Intravascular contrast agents have several side effects including alterations of the hemostatsis and the complement system. The effects on these systems may be one of the main causes of the ldquo;adverse contrast agent reaction.rdquo; In vitro and in vivo evidence is provided that both ionic and nonionic contrast media activate the plasma kallikrein with consecutive activation of the factor XII-contact phase and stimulation of the bradykinin generation. Furthermore, activation of the complement cascade via the classic and the alternative pathways was described to a various extent for intravascular application of contrast agents. In non-reactors, these alterations are transient and only have a limited extent indicating that these reactions are within the regulatory capacity of the kallikrein-kinin-factor XII system. In reactors, however, significant evidence for an extended activation of the kallikrein system is associated with reduced levels of C1-esterase inhibitor. Therefore, patients with alterations in these systems should be regarded as candidates for adverse contrast agent reactions.Furthermore, contrast media influence the blood coagulation, especially in contract to artificial surfaces (plastic or glass). In vitro findings suggest that there is a broad scope of modifications caused by contrast agents indicating a modification of the risk of thromboembolism during angiography. Preliminary data suggest that an inhibition of clot formation is more effective with ionic compared with nonionic contrast agents.In summary, radiographic contrast agents have an impact both on the hemostasis and the complement systems. The effects may be of importance for adverse reactions as well as for thromboembolic complications during angiography.
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