Expert perspective, each issue brings you a quick overview of expert opinions.
In this issue, we invited Professor Zhang Huimao, director of the Radiology Department of the First Hospital of Jilin University, to share with you the safe application of iodine contrast agents and the treatment of adverse reactions.
(It is recommended to watch in a wifi environment)
See the essence of the content below
The basic structure and classification of iodine contrast agents
Based on medical For the purpose of imaging, a specific substance is introduced into the human body to change the image contrast of local tissues of the body. This introduced substance is called a contrast agent.
Contrast agent classification
X-ray contrast agent (barium contrast agent, iodine contrast agent, CO2 contrast agent)
MRI contrast agent (gadolinium contrast agent agent, manganese contrast agent, iron contrast agent)
Ultrasound contrast agent
Nuclear medicine contrast agent
The development history of iodine contrast agent
Chemical properties of iodine contrast agent:
Chemical structure Open the APP to view the large high-resolution image
Chemical structure of sub-hypertonic contrast agent (-OH is a hydrophilic group, -CH3 is a hydrophobic group. The more hydroxyl groups and the fewer methyl groups, the better the hydrophilicity.) Open the APP to view the large high-resolution image
Isotonic contrast agent iodixanol: non-ionic, bis- Body, hexaiodine, water-soluble X-ray contrast agent; osmotic pressure: 290mOsm/L (isotonic)
Osmotic pressure: affects the function of blood cells and endothelial cells. The advantage of isotonicity is that it can reduce damage to endothelium and red blood cells, as well as local pain and fever, and avoid the impact of large fluctuations in blood volume. It can also reduce the impact on the heart and pulmonary circulation, reduce stimulation of the blood-brain barrier, and protect important organs. device.
Cardiovascular effects caused by high osmotic pressure: dehydration of blood cells, dehydration and damage of vascular endothelial cells, and interstitial fluid entering the blood vessels.
Performance of contrast agents with different osmotic pressures (top: red blood cells; bottom: endothelial cells)
Viscosity: refers to the resistance to liquid flow (mPa-s), Determined by intermolecular interactions. It is positively correlated with the concentration of contrast agent and negatively correlated with temperature. Therefore, clinical use of iodine contrast agent requires preheating to 37°C.
Comparison of viscosity of commonly used iodine contrast agents
Hydrophilicity: structure determines everything: hydrophilicity data are basically related to the number of hydroxyl groups and the number of methyl groups in the chemical structures of various iodine agents corresponding. The more hydroxyl groups and the fewer methyl groups, the higher the hydrophilicity.
The higher the water/n-octanol partition coefficient, the better the hydrophilicity
Classification of adverse reactions to contrast agents and their mechanisms
Like other drugs, The use of contrast media is not completely risk-free, and adverse effects may occur with all contrast media.
Adverse reactions to contrast media can range from mild physiological effects to rare, severe and life-threatening
Every contrast medium on the market has caused adverse reactions
1. Adverse reactions to iodine contrast media are classified according to their mechanisms:
Specific/allergic-like reactions (non-dose dependent): This type of adverse reactions has nothing to do with the dose, injection method and speed of iodine contrast media. The clinical manifestations are usually the same as an allergic reaction to a drug or other allergen, and in most patients who react, no antigen-antibody reaction can be recognized, such as rash, laryngeal edema, and anaphylactic shock (not anaphylaxis).
Non-specific/physiological-like response (dose-dependent): It is a physiological response of the body to the contrast agent, which is related to the dose, injection method, speed and physical and chemical properties of the iodine contrast agent. It generally manifests as the reaction of contrast media on organs or systems. The most commonly affected organs or systems are the kidneys, cardiovascular system, and nervous system.
2. Adverse reactions to iodine contrast media are classified according to severity:
3. Adverse reactions to iodine contrast media are classified according to time of occurrence:
Acute adverse reactions: Occurrence Within 1 hour after contrast medium injection. It can be divided into two categories: allergic-like reactions or physiological reactions, and its severity is generally divided into three levels (mild, moderate, severe).
Delayed adverse reactions: occur within 1 hour to 1 week after contrast medium injection. Similar to other drug eruptions, maculopapular rash, erythema, swelling, and itching are common. Most skin reactions are mild to moderate and self-limiting.
Very delayed adverse reactions: Adverse reactions that usually occur 1 week after contrast medium injection. It may cause hyperthyroidism, occasionally seen in patients with untreated Graves' disease or nodular goiter, the elderly, and/or those with iodine deficiency.
Treatment strategies for adverse reactions of contrast media
Coping with acute adverse reactions is one of the essential skills in clinical work, and it is also something that radiology departments need to be familiar with in clinical work.
1. Be familiar with the drugs and equipment to deal with acute adverse reactions:
Oxygen, epinephrine (1:1000), antihistamine H1 injection (diphenhydramine), atropine , beta2-agonist aerosols, anticonvulsants, intravenous rehydration fluids (normal saline or lactated Ringer's solution), and infusion tubes.
Equipment: blood pressure monitor, ECG monitoring, etc.
The department should be equipped with an emergency cart, and the examination room should have the emergency number of the hospital's resuscitation team.
Medical staff and technicians should receive regular training on acute adverse reaction handling and resuscitation techniques.
Equipment for collecting blood for tryptase and histamine determination should be readily available.
After contrast injection, the patient remains in the medical environment for observation for 30 minutes.
2. Principles for handling different adverse reactions:
Treatment of nausea, vomiting and urticaria
Treatment of diffuse erythema Open the APP to view large high-resolution pictures
p>
Treatment of bronchospasm and laryngeal edema Open the APP to view large high-resolution images
Treatment of hypotension
Treatment of hypertensive crisis Open APP to view large high-resolution images
p>
Treatment of pulmonary edema and epileptic seizures Open the APP to view large high-resolution images
Handling of hypoglycemia and anxiety (panic attacks) Open APP to view large high-resolution images
General allergy Treatment of similar reactions
Treatment and recommendations for delayed adverse reactions:
Treatment: Symptomatic treatment similar to skin reactions caused by other drugs, such as antihistamines, topical Use steroids and emollients.
Recommendation:
Patients who have had a reaction to contrast media or have been treated with interleukin-2 should be informed of the possibility of delayed skin reactions and should contact their doctor if they have any questions;
Skin testing can be used to confirm delayed skin reactions to contrast agents and to study cross-reactivity with other contrast agents;
To reduce the risk of repeated reactions, another contrast agent should be used, rather than the first application of the contrast agent that initiated the reaction. Avoid using contrast agents that have cross-reactivity as shown by skin tests;
Drug prophylaxis is generally not recommended
3. During the treatment of allergic reactions, the treatment plan should be reviewed regularly:
Radiologists and relevant staff should review treatment plans regularly (eg every 12 months) so that everyone can do their job effectively.
Knowledge, training, and preparation are key to ensuring appropriate and effective treatment of contrast-related adverse events.
Summary The development of iodine contrast agents has progressed from hypertonic to sub-hypertonic to isotonic, and their physical and chemical properties have been continuously optimized. The adverse reactions of iodine contrast agents cannot be ignored, and understanding their classification and mechanisms is the basis for safe application. It is crucial to master the treatment strategies for acute and delayed adverse reactions, timely identification and standardized treatment.
· Mild acute adverse reactions: self-limiting, generally do not require drug treatment, but should be closely observed;
· Moderate acute adverse reactions: require timely drug treatment and close observation Observe and be careful not to escalate to severe adverse reactions;
· Severe acute adverse reactions: timely identification and quick and effective rescue are required, and contact relevant rescue departments if necessary;
· Delayed adverse reactions Reaction: Most are self-limiting. Commonly used drugs are antihistamines, corticosteroids, etc.
Professor Zhang Huimao
Zhang Huimao
Professor, chief physician, doctoral supervisor
Department of Radiology, First Hospital of Jilin University Director
Standing Member of the Radiology Branch of the Chinese Medical Association
Standing Member of the Radiology Branch of the Chinese Medical Doctor Association
Chairman of the Radiology Branch of Jilin Provincial Medical Association
Chairman of the Medical Imaging Big Data and Artificial Intelligence Working Committee of the Radiology Branch of the Chinese Medical Association
Deputy Leader of the Abdominal Group of the Radiology Branch of the Chinese Medical Association
Chinese Medical Doctor Association Chairman of the Urogenital Committee of the Radiologist Branch
The content of this article is for medical professionals only