CONTRAST FAQs

WHAT ARE THE DIFFERENT TYPES OF CONTRAST?
Intravenous contrast for all imaging exams involving ionizaing radiation (CT, plain films, fluoroscopy, angiography) is iodine-based. IV contrast is used to opacify blood vessels. Depending on the phase of the study, contrast highlights the venous system or arterial system. Oral and rectal contrast is barium contrast, used to enhance the intraluminal gastrointestinal system. All MRI and MRA exams that use contrast use intravenous gadolinium-based contrast.

MY PATIENT HAS A CONTRAST ALLERGY. WHAT DO I DO?
Your patient has a documented allergy to IV iodinated contrast. Are there alternative imaging methods of obtaining an answer to your clinical question that does not involve using iodinated contrast (CT scan without contrast, US, MRI, nuclear medicine)? If a CT scan with IV contrast is warranted, your patient can be pre-medicated. Shellfish or iodine allergy is not a contraindication to the use of IV iodinated contrast and does not mandate a pretreatment regimen.

For non-emergent studies

Prednisone 50mg PO 13 hours prior
Prednisone 50mg PO 7 hrs prior
Prednisone 50mg PO + Benadryl 50mg PO/IM 1 hour prior

For emergent studies, administer the following meds and wait 15 minutes.

100 mg of Solumedrol I.V.
50 mg Benadryl I.V.

WHAT IS CONTRAST INDUCED NEPHROTOXICITY? HOW CAN IT BE PREVENTED?
Nephrotoxicity attributed to iodinated contrast agents occurs when there is a sudden change in renal status following administration of contrast media and no other etiology appears likely. The mechanism is believed to be twofold: direct tubular cell toxicity and renal vasoconstriction. The risk of contrast induced nephrotoxicity (CIN) is related to the degree of pre-existing renal disease and hydration. Clinically significant nephrotoxicity after administration of iodinated contrast media is highly unusual in patients with normal renal function. Risk factors for developing CIN include pre-existing renal insufficiency (serum creatinine level greater than or equal to 1.5 mg/dl), diabetes mellitus, dehydration, cardiovascular disease and the use of diuretics, advanced age (over 70), myeloma, hypertension, and hyperuricemia. Serum creatitine usually begins to rise within the first 24 hours, peaks within 96 hours, and usually returns to baseline within 7-10 days. The following measures can be performed to prevent CIN:

Hold metformin prior and 2 days after. Hold diuretics 1 day prior.

Cr 1.5 - 2.0, hydrate with IV NS; Mucomyst 1200 mg IV prior to CT or 600 mg PO BID before and after scan. Alternatively, give Bicarb 3ml/kg/hr 1 hour prior and 1ml/kg/hr 6 hours after (mix 3 amps in 1L of D5 water, bolus 500cc prior to CT, then 100cc/hr until it's gone).

Cr above 2.0, consider alternative study

CAN DIALYSIS BE USED TO TREAT CONTRAST INDUCED NEPHTROPATHY?
The best therapy for CIN is prevention, as outlined above. However, in those situations where prevention is difficult or in patients who are already on dialysis, can dialysis treat CIN? The role of dialysis for treatment of CIN is still controversial and is undergoing further research. There is no need for urgent dialysis in patients with ESRD. Dialysis immediately following administration of contrast is recommended for patients with renal insufficiency who require intermittent or occasional dialysis.

WHAT IS NEPHROGENIC SYSTEMIC FIBROSIS?
Nephrogenic systemic fibrosis or nephrogenic fibrosing dermopathy was first described in 1997. Until recently, gadolinium-based MR contrast agents were widely regarded as safe and non-nephrotixic, even in patients with impaired renal function. All available experience suggests that these agents remain generally very safe, but recently some patients with renal failure who have been exposed to gadolinium contrast agents have developed NSF, a syndrome that can be fatal. Further research is needed to determine the specific correlation between gadolinium-containing contrast agents, patient renal failure, and development of NSF. Until further information is available, patients with chronic kidney disease (estimated GFR <30 mL/min/1.73m2), or those who have had recent liver or kidney transplant or hepato-renal syndrome should not be administered gadolinium unless the benefits clearly outweigh the potential risks. For patients with ESRD who underwent gadolinium enhanced MR, immediate hemodialysis is recommended.