EVIDENCE-BASED ANSWER
Several interventions may reduce the risk of contrast nephropathy for high-risk patients; however, most evidence uses surrogate markers for clinically relevant outcomes. Because dehydration is a risk factor for developing contrast nephropathy, periprocedural hydration is routinely recommended (strength of recommendation [SOR]: C, expert opinion). Single studies have suggested that isotonic saline is associated with less risk than half-normal saline, and hydration with fluids containing sodium bicarbonate is more efficacious than those containing isotonic saline (SOR: B, single randomized controlled trial [RCT]).
Oral acetylcysteine lowers the risk of post-contrast elevations in creatinine if taken more than 24 hours before contrast administration (SOR: A, RCTs). Acetylcysteine’s low cost and favorable side effect profile make it an appealing option. Hypoosmolar contrast media are less likely to induce contrast nephropathy than hyper-osmolar media (SOR: A, RCTs). Finally, hemofiltration might be considered for patients with extremely high risk of developing contrast nephropathy (SOR: B, single RCT).
Evidence summary
Intravascular administration of radiocontrast is frequently associated with acute reductions in renal function, particularly for patients with risk factors (TABLE 1). Most studies have used operational definitions of contrast nephropathy based on predefined elevations in serum creatinine from baseline, the great majority of which are transient and clinically insignificant. It is unclear if interventions that reduce the rate of mild creatinine elevations (TABLE 2) also reduce the risk of clinically relevant adverse outcomes.
A single RCT showed decreased risk of contrast nephropathy for patients pretreated with intravenous fluids containing sodium bicarbonate compared with those pretreated with a sodium chloride solution (number needed to treat [NNT]=8.4).2 Another RCT showed that periprocedural hydration with isotonic saline is superior to half-normal saline in preventing contrast nephropathy (NNT=77).3 Several studies have demonstrated decreased risk of contrast nephropathy for high-risk patients when low-osmolality contrast media are used rather than high-osmolality contrast media (NNT=27).4 A single study suggested that iso-osmolar contrast media generate less contrast induced nephropathy than low-osmolar contrast media.5 Because the primary outcome in these studies was a change in serum creatinine, the NNTs listed above may not predict clinical outcomes.
Periprocedural administration of acetylcysteine reduces the risk of contrast nephropathy in high-risk patients (odds ratio=0.56; 95% confidence interval, 0.37–0.84). Oral acetylcysteine is effective if intervention is begun 24 hours before contrast administration.6 Preliminary evidence shows that intravenous administration of acetylcysteine immediately before contrast administration lowers the risk of contrast nephropathy.7 Oral acetylcysteine is low in cost and has no known side effects.
A single RCT suggests that hemofiltration initiated 4 to 6 hours before contrast administration reduces the incidence of contrast nephropathy among high-risk patients.8 The study was unusual in that patients in the intervention group experienced statistically significant reductions in several clinically relevant outcomes, including in-hospital mortality and cumulative 1-year mortality (in-hospital mortality, NNT=8.3; cumulative 1-year mortality, NNT=5). Hemofiltration is expensive and is not available in many institutions.
TABLE 1
Risk factors for the development of contrast nephropathy
| Advanced age |
| Diabetes mellitus |
| Chronic renal insufficiency |
| Congestive heart failure |
| Acute myocardial infarction |
| Cardiogenic shock |
| Renal transplant |
| Hemodynamic instability |
| Dehydration |
| Low serum albumin |
| Angiotensin-converting enzyme use |
| Nonsteroidal anti-inflammatory drug use |
| Furosemide use |
| Higher volume of contrast media |
| Source: Nikolsky et al, Rev Cardiovasc Med 2003.1 |
TABLE 2
Interventions to reduce risk of contrast nephropathy
| INTERVENTION | SOR | PROTOCOLS |
|---|---|---|
| Acetylcysteine (oral) | A | Acetylcysteine 600 mg PO twice daily is generally given for 2 days beginning on the day prior to the procedure.6 |
| Hypo-osmolar contrast media | A | A variety of protocols have been demonstrated to be effective.4 |
| Acetylcysteine (IV) | B | 150 mg/kg of acetylcysteine was given in 500 mL of normal saline over 30 min immediately before contrast followed by 50 mg/kg of acetylcysteine in 500 mL of normal saline over 4 h. 7 |
| Iso-osmolar contast media | B | Varying volumes of iodixanol, an iso-osmolar contrast medium, were used rather than iohexol, a low osmolar contrast medium.5 |
| Sodium bicarbonate | B | Patients were given 4.23% dextrose in H20 with 154 mEq of sodium bicarbonate added per liter. Fluids were begun 1 hour prior to contrast administration running at 3 mL/kg/hr for 1 hour and then at 1 mL/kg/hr until 6 hours after contrast administration.2 |
| Isotonic saline | B | 0.9% sodium chloride was run at 1 mL/kg/hr beginning at 8 a.m. on the morning of the procedure or as early as possible prior to emergency procedures. The infusion was discontinued at 8 a.m. on the morning following the procedure.3 |
| Hemofiltration | B | Hemofiltration was started 4 to 6 hours before the procedure. It was resumed after the procedure was completed and continued for 18 to 24 hours.8 |
| SOR, strength of recommendation. (For more on evidence ratings, see “Evidence-based medicine terms” on page 381. | ||