INTRAVENOUS CONTRAST

.Procedure Information


Intravenous (IV) Contrast is an important part of CT scans. It is an iodine-based "dye" that is administered by a radiographer or radiologist into a vein through a tube known as a cannula. The contrast medium then travels through the body, highlighting areas that may not have been visible before. This allows our radiologist to get a clearer image of the internal structures while reporting, which results in a more accurate diagnosis.

Preparation

While booking for a CT scan that may require IV contrast, you will be asked to fast for a minimum of two hours and to keep hydrated before the examination. During the registration process upon arrival, you will be asked to fill in a form that outlines your medical history and to give consent to the contrast procedure. The form will ask you questions such as kidney function problems, thyroid disease, diabetes, and known allergies. This allows our radiographer and radiologist to determine if you are fit to have IV contrast administered.

Safety Issues and Risks

After the contrast is administered, you may feel warm and have a metallic taste in your mouth. These reactions are harmless, and resolve quickly. The contrast is filtered through the kidneys and exit the body through urination over 24 hours. Any radiological examination requiring administration of iodinated contrast involves the risk of an adverse contrast reaction. While most reactions are minor, life threatening reactions may occur without warning. The contrast medium we us is iodine-based, which some people may be allergic to. It it essential to inform staff of any known allergies prior to the examination, so you can be assessed by our radiographer.
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Acute Contrast Reactions
Acute adverse reactions to iodinated contrast manifest within 60 minutes of injection of contrast medium. They may be classified as mild, moderate or severe.
Mild reactions include flushing, nausea, pruritus, vomiting, headache and a mild rash. They are usually self limited and resolve without specific treatment. Mild reactions may be seen in up to 3%* of patients contrast agent administration. Moderate contrast reactions include severe vomiting, marked rash, bronchospasm and fainting. Severe contrast reactions include respiratory arrest, cardiac arrest, pulmonary oedema and convulsions. Severe reactions are uncommon, occurring in 0.004%* (1 in 25,000) of contrast injections.
Our trained radiologist is always on site when contrast is being administered to a patient to deal with such situations. Our radiographers are also trained in CPR and first aid, and all necessary emergency equipment is kept close by.

Metformin and Renal Function

Metformin is a drug used in the treatment of Type II diabetes. Complications may occur due to Metformin accumulation in patients with renal impairment. In patients with abnormal renal function, they will be asked to stop taking metformin a day before the examination. If you are over 60, a renal function test should be requested by your doctor and available to us on the day of your scan. If you are on metformin and were asked to stop taking it for the scan, your renal function should be reassessed before recommencing it.

If you have further questions about IV contrast, our staff will be happy to help you on the day of your CT scan.

*Source: RANZCR Guidelines for Iodinated Contrast Administration, 2009