*4.14.1 Increased dose of contrast medium*

Based upon multiple sources, the relatively unhazardous cutoff point of contrast amount ranges from 70 mL up to 220 mL. However, very small doses as much as 20–30 mL are capable of inducing CIN. In a study that included patients performing coro¬nary angiography, each 100 mL of contrast medium administered was linked to a significant increase of 12% in the risk of CIN (OR = 1.12, p = 0.02) [32]. A clear accepted dose is four times the creatinine clearance.

## *4.14.2 High-osmolar and ionic CM*

Most side effects attributable to contrast media are linked to its hypertonicity. Currently, four main types of contrast media are used in practice today, including nonionic low-osmolar, ionic low-osmolar, nonionic iso-osmolar, and ionic high-osmolar contrast media. In a large study which compared the nonionic lowosmolality agent iohexol to the ionic high-osmolality agent meglumine/sodium diatrizoate in patients with preexisting renal impairment undergoing angiography, patients with renal impairment who received diatrizoate were 3.3 times more liable to develop CIN in comparison with those receiving iohexol [38]. NEPHRIC trial is a randomized, prospective study that made a comparison between the nonionic iso-osmolar CM iodixanol with the nonionic low-osmolar CM iohexol in 129 patients with renal impairment and diabetes undergoing coronary or aortofemoral angiography. The incidence of CIN was 3% in the iodixanol group and 26% in the iohexol group (p = 0.002) [39]. In one other randomized study, the incidence of CIN provoked by iodixanol and iohexol was compared in 124 patients with basal creatinine level >1.7 mg/dl. The incidence of CIN was 3.7% in iodixanol group and 10% in iohexol group (p > 0.05) [17]. In addition, CM are classified as ionic and nonionic. A randomized trial of 1196 patients performing coronary angiography showed that nonionic CM lowered the incidence of CIN in patients with preexisting renal impairment [38]. In high-risk patients, it is better to avoid the use the highosmolar and ionic CM to lower the risk of CIN.
