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Anesthesia for Diagnostic and Interventional Radiology Introduction The continuous advancement in diagnostic and interventional radiology techniques has led to increased demand for anesthesia services. The anesthesiologist can provide comfort and safety for the patient and perhaps contribute to the success and efficient completion of the procedure. This discussion will review the anesthetic considerations for management of a variety of procedures throughout the radiology suite. Diagnostic procedures are often noninvasive or without intense stimulation. Although some are painful, others may be safely executed with only intravenous sedation. Some studies may be prolonged with risk associated with movement and are best performed under general anesthesia. Little is gained from a technique that yields an inadequate study. The anesthesiologist must treat each patient as unique and not abide by routine. Risk factors associated with sedation complications: Depth of sedation/anesthesia Skill and training of practitioner Age of the patient Drugs used Monitors used Magnetic Resonance Imaging: MR is utilized for a multitude of diagnostic studies. The excellent resolution of MR can be severely degraded by any patient movement. In addition, the required intense magnetic fields create unique problems with the use of physiologic monitors, standard anesthesia machines, and ventilators. Anesthetic Considerations: Magnetic field disables monitoring equipment RF interference and risk of burns Hazards of ferromagnetic projectiles Patient distance/ inaccessibility Prolonged studies Distance from operating room/ post anesthesia care unit While pediatric patients constitute the largest group requiring sedation, adults with claustrophobia and critically ill or uncooperative patients may require anesthetic assistance. The goal of anesthesia for MRI is to provide immobility, safety and comfort for the patient while achieving the best diagnostic study. MR imaging data is acquired in 8-10 minute sequences; if patient movement occurs during that time the entire sequence must be repeated. Anesthetic techniques include: Chloral hydrate, given orally or per rectum Pentobarbital, intravenous or orally administered General anesthesia with ETT or LMA Propofol infusion with spontaneous ventilation /controlled ventilation Anesthetic technique is determined by the age of the patient, presence or ability to obtain an intravenous line and available equipment (anesthesia machine, ventilator). A frequent option is propofol infusion, this is preferable for children over 3 years of age. A bolus induction dose of 1-2 mg/kg is given followed by continuous infusion with spontaneous ventilation. The patient is positioned such that the airway remains open and a regular pattern of respiration is observed without signs of airway obstruction. The infusion rate of propofol that maintains this state is approximately 75-100 ug/kg/min. Many infusion pumps are rendered inoperable by the magnetic field or will function only at a considerable distance from the MR scanner (up to 6 feet). An alternative technique is the use of a gravity-fed infusion device or “drip chamber”. This allows easy titration of a dilute solution of propofol (3-5 mg/cc). While many consider this technique a form of “deep sedation”, it is actually total intravenous anesthesia and should be monitored carefully. Monitoring should include pulse oximetry, capnography, and non-invasive blood pressure. Interventional Radiology procedures: Angiography/embolization PIC lines, access catheters Ureteral stents Trauma interventional procedures Thermography of liver liver metastases These are more painful procedures requiring patients to lie supine without movement. Debilitated patients require careful attention and monitoring. Sedation/analgesia techniques or general anesthesia are options for management. TIPS- Transjugular intrahepatic portosystemic shunt Performed for patients with severe liver disease causing elevated portal venous pressure Right int jugular cannulation>catheter through RA to right hepatic vein * Respiratory motion control during passage into portal vein * Airway management in face of rapid GI hemorrhage * Potential liver capsule laceration with intraperitoneal hemorrhage Anesthetic technique depends on the severity of disease and degree of ascites. Interventional Neuroradiology (INR) procedures: Endovascular embolization of AVM’s Endovascular treatment of ruptured aneurysms Sclerotherapy of venous angiomas Balloon angioplasty of occlusive cerebrovascular disease Thrombolysis of acute thromboembolic stroke Carotid angioplasty with stent INR procedures are performed electively or urgently for a variety of CNS pathologies. Despite concern for neurologic evaluation, most neuroradiologists now prefer general anesthesia (with apneic periods) for optimal imaging of studies and techniques. Monitoring may include intra-arterial and central venous pressure catheters as well as neurophysiologic assessment. Additional goals may include optimizing intracranial dynamics and induction of hypertension/hypotension/asystole when necessary. A rapid return to consciousness is appreciated at the end of these procedures. Aneurysm ablation- Radiology Suite vs. OR Location/ anatomy of the aneurysm Age and grade of the patient Skill of the facility Luck of the draw Potential complications: Contrast reactions Embolization of particles Aneurysm perforation Cerebral ischemia Obliteration of physiologic arteries Brain swelling Knowledge of the risks and hazards of the different procedures and close collaboration with the neuroradiologist form the basis for appropriate management of a potentially fatal ischemic or hemorrhagic complication that may occur in 1-8% of cases. Conclusion The continued success of diagnostic and therapeutic interventional radiology is dependent upon patient safety and acceptance. The ever-increasing trend toward minimal invasiveness and ambulatory care mandates that better techniques evolve for patient recovery and well-being. Adherence to standards of care and development of safe practice patterns will provide for patient safety and continued scientific advancement. 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