Adverse radiographic contrast media reactions.

There are many unanswered questions about the mechanisms and prevention of adverse reactions to RCM. Serious reactions will likely occur less often in your experience if you observe these precautions: 1. Consider that every patient is a candiate for an adverse reaction when you request the contrast study. 2. Be particularly cautious in performing the study in those with previous reactions to RMC, those who are strongly atopic, and those in whom intravenous cholangiography is planned. Look for alternative diagnostic approaches in treating these individuals. 3. If there is any likelihood of increased reactivity, inform the patient, carry out a study with intravenous infusion in place and appropriate physician observation during and after the study, consider prestudy treatment with antihistamines and/or steroids, and be prepared to institute emergency measures should the need arise.     

Sonographic enhancement of renal cortex by contrast media.

The purpose of this study was to evaluate whether a phase shift contrast agent could enhance the renal cortex. Four doses of the contrast agent EchoGen ranging from 0.25 to 0.65 ml/kg were injected intravenously in three healthy dogs. Images of the kidney were recorded on a videotape before and after each injection. The images were evaluated visually and were computer-analyzed for brightness change caused by the contrast agent. Marked changes in cortical brightness were observed at the doses of 0.45 and 0.65 ml/kg. At lower doses the changes in image brightness were significantly reduced but measurable. The brightness peaked at 65 +/- 9 seconds after injection and gradually decreased to the baseline value in approximately 12 minutes. The video density varied nonlinearly with dose, and at low doses its value drifted below the baseline. This is believed to be due to attenuation of echoes by the contrast agent. The results of this study indicate that the microbubbles formed by phase shift contrast media are sufficiently small and persist long enough to enhance sonographic images of the cortex. Contrast media whose effect is based on the phenomenon of phase shift permit enhancement of the gray scale characteristic of the kidney. The enhancements last up to several minutes and have strong potential to allow investigation of perfusion in kidney.     

ESUR guidelines on contrast media

Since 1996 the Contrast Media Safety Committee of the European Society of Urogenital Radiology has released 15 guidelines regarding safety in relation to the use of radiographic, ultrasonographic, and magnetic resonance contrast media. The guidelines have been well received by the radiologic community in Europe and all over the world and comprise current standards for good practice at many institutions. The present report is an overview of the work accomplished by the European Society of Urogenital Radiology over the past 8 years. The committee has covered renal and nonrenal adverse events and other aspects of contrast media.     

Adverse reactions to contrast media

Knowledge of the physiological effects of contrast media helps radiology nurses to prepare patients fully. Hypersensitive reactions can progress rapidly so immediate nursing interventions and medical assistance are required. Pre-assessment, psychological support, vigilance, integrated monitoring and decision-making are the most effective prophylaxis.     

Pharmacology of nonionic roentgen contrast media

The non-ionic X-ray contrast media metrizamide, iopamidol, iohexol, and iopromide do not bind calcium and are less hyperosmolar than the conventional ionic contrast media, for instance amidotrizoate (diatrizoate), iothalamate, or ioglicate. Hence the use of non-ionic contrast media is associated with less undesirable side-effects that are attributable to hypertonicity such as an increase in circulating plasma volume, decreased deformability of red blood cells, damage of vascular endothelium with consequent activation of blood coagulation, the complement system and fibrinolysis, increased release of bradykinin and histamine, cardiac arrhythmias, diuresis, vasodilation and decreased blood pressure, pain and heat sensation. Because of less dilution the quality of imaging is also better. According to the intravenous LD50 in experimental animals the acute toxicity of non-ionic contrast media is lower than that of ionic media. With respect to contrast quality and the rate of side-effects the various non-ionic contrast media appear to be equivalent. Despite their higher price and higher viscosity it is probable that the non-ionic contrast media will replace the classical ionic media, especially in angio- and myelography.     

Nephrogenic systemic fibrosis and gadolinium-based contrast media

Nephrogenic systemic fibrosis (NSF) is a recently characterized systemic fibrosing disorder occurring in patients with underlying renal disease. This condition principally leads to skin thickening and hardening and may induce joint immobility and inability to walk. In 2006, clusters of NSF were associated to an exposure to gadolinium containing contrast agents during magnetic resonance imaging. Gadolinium has been detected in skin tissue of patients with NSF. Gadodiamide, a linear gadolinium chelate appears to be particularly at risk. During renal failure, gadodiamide accumulation may explain the development of NSF. Regulatory decisions have been taken to contraindicate gadodiamide in patients with severe renal impairment.     

Low-osmolality contrast media: a current perspective

Intravascular radiographic contrast media play a major role in diagnostic imaging. Recently, low-osmolality contrast media (LOCM) have become available in the United States. Because of their lower osmolality, these new agents cause fewer undesirable physiologic effects and fewer adverse reactions than do conventional agents after intravascular administration. Unfortunately, the cost of LOCM is substantially higher than the cost of conventional contrast media. Appropriate use of these newer, more expensive contrast agents must be based on a thorough knowledge and understanding of their chemistry, physiologic features, and relative safety. Some questions remain about these new agents. Further studies are needed to determine the nephrotoxicity of LOCM relative to that of conventional agents. In addition, LOCM have less anticoagulant capacity than do the conventional media; therefore, clotting may occur when the LOCM and blood mix in syringes and small catheters. This potential decrease in anticoagulation and its clinical implications should be further investigated. Finally, the mortality rate associated with use of LOCM needs to be determined in future studies in large numbers of patients.     

脂质体包裹对比剂在MR的应用

MR造影剂对肝脾的增强价值有限,但其被脂质体包裹后,就能作为肝脾特异性对比剂,还可用其作为血池对比剂.通过在脂质体膜上附加抗体或制成PH敏感脂质体,还可以进一步扩大脂质体的应用范围,对肿瘤的影像诊断会更加准确.本文对携带MR对比剂的脂质体的制造方式及最近的进展进行了描述,对其实用性及原理作了简单的介绍.     

Choosing contrast media for pediatric gastrointestinal examinations

The availability of the new low osmolality contrast agents during the last few years has necessitated a reconsideration of which is the most appropriate contrast agent to utilize in the gastrointestinal (GI) tract. There are some clinical situations in which these new agents have become the contrast media of choice (e.g., evaluation of suspected necrotizing enterocolitis, evaluation of suspected bowel perforation). There are many other clinical situations in which one needs to weigh the potential benefits of the new agents against significantly increased costs. This report reviews in detail the available contrast agents for studying the GI tract and outlines the advantages and disadvantages of each agent. The new agents are compared with existing agents such as barium and the hypertonic water soluble agents (e.g., gastrografin, hypaque, conray, etc.). Guidelines for the use of each agent are presented.     

Future directions in magnetic resonance contrast media

In June 1988 Gd DTPA became the first MR contrast agent to be approved for clinical use in adult patients in the United States. Initial approval was given for its use in imaging of the head. One year later approval was extended to include spine studies. This was soon followed by approval for use in children aged 2 years and older. Research is continuing to expand the applications of Gd DTPA in MR imaging of the musculoskeletal system, abdomen, and in MR angiography. Research is ongoing in the development of new agents, attempting to reduce toxicity, permit increased doses, or target specific organs. Gd DOTA has been in clinical use in Europe for approximately 1 year. Two neutral (nonionic) agents, Gd HP-DO3A and Gd DTPA-BMA, have just completed phase III clinical trials. Mn DPDP and AMI-25 are two targeted compounds that have entered clinical trials. Formulations intended for opacification of the gastrointestinal tract, with both Gd DTPA and magnetic particles, have been evaluated in Europe and in the United States.     

Nephrotoxicity of contrast media following cardiac angiography: pathogenesis, clinical course, and preventive measures, including the role of low-osmolality contrast media.

OBJECTIVE: To review the incidence, definition, clinical course, risk factors, pathogenesis and prevention of contrast-associated nephropathy (CAN) following cardiac angiography with emphasis on differences between high-osmolality contrast media (HOCM) and low-osmolality contrast media (LOCM). DATA SOURCES: Investigations in animal models and in patients following cardiac angiography. DATA EXTRACTION: Animal models of the pathogenesis of CAN are presented. Human studies describing the incidence, clinical course, risk factors, and prevention of CAN are reviewed. Comparative clinical trials of HOCM (diatrizoate, metrizoate) and LOCM (iohexol, iopamidol, ioxaglate) nephrotoxicity following cardiac angiography are critically evaluated. DATA SYNTHESIS: All clinical studies comparing CAN of HOCM versus LOCM following cardiac angiography have some methodologic limitations (e.g., small sample size, lack of control for other factors) that may affect renal function, lack of stratification for other reported risk factors, and variable or short follow-up periods. CONCLUSIONS: Whether the incidence of CAN following cardiac angiography is reduced with LOCM remains controversial. The incidence of CAN in patients with normal renal function does not appear to differ in patients treated with LOCM versus HOCM because few patients in each group develop renal failure. Additional controlled clinical trials comparing CAN of LOCM and HOCM in patients with renal dysfunction are needed. Because of greater product cost and scarcity of documented benefit compared with HOCM, selection of LOCM based on the presence of renal dysfunction cannot be recommended at this time.