Background: Previous work on contrast-induced acute kidney injury (CI-AKI) has identified contrast volume as a risk factor and suggested that there is a maximum allowable contrast dose (MACD) above which the risk of CI-AKI is markedly increased. We hypothesized that there is a relationship between contrast volume and CI-AKI and that there might be reason to track incremental contrast volumes above and below the MACD limit.
Methods and results: Consecutive patients undergoing percutaneous coronary intervention (PCI) were prospectively enrolled from 2000 to 2008 (n=10 065). Patients on dialysis before PCI were excluded (n=155). MACD was defined as (5 mL x body weight [kg])/baseline serum creatinine [mg/dL]) and divided into categories in which 1.0 reflects the MACD limit: < or =MACD ratios (<0.5, 0.5 to 0.75, and 0.75 to 1.0) and >MACD (1.0 to 1.5, 1.5 to 2.0, and >2.0). CI-AKI was defined as a > or =0.3 (mg/dL) or > or =50% increase in serum creatinine from baseline or new dialysis. Multivariable regression was conducted to evaluate the effect of exceeding the MACD on CI-AKI. Twenty percent of patients exceeded the MACD. Risk-adjusted CI-AKI increased by an average of 45% for each category exceeding the MACD (odds ratio, 1.45; 95% confidence interval, 1.29 to 1.62) Adjusted odds ratios for each category exceeding the MACD were 1.60 (95% confidence interval, 1.29 to 1.97), 2.02 (95% confidence interval, 1.45 to 2.81), and 2.94 (95% confidence interval, 1.93 to 4.48). CI-AKI for contrast dose <MACD showed no statistical difference (P=0.5).
Conclusions: Contrast volume is a key risk factor for CI-AKI and matters the most in the highest-risk patient. The incremental use of contrast beyond the MACD is associated with an increased risk of CI-AKI.