Radiopaque contrast agents are often used in radiography and fluoroscopy to help delineate borders between tissues with similar radiodensity. Most contrast agents are iodine based.
Iodinated contrast agents may be
Ionic
Nonionic
Ionic contrast agents, which are salts, are hyperosmolar to blood. These agents should not be used for myelography or in injections that may enter the spinal canal (because neurotoxicity is a risk) or the bronchial tree (because pulmonary edema is a risk).
Nonionic contrast agents are low-osmolar (but still hyperosmolar relative to blood) or iso-osmolar (with the same osmolarity as blood). Newer nonionic contrast agents are now routinely used at nearly all institutions because they have fewer adverse effects.
The most serious contrast reactions are
Allergic-type reactions
Contrast nephropathy (renal damage after intravascular injection of a contrast agent)
Allergic-type contrast reactions
Reactions vary in severity:
Mild (eg, cough, itching, nasal congestion)
Moderate (eg, dyspnea, wheezing, slight changes in pulse or blood pressure)
Severe (eg, respiratory distress, arrhythmias such as bradycardia, seizures, shock, cardiopulmonary arrest)
The mechanism is anaphylactoid (see Anaphylaxis); risk factors include the following:
A previous reaction to injected contrast agents
Asthma
Allergies
Treatment begins by stopping contrast infusion.
For mild or moderate reactions,
For severe reactions,
hydrocortisone have been administered (see American College of Radiology Manual on Contrast Media).
Contrast nephropathy
In contrast-induced nephropathy, serum creatinine typically begins to increase within 24 hours after administration of IV contrast; it peaks between days 3 and 5 and returns to baseline within 7 to 10 days.
Common risk factors include the following:
Preexisting renal insufficiency (elevated creatinine)
Diabetes mellitus, especially in patients with associated chronic kidney disease
Age > 70
Use of other nephrotoxic drugs
Dehydration
In patients at risk of acute kidney injury after receiving iodinated intravascular contrast, the following measures should be considered:
A reduced dose of contrast
Use of an iso-osmolar agent
Hydration
Many hydration regimens exist. One regimen suggests administration of normal saline at 100 mL per hour for a duration of 6 to 12 hours before the contrast administration and continued for 4 to 12 hours following the contrast injection (see American College of Radiology Manual on Contrast Media).
1).
Lactic acidosis
acute kidney injury from contrast administration are at risk for lactic acidosis. If the patient has chronic kidney diseaseAmerican College of Radiology Manual on Contrast Media).
Because many protocols dealing with contrast agents and reactions are specific and continually updated, it is important to discuss such details with the imaging department.
Pearls & Pitfalls
Reference
1. Weisbord SD, Gallagher M, Jneid H, et al: Outcomes after Angiography with Sodium Bicarbonate and Acetylcysteine. N Engl J Med 378(7):603-614, 2018. doi:10.1056/NEJMoa1710933
