• V K Shankar, A Handa, J Philips-Hughes, P Boardman, R Uberoi, and L J Hands.
• Nuffield Department of Surgery, John Radcliffe Hospital, University of Oxford, Headley Way, Headington, Oxford, OX3 7JE, UK. vkshankar@ukgateway.net
• Cardiovasc Intervent Radiol. 2006 Nov 1;29(6):1046-52.

Background/PurposePatients 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.MethodsWe 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.ResultsTEG 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).ConclusionThese 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.

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