IV administration of iodinated contrast typically takes place through an 18 to 22 gauge angiocatheter. There are other gauges of angiocatheter that can be used, however 18 to 22 gauge are the most common. There are two primary types of intravenous needles that are used for iodinated contrast administration:
An angiocatheter is a small plastic catheter that surrounds a needle. When the needle is inserted into a vein, the needle is retracted and the plastic catheter remains in the vein. This plastic catheter is the means through which the contrast media is administered.
A butterfly needle is a needle that is connected to a short length of connective tubing. The needle is inserted into a vein and the plastic “wings “of the butterfly needle are secured in place. The sharp part of the needle stays in the patient’s arm for the duration of the exam.
The typical doses of iodinated contrast range from 50-120mL, but can vary depending on several factors. Specific doses depend on:
Patient weight, age and renal function
Body part being imaged
Method in which body part is being imaged
There is a certain amount of iodine that must enter the patient’s blood stream in order for it to have its desired effects. In order for there to be sufficient iodine opacification during a CT examination, there must be 2-8 mg/mL of iodine in the patient’s bloodstream.
Iodinated contrast may also be administered through a central venous catheter if the device has been approved by the manufacturer for this use.
The most common types of central venous catheters are:
Peripherally inserted central catheters (PICC line)
The injection rate for a central venous catheter is dependent upon manufacturer specifications, but can range from 2-6 mL/sec.
Viability of central venous catheters should be tested with saline prior to injection of iodinated contrast. Failure to do so can result in damaging the central venous catheter, and may cause harm to the patient.
The amount of oral contrast administered for a CT examination will vary based upon departmental protocols and what part of the GI tract needs to be imaged. A typical protocol consists of 750-1500 mL of oral contrast 60-90 minutes prior to the CT examination.
Depending on the departmental protocol, patients may be asked to drink oral contrast just prior to entering the CT examination room in order to opacify the upper GI tract with barium.
If clinically indicated, barium can be administered through an enema for better visualization of the lower GI tract.
150-300 mL is an adequate amount of contrast for opacification of the lower GI tract (in most cases).
A negative contrast agent such as air, may also be administered.
In addition to oral and intravenous iodinated contrast administration, contrast can also be administered in other ways. Depending on the expected outcome of the exam and what anatomy is being imaged, iodinated contrast media may also be injected via:
Iodinated contrast is administered into the space surrounding the spinal cord.
This is done during a CT myelogram.
Iodinated contrast is administered directly into the joint space.
This is done during CT arthrogram of hip, wrist, ankle, etc.