Prekallikrein activation, C1 esterase inhibitor, and factor XII as predictors of adverse reaction to contrast media. A prospective study

Level of Plasma Prekallikrein and its Inhibitors in Reactors and Nonreactors during Intravenous Enhancement with Contrast Media

Complex contact activation systems may play a major role in the side effects of i.v. contrast media (CM). This is why quantitative measurements of several factors (plasma prekallikrein, hematocrit (hct), α-2-macroglobulin, α-1-antitrypsin, and C1-esterase inhibitor) were determined prior to and following the injection of CM during body CT examination in 5 patient groups, each (n = 10) receiving one of 5 different CM, including ioxaglate, meglumine iodamide, metrizamide, iohexol, and meglumine diatrizoate. The initial plasma prekallikrein level was available from 45 patients and was statistically lower in reactors (mean 90.6 μmol TAMe/ml/h; n = 13) than in nonreactors (mean 107 μmol TAMe/ml/h; n = 32) (p = 0.006), but there was no statistically significant difference in the decrease of plasma prekallikrein before and at 5 min after the injection for those 2 groups. The initial plasma C1-esterase inhibitor level was lower in reactors, while the plasma α-2-macroglobulin level was higher in that group than in nonreactors. The results indicate that the measurement of plasma prekallikrein combined with plasma C1-esterase inhibitor and α-2-macroglobulin measurement could be useful when predicting which patients are prone to CM reactions.

C1 inhibitor: molecular and clinical aspects

C1 inhibitor (C1-INH) is a serine protease inhibitor (serpins) that inactivates several different proteases in the complement, contact, coagulation, and fibrinolytic systems. By its C-terminal part (serpin domain), characterized by three beta-sheets and an exposed mobile reactive loop, C1-INH binds, and blocks the activity of its target proteases. The N-terminal end (nonserpin domain) confers to C1-INH the capacity to bind lipopolysaccharides and E-selectin. Owing to this moiety, C1-INH intervenes in regulation of the inflammatory reaction. The heterozygous deficiency of C1-INH results in hereditary angioedema (HAE). The clinical picture of HAE is characterized by bouts of local increase in vascular permeability. Depending on the affected site, patients suffer from disfiguring subcutaneous edema, abdominal pain, vomiting and/or diarrhoea for edema of the gastrointestinal mucosa, dysphagia, and dysphonia up to asphyxia for edema of the pharynx and larynx. Apart from its genetic deficiency, there are several pathological conditions such as ischemia-reperfusion, septic shock, capillary leak syndrome, and pancreatitis, in which C1-INH has been reported to either play a pathogenic role or be a potential therapeutic tool. These potential applications were identified long ago, but controlled studies have not been performed to confirm pilot experiences. Recombinant C1-INH, produced in transgenic animals, has recently been produced for treatment of HAE, and clinical trials are in progress. We can expect that the introduction of this new product, along with the existing plasma derivative, will renew interest in exploiting C1-INH as a therapeutic agent.

Contrast media for angiography: physicochemical properties, pharmacokinetics and biocompatibility

Contrast agents are used as diagnostic molecules for the visualization of the vascular system. Despite their rapid pharmacokinetic distribution, and their excretion within a few minutes, their injection is associated with clinical symptoms of relative bioincompatibility. Allergoid reactions and disturbances of the hemostatic system represent the main fields of biological investigations. Due to the extent of clinical and experimental works the ubiquitous interactions between these molecules and cellular and/or protein systems have emerged. The development of a new family of low osmolality ionic or non-ionic contrast molecules had decreased the incidence of minor reactions, but did not modify the frequency of severe accidents and even led to the emergence of new iatrogenic syndromes. Despite extensive laboratory investigations there are still no predictive criteria nor any specific therapeutic prevention of these allergoid reactions. The suggested future line of investigation concerns the physicochemical interaction of CM and targeted biological systems which may allow the analysis and predictivity of these interactions at the molecular level.