RCIS Cardiac Catheterization Techniques and Contrast Media 1 — Questions and Answers
Question 1: Which contrast agent property is most responsible for contrast-induced nephropathy (CIN)?
- High osmolality and viscosity causing renal tubular injury and vasoconstriction (Correct answer)
- Iodine content causing allergic nephritis
- Gadolinium chelation affecting tubular cells
- Low molecular weight causing rapid glomerular filtration
Correct answer: High osmolality and viscosity causing renal tubular injury and vasoconstriction
High osmolality contrast agents cause renal tubular toxicity and medullary vasoconstriction, which are the primary mechanisms of contrast-induced nephropathy.
Question 2: What is the standard pre-medication protocol for a patient with a prior contrast allergy undergoing elective catheterization?
- Antihistamine alone 1 hour before procedure
- Prednisone at 13, 7, and 1 hour before plus diphenhydramine 1 hour before (Correct answer)
- Pre-loaded epinephrine syringe only
- No premedication needed if prior reaction was mild urticaria
Correct answer: Prednisone at 13, 7, and 1 hour before plus diphenhydramine 1 hour before
The standard contrast allergy premedication protocol uses oral corticosteroids at 13, 7, and 1 hour before the procedure plus diphenhydramine 1 hour prior.
Question 3: The Cigarroa formula for maximum safe contrast dose is calculated as:
- 1 mL per kg body weight
- 3 mL/kg up to 300 mL total
- 5 cc × body weight (kg) ÷ serum creatinine (Correct answer)
- 2 mL/kg regardless of renal function
Correct answer: 5 cc × body weight (kg) ÷ serum creatinine
The Cigarroa formula (5 × body weight in kg ÷ serum creatinine) calculates the maximum safe contrast dose to reduce CIN risk based on individual renal function.
Question 4: Iso-osmolar contrast agents such as iodixanol differ from low-osmolar agents primarily by:
- Lower iodine concentration per mL
- Having osmolality equal to blood (~290 mOsm/kg), reducing osmotic stress on vessels and tubules (Correct answer)
- Not requiring renal excretion for elimination
- Being gadolinium-based rather than iodine-based
Correct answer: Having osmolality equal to blood (~290 mOsm/kg), reducing osmotic stress on vessels and tubules
Iso-osmolar contrast agents have an osmolality matching blood (~290 mOsm/kg), which minimizes osmotic-induced endothelial and renal tubular cell damage.
Question 5: A patient develops urticaria and bronchospasm during contrast injection — what is the first-line treatment?
- IV diphenhydramine and observation
- Epinephrine 0.3–0.5 mg IM or IV (Correct answer)
- IV corticosteroids
- Discontinue contrast and monitor vital signs
Correct answer: Epinephrine 0.3–0.5 mg IM or IV
Epinephrine is the first-line treatment for anaphylaxis or severe contrast reactions with bronchospasm, acting on alpha and beta receptors to reverse life-threatening symptoms.
Question 6: The primary mechanism by which IV hydration prevents contrast nephropathy is:
- Diluting contrast concentration in the tubules
- Increasing urine output to flush contrast through the kidneys, reducing tubular exposure time (Correct answer)
- Alkalinizing the urine to neutralize iodine toxicity
- Reducing the osmolality of the delivered contrast agent
Correct answer: Increasing urine output to flush contrast through the kidneys, reducing tubular exposure time
IV hydration increases renal blood flow and urine output, which dilutes contrast and accelerates its excretion, reducing tubular exposure time and osmotic injury.
RCIS Cardiac Catheterization Techniques and Contrast Media 1
Which contrast agent property is most responsible for contrast-induced nephropathy (CIN)?