The Interventional Suite as an Extension of the ICU

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Contents

Abstract

Interventional neuroradiology is rapidly gaining prominence in neurosurgery. As the field grows in sophistication and complexity, the neurointerventional suite must also evolve to incorporate features of the neurosurgical operating room and neurocritical care unit. This article discusses elements of the neurointerventional suite, including room design, staffing, pharmacological matters, and neurocritical care considerations. See tables 1-3 at end of article!

Key words

eurointerventional suite, critical care, neuroradiology

Introduction

As more complex neurointerventional procedures are performed in more patients with complicated central nervous system disorders, greater sophistication is needed in the organization and management of the neuroradiology suite. In addition, future technological developments, as well as an expanding role for neurointervention in the management of a wide array of disorders, call for a thoughtful and informed approach to planning. This article discusses the design and staffing of the modern endovascular suite, monitoring and pharmacological considerations, patient assessment and preparation, and pertinent neurocritical care issues. The goals of this article are to provide an introduction to residents and fellows new to the neurointerventional suite and serve as guidelines for experienced operators planning a new suite.

Organization of the Neurointerventional Suite and Essential Equipment

The neurointerventional suite should be dedicated to the neurointerventional service. The AHA Intercouncil Report on Peripheral and Visceral Angiographic and Interventional Laboratories produced detailed recommendations for the design and equipment needed for an interventional suite (5); although not designed specifically for neurointerventional suites, these guidelines serve as a useful resource for planning and equipment selection.The procedure room should be large enough to accommodate anesthesia personnel and their equipment, as well as additional personnel and equipment that may be needed for particular procedures. For instance, electroencephalography and other electrophysiology monitoring devices are required during Wada testing, along with the personnel to operate this equipment. The size of a typical interventional suite is at least 30 x 25 feet, or 750 square feet, with a ceiling height of 10 to 12 feet (5, 15). A separate entrance for patient transportation and another for personnel, usually from the control room, facilitates rapid room turnover and reduces crowding. Standard equipment should include wall-mounted light boxes, sinks for waste and for cleaning, telephones, and glass-fronted storage cabinets for equipment and devices.

To facilitate anesthesia, the room should be equipped with oxygen, suction, gas evacuation lines, and a separate telephone for anesthesia personnel.Biplanar digital subtraction angiographic equipment is preferable to a monoplanar system. Biplanar technique decreases time necessary for procedures, reduces radiation exposure, minimizes contrast dose, and offers a definite technical advantage by permitting simultaneous imaging of the anteroposterior and lateral planes. Rotational angiography is also useful in defining tortuous and intricate neurovascular anatomy. Four angiography video monitors are necessary and should be mounted on the ceiling. Two monitors are used to view digital subtraction angiograms; the other two are used for live fluoroscopic imaging during procedures. Ceiling-mounted equipment, such as video monitors and power-contrast injectors, are easier to manage and are less obtrusive than floor- or table-mounted devices.

Overhead lights should be controlled with a rheostat to allow dimming of the room lights. Foot pedals to control the lights and an overhead spotlight to illuminate procedures (such as during wire and catheter shaping and arterial access site closure) are helpful. The patient table should be capable of four-way motion, permitting wide excursion and pivot rotation. The table should also be able to be angled up to 30° from horizontal to facilitate myelographic procedures and Trendelenburg position in cardiovascular emergencies. A second table, within easy reach of the operator, is used for device preparation and placement of devices and materials for use during procedures. A third table is needed for procedures in which some materials, such as glue or particles for embolization, must be kept separate from the other devices. The power contrast injector should be capable of delivering rates up to 50 mL/sec, and ceiling-mounted or table–mounted injectors are preferred over floor models.

The control room contains the console for operating the angiographic equipment and should be spacious enough to accommodate ancillary personnel, as well as medical students and visitors (at least 130 square feet (5)). The control room window should be angled to reduce glare and should be equipped with a venetian blind to provide patient privacy during procedures such as Foley catheter placement. The control room should also contain a computer workstation to permit viewing, storage, and analysis of images.Needs for storage space and data management are often not considered during room planning. There should be enough space to store plenty of device stock, both within the angiography suite and in other rooms close by. Glass-fronted storage cabinets in the suite facilitate rapid device selection during procedures. A separate, out-of-room storage space should be at least 250 square feet (5). A separate, cooled and ventilated equipment room should contain transformers, power modules, and related equipment.

The recommended size for the equipment room is 100 square feet (5). The imaging data storage system should be able to store at least several weeks worth of imaging data to allow for rapid comparison of studies on patients who return for urgent follow-up, including patients who have suspected vasospasm in whom subtle caliber changes are easier to detect if previous studies are available real-time. A picture archiving and communication system (PACS) is a computer system that manages the acquisition, transmission, storage, distribution, display, and interpretation of medical images. PACS display systems are reviewed by Badano (3), and guidelines for the acquisition of and testing of PACS are discussed in depth by Samei and colleagues (24).

Radiation Safety

Staff Radiation Exposure

The National Council on Radiation Protection (NCRP) and Measurements has published guidelines for radiation exposure for medical personnel that are defined as “as low as reasonably achievable (20). Fluoroscopy is the major source of occupational radiation exposure in the angiography suite (9). The operating physician is at the greatest risk of receiving the maximum occupational dose (5). Placement of the x-ray tube under the table minimizes scatter radiation to the operator’s head and neck. Moveable, ceiling-mounted clear lead glass shields can be draped with sterile plastic and positioned over the patient, protecting the patient’s lower body and the operator from radiation exposure. Rolling floor-mounted x-ray shields should be available to shield anesthesia or other personnel.Lead aprons should provide at least 0.5 mm lead equivalent thickness. All full-time physicians, technologists, and nurses should wear custom-fitted aprons to ensure optimal coverage. Extra aprons should be available for anesthesia staff and visitors. Pregnant staff members should wear aprons providing 1.0 mm lead equivalent thickness; the NCRP-recommended maximum gestational radiation exposure is 5 mS per year (18). Other personal radiation protection devices include thyroid shields and lead glasses.

Patient Radiation Exposure

There is no defined maximum radiation exposure for patients, as the medical benefits are assumed to outweigh the presumed risks (18). Nevertheless, radiation exposure to patients should be minimized. The cornerstones of minimizing radiation dose to the patient include minimizing exposure time, using appropriate shielding, and maximizing distance from the x-ray source (5). The National Council on Radiation Protection and Measurements (NCRP) has made recommendations for the design of structural shielding (21) and x-ray equipment (

Personnel

The neurointerventional team is a multidisciplinary group with expertise in neurointervention, radiology techniques, and radiation safety. At the center of this group are the interventionists, technicians, and nurses. The team is supplemented by anesthesiologists and the anesthesia monitoring staff. It is critical that the individuals in the team are experienced, highly motivated, and flexible. The rapidly evolving field of neurointervention, combined with the complexity of the disorders and the procedures requires that the team function as a cohesive, adaptable unit. Moreover, the team should be large enough to allow organization of a call schedule that will provide continuous 24-hour availability. A highly organized team is critical, with a well-defined role for each member and a structured call schedule.

Neurointerventionists

The neurointerventionist is a neurosurgeon, neuroradiologist, or neurologist who has completed a dedicated fellowship in neurointerventional radiology, endovascular neurosurgery, or endovascular surgical neuroradiology, all of which refer to the same subspecialty. In-depth knowledge of the pathophysiology of neurovascular disease must be combined with a comprehensive understanding of neuroanatomy as well as fundamentals of neurocritical care and interventional techniques.

Neurointerventional technicians

Technicians in the neurointerventional suite have a background in basic radiology techniques and further expertise in computerized digital subtraction imaging. They are responsible for maintenance of the imaging equipment, processing of the images, and trouble-shooting during procedures. Other responsibilities include ordering and stocking catheters, wires, and other neurointerventional devices. At some institutions, neurointerventional technicians may also be responsible for patient positioning, and the establishment and maintenance of irrigation lines.

Nursing staff

Neurointerventional nurses should be registered nurses with a background in neurointensive care because the interventional suite is in many ways an extension of the neurological intensive care unit. Neurointerventional nurses are responsible for patient preparation before the procedure, the establishment of intravenous access, the administration of sedation and analgesia, monitoring of the patient’s condition, and maintenance of irrigation lines. Additional specific duties of the nursing staff include evaluation of the preprocedure laboratory tests, checking for allergies or drug reactions, verifying and witnessing informed consent for the procedure, placement of a Foley catheter, ventriculostomy and lumbar drain management, performance of an Allen test (1) before radial artery procedures, monitoring of peripheral pulses, and management of the arterial access site at the completion of the procedure. At some centers, a second nurse acts as the first assistant to the neurointerventionist during the procedure.

Monitoring

Aggressive and thorough monitoring of the patient’s condition during a neurointerventional procedure is critical. When possible, a neurointerventional procedure should be performed with the patient in an awake state to permit continuous assessment of neurological status. Monitoring of vital signs and pulse oximetry is routine;continuous arterial line and intracranial pressure (ICP) monitoring is performed as needed. An overhead monitor that projects the clinical data, including color-coded tracings, should be positioned next to the angiography monitors. Patients with subarachnoid hemorrhage or intracranial hemorrhage should undergo continuous arterial line monitoring of their vital signs by means of a radial artery line placed before the procedure. Alternatively, monitoring may be done via the arterial sheath in patients undergoing elective procedures, such as endovascular treatment of intracranial aneurysms. To obtain an adequate tracing, the sheath must be larger than the guide catheter; the authors use a 7-French femoral artery sheath (in combination with a 6-French guide catheter) when monitoring via the sheath is performed. Continuous monitoring of ICP should be performed in patients with a ventriculostomy. An ICP tracing on one of the overhead angiography monitors provides immediate feedback should an abrupt change in ICP occur during the procedure, such as the onset of intracranial hemorrhage.

Pharmacologic Considerations

Certain drugs should be available for easy and fast access (Table 1). During intracranial procedures during which intravenous heparin is administered, protamine should be drawn up in a sterile syringe and placed on the back table in preparation for intra-arterial administration in the event of an intracranial hemorrhage during the procedure.Atropine and dopamine should be drawn up and available for immediate use during angioplasty and stenting of the carotid bifurcation. Other medications, used on a more routine basis, are listed in Table 2.

Assessment, Preparation, and Periprocedural Management

Risk assessment

Anesthesia support should be readily available in the situation in which a decision is made for the administration of general anesthesia in order to continue or complete the procedure and in the event of an emergency. Although many neurointerventionists routinely use general anesthesia for most cases, such as aneurysm coiling, some operators prefer to work without general anesthesia whenever possible. This practice has been shown to be acceptable, with equivalent complication rates compared with cases managed by anesthesiologists (16). Any patient undergoing an endovascular procedure is also a potential candidate for an emergent neurosurgical procedure and should therefore be assessed for anesthetic risk before the procedure regardless of whether general anesthesia is planned. All patients undergoing anesthesia or conscious sedation should undergo assessment and risk stratification according to the American Society of Anesthesiologists (ASA) classification system (8) (Table 3). The ASA score predicts risk of death and major nonfatal complications. Although most hospital and state regulations require preprocedure assignment of an ASA score, this score does not predict cardiac risk to a strong degree. The Goldman classification is most commonly used by internists and cardiologists to determine the cardiac risk before surgery (2, 10) (Table 4). The primary care physician or cardiologist who is involved with preoperative risk assessment is increasingly acting on this information, with initiation of specific perioperative pharmacologic therapy and, in many instances, recommendation of an invasive coronary procedure (11). The management issue then becomes the timing of the cardiac intervention versus the neurological intervention.

Patient preparation

There are four specific areas of concern requiring preparation in advance of a neurointerventional procedure to minimize complications. These are the institution of beta blockers in patients at risk of cardiac ischemia, the use of antiplatelet agents in patients in whom stent placement is anticipated, the use of steroid and antihistamine therapy in patients with contrast allergies, and, finally, the adequate hydration of patients before they receive sedation, anesthesia, and a contrast bolus. The presence of any two of the following risk factors presents a risk of cardiac complications during general anesthesia: age 65 years or older, hypertension, smoking, diabetes, and hypercholesterolemia. Evidence has accumulated to indicate that cardiac risk during the induction of general anesthesia can be lowered with the routine use of beta blockade (2, 11).

The regimen recommended for beta blockade is initiation of therapy (generally, atenolol, 50-100 mg, daily]) and titration to a heart rate of less than 65 beats per minute (2).In patients undergoing carotid angioplasty and stenting, beta blockers and other antihypertensive medications should be held on the morning of the procedure because of the risk of bradycardia and hypotension during the procedure. In addition, beta blockers may exacerbate anaphylactic shock. Javeed and colleagues found emergent treatment with intravenous glucagon to be successful in such a case (14).Antiplatelet therapy is necessary for patients who undergo stent placement. Newly placed intravascular metal stents can induce platelet activation and thrombosis. Aspirin is a cyclooxygenase-1 inhibitor that irreversibly inhibits platelet aggregation but does not impede platelet adhesion or platelet-activated mitogenic activity. Clopidogrel is a thienopyridine derivative with potent antiplatelet action that inhibits adenosine phosphate-induced platelet aggregation. This drug works synergistically with aspirin, and evidence from the cardiac literature supports the use of combination antiplatelet regimens for patients undergoing stent placement (22). Clopidogrel, in combination with aspirin, has become the standard antiplatelet regimen for patients undergoing coronary angioplasty and stenting (12). When possible, patients undergoing stent placement should be placed on aspirin (325 mg daily) and clopidogrel (75 mg daily) for at least 3 days before CAS or be given a loading dose of aspirin (325 mg) and clopidogrel (300 mg) early on the day of the procedure. In some situations, such as emergent stent placement for the treatment of an arterial dissection, pretreatment with oral antiplatelet agents is not possible. In these situations, treatment with an intravenous glycoprotein (GP) IIb-IIIa inhibitor (e.g., eptifibatide) will provide immediate protection against platelet thrombosis.

The authors’ preferred regimen is to give a loading dose of eptifibatide, together with a loading dose of clopidogrel and aspirin (given either orally or via a nasogastric tube). A continuous infusion of eptifibatide is then administered for several hours to permit the clopidogrel and aspirin to take effect.Antiplatelet therapy may also necessary for some patients undergoing treatment of intracranial aneurysms. When stent-assisted coiling of a wide-necked aneurysm is planned, a combination of aspirin and clopidogrel is used in a regimen similar to that used for carotid stenting. Some operators advocate routine use of periprocedural aspirin for all aneurysm coiling cases to minimize risk of thromboembolic complications. When an acute thrombosis is encountered during aneurysm coiling, emergent treatment with a GP IIb-IIIa inhibitor can be effective.Serious reactions to contrast media are rare, encountered in less than 1% of patients (29). In a detailed analysis of anaphylaxis and anaphylactoid reactions during surgical and interventional procedures, contrast allergy was the cause in less than 10% of adverse events. Reactions to antibiotics, sedatives, neuromuscular blocking agents, and latex are more common (30). Patients at risk for contrast reactions include those with documented contrast allergies, asthma, penicillin allergies, and known hypersensitivity to skin allergens and shellfish (34). Patients at risk should receive prophylaxis; the usual regimen consists of a glucocorticoid (prednisone, 50 mg; 13, 7, and 1 hour before exposure) and an antihistamine (diphenhydramine, 50 mg, 1 hour before exposure). Other agents studied, including cimetidine and ephedrine (in addition to the above), have not shown a clear benefit for prophylaxis (17).Adequate hydration is essential in the avoidance of cardiac and central nervous system ischemia, smooth induction and maintenance of conscious sedation and general anesthesia, and avoidance of contrast-related nephropathy. Dehydrated patients are prone to having significant hypotensive episodes when given any agent that is even minimally vasodilating. Subsequent urgent treatment with pressors in a volume-depleted patient is a major cause of periprocedural cardiac ischemia. Attention to pretreatment volume status and judicious volume loading with isotonic saline is an effective means of complication avoidance.

Contrast nephropathy is the third-leading cause of hospital-acquired renal failure (7). Diabetes and any degree of renal insufficiency are risk factors for renal failure after the administration of contrast material. Adequate hydration, the use of low-osmolar contrast material, and minimizing the contrast burden are standard in patients at risk. The antioxidant, N-acetylcysteine (Mucomyst®, Bristol-Myers Squibb, New York) is believed to function as a free-radical scavenger and to stimulate intrarenal vasodilation. Acetylcysteine was shown in a randomized trial to reduce serum creatinine elevation in patients undergoing radiological procedures in which non-ionic, low-osmolality contrast material was used (28). Prophylactic administration of acetylcysteine (600 mg, twice daily) orally and 0.45 percent saline intravenously, before and after administration of the contrast agent, led to a significant decrease in serum creatinine concentrations in patients receiving this mixture compared with those receiving saline only. Subsequently, isotonic intravenous fluid was found to be superior to half-isotonic intravenous fluid in reducing the incidence of contrast-induced nephropathy in patients undergoing coronary angioplasty (23).

Conscious sedation

Most neuroendovascular procedures are performed without general anesthesia. The avoidance of general anesthesia is part of patient acceptance and demand for the procedure of carotid artery and stenting. In critically ill patients, those with altered mental status, uncooperative patients, and those with ruptured aneurysms, general anesthesia is advisable. The remainder will undergo the intervention in a conscious state after local anesthesia and sedatives have been administered.The drugs used most commonly in this setting are short-acting benzodiazepines, short-acting narcotics, and propofol. The goal of sedation is a cooperative and comfortable patient, with the ability to undergo a basic neurological examination, yet maintain a fixed position on the angiographic table for a prolonged period of time. Sedative regimens have been carefully studied in this setting and in the critical care unit. Midazolam has the advantage of quick onset, short acting (in comparison with other benzodiazepines but not when compared with propofol), reversible with flumazenil, and minimal hypotensive effect (13, 27, 33).

Intracranial pressure management

In certain cases, endovascular intervention may take place in critically ill patients with documented or suspected elevations in ICP or a complication during therapy may result in acute elevations in ICP. Monitoring ICP, generally via an external ventricular catheter, is best established before endovascular therapy and any initiation of anticoagulation therapy. An abrupt rise in ICP during an interventional procedure should raise suspicion for intracranial hemorrhage and should prompt the performance of a rapid neurological assessment, if possible, and angiography to look for evidence of contrast extravasation. In the absence of intracranial hemorrhage, sustained elevations in ICP (sustained >20 mmHg) can be treated with sedation and cerebrospinal fluid drainage. Therapy with mannitol is an option as well, but the dehydrating effects of contrast and mannitol in combination must be carefully monitored. The Brain Trauma Foundation guidelines for the management of severe head injury remain the primary resource and bibliography for a rational stepwise protocol for ICP management (4).

Future Developments

Several technological advances that are currently in progress offer promise in the continued evolution of the neurointerventional suite. Newer versions of imaging equipment, monitors, and ancillary devices such as power injectors are considerably smaller and easier use than earlier versions. Flat panel angiographic imaging, currently available, can lower x-ray dose and provide better image quality and resolution. Angiographic computed tomography enables angiographic imaging equipment to generate images of soft tissue, such as the brain, that are similar to computerized tomography images (www.medical.siemens.com). Magnetically guided angiography, currently available at some centers, uses extracranial magnets to help catheter and wire navigation (6, 25). This technology offers the potential to permit more precise intravascular navigation while shortening fluoroscopy and procedure times. Magnetic resonance imaging-guided angiography, with the potential advantages of detailed tissue imaging as well as the elimination of radiation exposure, is another innovation under development (26, 31, 32).

'Table 1. Medications that should be easily available for quick access or emergent use

Medication Purpose' '
Atropine Treatment of bradycardia or asystole during carotid angioplasty and stenting
Epinephrine Vasopressor
Fentanyl Analgesia
Heparin Anticoagulation
Labetalol hydrochloride Blood pressure control
Lidocaine ' Local anesthesia
Midazolam Sedation
Nitroglycerin parenteral Treatment of catheter-induced vasospasm
Nitroglycerin paste Prevention of catheter-induced vasospasm
Nitroglycerin tablets Treatment of angina
Protamine Reversal of systemic heparin anticoagulation

Table 2. Medications used routinely'

Medication Purpose
Acetylcysteine Treatment of patients with renal insufficiency
Aspirin (oral and suppository preparations) Antiplatelet therapy
Benadryl Treatment of allergic reactions
Clopidogrel Antiplatelet therapy
Dobutamine Blood pressure and heart rate support
Dopamine hydrochloride Blood pressure and heart rate support
Flumazenil Reversal of benzodiazepines
Furosemide Management of elevated intracranial pressure
Glucagon Control of gastric motility during spinal angiography, may be useful for treatment of anaphylaxis in patients on beta blockers
Glycoprotein (GP) IIb-IIIa inhibitor, parenteral (e.g., eptifibatide or abciximab) Antiplatelet therapy
Lidocaine (preservative-free, for provocative testing) Provocative testing of the retina or peripheral nervous system before embolization
Mannitol Management of elevated intracranial pressure
Naloxone hydrochloride Reversal of narcotics
Norepinephrine Vasopressor
Ondansetron Antiemetic
Phenylephrine Blood pressure and heart rate support
Propofol Sedation and analgesia
Sodium amobarbital (Amytal) Provocative testing before embolization of the central nervous system or for Wada testing '
Sodium methohexital (Brevital) Provocative testing before embolization of the central nervous system'
Sodium nitroprusside Blood pressure control
Vasopressin Vasopressor

Table 3. American Society of Anesthesiologists Physical Status Classification System* I. Normal healthy patientII. Patient with mild systemic diseaseIII. Patient with severe systemic diseaseIV. Patient with severe systemic disease that is a constant threat to lifeV. Moribund patient who is not expected to survive without the operationVI. Declared brain-dead patient whose organs are being removed for donor purposes The addition of an ‘E’ indicates emergency surgery. *Obtained from reference (8). Table 4. Goldman Cardiac Risk Index* Nine independent risk factors are evaluated on a point scale:

Risk Factor Points
Third heart sound (S3) 11
Elevated jugulovenous pressure 11
Myocardial infarction in past 6 months 10
Electrocardiogram shows premature arterial contractions or any rhythm other than sinus 7
Electrocardiogram shows >5 premature ventricular contractions per minute 7
Age >70 years 5
Emergency procedure 4
Intrathoracic, intra-abdominal, or aortic surgery 3
Poor general status, metabolic or bedridden 3
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