Peripheral Cannulation (Care & Advice)
What to expect before and after a contrast injection for your CT or MRI scan.
What is peripheral cannulation?
For some CT or MRI scans, a special dye also known as contrast medium is injected to enhance image quality. This requires a small plastic tube (cannula) to be inserted into a vein—usually in your arm or hand to allow the contrast to be safely delivered.
What should I expect during the procedure?
- A brief sting / pinch when the needle is inserted
- A warm / flushed sensation
- A metallic / bitter taste in your mouth (temporary)
To help make your experience smooth and comfortable, do let our team know if:
- It has taken multiple attempts to insert a cannula in the past
- You have any preferences or physical conditions that may affect where the cannula is placed
- You have any allergies, such as to tapes and dressings
After the procedure
- Stay hydrated by drinking at least 1 to 2 litres of water after the procedure to flush the contrast out from your body if you have no fluid restrictions
- Monitor the site for signs of infection such as redness, swelling and / or discharge
- Avoid heavy lifting on the injected arm for the rest of the day
- Apply cold compress over the injection site if there is pain / soreness
- Slight bruising is normal and you are advised NOT to rub the area
Possible risks
- Haematoma (“Blue-Black”) — resulting from a collection of blood that pools outside of the vein, under the skin (Patients who are on blood thinners have a higher risk)
- Pain / soreness over the injection site
- Extravasation — Leakage of the contrast into surrounding tissue
- Minor bleeding which can be stopped by applying pressure for 5 minutes (10-15 minutes if you are taking blood thinners)
In summary, peripheral cannulation is a routine and generally safe procedure that helps improve the accuracy of your CT or MRI scan. With proper aftercare—such as staying hydrated, monitoring the injection site, and avoiding strain on the arm—most patients recover quickly with minimal discomfort. If you notice any unusual or worsening symptoms, please seek medical attention promptly.