Ionic versus nonionic contrast media: A prospective study of the effect of rapid bolus injection on nausea and anaphylactoid reactions

Purpose: The purpose of our study was to evaluate the effect of bolus infusion of contrast medium (ionic versus nonionic) on the incidence of nausea and anaphylactoid reactions. Method: We prospectively studied 1,827 patients who had bolus enhanced body CT scans and divided them into four groups: 725 patients received higher osmolality contrast medium (HOCM) at the slower bolus rate of 1-2.5 mils (SLOW-HOCM group); 650 patients were in the FAST-HOCM group and received the same ionic contrast medium at 4-5 ml/s; 250 patients received lower osmolality contrast medium (LOCM) at 1-2.5 ml/s, forming the SLOW-LOCM group; and 202 patients in the FAST-LOCM group got the same nonionic agent at 4-5 ml/s. Results: We found no significant difference in the rate of nausea among the first three groups: SLOW-HOCM (3.9%), FAST-HOCM (4.9%), and SLOW-LOCM (3.2%). A statistically significant lower incidence of nausea (0.5%) was found in the FAST-LOCM group. Anaphylactoid reactions were significantly more common in both groups who received HOCM (8.3 and 9.1%) compared with the groups who received LOCM (2.0 and 2.5%). Conclusion: The bolus injection of warmed ionic contrast medium at a rate of 1-2.5 ml/s causes no significant increase in nausea compared with similar infusion rates of nonionic agents. For CT protocols that require infusion rates of 4-5 ml/s, the use of a nonionic agent is associated with a significantly reduced prevalence of nausea. The prevalence of anaphylactoid reactions is not affected by the rate of injection.