In radiography, radiography is used to take up a substance with a high atomic number and then to take a radiograph in the body to be diagnosed for medical diagnosis. With the continuous development of medical science and technology, iodinated contrast agents are widely used in clinical areas: such as enhanced CT, coronary angiography, interventional therapy and other clinical medical disciplines.
I. Iodine contrast agent classification
Iodine contrast agents are classified into ion contrast agents and nonionic contrast agents. Ionic iodine contrast agents are compound diatrizoate meglumine injections, non-ionic iodine contrast agents are ibuprofen alcohol injection, iopromide injection, iohexol injection and so on. The clinical consensus that non-ionic contrast agents are safer, more effective, and have a lower incidence of allergic reactions than ionic contrast agents has led to a large number of clinical applications.
1. Various angiographic radiographs, including: cerebral angiography, peripheral arteriography, internal visceral arteries, renal artery and aortic angiography.
2. Cardioangiography includes coronary angiography, arterial and venous digital subtraction angiography.
3. Intravenous urography and CT enhancement (including head and body CT).
III. Preparation before radiography
1. Fasting: A normal diet can be maintained up to 2 hours before the test. Within 2 hours before the examination, patients should be fasting.
2. Hydration: Adequate moisture must be given before and after intravascular contrast agent administration (hydration from the first 4 h to 24 h after use, with a maximum fluid volume of 100 ml/h). Especially for patients with multiple myeloma, diabetes, polyuria, hyperuricemia, as well as neonates, infants, young children and elderly patients.
3. Sedation: Anxiety, excessive excitement, anxiety and pain can increase the risk of adverse reactions or aggravate reactions associated with contrast agents. Patients may be given sedatives.
4. Heating before use Contrast agents heated to body temperature can be better tolerated and make injection easier due to reduced viscosity. The contrast agent needed on the day of the examination can be heated to 37[deg.] C. with a constant temperature oven. If protected from light, heating for longer periods of time will not change the chemical purity. However, it should not exceed 3 months.
5. Pre-experiments It is not recommended to use a small dose of contrast agent for allergy testing because there is no predictive value. In addition, the allergy test itself occasionally causes severe and fatal allergy tests.
IV. Usage and dosage of contrast agent
The commonly used 5 contrast agents are summarized from the following five aspects: arterial angiography, venography, angiocardiography, computed tomography, and intraluminal angiography:
V. Adverse reactions
Non-ionic contrast agents have fewer adverse reactions than ionic contrast agents. Severe reactions and lethal reactions are very rare. Common adverse reactions are mild sensory abnormalities, such as thermal sensation, coldness, and pain. Gastrointestinal reaction. Allergic reactions occur occasionally. Vagal response, iodine poisoning or iodine toxic mumps, nervous system reactions, cardiac complications, joint pain, etc.
In clinical practice, non-ionic contrast agent allergic reactions can be divided into 3 categories according to clinical manifestations:
1. Light allergic reactions: skin flushing, itchy skin. It often occurs in the face, neck, upper chest, conjunctival hyperemia, edema, headache, dizziness.
Even fever, chills, sweating, a few rashes, cough, mild urticaria and other symptoms.
This kind of reaction generally does not require medication, stop the injection. Let the patient rest quietly, take a deep breath, and observe the development of the reaction.
2. Moderate allergic reactions: including chest tightness, shortness of breath, respiratory symptoms such as breathing difficulties, severe vomiting, abdominal pain, diarrhea and other upper gastrointestinal symptoms. Occasional hoarseness, body twitches, etc.
This type of response is more critical than lighter ones. The injection should be stopped immediately and oxygen should be given, and anti-allergic drugs should be given appropriately.
Such as intramuscular injection of glucocorticoid dexamethasone, intramuscular injection of diphenhydramine, intravenous infusion of calcium preparations, blood volume and other anti-allergic treatment.
3. Severe allergic reactions: circulatory failure, acute respiratory distress complicated by pulmonary edema, multiple organ failure, circulatory purpura, cardiogenic shock, blood pressure drop, rapid pulse, clammy skin, confusion, sudden cardiac arrest, etc. .
Should be rescued immediately.
VI. Special populations
1. Patients with a history of allergies and allergies should be cautious when administering drugs. For these patients, antihistamine or corticosteroid drugs should be considered in advance to avoid or reduce the possible allergic reactions.
2. Recently used contrast agent, postponed re-contrast examination until renal function returned to pre-examination levels.
3. Age factor: infants under 1 year old and above 65 years old should take extra care. Ensure that there is sufficient water in the body before and after the use of contrast agent, and monitor the patient’s condition at any time so that the patient can be treated in time when adverse reactions occur.
4. Pregnant and lactating women should avoid X-rays at any time during pregnancy.
Therefore, regardless of the use of contrast agents, the pros and cons must be carefully weighed before the examination, and the clinician considers it necessary.
1. Have a history of iodine allergy and disable it.
2. Prohibit allergies to iodine contrast agents and their accessories. Patients with thyroid disease are disabled.
3. Iopromide: Hysterosalpingography is not allowed in patients with pregnancy and acute pelvic inflammatory disease. In acute pancreatitis, ERCP is prohibited. Intrathecal injections are contraindicated.
VIII. Drug Interactions
1. The use of iodinated contrast agents may cause transient renal insufficiency, which can cause lactic acidosis in diabetics taking metformin.
2. Patients treated with interleukin-2 within two weeks may have an increased risk of delayed reactions (flu-like symptoms and skin reactions).
3. All iodine-containing contrast agents will affect the determination of thyroid function, and the iodine-depleting capacity of the thyroid gland will continue for several weeks.
4. High concentrations of contrast agents in serum and urine will affect the laboratory determination of bilirubin, protein or inorganic substances.
5. In patients with abnormal liver function, the injection of iodine-containing contrast agents into the blood vessels after oral cholecystography can cause kidney toxicity.
6. Should not be directly mixed with other drugs. A separate infusion set should be used.
IX. Using Contrast Agent Summary
1. Although the risk of serious reactions is small, iodinated contrast agents may still show signs of anaphylaxis or other allergic reactions. Therefore, first-aid measures should be conducted in advance and necessary rescue medicines and equipment should be prepared to deal with possible serious reactions.
2. Injection of contrast agents through blood vessels may increase the condition of patients with homozygous sickle cell disease.
3. In vitro tests, non-ionic contrast agents have less influence on the coagulation system than ionic ones. When angiography is performed, great care must be taken in intravascular techniques. From time to time, catheters are perfused with heparinized saline to reduce thrombosis and embolism associated with the technique.
4. Before and after the use of contrast agent must ensure that the patient’s body has enough water. Infants younger than 1 year, newborns, severe heart disease and pulmonary hypertension require special attention.
5. Patients with acute encephalopathy, brain tumors, or epilepsy have to prevent epileptic seizures and require special attention. Alcohol abusers and drug addicts are at increased risk for seizures and neuropathological changes.
6. In order to prevent acute renal failure after the use of contrast agents, special attention should be paid to patients with existing renal impairment and diabetes, and the risk of heterosexual globulinemia is greater. Avoid any nephrotoxic drugs that aggravate the burden on the kidneys prior to contrast agent clearance, oral gallbladder contrast agents, arterial clamping, renal arterial plasty or other major procedures.
7. Contrast agents containing iodine can increase the symptoms of myasthenia gravis.
8. Patients with pheochromocytoma should be given alpha-blockers to prevent hypertensive crisis during interventional therapy.
9. Hyperthyroidism patients also need special attention. Patients with multiple nodular goiters may develop hyperthyroidism after using iodine contrast agents.
10. Patients who have used contrast media will observe at least 30 minutes because most serious adverse reactions occur during this time. However, experience shows that allergic reactions may also occur in hours or even days.
11. Make sure there is enough water in the body. If necessary, the infusion can be maintained intravenously until the contrast agent is removed from the kidney.
12. To prevent lactic acidosis, serum creatinine levels must be determined before intravascular injection of iodinated contrast agents in diabetics using metformin. For serum creatinine / patients with normal renal function, when the contrast injection must be disabled and can not be recovered Metformin medication within 48 hours. Abnormal patients, metformin and must be disabled to check postponed after 48h. The administration of metformin can only be restored after a constant renal function/serum creatinine level.
13, Iodinated contrast agents are secreted in milk in small amounts, so the risk of adverse reactions to the baby when the mother is used alone is minimal. After applying iodized contrast agent, it is recommended to stop breastfeeding for at least 24 hours.