Prevention and management of contrast-associated acute kidney injury: CAR Guideline

Risk Stratification

These screening guidelines focus on balancing risks (risk of CA-AKI, patient delays, and healthcare costs) as well as significant benefits of timely contrast-enhanced diagnostic imaging.

• For stable outpatients without a current (3- 6 months depending on institutional preference) eGFR on file, and those without a provided history of CKD on the requisition, the authors recommend a simple screening questionnaire to detect those who may have AKI or severe CKD.
• A current eGFR (within 7 days for inpatients, or upon presentation for ER patients) is recommended, however this should not delay emergent imaging examination.
• or non-emergent presentation of stable outpatients, inpatients, and emergency patients when eGFR is available.

Choice of contrast

• The authors do not recommend preferential use of iso-osmolar ICM for reducing risk of CA-AKI; those decisions should be made based on other factors (e.g., cost and availability).
• The authors discourage reduced dosing of IV contrast administration for CT examinations since that lowers parenchymal enhancement and recommend using the appropriate IV dose for high quality CT imaging in all patients.
• A pragmatic approach to ICM dosing for IA interventions using the necessary dose is recommended to achieve the diagnostic and therapeutic results but judiciously reducing dose when adjunctive imaging and doses are low yield or can be delayed.
• The authors do not recommend restricting repeat contrast doses in lower risk patients (eGFR >30, no AKI, IV route) or withholding repeat doses for emergency or inpatients who have life-threatening, or acute presentation of illness. The authors do recommend avoiding repeated contrast exposures within 48 hours for elective procedures if the patients at higher risk of CA-AKI (eGFR ≤30, AKI, intraarterial ICM administration). However, in the face of life-threatening illness, repeat dosing of ICM may be necessary and justified to establish a confident diagnosis and treatment plan.

Prophylaxis of CA-AKI

• The authors do not recommend oral or intravenous hydration for patients with eGFR >30 mL/min/1.73m2, receiving intravenous or intra-arterial ICM.
• or patients with eGFR ≤30 mL/min/1.73m2, receiving intravenous ICM, there is a lack of evidence on the benefit of volume expansion. Hence the working group makes no recommendation in this regard; institutions may choose practices best suited to their local environments.
• or patients with eGFR ≤30 mL/min/1.73m2, receiving intra-arterial ICM, some members of the working group endorsed a strategy of hydration and volume expansion using either intravenous hydration (with .9% saline or 1.26% sodium bicarbonate) or oral salt and water. Since there is insufficient evidence in this patient group the working group felt the use of hydration or not, and the route of hydration was best left to the judgment of the practitioner.
• The authors do not recommend the preferential use of iso-osmolar ICM for reducing the risk of CA-AKI. We recommend decisions about low-osmolar or iso-osmolar ICM be made based on other factors (e.g., cost and availability).
• The authors do not recommend any form of post-ICM administration renal replacement therapy, either dialysis or continuous renal replacement therapy for reduction of the risk of CA-AKI.
• The authors do not recommend N-acetylcysteine use for the prophylaxis of CA-AKI.
• The authors do not recommend initiating statins specifically for the prevention of CA-AKI.
• The authors do not recommend use of other pharmacological agents which have been described in the literature, including theophylline, prostaglandin E1, nicorandil, ascorbic acid, allopurinol, alpha-tocopherol, fenoldopam, natriuretic peptides, and trimetazidine.

Medication considerations

• The authors do not recommend stopping metformin before contrast injection, and/or re-testing kidney function afterwards, for patients with eGFR >30 mL/min/1.73 m2.
• The authors recommend that in patients with eGFR ≤30 mL/min/1.73m2 or AKI, metformin should be held at the time of, or prior to, ICM administration. Metformin should not be restarted for at least 48 hours and only then if kidney function remains stable (<25% increase compared with baseline creatinine) and the ongoing use of metformin has been re-assessed by the patient's clinical team.
• The authors do not recommend routinely discontinuing renin-angiotensin system inhibitors (ACEi and ARBs) prior to, or after, ICM administration.
• Routinely discontinuing diuretics prior to, or after, ICM administration is not recommended.

Post ACM administration statements

• The authors recommend a follow-up serum creatinine measurement 48 to 72 hours after intra-arterial ICM injection in all patients with eGFR ≤30 mL/min/1.73m2. For the remainder of the patients, the risk of AKI is extremely low, and routine testing is not warranted. However, any at-risk patient should be instructed to seek medical attention and kidney function testing if they develop increased shortness of breath, peripheral edema, or note a marked decline in urine output in the days following the imaging test.
• The authors recommend that clinical evaluation and management of AKI due to CA-AKI be undertaken according to the Kidney Disease Improving Global Outcomes (KDIGO) clinical practice guidelines for AKI and taking into account the Canadian Society of Nephrology (CSN) commentary on those guidelines.