Bicarbonate v Saline to Prevent Contrast Nephropathy

A decline in kidney function after contrast is associated with prolonged hospital stay, adverse cardiac events, and higher mortality both in hospital and in the long term. Deliberate administration of fluids is recommended to reduce the risk of contrast nephropathy. However, data to support specific recommendations are lacking and the optimal fluid regimen remains unclear. It has been hypothesized that alkalinization of tubular fluid might be beneficial by reducing pH dependent free radical levels. A recent trial found a lower frequency of creatinine rise \> 25% within two days of contrast with a 7 hour infusion of isotonic sodium bicarbonate than with saline infusion (Merten GJ, JAMA 2004). However, it remains to be proven that bicarbonate is superior as this trial has a number of methodological flaws. Comparison: IV 1/6 M sodium bicarbonate OR IV 0.9% saline, each isotonic fluid given at the same rate of sodium administration (3.25 ml/Kg over 1 hour pre-contrast, followed by 1.1 ml/Kg/hr for 6 hours for bicarbonate; 3.5 ml/Kg over 1 hour pre-contrast, followed by 1.2 ml/Kg/hr for 6 hours for saline). Total infusion time 7 hours (for both). Maximum rate of fluid permitted is that for a body weight of 110 Kg. Intra-vascular iso- or low-osmolality contrast in the minimal dose needed to complete the required imaging.