Current Clinical Concerns in CT: Results : IV Contrast Administration

Administering IV contrast in the setting of renal insufficiency

1. At what level of serum creatinine do you become anxious enough to withhold IV contrast (unless it is essential of course).

2. Do you consult the patient's referring physician if the creatinine is above a certain level? I'm assuming you use Visipaque for borderline or elevated serum Creatinine.

3. In patients with renal dysfunction:
i. Do you check creatinine or creatinine clearance?

ii. Do you hydrate?

iii. Do you stop ACE inhibitors or ARB?

4. Up to what level creatinine do you use Visipaque? [Two individuals asked this question].

5. Our vascular surgeon has requested that we do CT angio on patients with elevated creatinine (2.0 - 3.0). These patients are mainly being followed for endograft evaluation in patients with AAA's. What is your current protocol regarding such patients? I assume all patients get Visipaque.
i. Do you hydrate the patients before or after?

ii. Do you use a reduced dose of Visipaque?

iii. Do you get a follow up BUN/creatinine?

iv. Do you use mucomyst (N-Acetyl Cystein) at all?

References
Michael A. Bettmann Frequently Asked Questions: Iodinated Contrast Agents
RadioGraphics 2004; 24: 3-10.

• Summary: Many of the questions presented here are addressed in this recently published Radiographics article, which serves as an excellent reference.

Aspelin P, Aubry P, Fransson S-G et al. Nephrotoxic effects in high-risk patients underging angiography. NEJM 2003; 348(6): 491-9.

• Summary: This study involved 129 diabetic patients with serum creatinine levels of 1.5 to 3.5 mg per deciliter who were randomized to receive low-osmolar, nonionic monomeric iohexol or iso-osmolar, nonionic, dimeric iodixanol during coronary or aortofemoral angiography. The creatinine was measured for 3 days following the procedure, and compared to baseline. Results showed a significantly lower mean peak increase in creatinine from day 0 to 3 in the iodixanol group, The mean change in the creatinine concentration from day 0 to day 7 was significantly lower in the iodixanol group as well. A higher incidence of adverse events was noted in the iohexol group, including serious events related to contrast medium.

Letters to the Editor: Nephropathy induced by contrast medium NEJM 2003; 348; 22: 2257-2259.

• Summary: The following are comments with respect to the study by Aspelin et al, referenced above, in the form of letters to the editor in the NEJM.
  -More than twice as many patients in the iohexol group had proteinuria compared to the iodixanol group.
  -The patients' renal function in both groups was not considered severely impaired.
  -The measurement of serum creatinine level as the outcome variable does not equate with "clinically important adverse effects."
  -The duration of diabetes was different for the 2 groups.

Chalmners N, Jackson RW. Comparison of iodixanol and iohexol in renal
impairment.  British Journal of Radiology  1999; 72: 701-703.

• Summary:In this prospective, randomized study, patients were administered
  isosmolar iodixanol (nonionic dimer) to a nonionic monomer (iohexol).  
  Fifty-four patients with a median baseline creatinine of 269.5 were
  given a mean dose of 60 mL of iodixanol. Forty eight patients with a
  median baseline creatinine of 295 were given a mean dose of 52.5 mL of
  iohexol.  Creatinine levels were measured subsequent to angiography. In
  the iohexol group, 31% of patients had a creatinine increase of greater
  than 10%, and 10% of patients had a craetinine rise of more than 25%.  
  For comparison to 15% of the iodixanol group had a creatinine increase
  of more than 10%, and 3.7% had an increase in creatinine of more than
  25%.  The incidence of creatinine increase greater than 10% was
  statistically lower  with iodixanol. In either group, the increase in
  creatinine correlated with the dose of contrast. The authors conclude
  that nephrotoxicity may be slightly lower with iodixanol compared to
  iohexol.

Carraro M. Malalan F. Antonione R. Stacul F. Cova M. Petz S. Assante M.
Grynne B. Haider T. Palma LD. Faccini L. Effects of a dimeric vs a
monomeric nonionic contrast medium on renal function in patients with
mild to moderate renal insufficiency: a double-blind, randomized
clinical trial. European Radiology. 1998; 8(1):144-7.

• Summary: In this study of patients undergoing IV urography, patients
  with mild to moderate renal insufficiency were imaged with either
  iodixanol (nonionic dimer) or iopromide (nonionic monomer). The dose
  was 148 +/- 21.3 mL for iodixanol 320 mgI/mL and 153+/- 24 mL for
  iopromide 300 mgI/mL. The serum creatinine, urinary enzymes
  alanylaminopeptidase and N-acetyl-B-glucosaminidase, as well as urinary
  alpha-1-microglobulin and albumin levels were evaluated prior to the
  study and at 1h, 6h, 24h, 48h and 7 days following. Comparison showed
  no significant difference in urinary enzymes or serum creatinine. One
  patient who received iodixanol developed transient contrast induced
  nephropathy. The authors concluded that both agents had
  a low nephrotoxic potential in patients with mildly to moderately
  impaired renal function.