What are the clinical features and management strategies for preventing and treating contrast-induced nephropathy (CIN) in at-risk patients?

From the Guidelines

Contrast-induced nephropathy (CIN) should be prevented and managed through a combination of identifying high-risk patients, implementing prophylactic measures such as intravenous hydration with isotonic saline, minimizing contrast volume, and using iso-osmolar or low-osmolar contrast agents, as recommended by the most recent guidelines 1.

Clinical Features

CIN is characterized by acute kidney injury occurring within 48-72 hours after administration of iodinated contrast media, typically manifesting as an increase in serum creatinine by ≥0.5 mg/dL or ≥25% from baseline. Risk factors include pre-existing kidney disease, diabetes mellitus, advanced age, hypertension, heart failure, and dehydration.

Prevention Strategies

The most effective strategy for preventing CIN is intravenous hydration with isotonic saline (0.9% sodium chloride) at 1-1.5 mL/kg/hour for 6-12 hours before and after contrast exposure, as supported by recent guidelines 1. For urgent procedures, a bolus of 3 mL/kg/hour for 1 hour before contrast followed by 1-1.5 mL/kg/hour for 6 hours after is recommended. Minimizing contrast volume (keeping volume < 30 mL or < 3 mL/kg) and using iso-osmolar or low-osmolar contrast agents are also important.

Management of CIN

If CIN develops, management includes continued hydration, close monitoring of renal function and electrolytes, avoiding further nephrotoxic insults, and adjusting medication dosages for reduced kidney function. Dialysis is rarely needed but may be required in severe cases with significant fluid overload or electrolyte disturbances.

Role of N-Acetylcysteine and Sodium Bicarbonate

Recent studies have shown that N-acetylcysteine may not provide significant benefit in preventing CIN 1, and its use is not recommended as a standard prophylactic measure. Sodium bicarbonate is an alternative to saline hydration, but its effectiveness is still debated, and it is not recommended as a first-line treatment.

Key Recommendations

• Identify high-risk patients and implement prophylactic measures such as intravenous hydration with isotonic saline.
• Minimize contrast volume and use iso-osmolar or low-osmolar contrast agents.
• Temporarily discontinue nephrotoxic medications like NSAIDs, aminoglycosides, and metformin 48 hours before and after contrast exposure.
• Monitor renal function and electrolytes closely if CIN develops, and adjust medication dosages as needed.

From the FDA Drug Label

In patients at high risk for radiocontrast nephropathy, furosemide can lead to a higher incidence of deterioration in renal function after receiving radiocontrast compared to high-risk patients who received only intravenous hydration prior to receiving radiocontrast. The clinical features of contrast-induced nephropathy (CIN) include:

• Deterioration in renal function
• Increased risk of renal impairment
• Possible occurrence of lactic acidosis in patients with significant renal impairment Management strategies for preventing and treating CIN in at-risk patients include:
• Avoiding the use of furosemide in patients at high risk for radiocontrast nephropathy
• Using intravenous hydration prior to receiving radiocontrast
• Monitoring renal function closely in patients at risk for CIN
• Discontinuing metformin hydrochloride tablets at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/1.73 m^2 2 3

From the Research

Clinical Features of Contrast-Induced Nephropathy (CIN)

• Contrast-induced nephropathy is a common complication, particularly in high-risk patients, such as those with chronic kidney disease (CKD) and diabetes 4.
• The incidence of CIN does not appear to have changed appreciably in the last three decades, and it continues to be the third leading cause of hospital-acquired acute renal failure (ARF) 5.
• CIN is commonly defined as an increase in the baseline serum creatinine concentration of >25% or 0.5 mg/dl (44 micromol/l) 5.
• Patients who develop CIN after percutaneous coronary intervention sustain an increase in both short- and long-term mortality whether or not chronic kidney disease was present prior to contrast exposure 5.

Management Strategies for Preventing CIN

• The cornerstone of CIN prevention, in both the high and low risk patients, is adequate parenteral volume repletion 6.
• Hydration reduces (afferent) renovasoconstriction, the tubuloglomerular feedback, the tubulotoxic effects of contrast media (via dilution) and the oxygen radical formation 4.
• Use of the minimal necessary contrast media dose is recommended, as the nephrotoxic effect of contrast media is dose-dependent 7.
• The incidence of CIN has been shown to be lower when an iso-osmolar contrast media rather than a low-osmolar contrast media is used in patients with RI and diabetes 7.
• N-acetylcysteine is not consistently effective in reducing the risk for CIN, but due to low cost and low side effects, it is widely used 4, 8.

Identification of High-Risk Patients

• The commonly used methods for identifying patients at risk include use of patient questionnaires, review of medical history and measurement of serum creatinine levels prior to the administration of contrast media 7.
• Estimation of the glomerular filtration rate (GFR) before contrast media administration should be encouraged 7.
• Chronic kidney disease is the primary predisposing factor for CIN, and as estimated glomerular filtration rate <60 ml/1.73 m2 represents significant renal dysfunction and defines patients at high risk 6.

Treatment and Prognosis

• Treatment is limited to supportive measures while awaiting the resolution of the renal impairment 5.
• The diminished long-term survival in patients with CIN has been observed for both, those whose ARF is not severe enough to require dialysis as well as those requiring dialysis 5.
• Because of the lack of treatment options and because CIN is associated with serious short- and long-term sequelae, emphasis needs to be directed at preventative measures, identification of high-risk patients and education of all physicians involved in the care of these patients in order to reduce the incidence of CIN 5.