I. GENERAL CONSIDERATIONS

All radiologic procedures can be stratified as either diagnostic or interventional. The majority of these procedures are either noninvasive or minimally invasive and do not require patient management by a trained anesthesiologist. As such, the overwhelming majority of procedures in radiology are either performed without sedation or aided by conscious sedation provided by a trained nurse under the supervision of a qualified, nonanesthesiologist physician. These patients do not require recovery in a postanesthesia care unit (PACU).

Patients undergoing radiologic procedure may require management by an anesthesiologist for several reasons. These include the following:

A. Airway management is considered complex, i.e., maintaining a patent airway and mask ventilation is anticipated to be beyond the scope of practice of a nurse trained in conscious sedation.

B. Significant comorbidities (ASA physical status class III or IV) requiring management by a physician, i.e., cardiomyopathy, congestive heart failure, significant valvular heart disease, ongoing or potential cardiac ischemia, acute cerebral ischemia or elevated intracranial pressure (ICP), significant chronic obstructive lung disease, ongoing sepsis, multiorgan system failure, etc.

C. The patient cannot tolerate the position necessary for the procedure: prone, supine, lateral.

D. Pain from the procedure cannot be effectively alleviated with interventionist-provided local anesthesia, i.e., heat ablation of tumor.

E. Duration of procedure.

F. Altered mental status or developmental delay and cognitive impairment that prevent the ability to follow simple commands and remain immobile.

G. Significant tolerance to narcotic analgesics.

H. Patients requiring active resuscitation for life-threatening pathology, i.e., massive gastrointestinal hemorrhage, hemoptysis, septic shock.

These patients may require care after the procedure to recover from anesthetic management. Depending upon acuity, comorbidity, pathology requiring intervention, and outcome from the intervention, these patients may require intensive care for recovery.

It is beyond the scope of this chapter to discuss management of individual comorbidities that require management by an anesthesiologist. Rather, this chapter will discuss the acute circumstances associated with commonly encountered radiologic procedures that require anesthetic management and the impact of the procedure on postprocedure patient management.

II. CONTRAST AGENTS

A. Contrast Media. Intravenous or intra-arterial contrast media are frequently administered during diagnostic and interventional radiologic
procedures to enhance imaging. Contrast media may be either ionic or nonionic; complexed gadolinium may be administered for both MRI and x-ray-based imaging. Hypo- and iso-osmolar iodinated media are considered less nephrotoxic compared to that of hyperosmolar. Contrast material can produce diuresis, necessitating either need to void or bladder catheterization after administration.

B. Acute Contrast Media Reactions. Serious and/or fatal reactions are infrequent, but remain unpredictable. These are not dose related and do not require repeat exposure. Although not IgE mediated, they are considered anaphylactoid because of anaphylactic features. Symptoms can develop within 5 to 30 minutes of exposure, but can occur several hours after administration; these reactions can occur in the PACU after completion of the procedure. Nonimmediate adverse reactions are defined as occurring greater than 1 hour after administration, but most occur within 6 to 12 hours and frequency varies from 0.5% to 23%.

1. Risk factors include history of previous adverse reaction, asthma, hay fever allergy requiring medical therapy, and concurrent use of β-blockers or interleukin-2.

2. Reaction presents as generalized skin reactions, and may progress to airway obstruction, angioedema, or cardiovascular collapse.

3. Treatment of acute reactions is supportive. Generalized anaphylactoid reactions should be treated with immediate administration of corticosteroids, H₁ and H₂ blockers. Oxygen, epinephrine, β₂-agonists may be necessary for more severe reactions. Intubation may be necessary to treat bronchospasm, laryngeal edema, or upper airway edema. Circulatory support includes IV fluids and vasopressors as necessary.

4. All interventionists do not support routine prophylaxis of all patients. Strategies commonly include prednisone 50 mg PO given 13, 7, and 1 hour prior to imaging, with 50 mg diphenhydramine 1 hour prior to contrast administration. Hydrocortisone 200 mg IV may be substituted for oral prednisone in patients who cannot take oral medications. Alternatively, methylprednisolone 32 mg is given orally 12 and 2 hours prior to contrast administration with or without antihistamine. For emergency procedures, treatment with 50 mg of diphenhydramine IV and 200 mg of hydrocortisone IV or 40 mg of methylprednisolone every 4 hours until the procedure is completed has been used successfully. Patients with methylprednisolone, aspirin, or NSAID allergies, especially if they have a coexisting diagnosis of asthma, should be pretreated with 7.5 mg of dexamethasone or 6 mg of betamethasone every 4 hours until the study has been completed. Prophylaxis is not 100% effective in preventing reaction with exposure.

III. DIAGNOSTIC IMAGING PROCEDURES

A. CT, MRI, PET, PET/CT, ultrasound, and echocardiogram all require some level of cooperation and varying degrees of immobility for a variable duration of time to acquire adequate diagnostic images. Anesthetic management may be necessary to provide both immobility and hemodynamic/respiratory support during the procedure. The majority of patients that require anesthetic management:

1. Altered mental status and/or inadequate intellectual capacity to remain immobile and follow simple commands.

2. Suffer from overwhelming anxiety associated with imaging conditions (claustrophobia).

3. Cannot tolerate positioning because of pain.

4. Possess significant comorbidity that interferes with adequate positioning to conduct the study, i.e., congestive heart failure or pulmonary hypertension significant enough to prevent assuming recumbent position.

Anesthetic management varies from mild sedation to full general anesthesia with instrumentation of the airway and mechanical ventilation depending upon the circumstances. Because there is minimal stimulation associated with imaging, only a light general anesthetic is required, sufficient to provide adequate conditions to obtain quality images. Recovery is usually rapid and requires only supportive care of comorbidities before discharge from the PACU.

Postimaging care for patients undergoing PET and PET/CT has a special concern because body fluid, mostly urine, may contain a significant amount of radioactivity as the PET isotope-labeled contrast is cleared from the body. Appropriate disposal and handling is required to ensure the safety of health care workers and other patients. Because disposal and caution over contact and exposure differ with isotope and contrast, it is recommended to contact the PET facility directly for instructions.

B. Angiography is generally a painless but invasive diagnostic procedure performed to visualize either the arterial or venous systems. Angiography can be performed to interrogate any vascular system, but is most commonly used to investigate the cerebral, abdominal, and peripheral vasculature and circulation. The process requires accessing the vascular system (arterial or venous) by placement of a cannula or sheath; this is performed most commonly under local anesthesia. Catheters are inserted through the vascular access and maneuvered into position for injection of contrast material. Once access is obtained, the process is painless, with patients doing well with only minimal sensation. The usual discomfort is frequently related to injection of contrast and may vary from minimal to painful depending upon location and quantity of injection.

1. Only children or uncooperative adults will require general anesthesia for angiography, although general anesthesia may be required for cases of potentially long duration.

2. Adult patients requiring general anesthesia for intracranial angiography may have depressed mental status because of elevated ICP, encephalopathy, recent stroke, or intracerebral hemorrhage. Spinal angiography may require several hours so that each vessel supplying the spinal cord can be identified and imaged.

3. At completion of the procedure, the vascular access may be removed. The site of penetration in the accessed arterial wall is closed by means of either a “closure device” that repairs the vessel wall or simple direct pressure on the area until bleeding stops. In either case, the accessed limb must remain straight and immobile for a period of time up to 6 hours to prevent hematoma formation at the site of vessel penetration. Hematoma formation with significant blood loss is an infrequent but potential complication. Hematoma formation requires immediate recognition and direct pressure at the access site. Occasionally, reversal of anticoagulation may be necessary and, more rarely, surgical exploration to repair the vessel. Hematoma formation is less likely after removal of venous cannula because of the lower venous pressure; time for immobilization is less.

IV. INTERVENTIONAL PROCEDURES

A. Endovascular embolization is performed for a wide variety of different pathologies of the arterial and venous systems of both the systemic
and pulmonary vasculatures. Embolization is the intraluminal deposition of material (coils, balloons, particles, and solid or gel material) in order to obstruct blood flow in a vessel.

1. Cerebral circulation: to treat ruptured and unruptured cerebral aneurysms, interrupt blood supply to intracranial and extracranial arteriovenous (AV) fistulas and malformations, and interrupt blood supply of vascular tumors before surgery.

2. Extracranial circulation: to terminate the blood supply to vessels in the nose or pharynx producing epistaxis.

3. Abdominal and pelvic circulation: to identify and interrupt blood supply of both arterial and venous vessels producing active bleeding in organs within the abdomen and pelvis. These may include the gastrointestinal tract, liver, kidney, urogenital system, portal system, and gastric and esophageal varices. Uterine myoma may also be treated with embolization.

4. Peripheral circulation: to identify and interrupt blood supply to peripheral arterial and venous malformations and vascular tumors before surgical resection.

B. Embolization, as with angiography, requires obtaining access to the vascular tree, most commonly via the femoral artery. Similar to angiography, the anesthetic goal is to provide a still field during advancement of an intravascular catheter and deployment of the occlusive material. These procedures are relatively painless, with little stimulation from the procedure. The right internal jugular vein may be used for access to the portal system if a transjugular intrahepatic portosystemic shunt (TIPSS) is in place or is to be created (see below). Alternatively, the portal venous system may be accessed by direct percutaneous puncture.

V. PACU CONCERNS

A. Hematoma formation at the site of access or uncontrolled bleeding from the puncture site.

B. Hypertonic contrast agents may produce diuresis; bladder catheterization and fluid replacement may be necessary.

C. Hypertension should be avoided, particularly when the arterial system has been accessed, because it may increase the risk of hemorrhage at the site of access or the treated pathology. β-Blockers, calcium channel blockers, hydralazine, nitroglycerin, and sodium nitroprusside may be necessary to treat hypertension.

D. Systemic anticoagulation (heparin or argatroban) may be necessary during procedures to prevent thrombus formation on the catheter. Coil embolization of cerebral aneurysm may require anticoagulation to minimize propagation of thrombus from the embolization coils. Anticoagulation is monitored by activated clotting time, prothrombin time (PT) or activated partial thromboplastin time (APTT). Platelet inhibitors such as eptifibatide (Integrilin) may be administered by bolus and/or continuous infusion to minimize platelet aggregation. For some procedures, patients may receive aspirin and/or clopidogrel before or during the procedure. Reversal of anticoagulation may be necessary at the end of the procedure in order to prevent hematoma formation for removal of the vascular sheath. When patients are to remain anticoagulated, the vascular access sheath is usually left in place. When the vascular access sheath remains in the femoral artery, flexion at the hip is restricted, thus preventing the patient from being able to sit upright. This can present as a problem in patients with severe lung disease. Reverse Trendelenburg position may be helpful to aid in spontaneous ventilation. Alternatively, postprocedure mechanical
ventilation may be necessary in severe cases until the sheath is removed and mobility at the hip is possible to prevent respiratory compromise or failure.

E. Procedures and Potential Intra- and Postprocedure Complications

1. Intracranial procedures

a. Rupture of an inadequately obliterated cerebral aneurysm, AV fistula, or malformation; dissection or rupture of a blood vessel; inadvertent occlusion of a blood vessel: If intracranial hemorrhage is suspected, immediate placement of a ventriculostomy drain may be necessary to drain cerebrospinal fluid (CSF) and reduce ICP. Significant intracranial hemorrhage presents as sudden-onset headache and altered mental status, often associated with hypertension. ICP elevation may require emergent intubation to control the airway and initiation of hyperventilation. In addition, diuresis or pharmacologic maneuvers (propofol infusion) may be necessary to reduce ICP. Immediate CT scan may be necessary to determine the extent of hemorrhage, and emergency surgery may be required to remove the hematoma in order to decompress the brain.

b. Acute stroke from obstruction of a cerebral vessel: This may be either thrombotic or embolic and related to the site of the procedure. Presentation is altered mental status and development of a focal deficit on neurologic exam. Effective treatment requires prompt diagnosis and potential return to the embolization suite for angiography and thrombolytic therapy. Deployment of an intravascular stent may be necessary after recannulization of the vessel to maintain vessel patency. Anticoagulation may be maintained in the postprocedure period.

2. Embolization for control of epistaxis and extracranial vascular lesions presents potential problems of postprocedure hemorrhage, hemodynamic instability, and large amounts of blood in the airway and stomach with risk of aspiration. Typed and cross-matched blood should be available to treat blood loss anemia. The nose and nasal pharynx may be packed to prevent further bleeding even after completion of the embolization. The branches of the external carotid artery are more commonly the bleeding source; nonetheless, traversing the carotid artery carries the potential for stroke or carotid artery dissection and rupture. Hematoma formation and sudden neurologic deterioration are signs of potential catastrophe.

3. Embolization for gastrointestinal bleeding: Arterial embolization is used to treat acute nonvariceal gastrointestinal hemorrhages of the upper or lower GI tract not accessible to endoscopic approach. Similarly, bleeding from gastric and esophageal varices is common with portal hypertension from cirrhosis and may require venous embolization or portal decompression with a TIPPS procedure (see below). Although this procedure can be performed under sedation, typically general anesthesia is required in cases of massive blood transfusion, obtundation, or risk of aspiration in patients with depressed mental status. Care should be taken concerning extubation because of aspiration risk with potentially large amounts of blood in the stomach. Hemodynamic resuscitation may require volume replacement with blood products to correct anemia and disorders of coagulation; vasopressors may be necessary to maintain perfusion pressure. Octreotide infusion is often administered to promote vasoconstriction of varices. Massive transfusion requires close attention to pH, calcium replacement, electrolytes, and maintaining body temperature; alterations may persist in the postprocedure period. Embolization
may not completely stop the hemorrhage; in such cases, resuscitation may continue in the postprocedure period.

4. Embolization of pulmonary and bronchial vasculature

a. Bronchial artery embolization is an effective treatment for massive hemoptysis arising within cavitary pulmonary lesions (tuberculosis, abscess), bronchiectasis, and primary and metastatic pulmonary tumors. The angiographic approach is via the femoral artery; bronchial arteries arise from the thoracic aorta. Although these procedures may be performed with sedation, cases of ongoing or massive hemoptysis typically require general anesthesia and endotracheal intubation for airway control and pulmonary toilet. Lung isolation with a double-lumen tube or bronchial blocker may be necessary to maintain ventilation of the normal lung. Bronchoscopic examination of the airway may be necessary to confirm patency and suction under direct visualization to remove blood, thrombus, and embolic material before extubation. Patients may develop progressive decline in blood oxygen saturation in the postprocedure period because of a number of reasons including ongoing hemorrhage, retained thrombus or embolic material in the airway, and reaction to massive transfusion.

b. Pulmonary artery embolization may be necessary in the event of hemoptysis from pulmonary artery rupture. The approach is from the internal jugular vein similar to placement of a pulmonary artery catheter. Concerns for recovery are similar to those for bronchial artery embolization. In addition, there may be significant loss of perfused lung from embolization that can contribute to postprocedure hypoxemia.

VI. SPECIFIC NEURORADIOLOGIC PROCEDURES

A. Trigeminal Neuralgia. Percutaneous neurolysis of trigeminal ganglion and/or terminal nerves is effective therapy for management of this disorder of chronic pain. Frequently, patients may have multiple sclerosis as comorbidity. Although brief periods of general anesthesia (methohexital 0.5 to 1.0 mg/kg IV or propofol 1 to 2 mg/kg IV) are necessary for the actual ablation because of pain, ongoing neurologic examination and pain evaluation during positioning of the electrode require an awake and fully cooperative patient. Hypertension is common during lesion formation, and invasive blood pressure monitoring may be necessary in some patients. Postoperative concerns include hematoma formation at the tract of approach (infratemporal fossa) and lesion site (foramen ovale). Patients may also require pain medication depending upon the success of the procedure.

B. Lumbar puncture is a procedure rarely requiring the need for anesthetic management. General anesthesia is necessary only in cases of uncooperative patients (dementia and/or delirium, encephalitis), profound anxiety, or pain with positioning that precludes a successful procedure. As with diagnostic imaging, postprocedure recovery concerns are related to the altered mental status of the patient population. Care should be taken with the decision to extubate, because these patients may have depressed gag reflexes or baseline obtundation because of depressed mental status. These patients are at risk for aspiration in the postprocedure period.