IV Contrast – FAQs
See below for answers to some of the most frequently asked questions about iodinated contrast media.
Recommendations for Patients Taking Metformin? However, the ACR Committee on Drugs and Contrast Media recommends that patients taking metformin can be classified into one of the following categories based on renal function: Category I “In patients with no evidence of AKI and with eGFR ≥30 mL / min/1.73m2, there is no need to discontinue metformin either prior to or following the intravenous administration of iodinated contrast media, nor is there an obligatory need to reassess the patient’s renal function following the test or procedure.” “The ACR Committee on Drugs and Contrast Media recognizes that the U.S. Food and Drug Administration (FDA) guidelines for metformin advise that for patients in whom an intravascular contrast study with iodinated materials is planned, metformin should be temporarily discontinued at the time of or before the study, and withheld for 48 hours after the procedure and reinstituted only after renal function has been re-evaluated and found to be normal. However, the committee concurs with the prevailing weight of clinical evidence on this matter that deems such measures unnecessary in some situations.” Category II “In patients taking metformin who are known to have acute kidney injury or severe chronic kidney disease (stage IV or stage V; i.e., eGFR< 30), or are undergoing arterial catheter studies that might result in emboli (atheromatous or other) to the renal arteries, metformin should be temporarily discontinued at the time of or prior to the procedure, and withheld for 48 hours subsequent to the procedure and reinstituted only after renal function has been re-evaluated and found to be normal.” Metformin is a biguanide oral antihyperglycemic agent used to treat patients with non-insulin-dependent diabetes mellitius. Metformin is contraindicated in patients that have compromised renal function. Patients with compromised renal function will have elevated serum levels of metformin and are at risk of developing lactic acidosis. Lactic acidosis can be fatal in about 50% of cases, but this condition only occurs at a rate of 0-0.084 cases per 1,000 patient years. Because iodinated contrast agents are associated with nephrotoxicity, acute renal failure or a reduction in renal function caused by iodinated contrast media could potentially cause an accumulation of metformin and resultant lactate accumulation, hence the above recommendations for withholding metformin use for 48 hours following contrast administration. References Recommendations for Breast Feeding Patients? However, the ACR recommends that “If the mother remains concerned about any potential ill effects to the infant, she may abstain from breast-feeding from the time of contrast administration for a period of 12 to 24 hours. There is no value to stop breast feeding beyond 24 hours. The mother should be told to express and discard breast milk from both breasts during that period. In anticipation of this, she may wish to use a breast pump to obtain milk before the contrast-enhanced study to feed the infant during the 24-hour period following the examination.” If an iodinated contrast agent is administered to a breast-feeding patient, studies have shown that less than than 1% of the administered maternal dose of contrast medium is excreted into breast milk in the first 24 hours, and less than 1% of the contrast medium in breast milk ingested by an infant is absorbed from the gastrointestinal tract. “Therefore, the expected systemic dose absorbed by the infant from the breast milk is less than 0.01% of the intravascular dose given to the mother. This amount represents less than 1% of the recommended dose for an infant being prescribed iodinated contrast material related to an imaging study.” There is no reported evidence of the theoretical risks of contrast agent-induced toxicity and allergic sensitization or reaction in newborns, but there is also little information regarding the safety of these agents in this population. It is also unclear as to what effects, if any, the iodine in contrast agents may have on fetal thyroid function. Both iodinated and gadolinium-based intravenous contrast media have plasma half-lives of approximately 2 hours and are therefore nearly completely cleared from the bloodstream within 24 hours, hence the above recommendations. References The ACR states that “Paraproteinemias, particularly multiple myeloma, are known to predispose patients to irreversible renal failure after high-osmolality contrast media (HOCM) administration due to tubular protein precipitation and aggregation; however, there is no data predicting risk with the use of low-osmolality or iso-osmolality agents.” In addition, the ACR suggests oral or IV hydration for 6-12 hours prior to receiving contrast, and also for at least 6-12 hours after. *The 2008 Version 6 of the ACR Manual on Contrast Media listed an example hydration protocol for patients with multiple myeloma “beginning 6 to 12 hours before contrast medium use and continuing for at least 6 to 12 hours after,” but subsequent versions of the Manual omitted this recommendation. References Recommendations for Patients with a Renal Transplant or Single Kidney? Reference References A study by Bessell-Browne and O’Malley concluded that “IV administration of nonionic contrast material for CT is a safe practice for patients with pheochromocytoma and related tumors even without α-blocking medication.” The ACR also states that for patients with pheochomocytomas and paragangliomas “There are scant data to support the need for specific precautions in these patients when low osmolar contrast media is used,” but does recommend avoiding direct injection of contrast medium into the adrenal or renal artery. References Additional References
Recommendations for Patients with Multiple Myeloma?
Multiple myeloma was once thought to be a significant risk factor for developing contrast nephropathy. However, the incidence of contrast nephropathy in myeloma patients is only 0.6-1.25% compared to the risk of 0.15% in the general public. Furthermore, the risk has subsequently been shown not to be related to myeloma itself, but rather to the presence of associated dehydration, hypercalcemia, infection and Bence Jones proteinuria. Hypercalcemic patients experience emesis and nephrogenic diabetes insipidus, both causing dehydration and cast formation, and these patients also suffer from direct toxic effects of elevated calcium (nephrocalcinosis). Infection causes dehydration and may involve the use of nephrotoxic antibiotics. Bence Jones proteinuria leads to precipitation of protein casts in dehydrated patients causing acute renal failure. Bence Jones proteins can also have a more chronic toxic effect on tubular cells. Older contrast agents were noted to form precipitates with Bence Jones protein in vivo, but this is not seen with modern agents. These conditions are all risk factors for acute renal failure in multiple myeloma patients that exist in the absence of contast media.
Recommendations for Patients with Sickle Cell Disease?
Recommendations for Patients with Known or Suspected Pheochromocytoma?