Iodine-containing contrast agents can cause mild, severe and fatal side reactions that often occur early, but can sometimes be delayed.They are unpredictable, but more likely to occur in patients who have a history of allergic reactions and diseases: urticaria, bronchial asthma, eczema, hay fever, allergic reactions to food or medicines, or a history of increased sensitivity in an earlier survey using iodine-containing contrast agent. At present, these reactions can not be predicted from the results of a sample for sensitivity to iodine or other methods.
General Precautions:
It is recommended to be careful in patients with severe hepatic insufficiency, chronic heart failure, severe respiratory failure and anamnestic data on allergies or hypersensitivity to iodine.
Particular caution is required in patients with hyperthyroidism or benign nodular goiter.
Precautions associated with dehydration and kidney function in the patient:
Dehydration may be exacerbated by the osmotic effect of these agents.
In patients with chronic renal failure, diabetes mellitus, myeloma, hyperuricemia, and in infants in a state of dehydration, oliguria and anuria can develop.For this reason, these patients are advised to avoid limiting water intake prior to the examination and to maintain sufficient diuresis.
The introduction of large doses of radiopaque means with high speed to patients with chronic heart failure leads to a transient increase in the osmotic load on the circulation. For this reason, these patients need monitoring for several hours to detect any delayed hemodynamic disorders.
Due to the risk associated with the use of the drug, the following is important during the diagnostic procedure:
- the physician should provide constant medical supervision (in particular, for heart rate and blood pressure);
- It is necessary to maintain venous access for emergency therapy of any adverse reactions.
In patients with pheochromocytoma or suspected of it before intravascular administration of the drug should be prepared appropriate resuscitation equipment.
Indicators of thyroid function:
- if it is necessary to determine the function of the thyroid gland, the examination should be performed before angiography,because the latter leads to a transient massive overload of the body with iodine, which suppresses the iodine clearance in the thyroid gland and the absorption of radioactive iodine for a period of not less than 1 week.
Determination of protein in urine using strong acids after the use of triiodinated water-soluble contrast agents may give a false positive result.
Therapy at the onset of adverse reactions or reabsorption
With mild and moderate adverse reactions:
- stop the introduction of contrast;
- monitor heart rate and blood pressure;
- if necessary, administer antihistamines and glucocorticosteroids, and also start oxygen therapy.
In case of serious reactions:
- stop the introduction of contrast and monitor the function of breathing and cardiovascular system.
Cardiovascular disorders
Preservation of venous access during the examination procedure allows the infusion of large doses of glucocorticosteroids (1 - 2 g of hydrocortisone). Simultaneously it is necessary to carry out oxygen therapy, to introduce vasopressors, plasma, electrolytes taking into account the parameters of hemodynamics.
When the symptoms increase, intensive care should be provided in a specialized department.
Disturbance of ventilation
Rare breathing with inspiratory dyspnea, which is a manifestation of the laryngeal edema, requires endotracheal intubation and the administration of large doses of glucocorticoids. At attacks of a bronchial asthma it is necessary intravenous introduction of glucocorticoids and / or bronchodilators.
Neurological disorders
Attacks of tetanic convulsions usually terminate after exhalation in a bag (respiration in a closed loop) or the administration of calcium gluconate. Conventional cramps are stopped by intramuscular injection of diazepam.
Renal damage
If rehydration and other necessary measures prove ineffective, oliguria and anuria may require dialysis.