What interventions reduce the risk of contrast nephropathy for high-risk patients?

Journal of Family Practice, April, 2005 by Paul D. Grossman, Martha Burroughs

* 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. Hypo-osmolar 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? 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)s 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.

* Recommendations from Others The American College of Radiology' recommends using low-osmolality contrast media for patients with renal insufficiency, particularly those with diabetes. (9) Clinical Evidence found support for the use of low-osmolality contrast media, periprocedural hydration, and acetylcysteine as interventions to reduce the risk of contrast nephropathy. (10)

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?

TABLE 2
Interventions to reduce risk of contrast nephropathy

INTERVENTION     SOR   PROTOCOLS

Acetylcysteine   A     Acetylcysteine 600 mg PO twice daily is
(oral)                 generally given for 2 days beginning on the day
                       prior to the procedure. (6)

Hypo-osmolar     A     A variety of protocols have been demonstrated to
contrast media         be effective. (4)

Acetylcysteine   B     150 mg/kg of acetylcysteine was given in 500 mL
(IV)                   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      B     Varying volumes of iodixanol, an iso-osmolar
contast media          contrast medium, were used rather than iohexol,
                       a low osmolar contrast medium. (5)

Sodium           B     Patients were given 4.23% dextrose in [H.sub.2]O
bicarbonate            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         B     0.9% sodium chloride was run at 1 mL/kg/hr
saline                 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.