Contrast-induced nephropathy (CIN) is the third most frequent cause of hospital-acquired acute renal failure. Different regimes in the prophylaxis of CIN have been investigated in the last years. Recent Meta-analysis show a reduced incidence of CIN when theophylline is administered to the patients especially in patients with already existing renal impairment. Furthermore hydration with bicarbonate seems to to be superior to hydration with sodium chloride alone. The combination of the two prophylaxis has not been investigated yet.

Aim of this prospective randomized trial is to investigate the effect of hydration with sodium bicarbonate compared to saline in addition to theophylline prophylaxis which all patients receive.

Inclusion Criteria:

Increased risk for contrast induced nephropathy defined as:

• Serum creatinine level ≥ 1.1 mg/dl OR
• Serum creatinine level ≥ 0.8 mg/dl plus an additional risk factor like diabetes mellitus, renal failure in past medical history or nephrotoxic medication (aminoglycoside, vancomycin, amphotericin B, diuretic)

Exclusion Criteria:

• pre-existing renal replacement therapy
• unstable serum creatinine levels (difference of more than ±0.4 mg/dl within 3 days before contrast application)
• contraindications for theophylline or sodium bicarbonate (allergies, tachycardia, alkalosis, hypokalemia)
• additional interventions that might influence renal function