This document discusses adverse reactions to iodinated contrast media used in medical imaging. It notes that while anaphylactic reactions are rare, occurring in 0.6% of cases, almost all life-threatening reactions happen within 20 minutes of intravenous injection. Non-ionic low-osmolar contrast agents carry a lower risk than older varieties. Risk factors include a history of previous reaction, allergies, hyperthyroidism, and anxiety. Prophylaxis with corticosteroids may help reduce risks. Reactions are classified as mild, moderate, severe or delayed based on symptoms and timing. Treatment involves oxygen, bronchodilators, epinephrine and corticosteroids depending on severity of symptoms.

1. IODINATED CONTRAST MEDIA
ADVERSE REACTIONS
ARYA PRASAD
PG RESIDENT

2.  Referred to as contrast allergies (erroneously)----- are an
uncommon group of symptoms and signs, with different
degrees of severity, that may occur after the administration of
these drugs
 Anaphylactic-type reactions to iodinated contrast agents are
rare, accounting for 0.6% of cases with only 0.04% considered
aggressive.

3.  Almost all contrast reactions that are life-threatening occur
within 20 min of intravenous injection.
 Now iodinated contrast media have evolved and become
progressively safer.
 It is well established that non-ionic low-osmolar contrast
agents, are safer than older high-osmolar or ionic contrast
media.

4.  The majority of the reactions are not immune-mediated, and
therefore not true allergic reactions
 Hence contrast media hypersensitivity reactions is a better
term.

5. Route of administration
 M/c seen after the intravascular (intra-arterial/intravenous)
administration of contrast agents.
 Other routes used to give contrast agents may also rarely result in
hypersensitivity
 This has been reported following exposure during most
fluoroscopic procedures, including enemas, hysterosalpingography,
sialography, arthrograms and renal tract studies

6. Risk factors
 history of a previous reaction to iodinated contrast media
 details of the previous reaction should be obtained and
alternatives(e.g. non-contrasted study, ultrasound, MRI) may be
considered
 nearly 200x increased risk

7. Risk factors
 Hyperthyroidism: ~3.5x increased risk
 family history of hypersensitivity reaction to iodinated
contrast media: ~14x increased risk

8. Risk factors
 Family history of hypersensitivity reaction to iodinated
contrast media: ~14x increased risk
 Anxiety -- studies have shown patients with high anxiety
have a somewhat elevated risk of 'non-vagal' adverse
reactions

9.  allergic diseases including asthma
 not a contraindication, although these patients have 6-10x
more risk of developing severe contrast reactions
 remember that the risk of severe reactions is small (0.04% to
0.0004% of the patients receiving a non-ionic and low-
osmolality iodinated contrast)

10.  previous history of multiple allergies
 it is not a contraindication - a more detailed history should be
obtained
 keep in mind that shellfish allergy and skin irritation/"allergy"
to topical iodine antiseptic is not associated with an increased
risk of contrast reactions

11. Prophylaxis
 Prophylaxis with antihistamines and change of the iodinated
contrast material used can both reduce the occurrence of a
recurrent hypersensitivity reaction
 A typical premedication regimen for adults includes
prednisolone 50 mg orally 13 hours prior and again 1 hour
prior.

12. Prophylaxis
 Oral corticosteroid therapy should begin at least 6 hours prior
to administration of contrast media.
 Oral non-sedating antihistamines may also be added in
addition to the corticosteroid regimen

13.  Local departmental protocols should be adhered to.
 While premedication with corticosteroids, with or without
antihistamines, has been shown to reduce the occurrence and
severity of anaphylaxis, there is a lack of evidence that it
reduces the risk of death following breakthrough anaphylactic
reaction

14. Acute contrast reaction
 Corresponds to reactions within 60 minutes after the
intravenous administration of the contrast media, which do
not involve antibodies, and are not dose-dependent
 They are referred to as idiosyncratic or "pseudoallergic"
reactions and maybe subdivided by severity with small
regional differences noted.

15.  mild
 self-limiting manifestations that usually resolve without any
specific treatment, e.g. nausea, vomiting, flushing, pruritus,
mild urticaria, and headache
 occur in ~3% of patients receiving a non-ionic and low-
osmolality iodinated contrast
 treatment: supportive measures are enough

16. moderate:
 symptoms that are more prominent and demand medical
attention with specific treatment, e.g. marked urticaria, severe
vomiting, bronchospasm, facial edema, laryngeal edema, and
vasovagal attacks.

17. TREATMENT:
 urticaria: the use of antihistamines or intramuscular
epinephrine is advised in some situations.

18. TREATMENT:
 bronchospasm:
oxygen should be offered by mask (6-10 liters/min),
beta-2-agonists (e.g. terbutaline, albuterol) metered-dose
inhaler (2-3 deep inhalations),
intramuscular epinephrine should be considered if decreased
blood pressure

19. severe
 Reactions that usually represent a progression of the
moderate symptoms and are life-threatening, e.g.
respiratory arrest, cardiac arrest, pulmonary edema,
convulsions, and cardiogenic shock

20. severe
 Estimated to occur in 0.04% to 0.0004% of the patients
receiving a non-ionic and low-osmolality iodinated contrast
 The risk of death is rare, estimated 1:170,000

21. Current RANZCR guidelines for severe reactions
recommend:
 supine positioning
 airway protection if required and high flow oxygen
 IM epinephrine 1:1000 0.5 mL in thigh

22. Current RANZCR guidelines for severe reactions
recommend:
 smaller doses if pediatric or <25 kg (see local guidelines)
 additional measures include albuterol nebulisers,
corticosteroids, and nebulised epinephrine as guided by
symptoms

23. Delayed contrast reaction
 Those reactions happening between one hour to one week
after the contrast administration.
 They are commonly non-severe skin manifestations such as a
maculopapular rash.
 Angioedema, erythema, and urticaria are also reported less
frequently. Iodide mumps has also been rarely reported.