Radiocontrast Media Hypersensitivity Reactions Causes

Radiocontrast Media Hypersensitivity Reactions

RCM

A patient who has experienced an immediate hypersensitivity reaction (IHR) to Radiocontrast Media “RCM.”
There is an increased risk for recurrent IHR with the subsequent exposure to RCM.
Measures to prevent recurrent reactions to RCM in patients with past IHRs will be discussed here.

Clinical History:

Any patient reporting an “allergy” to radiocontrast medium (RCM) should be carefully questioned to determine whether the past reaction was consistent with an immediate hypersensitivity reaction (IHR) or another type of reaction. The recommendations described here are only intended for the prevention of recurrent IHRs.

IHRs to RCM develop within one hour of administration and may begin within five minutes. IHRs have signs and symptoms that are similar or identical to those of anaphylaxis, including the following:

Premedication regimens:

One widely-used approach combines glucocorticoids and H1 antihistamines with nonionic low osmolar contrast material.
Prednisone, given orally 13 hours, 7 hours, and 1 hour before (in adults, 50 mg per dose; in children, 0.5 to 0.7 mg/kg per dose, up to 50 mg per dose).
If oral administration is not feasible, methylprednisolone may be administered intravenously at the same time intervals (in adults, 40 mg; in children, 0.5 mg/kg up to a maximum of 40 mg per dose).
Diphenhydramine, orally or parenterally given 1 hour before (in adults, 50 mg; in children, 1.25 mg/kg, up to 50 mg). Other antihistamines have not been studied in this setting.

Use of a different radiocontrast agent — To avoid a recurrent IHR:

The various types of RCM are most commonly categorised by osmolality current IHR

Categories of agents:

The various types of RCM are most commonly categorised by osmolality

High osmolar contrast material (HOCM) agents have osmolalities ≥1400 mosm/kg and
low osmolar contrast material (LOCM) agents have osmolalities between 500 and 900 mosm/kg.
The lowest osmolality agents are iso-osmolar agents, which are isotonic relative to serum

Low or iso-osmolar contrast agents — LOCM agents:

cause significantly fewer IHRs compared with HOCM, and nonionic LOCM agents are recommended for any patient with a previous IHR
In most centres, the use of nonionic LOCM agents for all intravascular procedures has become a widespread practice
For patients who developed IHRs to HOCM agents in the past, either a nonionic LOCM, an iso-osmolar agent (iodixanol), or a gadolinium-based agent should be used for future procedures, in combination with premedications.
For patients who experienced a hypersensitivity reaction to a nonionic LOCM in the past, we suggest either an iso-osmolar agent (iodixanol) or gadolinium-based agent, in combination with premedications

Gadolinium-based agents used in MRI — Gadolinium-based chelates

Are an alternative for patients with a range of adverse reactions to iodinated contrast agents
Caution should be used in administering gadolinium to patients with moderate to advanced renal failure due to the association with nephrogenic systemic fibrosis.

Radiographic contrast media nephrotoxicity related to intravenous contrast use:

a. Incidence

Third leading cause of inpatient AKI(Acute Kidney Injury)
Less than 2% and up to 50% of patients, depending on risk iii. Associated with a high (34%) in-hospital mortality rate

b. Pathogenesis

Direct tubular toxicity caused by reactive oxygen species
Also may cause renal ischemia (prerenal picture secondary to volume depletion) because of intrarenal hemodynamic alterations
- Most contrast agents are hyperosmolar (more than 900 mOsm/kg), which leads to osmotic diuresis and dehydration.
- Some contrast agents also cause systemic hypotension on injection and renal vasoconstriction.

c. Presentation

d. Risk factors for toxicity

Preexisting kidney disease (SCr more than 1.5 mg/dL or CrCl less than 60 mL/minute)
Diabetes mellitus
Volume depletion
Age older than 75 years v. Anemia
Conditions with decreased blood flow to the kidney (e.g., CHF)
Hypotension
Other nephrotoxins
Large doses of contrast (more than 140 mL) and hyperosmolar contrast agents

e. Prevention

Hydration. Intravenous isotonic saline is more effective than half-isotonic saline in preventing contrast-induced nephropathy. Begin 6–12 hours before the procedure. Maintain urine output greater than 150 mL/hour. The addition of sodium bicarbonate is widely used, but data are conflicting on efficacy.
Use an alternative imaging study, if possible.
Discontinue nephrotoxic agents. Avoid diuretics.
Use low-osmolar or iso-osmolar contrast agents in patients at risk (more expensive).
Medications used to prevent contrast-induced nephropathy:
- Acetylcysteine—Antioxidant and vasodilatory mechanism. Accumulating glutathione takes time, so it may not be as effective in emergencies. Various dosing recommendations. Widely used. Conflicting evidence. Considered safe.
- Ascorbic acid—Antioxidant. One large study showed benefits when used immediately before. Not confirmed. Give oral ascorbic acid 3 g before the procedure and 2 g twice/day for two doses after the procedure. It May have a role in emergency cases
- Theophylline—May reduce contrast-induced nephropathy
- Fenoldopam—Avoid, given the CONTRAST (Controlled Multicenter Trial Evaluating Fenoldopam Mesylate for the Prevention of Contrast-Induced Nephropathy) trial, which showed no benefit on contrast-induced nephropathy and an increased incidence of hypotension.
- Others

f. The Joint Commission standards on medication management regarding radiologic contrast media.

g. Nephrogenic systemic fibrosis (also known as nephrogenic fibrosing dermopathy)

Rare but associated with gadolinium-based agents used in high doses for magnetic resonance angiogram
Occurs in patients with moderate CKD to end-stage kidney disease (ESKD) given intravenous contrast, and systemic acidosis seems to be a risk factor (Magnevist, Omniscan, and OptiMARK considered inappropriate for use in patients with AKI or CKD)
Onset 2–18 days after exposure
Presents as burning, itching, swelling/hardening/tightening of the skin, skin patches, spots on the eyes, joint stiffness, and muscle weakness
Can cause organ damage, and deaths have occurred.

Approach for Emergent Procedures:

Methylprednisolone, 40 mg IV immediately and every four hours until completion of procedure and Diphenhydramine, 50 mg PO/IV/IM, one hour before RCM administration and Use of the lowest osmolal RCM agent available.