A 62-year-old man with diabetes mellitus (eGFR 45 mL/min/1.73m²) and hypertension is scheduled for coronary angiography. Regarding contrast media selection and adverse reaction prevention, all of the following are appropriate management steps EXCEPT:

Explanation

## Contrast-Induced Nephropathy (CIN) Prevention in High-Risk Patients ### Risk Stratification **Key Point:** This patient has multiple CIN risk factors: - Diabetes mellitus - Moderate renal impairment (eGFR 45) - Age >60 years - Hypertension ### Evidence-Based Prevention Strategy | Intervention | Evidence | Recommendation | |--------------|----------|----------------| | **Contrast selection** | LOCM/IOCM reduce osmotic injury | Use LOCM or IOCM; avoid HOCM | | **Volume minimization** | Dose-dependent risk | Limit to <3 mL/kg (or <100 mL if possible) | | **Hydration** | Reduces medullary hypoxia | 0.9% NaCl 1 mL/kg/hr pre- and post-procedure | | **Metformin hold** | Lactic acidosis risk if CIN occurs | Stop 48 hrs before; restart after 48 hrs if eGFR stable | | **NAC** | Multiple RCTs show NO benefit | NOT recommended as routine nephroprotection | **High-Yield:** NAC is NOT effective for CIN prevention. Multiple randomized controlled trials (PRESERVE-S, PRESERVE-Trial) have shown no reduction in CIN incidence or mortality with NAC. It is no longer recommended by major guidelines (ACC/AHA, ESC). **Warning:** Do NOT rely on NAC as a substitute for hydration and contrast minimization. The cornerstone of CIN prevention remains adequate saline hydration and judicious contrast use. ### Why Each Statement Is Correct (Except Option 3) 1. **Contrast selection and volume** — Correct. LOCM/IOCM and volume <3 mL/kg are standard recommendations. 2. **Hydration protocol** — Correct. Isotonic saline 1 mL/kg/hr for 12–24 hours perioperatively is the gold standard. 3. **Metformin management** — Correct. Metformin should be held 48 hours before and restarted 48 hours after contrast (or when renal function confirmed stable) to prevent lactic acidosis. 4. **NAC as nephroprotection** — **INCORRECT.** NAC is NOT effective for CIN prevention. Current evidence does not support its routine use, and it should not be promoted as a definitive protective measure. **Clinical Pearl:** Sodium bicarbonate (1.26% IV at 3 mL/kg/hr) was once proposed but has also fallen out of favor; hydration with normal saline remains the evidence-based standard. [cite:Harrison 21e Ch 297]