxaglate caused further increases in thrombin-antithrombin complex, prothrombin fragments 1 + 2 and beta-thromboglobulin. The degree of activation was similar for both agents. Anticoagulant effects were not observed. The haemorheological effects were compatible with haemodilution by 5-8%, again without differences between the contrast agents. Contrary to the findings from in vitro studies, we found no significant differences between the effects of the non-ionic Iopromide and the ionic Ioxaglate on coagulation and platelets. Both agents activated these systems to a limited, but identical, degree. Our results support the notion that the catheterization procedure per se may represent a source of haemostatic activation and that the ionic contrast agent studied has insufficient anticoagulant effect to prevent clotting activation being induced by the contrast medium.