Iodinated Contrast Media

Iodinated contrast agents are often used in diagnostic and therapeutic radiologic procedures to assist imaging. Soluble contrast agents use iodine (atomic number 53) to absorb x-rays. Older ionized contrast media were hyperosmolar and relatively toxic.^[14] Nonionized contrast media have low osmolality, have improved side effect profiles, and are being used with increasing frequency.^{[15] [16] [17] [18] [19]} Adverse reactions to contrast media range from mild to immediately life-threatening, and etiologies include direct toxicity, idiosyncratic reactions, and allergic reactions, either anaphylactic or anaphylactoid ( Table 69-1 ). Predisposing factors include a history of bronchospasm, history of allergy, underlying cardiac disease, hypovolemia, hematologic disease, renal dysfunction, extremes of age, anxiety, and medications such as β-blockers, aspirin, and nonsteroidal anti-inflammatory drugs.^[20] Prompt recognition plus treatment of contrast media reactions is important to prevent progression of less severe reactions and lessen the impact of severe reactions. Treatment is symptomatic, for example, oxygen and bronchodilators to treat bronchospasm. Severe or resistant bronchospasm may require treatment with epinephrine. Typically, corticosteroids and antihistamines are given to symptomatic patients under the assumption that the etiology is immunologic. Patients who have had previous reactions

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Renal dysfunction is well documented in association with radiologic contrast media, particularly in patients with preexisting renal dysfunction and most especially in patients with preexisting renal dysfunction related to diabetes.^[20] High-osmolality contrast agents are associated with greater nephrotoxicity than low-osmolality agents are. Most cases of new or worsened renal function related to contrast media are self-limited and resolve within 2 weeks. However, some patients may progress to the point of requiring dialysis. Prevention of renal dysfunction related to contrast media has been based on fluid administration before, during, and after the procedure and the use of low-osmolality contrast media. Recent studies have demonstrated a reduction in contrast media nephrotoxicity by the administration of acetylcysteine.^{[22] [23] [24]} Life-threatening lactic acidosis may develop in non-insulin-dependent diabetic patients who are receiving metformin and have preexisting renal dysfunction if their renal function declines further.^{[20] [25]} Extra care is needed when patients taking metformin receive radiologic contrast media.