The necessity of preheating contrast media for IVP injection

Preheating contrast media prior to injection for intravenous pyelography is a traditional routine procedure in the department of radiology. Although it may be helpful in facilitating the rate of injection, the result of preheating the substance is instability, therefore, we question the necessity of this routine practice. A comparative study of 5670 and 6448 patients in two groups receiving nonionic contrast media Iopromide with and without preheating, respectively, prior to injection for intravenous pyelography were carried out from August 1989 through July 1999. A small number of patients who received preheated contrast media experienced warmness locally at the injection sites and such sensation may also extended to the upper arm during injection. Few other patients complained of discomfort heat sensation at the injection sites. The majority of patients who did not receive preheated contrast media experienced coolness locally at the injection sites and the sensation also extended to upper arm during injections. No patients ever complained of any discomfort in this group. There were no obvious differences in the incidences of general adverse reactions between the two groups. We concluded that the preheating of contrast media prior to intravenous pyelography could be eliminated from routine procedure without additional adverse reactions.