Contrast Nephrotoxicity: A Randomized Controlled Trial of a Nonionic and an Ionic Radiographic Contrast Agent

Experimental studies have suggested that nonionic contrast agents are less nephrotoxic than ionic contrast agents. To examine the relative nephrotoxicity of the two types of agents, we randomly assigned 443 patients to receive either iopamidol (nonionic) or diatrizoate (ionic) for cardiac catheterization. The patients were stratified into low-risk (n = 283) or high-risk (n = 160) groups, on the basis of the presence of diabetes mellitus, heart failure, or preexisting renal insufficiency (base-line serum creatinine level, >133 μmol per liter). Serum and urine analyses were performed at base line and 24 and 48 hours after the infusion of contrast material. Nephrotoxicity was defined as an increase in the serum creatinine level within 48 hours of at least 44 μmol per liter. The median maximal rise in the serum creatinine level was 18 μmol per liter in both the diatrizoate group (n = 235) and the iopamidol group (n = 208) (P not significant; power to detect a difference >9 μmol per liter, >90 percent). Creatinine levels increased by at least 44 μmol per liter (0.5 mg per deciliter) in 10.2 percent of the patients receiving diatrizoate and 8.2 percent of the patients receiving iopamidol (P not significant). Among the high-risk patients, creatinine levels increased by at least 44 μmol per liter in 17 percent of the patients in the diatrizoate group, as compared with 15 percent of the patients in the iopamidol group (P not significant). We were unable to demonstrate a difference in the incidence of nephrotoxicity between patients receiving a nonionic contrast agent and those receiving an ionic contrast agent. THE administration of radiographic contrast mediums continues to be a common cause of renal injury acquired in the hospital.^{1 2 3 4} Conventional radiographic contrast agents, as exemplified by sodium diatrizoate (Fig. 1), use iodine (300 mg per milliliter) to absorb x-ray photons in order to achieve radiographic visualization; such agents are highly osmolar (1500 mOsm per liter) and highly charged.^5,6 These characteristics are believed to contribute to both the nephrotoxicity and the allergic reactions associated with these agents. New contrast agents such as iopamidol (Fig. 1) have been developed that have lower osmolarity (796 mOsm per liter) and are nonionic, yet retain…