• Contrast agents are required in the cardiac catheterization procedures.
• Can cause fatal allergic reactions.
• It is important to know the history of any previous contrast exposure and allergy..
• “Iodine” gives it “radioopaque” and causes allergy too.
• Patients with seafood allergy as some “shellfish” have iodine are prone for adverse reactions.
Ideal Contrast Media in Angiography:-
• Water soluble
• Chemical and heat stable
• Biologically inert (no antigen)
• Low viscosity
• Low or Iso-osmolar,
• excreted Selectively through the kidneys
Mechanism of action of Contrast Media:-
• Iodine has atomic number, increases the attenuation by increasing the linear coefficient of radiation.
Classification:-2 major classes
Ionic - Dissociate into ionic particle in solution and Non-ionic - do not dissociate
High osmolar Ionic = Diatrizoate (Hypaque)
Low osmolar Ionic = Ioxaglate
Low osmolar Non Ionic = Iohexol (omnipaque)
Iso osmolar Non Ionic= Iodixanol ( visipaque)
All agents are derivatives of “Benzoic acid”,only number of iodine molecules , ionic and osmolar composition vary.
Low osmolar, non ionic are safer, produce less side effects.
Volume of CM :-
Ionics = 2-3ml/kg
Non-ionics = 5ml/kg
Also calculated as = 5.weight / Sr Creatinine (mg/dl)
1. Nausea vomiting
2. Flushing (due to vasodilatation)
3. Pain and burning sensation at the site of injection.
5. Urine output –may increase due to hypertonicity diuresis occur initially it increases circulatory
blood volume by osmotically shifting fluid into vascular space.
Classification of contrast- induced anaphylactoid reactions :-
Minor - urticaria(limited)/pruritus /erythema
Moderate – urticaria (diffuse)/ angioedema /lanyxngeal edema/bronchospasm
Severe - cardiovascular shock/ respiratory arrest /cardiac arrest.
Different diagnosis for severe reactions :-
1. Vasovagal reaction, 1. Hypovolumia
2. Cardiogenic shock 2. Dehydration
3. RV infection 3. Blood loss
4. Cardiac tamponade 4. Sepsis
5. Cardiac rupture 5.Drug related-Narcotics, benzodiazepines,protamine
Ionic contrast agents produce hypotension by-
-Transient myocardial dysfunction
-Decreasing circulating volume after osmotic diuresis .
Indications for low osmolar non-ionic agents –
Unstable ischaemic syndrome
H/O contrast allergy
Severe valvular heart disease ( severe AS)
IMA and peripheral vascular injections
Anticipated use of large volume of contrast agents
EF < 30>
Both ionic and nonionic agents are Anticoagulant & Antiplatelet.
Trans placental / milk passage can cause iodine mumps or hypothyroidism in child.