Organization and Administration

A collaborative relationship between extramural and anesthesiology departments is critical to providing safe patient care. At a minimum, safe patient care requires appropriate anesthesia equipment and monitors, adequate space, and experienced ancillary providers who are knowledgeable in anesthesia and facile in providing assistance if needed. Each off-site area has its own needs, goals, and guidelines. It is ideal to designate a team of anesthesiologists committed to providing extramural anesthesia care and troubleshooting the logistical challenges in the various locations. Each member should rotate regularly through the different extramural sites in order to maintain familiarity with the procedures, to foster a relationship with the physicians and ancillary personnel, to understand the anesthesia demands unique to each site, and sharing information about ongoing advances. Technological advances are particularly expanding in the field of radiology, and complicated imaging studies challenge the anesthesiologist to have an understanding of the unique conditions that each study requires. Understanding these requirements will guide the anesthesiologist in developing a management plan (Lee et al, 2008).

In the past, extramural locations were not designed with the anesthesiologist in mind. The need for anesthesia had not been anticipated when off-site locations were planned. It is only within the past decade that the demand for anesthesia services in these sites has burgeoned. Thus, most off-site locations have not been configured to support the capabilities for anesthesia. Ideally, anesthesiologists should be involved in the early stages of site design to ensure that minimum standards for anesthesia delivery are met and to troubleshoot engineering issues and advocate for adequate space for anesthetic induction and emergence (Committee on Drugs, 1992; American Academy of Pediatrics Section on Anesthesiology, 1999). Physical plant considerations for MRI-site planning have been previously described (Koskinen, 1985). When anesthesia services are requested, these sites may not meet minimum standards and may require reengineering to meet minimum requirements of the American Society of Anesthesiologists (ASA) (House et al., 1994). The anesthesia machine should be equipped with back-up supplies of E cylinders filled with oxygen and nitrous oxide. If pipeline oxygen is not available, then oxygen should be supplied from H cylinders (6600 L) rather than the smaller E tanks (659 L).

Scavenging systems should be carefully evaluated in the extramural location. Unlike the operating room, passive scavenging systems may not always be possible. A safe means of active scavenging may be provided by the vacuum at the wall or wall suction canisters. A scavenging system should be dedicated solely to waste gases. Many MRI scanners do not have wall suction because MRI-compatible wall suction is not widely available. If the suction is located outside the MRI suite, then a mouse-sized hole may be created in the suite’s wall to allow suction tubing to be passed inside (Koskinen, 1985).

Electrical circuitry and lighting in extramural locations may not be up to operating room standards, even if the outlets are grounded and up to hospital grade. Although some extramural locations carry minimal risk of electrical shock or electrocution, these sites do not have line-isolation monitors (LIMs) and therefore do not warn of excess leakage of current. Supplemental lighting for recordkeeping, label verification, establishment of intravenous (IV) access, and visualization of the patient is critical. Even under the best circumstances, for example, lighting is dim in the MRI scanner, and monitoring by simple clinical observation can be limited. Anesthesia personnel may not always remain in the imaging suite, particularly during ionizing radiation imaging, computerized tomography (CT) scanning, and radiation therapy. Monitoring capabilities via remote television or hardwiring through reinforced walls can allow video display of the patient and the physiologic monitors within.

A storage area large enough to stock anesthesia equipment and supplies must be easily and quickly accessible. This area should be routinely checked, restocked, and kept locked when anesthesia services are not required. The need for redundancy of nondisposable supplies is a matter of philosophy. Are two laryngoscopes enough, or should there be a third? Is one electrocardiograph (ECG) monitor enough, or should there be a battery-operated monitor for back-up and transport? Drugs should be checked according to the usual operating-room routine, and expired medications should be replaced. Gas-cylinder supplies must be reliable, especially in areas without piped oxygen. A code cart should be conveniently located in an area known to all physicians and ancillary personnel. This cart should be routinely checked and restocked. With larger volumes of patients necessitating significantly sized critical care areas, strong consideration should be given to having a difficult-airway cart available at extramural locations.

Finally, extramural anesthetizing locations are often distant from the operating room. Patients may need to remain anesthetized during transport to or from the extramural location. For these circumstances, assured elevator access with key-controlled emergency overrides is a must. All anesthesiologists who deliver extramural services should be familiar with their surroundings. Checklists are invaluable to guarantee consistent patient care, anesthesia monitoring, equipment, documentation, and back-up assistance.

Personnel, Support, and Logistics

Support and medical personnel in nonsurgical areas may not be familiar with the requirements of an anesthesiologist, thus providing an important educational and training opportunity. Proper training facilitates teamwork and minimizes chaos in critical situations. A standard anesthesia cart at each anesthetizing location should be fully stocked with essential medications, necessary additional equipment, a spare self-inflating bag, endotracheal tubes, laryngeal mask airways (LMAs), suction catheters, IV supplies, laryngoscope handles and blades, and a variety of oral and nasopharyngeal airways.

Leadership is crucial; a director of anesthesia services at an extramural location can orchestrate, facilitate, and coordinate anesthesia services. This director can also serve as a consultant for the other medical and nursing staff. By being available to answer questions, do on-site consultations, examine patients, and provide back-up support or emergency-airway expertise, the anesthesiologist can also support a nurse-administered sedation program. Nurses who provide sedation under the supervision of the ordering extramural physician (e.g., gastrointestinal, radiologic, or dental) should have Pediatric Advanced Life Support (PALS) and Basic Life Support (BLS) certifications. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) (2009) requires that individuals who administer sedation are able to rescue patients from whatever level of sedation or anesthesia is achieved, whether intentional or unintentional. All children scheduled for nursing sedation during a scan should receive a prescreening telephone call from a radiology nurse the day before the scheduled scan. Often, these telephone calls are made after business hours to ensure that a parent is home. The nurse reviews the medical history, relays fasting instructions, and reminds the parent to administer the child’s routine medications with a sip of clear fluid. The supervising physician must give final approval for sedation after reviewing the child’s medical history and current medical status and before ordering the medications. To minimize the chance of drug-delivery error or miscalculation, it is helpful to have preprinted order sheets or a computerized order-entry template.

It is crucial to know whom to call for assistance if a problem arises. A speed-dial system should be available from all extramural anesthetizing location sites in order to immediately request emergency back-up help.

Scheduling and Preparation of Patients

Appropriate planning for an anesthetic begins with a familiarity with the procedure. The requesting service orders the procedure and then leaves the logistics of scheduling to the extramural service. Radiologists recognize that involvement with anesthesia lengthens their total time commitment to a patient and potentially limits the number of procedures accomplished in a day (Winter, 1978; Cremin, 1990). A well-coordinated system to screen patients on the day of the procedure is important. Experienced personnel, ideally a certified pediatric nurse practitioner (CPNP), should be designated to take initial vital signs, review recent medical history, begin IV lines if necessary, and familiarize the family with the upcoming procedure, including anesthesia.

Screening patients for extramural procedures may be challenging and time consuming. Many children are chronically ill, nutritionally impaired, and have complicated medical conditions. These issues must be carefully addressed through attention to the patient’s history, physical examination, old medical records, outside consultations, and close communication with other medical colleagues. Several consultants may need to confer in order to fully understand the patient’s current state of health. Not every procedure is elective. Urgent procedures may be required despite an upper respiratory tract infection (URI), ongoing pneumonia, deteriorating physical status, untreated gastroesophageal reflux, sepsis, or hemodynamic instability. In these situations, consultation between the anesthesiologist, the requesting physician, and the radiologist should confirm urgency. Anesthesia plans should be adjusted to accommodate the requirements of the procedure (e.g., holding breath for a CT scan of the chest) and the patient’s medical condition.

It is not always possible for an anesthesiologist to provide sedation and anesthesia for all children when there is a large volume of cases. A structured nursing sedation program can provide safe and effective sedation. In many hospitals, the extramural department (gastroenterology, radiology, cardiology) outsources responsibility for sedation to another department, which could include pediatrics, hospital medicine, anesthesiology, intensive care, or emergency medicine. After screening the patient, an appropriate referral for either general anesthesia or procedural sedation is the usual result. Because MRI is a unique environment, it is more efficient to have the MRI nurses screen patients before and on the day of the procedure. To ensure consistent decision making, the anesthesiology and radiology departments should develop a set of guidelines and easily identifiable “red flags ”to help in this triaging process (Table 33-1). If any questions arise, additional medical history needs to be clarified, or additional studies need to be performed, the nurse and anesthesiologist confer before making the final decision regarding general anesthesia or procedural sedation. In addition, chronically ill children often have electrolyte disturbances, coagulation and hematologic abnormalities, and hemodynamic instability. A consent for the administration of general anesthesia or procedural sedation must be obtained in parity with policies established for anesthesia in the operating room.

TABLE 33-1 Red Flags for Sedation

Because gastroesophageal regurgitation is common in infants, a detailed clinical history should be taken with regard to the incidence and timing of the regurgitation. If the reflux is predictable (i.e., only associated with mealtimes or soon thereafter) infants are usually approved for procedural sedation. Fasting guidelines are adjusted to minimize the risk of reflux. For example, if the infant has refluxes within 2 hours of eating solid food but never after 3 hours, the fasting guidelines for this infant may be extended to 6 hours for solids.

Selection of Agents and Techniques

The selection of an anesthetic technique in an extramural location depends on the patient’s underlying medical condition, age, drug tolerance, and anticipated procedure. The airway management may be influenced by the procedure itself, anticipated postprocedure course (e.g., intensive care unit [ICU] or postprocedure intubation) and past anesthetic course (e.g., difficult intubation). The assistance of an anesthesiologist is often sought when sedation administered by the radiologist has failed in the past; it is important to be aware that parents and radiologists may have the expectation that anesthesia will provide ideal conditions and guarantee successful completion of the procedure (Hubbard et al., 1992).

Premedication has many purposes: the relief of anxiety, easy separation from parents, sedation, analgesia, amnesia, reduction of salivary and gastric secretions, elevation of gastric pH, and decreased cardiac vagal activity. Medications should be adjusted to the psychological and physiologic condition of the patient and family. Parent-present inductions may be offered when the presence of a parent has a calming effect on the child. In the event of potentially detrimental parent anxiety, premedication may be preferable to a parent-present induction (Kain et al., 2001).

Barbiturates may be useful as the sole method of providing sedation. Pentobarbital, for example, has the advantage of providing sedation, causes minimal respiratory and circulatory depression, and is rarely associated with adverse events (Karian et al., 2002). Barbiturates have no analgesic properties. They can produce paradoxical reactions, especially in children. No antagonist to barbiturates is available, thus dosing should be carefully titrated. IV pentobarbital by titration has been used successfully by radiologists while monitoring oral and nasal air flow, oxygen saturation with a pulse oximeter (SpO₂), end-tidal carbon dioxide, and cardiac rate and rhythm, with transient decreases in SpO₂ in up to 7.5% of patients; interventions have included stimulation and head repositioning (Strain et al., 1988; Rooks et al., 2003).

Other studies have described the use of pentobarbital both in the oral and IV forms (Chung et al., 2000; Mason et al., 2001a). For infants younger than 1 year of age, oral pentobarbital is more successful and carries a lower rate of adverse events compared with chloral hydrate (Rooks et al., 2003). The long half-life of pentobarbital (approximately 24 hours) requires careful and conservative recovery and discharge guidelines. The dosage of oral pentobarbital is 2 to 6 mg/kg and up to 9 mg/kg in patients who are receiving barbiturate therapy.

Sodium thiopental in a mean induction dose of 6 mg/kg and a mean total dose of 8.5 ± 3 mg/kg has been used successfully as the sole anesthetic for CT and MRI in 200 children from 1 month to 12 years of age (Spear et al., 1993). Methohexital has a shorter recovery time than thiopental and is more effective than oral chloral hydrate (Manuli and Davies, 1993). Methohexital-induced seizures in patients with temporal lobe epilepsy have been reported. Thiopental or pentobarbital are alternatives for these patients (Rockoff and Goudsouzian, 1981). For patients taking barbiturate-containing anticonvulsant medications, a higher dose limit is generally more successful. Methohexital has also been used intramuscularly (IM) for radiotherapy in doses of 8 to 10 mg/kg. The onset time via this route is often twofold to threefold longer than rectally administered methohexital (Jeffries, 1988).

Although propofol does not have a labeled indication for children younger than 3 years of age, propofol has been used extensively in this age group as a means of providing sedation or anesthesia. Propofol sedation by bolus or continuous infusion for MRI scans of the brain can provide successful imaging conditions but with the risk of need for airway intervention and respiratory compromise (Vangerven et al., 1992; Cravero et al., 2009). Fatal metabolic acidosis and myocardial failure associated with lipemic serum have been reported in five children who were admitted to the ICU for respiratory support for upper respiratory tract infections while being sedated with continuous infusion propofol (Parke et al., 1992). Bloomfield and others (1993) have suggested a continuous infusion beginning at a rate of 99 mL/hr until the patients fall asleep (usually over 1 to 3 minutes) and then a decreasing rate during treatment, a strategy that works very well. Patients were typically awake, alert, and taking clear liquids 20 minutes later (Bloomfield et al., 1993).

Opiates reduce anesthetic, preprocedure, and postprocedure analgesic requirements. They are reversible with naloxone. Whereas narcotics may be unnecessary for diagnostic procedures that are not painful, they may be very useful for therapeutic interventions, especially for patients with postprocedural pain. They are also useful after anthracycline chemotherapy, with documented impaired myocardial function (Burrows et al., 1985). Because narcotics depress the ventilatory response to carbon dioxide (CO₂), this respiratory depression may be of particular concern for children with increased intracranial pressure. Narcotics may also worsen preexisting nausea and vomiting.

Benzodiazepines have the advantage of anxiolysis with minimal vomiting and cardiorespiratory depression. Diazepam is painful during IV injection and may lead to thrombophlebitis; midazolam is water soluble and therefore may be more suitable intravenously or intramuscularly. The elimination half-life of midazolam averages 2.5 hours, compared with 20 to 70 hours for diazepam (Greenblatt et al., 1981; Reves et al., 1985). Young patients or patients with significant liver disease may have prolonged duration and exaggerated effect of the benzodiazepines.

Preparation of the stomach and aspiration prophylaxis are of particular concern for urgently scheduled cases (outside of fasting guidelines) or when the medical history suggests aspiration risk. If using H₂-receptor antagonists, bronchospasm may occur in patients with asthma because of the relative increased availability of H₁-receptors. H₂-blockers may also inhibit metabolism of other concurrently administered medications. Metoclopramide accelerates gastric emptying and increases tone in the lower esophageal sphincter, but it is associated with a significant incidence of extrapyramidal side effects in children (Sledge et al., 1992). Ondansetron works synergistically with other agents through its vagal blocking actions in the gastrointestinal tract, as well as through its inhibition of the chemoreceptor trigger zone via serotonin receptor antagonism, particularly for patients undergoing radiation therapy with pulses of chemotherapy (Burnette and Perkins, 1992; Figg et al., 1993).

Ketamine has enjoyed great popularity during the past 30 years for sedation, analgesia, or anesthesia outside the operating room because of its support of the cardiovascular and respiratory systems. Ketamine-induced nightmares, hallucinations, delusions, and agitation are rare in children (Sussman, 1974; Hostetler and Davis, 2002). Karian and others (2002) have reported on a ketamine-sedation program for use in interventional radiology. In this program, IV or IM ketamine was administered in the interventional radiology suite by credentialed nurses and radiologists to patients undergoing select procedures. This protocol has allowed painful procedures to be tolerated by patients who previously would have required general anesthesia (Karian et al., 2002).

Dexmedetomidine, although not approved by the Food and Drug Administration (FDA) for pediatric use, obtained approval in October 2008 for adult procedural sedation in areas outside of the ICU. Particularly for pediatric sedation for radiologic imaging studies, dexmedetomidine alone in high dosages can achieve immobility for MRI and CT examinations (Mason et al., 2006, 2008a, 2008b). Its use for procedural sedation has still to be explored further, because its clinical application has been examined only in small studies and often in combination with ketamine (Barton et al., 2008).

Some patients require general anesthesia because of previous sedation failures, the need for a secure airway, or procedural logistics. Newer, less-soluble anesthetic agents such as sevoflurane and desflurane have pharmacokinetic profiles that compare favorably with propofol in adults; there seems little reason to think that this would not be the case with children, although pediatric anesthesiologists often avoid using desflurane because of its pungency and associated airway irritability (Van Hemelrijck et al., 1991). Since its introduction to clinical practice in the mid-1990s, sevoflurane has become the volatile anesthetic of choice in children. Its lack of airway irritability as a side effect and its ability to provide children with stable hemodynamic function, together with its rapid onset and offset make sevoflurane a useful agent for children (Furst et al., 1996).

Regional anesthesia, rarely administered outside the pediatric operating room, nevertheless remains a valid choice in some circumstances. Intercostal nerve blocks may be useful for lung or rib biopsies, chest tubes, biliary or subphrenic drainage procedures, and insertion of biliary stents. Nerve block of the brachial plexus by the axillary, interscalene, or supraclavicular route has been reported for the brachial approach to catheterization and neuraxial block of the lower extremities for femoral catheterizations and percutaneous approaches to the kidneys (Eggers et al., 1967; Ross, 1970; Lind and Mushlin, 1987). Spinal anesthesia in conjunction with regional hyperthermia and limb exsanguination has been successfully used for repeated painful radiotherapy on lower extremities (Spencer and Barnes, 1980).

Indwelling central catheters are implanted in the majority of radiotherapy patients and can be used for induction and maintenance of anesthesia, blood draws, IV fluid administration, and chemotherapy. Dressing changes are often accomplished in conjunction with the sedation or anesthesia. Antiseptic preparation of all injection sites with povidone-iodine and alcohol is critical. At the end of the session the catheter should be carefully flushed with heparinized saline. An alternative to central catheters is the use of a heparin-lock peripheral IV port, changed weekly, with careful parental instruction. Smoothness of emergence is particularly important after angiographic procedures because of the risk of a dislodged clot or bleeding at the puncture site. Some patients have been heparinized without protamine reversal. Unlike adults, sand bags and weights are not routinely applied to angiographic cannulation sites of children.

Occasionally, the loss of self-control with sedation results in dysphoria, and some patients fare better when they are completely awake. Minimal medication may be preferable in patients with complicated and unstable medical conditions who may not tolerate the anesthesia or sedation. Some procedures (e.g., unilateral carotid barbiturate injection or the Wada test) may require conversation, interaction, and responsiveness of the patient. In these situations, no sedation may be the best alternative.

Radiology

Embolization Procedures

Interventional techniques include nonvascular and vascular interventions (Towbin and Ball, 1988). In vascular interventions, embolization and sclerotherapy have become important techniques for treating vascular malformations, aneurysms, fistulas, and hemorrhage; for accomplishing renal ablation; and for presurgical embolization of hypervascular masses. Percutaneous transluminal angioplasty and fibrinolytic therapy are increasing in pediatric institutions; great success is being reported, even in the smallest infants, and the important contribution that adequate sedation and analgesia can make to ultimate outcome has been recognized (Diament et al., 1985).

Vascular malformations are congenital aberrant connections between blood vessels and may be composed of lymphatic, arterial, and venous connections. These lesions, although present at birth, are often discrete and not clearly visible. As the child grows, the vascular malformation may expand rapidly, growing with the child. This rapid proliferative phase may occur in response to hormonal changes (e.g., pregnancy or puberty), trauma, or other stimuli (Jackson et al., 1993). Vascular malformations may be high-flow or low-flow lesions, depending on which vessels are involved. High-flow lesions include arteriovenous fistulas, some large hemangiomas, and arteriovenous malformations. Particularly with large lesions, high-output cardiac failure and congestive heart failure with the potential for pulmonary edema should be anticipated and sought out in the medical history and physical examination. Low-flow lesions consist of venous, intramuscular venous, and lymphatic malformations. Surgical resection of symptomatic vascular malformations may be hazardous as well as unsuccessful—any vascular element not resected may enlarge and cause further problems.

Because vascular malformations enlarge over time, even asymptomatic lesions may require intervention. Patients with symptoms may suffer from pain, tissue ulceration, disfigurement, airway or cardiovascular compromise, impairment of limb function, coagulopathy, claudication, hemorrhage, and progressive nerve degeneration or palsy. Because large vascular lesions require multiple embolizations, parents and patients are often comforted by seeing familiar anesthesiologists, another benefit of having a core group of anesthesiologists in the radiology suite. Vascular embolization is also used as a bridge to surgical resection. Successful embolization and sclerotherapy decrease the size of the malformation and reduce blood flow to the lesion, thereby decreasing surgical risks.

When embolizing vascular malformations, radiologists often aim to cut off not only the feeding vessels but also the central confluence (nidus) where much of the arterial shunting occurs. Embolic agents include stainless-steel minicoils, absorbable gelatin pledgets and powder, detachable silicone balloons, polyvinyl alcohol foam, cyanoacrylate glue, and ethanol. The choice of agent depends on the clinical situation and the size of the blood vessel. When permanent occlusion is the goal, polyvinyl alcohol foam and ethanol are often employed. Both occlude at the level of the arterioles and capillaries. Medium to small-sized arteries may be occluded with coils, the equivalent of surgical ligation. Particularly in trauma situations, when only temporary occlusion (days) is the goal, absorbable gelatin pledgets or powder are used (Coldwell et al., 1994).

Large hemangiomas may be associated with the coagulopathy of Kasabach-Merritt syndrome. In this condition, the hemangioma traps and destroys platelets and other coagulation factors, resulting in thrombocytopenia and an increased risk of bleeding. As the hemangioma involutes, the coagulation status improves (Mulliken and Young, 1988). A condition described as systemic intravascular coagulation (SIC) can occur after the embolization of extensive vascular malformations. This condition is marked by an elevated prothrombin time (PT) with a decrease in coagulation factors and platelets.

Absolute (99.9%) ethanol is injected in vascular malformations to promote sclerosis. Ethanol may produce a coagulum of blood and cause endothelial necrosis (Becker et al., 1984). Sclerotherapy or embolization with absolute ethanol increases the risk of developing a postprocedure coagulopathy marked by positive D-dimers, elevated PT, and decreased platelets (Mason et al., 2001b). Ethanol causes thrombosis, because it injures the vascular endothelium. Ethanol also denatures blood proteins. Extensive ethanol injections can cause hematuria, and urinary catheters should be inserted to monitor urine output, diuresis, and hematuria. Especially with children scheduled for outpatient surgery, liberal fluid replacement ensures that the hematuria clears before discharge. Ethanol can cause neuropathy and tissue necrosis if it is not injected selectively. Using selective catheterization and direct percutaneous puncture, care is taken not to expose normal blood vessels to the ethanol. In addition to the risk of hematuria, ethanol also can produce significant serum alcohol levels. Mason and others (2000) note that up to 1 mL/kg of ethanol can be administered and that serum ethanol levels have been greater than the intoxication level of .008 mg/dL (Fig. 33-1). Patients with high serum-ethanol levels may be either sedated or extremely agitated, depending on their particular response to intoxication.

FIGURE 33-1 Relationship between ethanol administered (mL/kg) and serum ethanol level (mg/dL).

Embolization or balloon occlusion of arterial venous malformations, vascular tumors, intracranial aneurysms, and fistulae carries considerable risk of catastrophic results. Risks include a sudden intracranial hemorrhage, acute cerebral ischemia, or catheter or balloon migration. If sedated, the patient may require urgent airway management. Long cases require a urinary catheter, especially if contrast material is used.

Cerebral angiography requires motionlessness as well as exquisite control of ventilation. Anesthetic technique, in choice of agent as well as in control of arterial CO₂ tension, may affect cerebral blood flow and hence the quality of the scan. Cerebral angiography may be performed in children for the diagnosis or follow-up study of Moyamoya disease, and these children should have anesthetic techniques that minimize the risk of transient ischemic attacks (TIAs) and stroke during the procedure (Soriano et al., 1993). Other considerations include controlled hypercarbia to promote vasodilation and facilitate access and visualization of the vasculature for the radiologist. In the event of vasospasm or difficult access of small, torturous vessels, locally administered (through the catheter) nitroglycerin in small doses (25 to 50 mcg) may facilitate visualization and access. Occlusion of the venous portion of the arteriovenous malformation (AVM) without complete occlusion of the arterial inflow vessels could result in acute swelling and bleeding. Vascularity reduction through occlusion of major feeder vessels is the goal of embolizing large AVMs before planned surgical excision. This may be accomplished as a staged procedure over several days, involving repeated anesthetics or sedation sessions.

Angiographic imaging may be enhanced through the use of glucagon. Glucagon is efficacious for digital subtraction angiography, visceral angiography, and selective arterial injection in the viscera. When needed, glucagon is administered intravenously in divided doses of 0.25 mg to a maximum of 1 mg. Risks include glucagon-induced hyperglycemia, vomiting (particularly when given rapidly), gastric hypotonia, and provocation signs of pheochromocytoma (McLoughlin et al., 1981; Chernish et al., 1990; Jehenson, 1991). Children who receive glucagon should routinely receive prophylactic antiemetics.

The ability to intermittently assess neurologic function and mental status is invaluable during embolization procedures, but it may not be practical in children because of fear, pain, and movement. General anesthesia permits easier control of blood pressure and ventilation and eliminates the concern about patient movement. For children, general anesthesia is often preferred when performing high-risk procedures that require immobility and periods of breath-holding. Preprocedural assessment should include any history of seizures, bleeding, treatment with anticonvulsants or anticoagulants, neurologic symptoms, and evaluation of intracranial-pressure status. It is important to determine whether the patient has had any TIAs or has evidence of cerebrovascular occlusion. Vasodilator agents (calcium channel blockers) or nitrate derivatives may need to be administered after embolization. Because many patients are anticoagulated during the procedure, a preoperative coagulation profile should be obtained. A variety of anticoagulants may have to be on hand as well to prophylaxis for thrombosis (Bidabe et al., 1990).

Morbidity associated with embolization is not negligible. Arteriovenous malformations (AVMs) involving the head and neck often require cannulation of the external carotid artery branches and the thyrocervical trunk. All patients scheduled for embolization should be typed and cross-matched for blood. Those patients who undergo embolizations of AVMs of the head and neck are at risk for stroke, cranial nerve palsies, skin necrosis, blindness, infection, and pulmonary embolism (Riles et al., 1993). It is important to assess and document full return of neurologic status after the patient is extubated.