Use of radiopaque contrast agents for the interventional pain physician.

Intravenous contrast (IV) agents are used by Interventional Pain Management specialists for accurate localization of needle positions and spread of contrast agents to delineate pertinent anatomy. IV contrast agents are classified chemically as non-ionic or ionic monomers and dimers. Non-ionic IV contrast agents are more hydrophilic which makes them less neurotoxic. They also have a lower osmolality and produce fewer side effects. The desirable properties of IV contrast agents include satisfactory radiopacity, stability, pharmacological inertness and minimum sensitization. Physicians must obtain an informed consent for use of IV contrast agents prior to the procedure. A detailed history of allergies to iodine containing foods is a contraindication to using IV contrast agents. Reactions to IV contrast agents may produce mild to severe symptoms. Facilities where IV contrast agents are administered must be well equipped with resuscitation equipment, medications and available trained staff. Pretesting with a small intradermal dose or subcutaneous injections, will not predict adverse reactions. Premedication with antihistamines, anticholinergics and diazepam is less effective than with corticosteroids. Pretesting cannot be relied upon to predict severe reactions and may itself be hazardous for the patient. The frequency of renal insult is especially high with pre existing azotemia, diabetes mellitus or elevated serum creatinine. Patients over the age of 65 years, with multiple myeloma, hypertension or hyperuricemia are at increased risk for developing nephrotoxicity.