Contrast Media + Adverse Effects

Question 1

What is CIN? Who does it usually occur in?

Answer 1

Contrast induced nephropathy!

Acute renal failure within 24-72 hrs of exposure of a contrast agent that can’t be attributed to other causes

Usually occurs in patients with pre-existing renal impairment or DM

Question 2

How would you prevent CIN/adverse contrast reaction?

Answer 2

Thorough history (PMH of renal problems/DM, nephrotoxic DHx, allergy status/Hx of atopy)
Investigations: eGFR/U+Es BEFORE giving contrast (after giving contrast monitor eGFR for 5 days)
Discontinue nephrotoxic drugs if on them
Consider alternative Ix
Choose contrast agent at lowest dosage possible
Encourage oral or IV hydration (if old likely dehydrated –> falls)
In high risk pts: give N-acetyl cysteine
If reaction occurs stop contrast medium immediately

Question 3

What might iodine contrast cause in pts? Who should it be avoided in possibly?

Answer 3

Both hypo and hyperthyroidism

Avoid in these groups

Question 4

What can iodine contrast be used for?

Answer 4

IV: CTPA, CT head (SOL), angiography (coronary), IVP,

Other: hysterosalpingogram, cholangiogram, sialogram, micturating cystourethrogram

Oral: CT abdo if barium contraindicated (why? Because iodine water soluble and barium isn’t and can’t be used if fistula or bowel obstruction)

Question 5

Who is most at risk of toxic effects of contrast (iodine)?

Answer 5

Cardiac impairment
Renal impairment
DM
Hx of atop your (asthma eczema hay fever)

Question 6

What are the disadvantages of barium enema?

Answer 6

• adequate bowel prep is needed
• CT contraindicated few days after (dense)
• increased radiation dose
• risk of chemical peritonitis or pneumonitis –> therefore CI in pts with fistula or bowel obstruction (perforation) –> use iodine contrast instead

Question 7

What are iodine based contrasts associated with?

What are gadolinium based contrasts associated with?

Answer 7

Iodine –> CIN(contrast induced nephropathy)

Gadolinium –NSF (nephrogenic systemic fibrosis)

Question 8

What type of MRI is gadolinium used it?

Answer 8

It enhances T1 weighted MRI

Question 9

What is the gold standard for PE Ix? What can be used instead if contraindicated?

Answer 9

CTPA (using iodine contrast)

V/Q scan (ventilation perfusion scintigraphy) using technetium 99 if pregnant

Question 10

If someone is at high risk of NSF but requires gadolinium MRI, what should you do?

Answer 10

High risk if eGFR <30

If absolutely necessary give them lowest dose possible of gadolinium and use haemodialysis after

Question 11

What adverse effects are associated with iodine agent?

Answer 11

1. hypersensitivity/allergic reaction
2. nephrotoxic (DM, renal, one kidney)
3. hypo/hyperthyroid
4. N+V
5. CIN

Question 12

Who is at risk of the adverse effects of iodine?

Answer 12

1. Atopy
2. DM
3. decreased renal function
4. cardiac impairment (look for in Hx)

Question 13

What are the problems with barium salts?

Answer 13

CT contraindicated few days after (dense)
adequate bowel prep needed
^^ radiation dose
^ risk chemical peritonitis or pneumonitis (therefore use water soluble iodine)