What are the best strategies to prevent contrast‑induced nephropathy in an adult undergoing contrast‑enhanced imaging who has reduced estimated glomerular filtration rate, diabetes mellitus, volume depletion, congestive heart failure, or is taking nephrotoxic medications?

Prevention of Contrast-Induced Nephropathy in High-Risk Adults

Intravenous isotonic saline (0.9% NaCl) at 1.0–1.5 mL/kg/hour starting 3–12 hours before and continuing 6–24 hours after contrast exposure is the single most effective preventive strategy, combined with minimizing contrast volume to <350 mL or <4 mL/kg and using low-osmolar or iso-osmolar agents. 1

Risk Stratification Before Contrast Administration

Identify High-Risk Patients

• Measure eGFR within 4 weeks before contrast in all patients who are >60 years old, have diabetes mellitus, chronic kidney disease, heart failure, hypertension requiring treatment, or are taking metformin. 2
• Pre-existing renal impairment (eGFR <60 mL/min/1.73 m²) is the principal risk factor for contrast-induced nephropathy (CIN). 1
• Diabetes mellitus combined with renal impairment markedly increases risk, with CIN rates of 20–50% in this population. 3
• Congestive heart failure (NYHA class III/IV or history of pulmonary edema) is a major independent risk factor. 1
• Volume depletion significantly elevates CIN risk. 4
• Use the Mehran risk score to quantify CIN probability: patients scoring >16 have a 57.3% CIN risk and 21.6% dialysis risk. 3, 1

Calculate Risk Score Components

• Award points for: hypotension (5), intra-aortic balloon pump (5), chronic heart failure (5), age >75 years (4), anemia (3), diabetes (3), serum creatinine >1.5 mg/dL (4), eGFR 40–60 mL/min (2), eGFR 20–40 mL/min (4), eGFR <20 mL/min (6), and 1 point per 100 mL contrast volume. 3

Mandatory Pre-Procedure Interventions

Discontinue Nephrotoxic Medications

• Stop NSAIDs, aminoglycosides, and amphotericin B at least 24–48 hours before the procedure. 3, 1, 5
• Temporarily hold ACE inhibitors, ARBs, and diuretics in patients with eGFR <60 mL/min/1.73 m² who have serious intercurrent illness. 1

Metformin Management Protocol

• For patients with eGFR 30–60 mL/min/1.73 m²: Stop metformin at the time of contrast exposure, hold for 48 hours, and restart only after confirming stable renal function at 48-hour reassessment. 2
• For patients with eGFR >60 mL/min/1.73 m² and low risk (no diabetes with renal disease, heart failure, liver disease, alcoholism, or intra-arterial contrast): Stop metformin at the time of contrast and hold for 48 hours; may restart without mandatory renal reassessment. 2
• For patients with eGFR <30 mL/min/1.73 m²: Metformin is contraindicated; discontinue before the procedure. 2
• Arrange alternative glucose-lowering therapy during the 48-hour hold to prevent hyperglycemia. 2

Hydration Protocol (Class I Recommendation)

• Administer intravenous 0.9% NaCl at 1.0–1.5 mL/kg/hour beginning 3–12 hours before contrast and continuing 6–24 hours after the procedure. 3, 1
• In patients with left-ventricular ejection fraction <35% or NYHA class >II, reduce the infusion rate to 0.5 mL/kg/hour to avoid volume overload. 1
• Intravenous hydration is superior to oral hydration for high-risk patients. 1
• Do not use oral fluids alone in patients at increased risk of CIN. 3

Alternative Hydration: Sodium Bicarbonate

• Isotonic sodium bicarbonate (154 mEq/L in dextrose-water) at 3 mL/kg over 1 hour before contrast, followed by 1 mL/kg/hour for 6 hours after, may be used as an alternative to saline. 3, 1
• However, evidence is mixed: some guidelines classify bicarbonate as Class IIa (reasonable) while others rate it Class III (not indicated). 1
• Saline remains the default choice because bicarbonate requires manual preparation with risk of compounding errors and hypertonic administration, whereas premixed saline is immediately available. 3

Contrast Selection and Volume Minimization (Class I)

Choose Appropriate Contrast Agent

• Use only low-osmolar or iso-osmolar contrast media; avoid high-osmolar agents. 3, 1, 6
• In the highest-risk patients (eGFR <30 mL/min/1.73 m²), prefer iso-osmolar media. 1
• The incidence of CIN is lower with iso-osmolar contrast (iodixanol/Visipaque) compared to low-osmolar iohexol in patients with renal insufficiency and diabetes. 3

Minimize Contrast Dose

• Limit total contrast volume to <350 mL or <4 mL/kg. 1
• Keep the contrast-volume/eGFR ratio <3.4. 1
• In patients with eGFR <30 mL/min/1.73 m², as little as 30 mL may cause acute kidney failure. 3
• The nephrotoxic effect of contrast is dose-dependent; use the minimum necessary volume. 6, 5

Adjunctive Pharmacologic Strategies

High-Dose Statin Therapy (Class IIa)

• Consider short-term high-dose statin therapy in high-risk patients: rosuvastatin 20–40 mg, atorvastatin 80 mg, or simvastatin 80 mg. 1

Furosemide with Matched Hydration (Class IIb)

• In patients where pre-procedure hydration cannot be achieved, administer 250 mL IV saline bolus (150 mL if left-ventricular dysfunction) with IV furosemide 0.25–0.5 mg/kg, then match fluid infusion to urine output. 1
• Proceed once urine output exceeds 300 mL/hour; continue matched hydration for 4 hours post-procedure. 1

Prophylactic Hemofiltration (Class IIb)

• For patients with eGFR <30 mL/min/1.73 m² undergoing complex procedures, prophylactic hemofiltration (≈1000 mL/hour fluid replacement) may be considered, though evidence is limited. 1

Interventions That Do NOT Work (Class III)

N-Acetylcysteine Is Ineffective

• Do not use N-acetylcysteine for CIN prevention; the ACT trial showed identical CIN incidence (12.7%) in NAC versus control groups, and meta-analysis confirmed no benefit (RR 1.05; 95% CI 0.73–1.53). 1
• The American College of Cardiology assigns Class III, Level A evidence against NAC administration. 1

Other Ineffective Interventions

• Do not use loop diuretics (furosemide) or mannitol for prophylaxis; they may cause harm. 1
• Prophylactic hemodialysis is not recommended for CKD stage 3 patients. 1
• Dopamine, calcium-channel blockers, fenoldopam, atrial natriuretic peptide, and endothelin-receptor antagonists lack proven efficacy. 1

Post-Procedure Monitoring

Renal Function Reassessment

• Measure serum creatinine and calculate eGFR 48–96 hours after contrast administration. 1
• CIN is defined as either a >25% increase or a >0.5 mg/dL rise in serum creatinine within 48 hours of contrast exposure. 4
• CIN is usually transient, with creatinine peaking at 2–3 days and returning to baseline within 7–10 days. 5

Timing of Subsequent Surgery

• For patients with moderate-to-severe CKD requiring coronary artery bypass grafting after coronary angiography, delay surgery until renal function has recovered from contrast exposure. 1

Common Pitfalls to Avoid

• Failing to measure eGFR before contrast in at-risk patients—relying on serum creatinine alone underestimates renal dysfunction, especially in elderly patients and those with reduced muscle mass. 3
• Restarting metformin without reassessing renal function in patients with eGFR 30–60 mL/min/1.73 m² or high-risk features (heart failure, liver disease, alcoholism, intra-arterial contrast). 2
• Using oral hydration alone in high-risk patients instead of intravenous fluids. 3
• Administering N-acetylcysteine as a substitute for standard hydration—this provides no benefit and delays proven interventions. 3, 1
• Failing to discontinue nephrotoxic medications (NSAIDs, aminoglycosides) before the procedure. 3, 1
• Exceeding safe contrast volumes (>350 mL or >4 mL/kg) in high-risk patients. 1