Contrast is given to patients who are to undergo, for example, magnetic resonance imaging or coronary angiography. Before these tests, a special questionnaire is completed. It contains information on the side effects that the contrast agent can cause, as well as a question about allergy to contrast. Most patients wonder what the contrast is and how they can know if they are allergic to it, if they haven't had it yet. We explain this mystery below.
Contrastis a contrast agent used in diagnostic imaging. On rare occasions, some patients may beallergic to contrast . The contrast agent is administered to patients undergoing magnetic resonance imaging or computed tomography. Contrast is also widely used in interventional cardiology, both in diagnostics and the procedures themselves.
Contrast in interventional cardiology
- Contrast is needed to visualize the coronary arteries in interventional cardiology procedures. Thanks to it, we can see the coronary arteries and on this basis determine their anatomy and the nature of atherosclerotic lesions. First of all, do these changes occur, what are they and where are they located? Thanks to this, we can make a decision about the appropriate treatment. On this basis, we can treat the patient conservatively, i.e. with pills, we can offer a repair procedure, i.e. a coronary angioplasty procedure. In the case of very advanced lesions, the patient may require cardiac surgery and consideration of surgical treatment. There is still the saddest option, when the degree of advancement and destruction of the coronary vessels does not allow for anything other than pharmacological treatment. During coronary angioplasty, the contrast makes it possible to assess the correct setting of the guide wire, i.e. the wire on which we insert the equipment into the coronary artery, the balloon catheter with which we widen the atherosclerotic lesion, and finally whether the positioning of the coronary stent is correct and whether the blood flow is correct after the procedure. It also allows us to determine whether we are dealing with postoperative complications, which may occur, for example, in the case of a rupture of the inner layer of the vessel - explains in detail Dr. Janusz Szczupak, head of the Invasive Cardiology Center,Electrotherapy and Angiology in Krosno.
Thanks to the contrast, doctors can see our coronary vessels on the monitors, the contrast is a measure that is clearly visible under X-rays. Without providing a contrast, it is impossible to see it. Contrast is used in a variety of but not all imaging methods.
Imaging tests using contrast
- Some imaging methods require contrast. It will mainly be computed tomography, which with the use of contrast gives good imaging of the structures of the heart and vessels. MRI uses a different type of contrast that is not harmful to the kidneys. However, in echocardiographic examinations, all examinations are basically done without contrast. Optical coherence tomography, on the other hand, requires a small amount of contrast due to the fact that we have to rinse the vessel from the blood and at the time of imaging there must be only fluid - explains Prof. Dariusz Dudek, director of the New Frontiers in Interventional Cardiology (NFIC) workshop in Krakow.- Contrast contains small amounts of iodine, these are low-ion contrasts, therefore they are not a problem for patients with e.g. hyperthyroidism, patients allergic to various compounds containing iodine. This amount is really small - explains Dr. Szczupak. Contrast is the only means that allows shading. It has also evolved over the years. According to Dr. Szczupak, the content of iodine and particles has changed and now it is the so-called low osmolar contrast with trace amounts of iodine. It is qualitatively better and gives less side effects. Nevertheless, it is a foreign substance that we introduce into the body.
Contrast: complications, sensitization and shock
Patients who are to be given contrast should remember a few things. - First of all, the patient must carefully read the consent for diagnosis and treatment with the use of contrast. He must be aware of the risk of allergy to contrast, exacerbation of chronic kidney disease, possibly with the need for dialysis. This applies to a small group of patients, however, the patient should be familiar with the risks of the treatment used. Contrast is not an indifferent substance - says Dr. Szczupak. Dr. Szczupak also says that the worst form of allergy to contrast is anaphylactic shock, which is fortunately rare. Doctors have a developed course of action in the case of a patient's allergy to contrast. In every situation when we have a patient allergic to any allergen, the patient has a biological test - he has a small amount of contrast administered intravenously and then we observe whether or not there is an allergic reaction. If there is no thisreaction, then we can safely perform the procedure. If there is a slight reaction, antiallergic drugs are administered. Another biological test is made and then the procedure is performed - explains Dr. Szczupak. Doctors emphasize that contrast should not be indiscriminately. Therefore, there are certain standards when it comes to providing contrast. The more contrast, the greater the risk of kidney damage. The biggest problem is patients with impaired kidney function, the so-called low GFR (glomerular filtration rate), i.e. below 30-40. They should give little contrast and doctors try to do so. 1 ml of contrast corresponds to one unit of this GFR. With a GFR value of 20, no more than 20 ml of contrast should be administered. It is extremely difficult because the amount is small. - With this amount of contrast, coronary angiography can be done, but not plastic surgery. These are really small amounts of contrast. We use an average of 50-60 ml for coronary angiography, about 100 ml for plastic surgery. If we know that a patient has a kidney problem, we rehydrate him and it works, but we need to spend some time rehydration. Of course, this risk is higher - emphasizes Dr. Szczupak.The text was written on the occasion of the international workshop New Frontiers in Interventional Cardiology (NFIC) in Krakow.
ImportantA patient who knows that he will be given contrast should go to the test with the current result of the creatinine level. This is important because the contrast is eliminated from the body with the help of the kidneys, which must be functional. In extreme cases, renal failure may occur, which necessitates dialysis of such a patient.