Radiological Contrast Media.
Contrast Media is a chemical substance of very high or very low atomic number or weight, therefore it increases or decreases the density of the organ under examination.
A substance which when introduced into the body will increase the radiographic contrast in an area where it was absent or low before.
Contrast procedures have been developed to increase the native contrast of organs in order to separate them from surrounding tissues. There are many situations where they can be a useful supplement to the information gained from routine radiographic examination. They can provide information on the size, shape and position of structures. They might help outline the internal structure of an organ, including its mucosal pattern and sometimes help assess its function.
What is an ideal contrast media?
An ideal contrast is which is Easy to administer, High water solubility, No toxicity, Stable Compound, Concentrate in area of interest, Should have rapid elimination and Cost effective.
What are the modes of administration?
Radiological contrast can be administer through Orally, Rectally, Intravenously – (injection/ infusion), mechanically – Filling of a body cavity or potential space and Intra-muscularly.
What are the uses Of Contrast Media?
They are used for many radiological procedures like Arteriography, Angiography (DSA) – Cardiology, Venography (replaced by ultrasound Doppler), IVU, Fluoroscopy – Alimentary tract, HSG, sialography, CT, MRI, Ultrasound – Liver, kidney, Myelography (replaced by MRI) andArthrography – Knee joints.
Classification of Contrast Media: –
X-Ray & CT Contrast are classified toPositive CMand Negative CM.
Positive contrast agents have a high atomic number, either barium sulphate or iodine and appear more radiopaque than the surrounding tissue and appears white on radiographic film. Barium sulphate used for digestive system abnormalities and Iodinated contrast medium used for all the parts like angiography, myelography, HSG etc of body as it is watery soluble contrast media and easily excreted from the body.
Negative contrast agents are gases of low density like air which appear radiolucent. Low atomic number material and appears black on film. Examples are Carbon dioxide, Oxygen and Air.
There are a few conditions like the integrity of gut wall compromised or GI Perforation, previous allergic reactions to barium, and suspected fistula between esophagus and lung in which the barium sulfate should not use for diagnostic purposes.
For iodinated contrast media, contraindications are History of Allergies, Pregnancy, Renal Failure, Asthma, Diabetes, and Cardiac Diseases. The contrast should avoid for such conditions because it can be dangerous to the patient’s health and life.
Adverse reactions of iodinated contrast media: –
In clinical medicine, every technical procedure and every drug is given to a patient by whatever route (oral, rectal, IV, IA, intrathecal) may cause adverse drug reactions (ADRs), which are sometimes fatal. It is inevitable that even when administered appropriately, RCM will very occasionally result in a severe or even fatal ADR, sometimes leading to litigation.
It has become increasingly difficult to defend inappropriate indications, inadequate resuscitation facilities, and inappropriate experience, especially in small imaging departments, in either private or public hospitals. Adverse reactions to RCM may be divided into:
1. Idiosyncratic anaphylactic reactions
2. Non-idiosyncratic reactions and
3. Combined reactions. These reactions can be minor, moderate and severe and their effects to the patients.
Treatment for adverse reactions: –
If the patient is having minor effects then there is no need for treatment only attention and relaxing to the patient is required, if the patient is having moderate reaction then there is no need to hospitalize the patient but required treatment immediately and if patient is having severe reaction the patient should shift to the hospital immediately for appropriate treatment.