Evaluation of Safety Guidelines on the Use of Iodinated Contrast Material: Conundrum Continued.

OBJECTIVES: Recently, safety guidelines for the use of intravascular iodinated contrast material have been updated, and the recommended threshold for giving prophylaxis to prevent contrast-induced nephropathy (CIN) has been reduced to estimated glomerular filtration rate (eGFR) less than 30 mL/min/1.73 m. Data on this population in the context of CIN, especially evidence for efficacy of the recommendation of prophylactic intravenous hydration, are lacking. The aim of the current study was to test implicit assumptions underlying the guideline update: (1) patients with eGFR <30 mL/min/1.73 m, as opposed to former high-risk patients with eGFR ≥30 mL/min/1.73 m, are at high risk of CIN and other unfavorable outcomes after intravascular iodinated contrast material administration; (2) prophylactic intravenous hydration mitigates this risk; and (3) the risk of administering prophylactic intravenous hydration does not outweigh the positive preventive effect.

MATERIALS AND METHODS: Retrospectively, data were collected from all patients with eGFR <30 mL/min/1.73 m referred for an elective procedure with intravascular iodinated contrast material administration and excluded from the AMACING trial (A MAastricht Contrast-Induced Nephropathy Guideline trial). We compared these patients with those prospectively included in the AMACING trial (with eGFR 30-59 mL/min/1.73 m and risk factors). Main outcomes were CIN (defined as an increase in serum creatinine by more than 25% or 44 μmol/L within 2-6 days postcontrast exposure), dialysis and mortality within 35 days postcontrast exposure, and complications of prophylactic intravenous hydration.

RESULTS: A total of 28,803 patients referred for an elective procedure with intravascular iodinated contrast administration were prospectively screened for inclusion in the AMACING trial. One hundred fifty-seven (0.5%) patients had eGFR <30 mL/min/1.73 m, and 155 received intravascular iodinated contrast material. Standard prophylaxis was given to 119/155 of these patients. Data on 2- to 6-day serum creatinine, 35-day dialysis 35-day mortality, and complications of prophylactic intravenous hydration were available for 59/119 (50%), 118/119 (99%), 119/119 (100%), and 119/119 (100%) standard prophylaxis patients, respectively. Incidences in eGFR <30 mL/min/1.73 m versus AMACING patients are as follows: CIN 13.6% versus 2.7% (P = 0.0019); 35-day dialysis 0.9% versus 0.0% (P = 0.2646); 35-day mortality 9.2% versus 0.0% (P < 0.0001); complications of prophylactic intravenous hydration 5.9% versus 5.5% (P = 0.8529).

CONCLUSIONS: Postcontrast incidences of CIN and mortality at 35 days are significantly higher in the population with eGFR <30 mL/min/1.73 m than in the former high-risk population with eGFR 30 to 59 mL/min/1.73 m, even after prophylactic intravenous hydration. The risk of complications of prophylactic intravenous hydration is similar and substantial in both populations. Obtaining evidence from a randomized trial that efficacy of prophylactic intravenous hydration outweighs the risk of complications is important but may not be feasible.