INTRODUCTION TO INTERVENTIONAL RADIOLOGY
Interventionalist radiologists are trained in performing diagnostic and therapeutic interventions in patients. This requires expertise in imaging, technical skills, pharmacology, sedation/anesthesia, and management of patients preprocedure and postprocedure. A well-rounded interventionalist understands disease processes and how they adversely alter normal physiology. They use this knowledge to work up the patient appropriately, use different imaging modalities to tailor a custom treatment for each patient, skillfully and safely perform the procedure, and follow up the patient to ensure optimal outcome.
This chapter is a basic outline of Interventional Radiology (IR) meant to introduce medical practitioners in other fields to the practice of IR. It contains the most common techniques, tools, and procedures involved in IR today. IR practice is diverse, innovative, and flexible. It is based on the practitioner preferences, training, experience, and ongoing literature review. The procedures covered in this chapter are performed commonly and may vary depending on the institution and interventionalist performing them.
The workup starts with a thorough history and physical, with particular attention to pertinent medical and surgical history, history of allergies, current medications, and a focused physical exam. It is necessary to identify risk factors for contrast allergy, contrast-induced nephropathy, and bleeding.
Previous reaction to a contrast agent and a history of allergies or asthma place the patient at a higher risk for an allergic reaction to contrast during or after the procedure. Contrast reactions are covered in chapter 1 of this book. Pretreatment with a histamine blocker like diphenhydramine and a steroid such as prednisone can help reduce the risk of contrast reaction during the procedure. Low-osmolar contrast agents and carbon dioxide angiography can be used in patients with a history of moderate to severe contrast reaction. It is important to discuss alternative treatments or risk versus benefit of using contrast during an intervention with the patient prior to starting the procedure.
CONTRAST-INDUCED NEPHROPATHY (CIN)
CIN is defined as an increase in baseline creatinine by either 0.5 mg/dL or 25% after 1 to 3 days following administration of contrast. The renal function generally returns to baseline after a week. Pharmacologic agents such as N-acetylcysteine (Mucomyst), use of a limited volume of low osmolar contrast agents, carbon dioxide as an alternative contrast agent, and preprocedural and postprocedural hydration with saline can lower the risk of CIN.
Routine laboratory tests include prothrombin time (PT), activated partial thromboplastin time (PTT), platelets, and international normalized ratio (INR). Table 8.1 illustrates safety threshold and steps to rectify abnormalities of these parameters.
Important Preprocedural Hematologic Parameters