All contrast media used in surgery contain iodine; therefore a thorough patient history of allergies or reactions to iodine must be obtained and noted in the chart (this includes shellfish allergies). The circulator will also check for a history of patient allergies or reactions to iodine during the preoperative assessment.

If the patient has a positive history for iodine reaction and use of contrast media is anticipated during the surgical procedure, the anesthesia care provider and the surgeon should be alerted before patient transport to the operating room. The surgical technologist should prepare for these patients by having selection of nonionic contrast agents available in the operating room.

Most reactions to ROCM are mild and limited, requiring little or no treatment. However, severe allergic reactions can result in a life-threatening condition called anaphylaxis (see Chapter 16), which requires a rapid and definitive treatment protocol.

The use of ROCM provides an excellent example of pharmacokinetics in action.

When administered intravenously, a contrast agent is absorbed immediately because it directly enters the circulatory system for distribution. The agent is diluted by the circulating volume of blood as it continues to be distributed. Most ROCM are not highly bound to circulating plasma proteins and do not undergo significant biotransformation in the liver. Thus ROCM molecules are excreted virtually unchanged through renal glomerular filtration. The presence of active ROCM in the urinary system enables visualization of the kidneys, ureters, and bladder with intravenous urography (IVU). Intra-arterial administration of ROCM (e.g., as seen in surgery during placement of aortic endostent grafts or femoral embolectomy) enables immediate visualization of intended blood vessels on an arteriogram.