Preparation before contrast examination

As the saying goes, if you want to do your work well, you must first sharpen your tools. In order to obtain better, more direct and effective results from contrast examination, it is necessary to make preparations in advance. Contrast examination, in layman's terms, is an examination method that introduces contrast agents into organs or surrounding areas that lack natural contrast to produce obvious contrast. So do you know what preparations you need to make before angiography? First of all, we need to understand the relevant content of angiography.

1. Contrast agents There are two types of contrast agents commonly used in clinical practice:

(1) High-density contrast agents: Barium agents (such as barium sulfate) are used for contrast imaging of the digestive tract; iodine agents (such as sodium iodide, iodized oil, and diatrizoate) are used for contrast imaging of the bronchi, gallbladder, cardiovascular system, and renal pelvis.

(2) Low-density contrast agents: These include gases such as air, oxygen, and carbon dioxide. They are used for imaging of the ventricles, back of the eyeball, spinal canal, colon, bladder, knee joints, etc.

2. Imaging methods There are two commonly used imaging methods:

(1) Direct introduction method:

① Oral entry method, such as gastrointestinal barium meal examination

② Retrograde entry method, such as urography, hysterosalpingography, barium enema colonography, etc.

③ Surface puncture entry method: Inject the contrast agent directly or through a catheter into the organ or tissue, such as cardiovascular angiography.

(2) Indirect introduction method: also known as physiological excretion method. Contrast agents are mainly introduced into the body through intravenous injection. After circulating through the blood, they are excreted through a certain organ and temporarily stay in its channel to make the organ visible, such as cholecystography, intravenous cholangiography, intravenous urography, etc.

3. Preparation before contrast examination Due to the differences in the contrast examination site, type of contrast agent and contrast method, the preparation and precautions required before the examination are also different. Therefore, nurses are required to master the specific requirements of various imaging examinations, assist patients in making various preparations, and be able to deal with problems that arise during the examination in a timely manner. The following preparations must be made before the angiography examination:

(1) Find out whether the patient has any contraindications to angiography, such as severe heart, liver, or kidney disease or allergic constitution.

(2) Before the examination, explain to the patient the purpose, method, precautions, and possible adverse reactions of the examination.

(3) For any imaging examination that requires the use of iodine contrast agents, an iodine allergy test must be performed in advance. The imaging examination can only be performed if the allergy test is negative. Iodine allergy test method:

① Conjunctival test: Use 35% iodine contrast agent to drip into the conjunctiva of the eyeball and observe the results after 15 minutes. If the conjunctiva is congested, it is considered positive.

② Intradermal test: Inject 0.1 ml of 3% iodine into the skin and observe the results after 10 to 15 minutes. If redness, swelling, and nodules appear on the local skin with a diameter of more than 1 cm, it is considered positive.

③ Intravenous injection test: Inject 1 ml of 30% iodine contrast agent intravenously and observe the results after 15 minutes. If there is chest tightness, palpitations, shortness of breath, nausea, vomiting, dizziness, headache, urticaria, etc., it is positive.

④ Sublingual test: Place a few drops of contrast agent under the tongue and observe the results after 5 minutes. If there is tongue numbness, thick tongue or tongue swelling, it is considered positive.

(4) Be prepared for emergency treatment: prepare emergency medicines and equipment before the examination; if an allergic reaction occurs during allergy testing or angiography, it should be treated promptly according to the severity of the reaction. Mild cases (such as dizziness, facial flushing, chest tightness, shortness of breath, nausea, vomiting, rash, etc.) generally improve after rest or oxygen inhalation, and anti-allergic drugs should be used if necessary.