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

Effect of the radiographic contrast material iopamidol on hemostasis: an observational study in thirty cardiac patients

BACKGROUND

In vitro studies have shown that nonionic radiographic contrast material may induce the generation of thrombin in blood, whereas ionic contrast agents, such as iohexol, do not. However, knowledge of the effects of contrast material on coagulation and fibrinolytic systems in vivo is limited.

OBJECTIVE

This study was designed to assess the effects of the nonionic radiographic contrast material iopamidol on hemostasis in patients undergoing coronary angiography or cardiac catheterization.

METHODS

Patients aged ≥18 years with chest pain and/or dyspnea who underwent coronary angiography or cardiac catheterization with intra-arterial contrast material were assessed for hemostasis. Blood samples were drawn before and 3 minutes after injection of iopamidol. Complete blood count and coagulation profile (bleeding time, clotting time, clot retraction time, euglobulin lysis time [ELT], prothrombin and partial thromboplastin times, coagulation factor I [CFI] level, and platelet factor 3 [PF-3] availability) were assessed. The natural coagulation inhibitors protein C, protein S, and antithrombin III (AT-III) also were measured.

RESULTS

Thirty patients (7 males, 23 females; mean [SD] age, 51.3 [20.2] years; range, 17-79 years) were included in this single-center study. All hematologic variables (hemoglobin, white blood cell count, and platelet count) decreased significantly (P<0.001, P<0.001, and P<0.05, respectively) after administration of iopamidol but remained within normal limits. Mean levels of protein C, protein S, and AT-III did not change significantly after administration of iopamidol. Bleeding time was not changed significantly, and PF-3 availability was prolonged in both groups, but the changes were not statistically significant.

CONCLUSIONS

In this study population, although hemostasis remained grossly intact after injection of nonionic contrast material, the coagulation system may have been affected by the accelerated consumption of CFI and platelets. The affected variables were platelets, clot retraction time, ELT, and natural coagulation inhibitors (protein C, protein S, and AT-III). Although the natural coagulation inhibitors remained within the normal range, the correlations were found significant. These changes in hemostasis affected the vascular phase. If the vascular compartment, especially the endothelium, remained intact, the infusion of nonionic agents in low concentrations might be safe for angiography and other procedures; however, more studies are needed.

Effect of iodinated low-osmolar contrast media on the hemostatic system after intraarterial and intravenous contrast administration

PURPOSE

Some of the adverse clinical effects of intravascular radiological contrast agents include the interference of these contrast media with normal hemostatic processes. The aim of this report was to investigate in vivo whether a non-ionic iodinated contrast agent possess prothrombotic or anticoagulant properties.

MATERIAL AND METHODS

Hemostatic parameters: vWF (von Willebrand factor), F1+2 (prothrombin fragments 1+2), TAT (thrombin-antithrombin complexes), D-Dimer, β-TG (beta-thromboglobulin) were measured in a group of 35 patients. Blood samples for laboratory investigations were collected before and 30 min after the administration of a iodine contrast agent.

RESULTS

There was observed statistically highly significant contrast-induced increase in TAT and F1+2 (p = 0.005 and p = 0.008, respectively). D-Dimer increase and decrease of β-TG and vWF after contrast medium administration were non significant. The volume of contrast medium has no influence on the assessed hemostatic parameters, while the type of contrast medium and/or the route of the contrast administration may significantly affect hemostatic parameters.

CONCLUSION

We found significant effects of non-ionic agents on hemostatic activation. These effects may be important for adverse reactions and for thromboembolic complications.

Neuroimaging in assessment of risk of stroke in children with sickle cell disease

PURPOSE

Stroke and subclinical "silent infarcts" are major causes of morbidity in children with Sickle Cell Disease (SCD). Ischemic strokes are more common in younger children while hemorrhagic strokes are more frequent in adults. The goal of neuroimaging in acute stroke is to document whether the stroke is ischemic or hemorrhagic, to assess the extent of parenchymal abnormalities and to determine the presence of other cerebrovascular lesions. Computed Tomography (CT) is the primary modality for the assessment of acute stroke patients because of its 24/7 availability and ability to exclude hemorrhagic causes. Magnetic resonance imaging (MRI) and MR angiography (MRA) are recommended to determine precisely extent of infarction and detect cerebrovascular abnormalities. The goal of neuroimaging in patients with hemorrhagic stroke is to identify an arteriovenous malformation or aneurysm(s) amenable to surgery or catheter intervention.The risk of first stroke is very high in asymptomatic children with intracranial arterial mean velocities over 200 cm/s on transcranial Doppler (TCD) examination. The risk can be substantially reduced if chronic blood transfusions are timely implemented. Large cerebral vessel disease detected by TCD can be confirmed or excluded by MRI/MRA. Those with evidence of parenchymal and/or cerebrovascular lesions should be followed by preventive therapy. In patients with neurologic symptoms and negative MRI/MRA findings Positron Emission Tomography or single photon emission CT is recommended. There are no specific neuroimaging findings that suggest that blood transfusions can be safely halted in children with SCD.

Clinical and Experimental Evidence for Prevention of Acute Renal Failure Induced by Radiographic Contrast Media

Acute renal failure still occurs as a complication after radiographic examination using iodinated radiocontrast medium. The incidence rate of radiocontrast medium-induced nephropathy (radiocontrast nephropathy) is low (2 - 3%) in general. However, the rate is remarkably elevated in patients with pre-existing renal insufficiency. Radiocontrast nephropathy is associated with increased morbidity and mortality, particularly in patients with percutaneous coronary interventions. Although the reduction in renal blood flow and direct toxic action on renal tubular cells are considered to be involved, little is known about the etiology of radiocontrast nephropathy. A number of agents that improve renal circulation have been clinically tested for prevention of radiocontrast nephropathy, but none of them has succeeded. Protection of renal tubular cells against oxidative stress is another approach to avoid radiocontrast nephropathy. Prophylactic effects of antioxidants such as N-acetylcysteine and ascorbic acid have been reported by several investigators, although the effectiveness of these compounds is still a matter of debate. At present, hydration is regarded as the only effective, though incomplete, prophylactic regimen for radiocontrast nephropathy. Recently, we have shown that caspase-dependent apoptosis is an important factor in the pathogenesis of radiocontrast nephropathy and clarified cellular mechanisms underlying the radiocontrast media-induced apoptosis. This review summarizes clinical and experimental evidence for the etiology and prevention of radiocontrast nephropathy.