Introduction
Anesthesia for pediatric interventional radiology (IR) procedures is a rapidly increasing, highly challenging, very rewarding area of practice. Anesthesiologists are finding their services in greater demand than ever in radiology, both diagnostic and interventional [1,2]. Referring services increasingly recognize the expanding range of diagnostic questions that can be answered and the minimally invasive procedures which can be performed by radiologists. However, while an adult patient can tolerate these procedures with little or no anesthesia, a child may require at least sedation and often a general anesthetic for their safe completion. In our own institution, we have experienced a nearly two-fold increase in anesthesia cases in the IR suite over the past decade, such that there are now two or three dedicated anesthesia teams in IR each workday.
The purpose of this chapter is to describe the challenges inherent in IR and outfield anesthesia, the range of cases generally performed in the IR suite, and ways in which safe and successful anesthesia can be provided in this environment.
Preoperative Workup and Safety
Any discussion of pre-anesthetic workup of patients for IR must perforce include the overall context of safe practice. The challenges inherent in administering anesthesia in IR and in any non-operating room location are myriad and well-described [3]. The physical obstacles are obvious: crowded, poorly lit procedure rooms with little leeway for anesthesia equipment, possibly unfamiliar or poorly maintained anesthesia equipment and monitors, physical separation of the patient from the anesthesiologist and remoteness from the main operating room anesthesia support. The nursing and support personnel in IR may be unfamiliar to the anesthesiologist. These personnel may also be less familiar with the fine points of anesthetic care and how they can help the anesthesiologist, both with routine care and when a crisis develops [4].
Less overt but equally significant are the intrinsic challenges of the patients themselves [1]. There is a tendency among referring services to equate “less invasive” with “less risky.” As a result, patients who are deemed to be poor surgical candidates for an open procedure will be sent to IR, where anesthesia or sedation will have to be administered nonetheless. The combination of a relatively minor interventional procedure with major patient comorbidities is a constant of life in IR anesthesia; an informal survey of cases in our institution found that up to 30 percent of cases in IR are emergent add-ons, with an ASA Physical Status of 3 or greater. Additionally, there may be greater variability in the workup of patients for radiology, increasing the risk that important information or the opportunity for timely pre-procedure medical corrections may be missed.
How, then, does one safely and successfully administer anesthesia in such a potentially daunting environment? A number of factors are crucial, and most involve standardizing practice in the outfield to that in the main operating room. Over the years, the practice of anesthesia in the operating room setting has achieved a high degree of safety and reliability, and rather than re-invent the wheel the goal of caregivers in the outfield should be to export these proven practices. It should be noted that standardization is not just good practice, it is a goal encouraged by both the Centers for Medicaid and Medicare and The Joint Commission [5].
Pre-anesthetic review of patients should be the same regardless of ultimate anesthetizing location. In our institution all pre-anesthesia patients have a chart review followed by a preoperative clinic visit or inpatient examination by an anesthesiologist when indicated. While emergent add-on patients – a significant percentage of cases in IR – may have an abbreviated review, this process allows a large number of patients to be reviewed and optimized well before they arrive for their procedure. Anesthesiologists need to act as the final arbiter of whether a child is able to undergo the physiologic stress of anesthesia for a procedure, regardless of the location in which that anesthetic will be delivered, and should be empowered by their institution to act in that role.
The presence of familiar equipment and monitors is essential. The IR suite should be equipped with the same anesthesia machines, monitors, and carts that are present in the main operating room, with the goal of reducing or eliminating errors due to unfamiliar or poorly maintained equipment. Stocking of anesthesia medications and supplies should likewise be standardized to that of the main operating room. Care of a complex patient should never be compromised by outdated equipment or inadequate supplies.
Post-anesthesia care should likewise be consistent with the main operating room. While in a busy radiology department it is often desirable to have a dedicated post-anesthesia recovery unit (PACU), standards for monitoring and discharge should be the same as those in the main PACU. Anesthesiologist coverage of these outfield PACUs should be explicitly delineated in case of emergency.
Emergency equipment such as defibrillators and “code carts” must be readily accessible and familiar to staff in the IR suite. While less-commonly used equipment such as difficult airway carts and malignant hyperthermia treatment carts may not be kept in the suite, protocols for their fast delivery must be well-understood. Protocols for summoning outside help, additional anesthesiologists, or the hospital “code team” must be well-delineated and easily activated in times of need. A very valuable exercise is regular simulation of emergency situations, so that everyone in the IR suite understands how they can contribute in the event of an emergency [6].
The most important element in the delivery of safe outfield care is communication within a committed, well-trained group of physicians, nurses, and radiology technologists. When the possibility of anesthesia backup is several minutes away, it is the personnel in IR who will be the anesthesiologist’s first, best resource in an emergency. Having a team of people, all of whom know the case and are invested in the patient’s safety, is crucial. One way to facilitate this is morning “board rounds” in which each patient is discussed in the presence of the radiologists, anesthesiologists, nurses, and technologists. At this time the procedure, expected complications, technology requirements, and anesthesia concerns are reviewed. This both clarifies the logistical issues of the day and helps foster a community approach to the care of the patient. It can be useful to have a core group of anesthesiologists who are familiar with both the procedures and the personnel in IR, who can work effectively in that setting and act as a resource for their colleagues who are less comfortable in that setting.
Procedures
A day in a pediatric IR suite can include vascular procedures such as a cerebral angiogram or sclerotherapy of a peripheral vascular anomaly. Nonvascular procedures include abscess aspiration, ascites drainage, primary feeding tube placement, bone or soft tissue biopsy, and PICC line placement. These can be performed on patients ranging from a baby a few hours in age to an obese young adult – a range of cases and anesthetic requirements that can be dizzying.
Choice of anesthetic depends on a combination of patient-based and procedure-based factors. A mature older child may be able to tolerate a relatively minor procedure with light sedation and local anesthesia; however, in many cases the needs of the patient and procedure will necessitate a patient who is at minimum deeply sedated. Knowledge of the procedure to be performed, its length, the necessity for apneic episodes, likely complications, need for exams postoperatively, and pain medication requirements will all influence one’s choice of technique.
Biopsies and Drain Placements
Drainage of fluid collections and biopsies are some of the most common procedures performed in any IR suite. The patient population can run the gamut from the otherwise healthy child with a suspicious lump to a child after liver transplant with a bile collection and septic physiology. These can often be performed with ultrasound guidance, although deeper targets or those near vital structures can require CT guidance.
The location of the tissue to be biopsied or drained and the imaging mode to be used help determine the type of anesthesia required, although the patient’s overall health will always be the final determinant. For patients who cannot be placed supine, such as those with large pleural effusions or an anterior mediastinal mass, the radiologist can perform the procedure under ultrasound guidance with the patient in a semi-recumbent or even frank upright position. This is a situation where good pre-procedure communication will ensure safe and speedy completion.
Ultrasound-guided procedures generally can be done with moderate to deep sedation even in young infants, since the radiologist will be able to watch the needle continuously during the procedure. Soft tissue biopsies are not very painful postoperatively, particularly if local anesthetic has been utilized, and moderate intraoperative narcotic may be sufficient. Placement of a drainage catheter does involve more discomfort, although infiltration of local anesthesia can mitigate this.
CT-guided procedures, e.g., biopsy of bony lesions, require an immobile patient under general anesthesia since any motion necessitates another round of scanning and more patient irradiation. Bone biopsies tend to be more painful than soft tissue biopsies, and should be treated accordingly. Ketorolac is quite helpful, if the child is old enough for it to be safely administered.
Complications from these procedures are quite rare. They include bleeding and puncture of non-target structures [7]. Biopsies of solid organs should all have blood bank specimens sent, although the chance of needing transfusion is quite low [8]. Drainage of an abscess will occasionally result in changes in hemodynamics reminiscent of sepsis. These are generally short-lived and responsive to supportive therapy [7].
PICC Placement
This procedure is often done on some of the sickest patients in the hospital. Everything else being equal, which it rarely is, patients for percutaneously inserted central catheter (PICC) insertions only require sedation to lie still. If a patient is very small (5 kg or less) or has had multiple lines placed previously, it is very possible for this procedure to require multiple attempts and take well over an hour, in which case it may be desirable to place a laryngeal mask airways (LMA) or endotracheal tube (ETT). Pain medication is rarely necessary, as local anesthetic can be given at the insertion site. As above, if a patient’s status is such that little sedation can be safely given, i.e., a patient with poorly palliated congenital heart disease, it is essential to communicate this to the radiologist before the procedure so that they can decide if they will be able to perform the procedure on a patient who may not be completely still.
Sclerotherapy of Vascular and Lymphatic Malformations
Vascular malformations (VMs) and lymphatic malformations (LMs) are slow-flow congenital vascular lesions which can be treated by a variety of IR methods [9,10]. The most common is chemical sclerotherapy to scar a lesion’s endothelium. The various agents are discussed below. Additionally, endovenous and cutaneous laser therapy may be employed, glue may be injected or coils deployed. Patients may have isolated lesions of a few centimeters’ diameter or syndromes such as Klippel–Trenaunay or CLOVES, whose lesions encompass an entire extremity or more (see Figure 32.1) [11,12]. In the past, common practice was to not treat asymptomatic VMs and LMs until the patient was old enough to complain about cosmesis. However, recent evidence suggests these lesions will inevitably continue to grow and become more difficult to treat [13,14], making it increasingly common for younger patients to present for treatment.
These cases and embolizations of intracranial vascular anomalies (see below) tend to be the longest procedures in IR, lasting 8–10 hours for extensive lesions. Depending on positioning and length of procedure, these cases can be done with an ETT, LMA, or even sedation. Blood loss is not significant as a general rule, but good access to ensure adequate hydration is a must, and arterial lines are rarely necessary.
These procedures may begin with significant contrast loads from venography. Euvolemia to slightly hypervolemia is recommended to offset the osmotic diuretic effect of IV contrast [15]. Sclerosants such as alcohol and sodium tetradecyl sulfate (STS) cause hemolysis in a dose-dependent fashion. If hematuria is noted or expected, our practice is to infuse saline with bicarbonate at the maintenance rate and use crystalloid for any other needed hydration, which should be generous [16].
Large ectatic veins with slow flow are at high risk of intralesional thrombosis. This can act both as a source of potentially fatal thromboembolism, and as a nidus of consumptive coagulopathy [17,18]. Treatment for this is anticoagulation, which slows clot formation in the lesion and makes clotting factors available for the rest of the body. A similar coagulopathy can develop in a patient with a large macrocystic LM if there is hemorrhage into the cyst. Periprocedure anticoagulation should be discussed with a hematologist familiar with this pathophysiology.
Cervicofacial VMs or LMs can be particularly challenging (see Figure 32.2). Intubation may be difficult due to involvement of the tongue or floor of the mouth, and in some severe cases a tracheostomy tube may be placed before a course of treatment starting in early infancy. Even if intubation is accomplished, it is important to recognize that post-procedure swelling from all chemical sclerosants will increase for several hours after instillation, and extubation should be carefully considered if a lesion is treated near the airway. Our practice is to slightly undersize endotracheal tubes for a low initial air leak. If the leak has increased at the end of the case, maintaining intubation for a few hours to determine if extubation is safe after swelling peaks may be advisable. Postoperative intubation can be necessary for several days.
Figure 32.2 Twelve-year-old female with cervicofacial lymphatic malformation. This patient required tracheostomy as an infant due to severe airway obstruction.
Sclerotherapy Agents
STS. Sodium tetradecyl sulfate is moderately painful on injection, and causes tissue swelling that adds to postoperative pain. STS’s potential for causing hematuria is mentioned above. Post-procedure pain responds well to moderate doses of narcotics with ketorolac when appropriate. Skin ulceration is possible if STS is injected into vessels immediately under the skin, but more systemic adverse effects are rare [19].
Alcohol. Alcohol is quite painful at the time of injection, and the patient will often respond with transient increases in heart rate and blood pressure. It is important not to over-treat this acute response; it is possible to over-narcotize a patient with a potentially significant blood alcohol level [20]. Possible hematuria is mentioned above. There can also be local swelling and postoperative skin ulceration. Serious systemic effects up to cardiovascular collapse have been described with larger doses [21]. Alcohol can be quite nauseating in the postoperative period, and aggressive PONV prophylaxis is required. Postoperative pain usually requires moderate narcotics and ketorolac.
Doxycycline. Doxycycline is less painful on injection, but due to its acidity (pH 1–2) it is very painful postoperatively. Patients report the worst pain for the first few hours post-procedure. These patients need generous doses of narcotic, with ketorolac if indicated. Clonidine can be helpful as an analgesic and slight sedative in the postoperative period. Deep extubation is often helpful as patients can then sleep through the most painful postoperative period. Of all the sclerosants, doxycycline causes the most significant postoperative swelling [22,23].
Bleomycin. Bleomycin is the newest agent being used for treatment primarily of head and neck lesions. It causes less swelling than doxycycline, and may be less painful, with pain medicine requirements similar to those for STS. While pulmonary fibrosis and interstitial pneumonia have been reported with chemotherapy doses, bleomycin doses for sclerotherapy are much lower and such complications have not been described [24,25].
Lymphangiography
This procedure is performed by accessing lymph nodes in the groin with a tiny needle, through which a lipid-contrast mixture is slowly infused to define the central conducting lymphatics [26]. Patients may present with thoracic effusions or chylous ascites from congenital defects in lymphatics or after cardiac or thoracic surgery. Appropriate management of these patients’ comorbidities is the most challenging aspect of their anesthetic. It is essential that the patient be absolutely still since once access to a lymph node is lost it cannot be reestablished. While this can be achieved with very deep sedation, the need for apnea should be discussed with the radiologist. This is not a painful procedure, but can take anywhere from one hour to several hours for cases of disordered lymphatic flow. Embolization of the conducting lymphatics can take many hours and similarly requires an absolutely still patient.
Diagnostic Cerebral Angiography
Diagnostic cerebral angiograms are generally quick procedures, taking less than one hour. They are the gold standard for delineating vascular pathology, such as arteriovenous malformations (AVM) and vasculitis [3,27]. As an infant or young child cannot cooperate either with being still or the required intermittent apnea, these cases are performed with endotracheal intubation. Arterial catheters are rarely necessary. Contrast loads can be significant, so generous hydration is recommended. The most common complication is bleeding at the femoral puncture site [28,29]. Thus, for both diagnostic angiograms and for AVM embolizations, deep extubation possibly supplemented by α2 agonists prior to extubation should be considered, as patients need to lie flat for several hours after arterial decannulation [30,31]. Pain is not usually significant after these procedures.
Embolization of Cerebral Arteriovenous Malformations
Intracranial AVMs requiring treatment are uncommon in the very young patient, but are particularly challenging to manage when they do manifest. In utero or in young infants these lesions, which are often Vein of Galen malformations, tend to present with heart failure [6,32]. Depending on the severity of heart failure, the prognosis even after treatment for Vein of Galen malformations is poor. Older children with either Vein of Galen malformations or other AVMs more commonly present with hydrocephalus or intracranial hemorrhage, which can be devastating [33].
Cerebral AVMs can be treated in a variety of ways. Coils or balloons can be deployed, particulate matter can be injected, and sclerosing agents or various forms of glue can be injected. Cerebral embolization procedures tend to be quite prolonged. They are almost universally performed with endotracheal intubation and consistent muscle relaxation, as motion could be catastrophic. Blood loss from these cases is usually minimal, but good access for hydration is necessary to offset the diuretic effect of intravenous contrast [15]. The radiologist instills heparinized saline via the femoral catheter to reduce the chance of microemboli [34]; this can result in a significant amount of fluid over a long case. Close blood pressure control is generally required for treatment of intracranial AVMs, requiring an arterial catheter. Vasoactive medications are rarely necessary to keep blood pressure below a predetermined maximum, but must be readily available. Pain is not usually significant after these procedures. As mentioned above, deep extubation possibly supplemented by α2 agonists should be considered, as patients need to remain flat postoperatively.
Hemodynamic changes may occur during AVM embolization. In some patients with heart failure due to high cardiac output, treatment of the AVM can result in almost immediate improvement in the patient’s physical status [35]. Embolization with ethylene vinyl alcohol copolymer glue (Onyx, Covidien, Plymouth, MN) has been reported to induce bradycardia [36]. Due to alterations in flow dynamics in a treated AVM, there may be a period of increased risk of hemorrhage [37,38]. This is particularly true if embolization has not been complete, as in the case of embolizations done presurgical resection [39].
Post-embolization care emphasizes control of blood pressure to avoid sudden increases [39], although there are few descriptions of how to achieve this in pediatric patients. Our group has had success with a continuous low-dose infusion of dexmedetomidine, but we have not attempted this on young infants, who we tend to keep intubated and sedated.
The most common complication is again bleeding at the femoral artery puncture site. With injection of embolic agents, there is always the possibility of inadvertent closure of arteries supplying nearby normal brain tissue, either through glue migration or because the target vessel supplies both normal and abnormal tissue. This latter risk is fortunately extremely low [35].
Intra-Arterial Chemotherapy Injection
Injection of chemotherapy into a tumor’s feeding artery is a therapy described for retinoblastoma, and thus may be performed in quite young children [40]. Access is obtained via the femoral artery, and chemotherapeutic agents are injected specifically into the affected ophthalmic artery. Anesthesiologists can assist by giving oxymetazoline nasal spray to the ipsilateral nostril just prior to chemotherapy injection to shrink the nasal branch of the ophthalmic artery and drive flow to the ophthalmic portion [41]. Albuterol is given at the same time since this protocol is associated with a not insignificant incidence of bronchospasm. Prophylaxis for PONV should be given even in young patients.
Conclusion
In many institutions, including my own, the not-quite-joking question to any anesthesiologist who is often assigned to IR is “Who’s mad at you?” It can certainly seem like a less-desirable assignment to be sent outside the familiar surroundings of the main operating rooms if one is unprepared for it. I recommend fluency with the proposed procedures, proper equipment selection and setup, adequate preoperative workup of patients, and an IR staff with the training and motivation to provide effective backup in an emergency. Once this is ensured, the anesthesiologist can focus on providing exceptional care to some of the most challenging patients in the hospital
References
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