Contrast radiology

There are 3 main risks associated with using contrast:

1) Allergic reactions
  • Reactions occur in 0.15% of cases.  These are classified as 'severe' in just 0.04% of cases.
  • Allergic reactions are 6 to 10 times more common in asthmatics; non ionic low or iso-osmolar agents should be used for these patients.

2) Contrast nephropathy
  • This is defined as an impairment in renal function (an increase in serum creatinine by more than 25% or 44micromol/l) within 3 days of administration of IV contrast in the absence of an alternative aetiology
  • Risk of contrast nephropathy is increased in patients with:
    • eGFR <60
    • dehydration
    • CCF
    • gout
    • age >70
    • concurrent use of nephrotoxic drugs, eg NSAIDs or gentamycin
  • The risk of contrast nephropathy can be reduced by:
    • using the smallest possible dose of contrast
    • ensuring the patient is well hydrated before and after the procedure either orally or, if the contrast is to be given arterially or at high dose, by IV fluids
    • there is currently insufficient evidence to support the use of n-acetyl cysteine in prevention of contrast-induced nephropathy
  • There is no need for metformin to be stopped routinely for contrast investigations as long as the eGFR is >60.  If it is below this level, stopping for 48 hrs before and after the investigation should be considered.

3) Extravasation
  • Conservative management is sufficient in most cases - elevate limb and apply ice packs.
  • Plastic surgeon input may occassionally be required.

Other points:
  • Contrast can be used in breastfeeding mums with no special precautions.
  • Contrast cannot be used in patients who are hyperthyroid.
  • There is a specific risk of a delayed skin rash if contrast is given to patients on interleukin-2 therapy.

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Secret collector of interesting anonymised ECGs. Fan of the Bath Photomarathon. Lover of cream teas. [Sarah Hudson] (Your Picture)