Medical technology and innovation continue to drive change in the anesthesia work environment. One area of rapid growth is interventional neuroradiology (INR). The number, variety and complexity of conditions that can be treated in pediatric and adult patients continue to expand (Table 1). This discipline is a chimera of neurosurgery, neurology and radiology. It has the potential to offer cures and palliative care for a wide range of disease processes that were only amenable to surgical intervention in the recent past. INR is now a part of every neurosurgeon’s residency training. The proceduralist, however, may be a neurosurgeon, a neurologist or a radiologist.
Anesthesiologists are essential to this process as these procedures can be long, uncomfortable and require manipulation of physiological parameters such as blood pressure. Currently, most of these cases are done in the radiology department, which is likely remote from the O.R. The anesthesiologist has to contend with a host of problems that are inherent to remote locations, including a lack of emergency assistance; cramped, dark rooms; and unfamiliar surroundings and equipment. This situation will change in the future as hybrid O.R.s with biplane technology are built.
The International Subarachnoid Aneurysm Trial (ISAT)1 established the importance of endovascular coiling in the treatment of cerebral aneurysm. In this study, patients who were treated with aneurysm coiling did as well or better than those treated with traditional surgical clipping. The patients treated with coiling did have higher rates of early rebleeding. In addition to coiling, cerebral endovascular stents are now being used to treat aneurysms that previously could only be treated with surgical clipping. These include wide neck, and large or giant aneurysms.
Table 1: Common Procedures in INR That Require Anesthesia
Balloon Angioplasty of Cerebral Vasospasm
Embolization of AVM
Treatment of Cerebral Aneurysm
Preoperative Embolization of Brain Tumors
Thrombolysis of Acute Stroke
Functional Examination such as Carotid Occlusion or Wada Test
What are the anesthetic considerations for these procedures? The first and most important decision in the INR suite is the type of anesthesia: general anesthesia or conscious sedation? This decision is made after a thorough discussion between the anesthesiologist and the proceduralist. The proceduralist must communicate his or her expectations and needs; for instance, if no patient movement is a priority, then general anesthesia is a necessity. Immobility can be achieved with conscious sedation, but it’s guaranteed with general anesthesia. If the case is likely to take many hours, then starting with general anesthesia may save all parties time and trouble. The big advantage to conscious sedation is the ability to continuously assess the neurological status of the patient. These elements must be considered before a final decision is made.
Anticoagulation with heparin is necessary to prevent thromboembolic complications during and after INR procedures. A baseline activated clotting time (ACT) and subsequent ACT will need to be monitored. The ACT can be drawn by the proceduralist off a side port of the femoral artery introducer sheath or from a radial artery catheter placed by the anesthesiologist. Many of these cases will require blood pressure monitoring into the postoperative period, so a separate A-line is helpful.
Increasingly, antiplatelet agents are being utilized in the management of cerebrovascular disease. All of the antiplatelet agents have long durations of action and have been associated with major bleeding. Unlike heparin, the anticoagulation cannot be reversed. Patients will need platelets if intracranial hemorrhage occurs.
Another typical INR procedure is the embolization of arteriovenous malformations (AVMs). Embolization is sometimes done in stages, with the ultimate goal being surgical resection of the entire lesion. Two commonly used agents, n-butyl cyanoacrylate and Onyx, are injected into the arterial feeder vessels of the AVM in order to obliterate them. The proceduralist may ask for induced hypotension during this phase to prevent a systemic embolization. An arterial catheter is necessary to perform induced hypotension safely. Onyx has been associated with oxygen desaturation, making blood gas analysis important during the procedure.2
The treatment of acute ischemic stroke (AIS) is an emerging INR procedure. Acute stroke centers are being established all over the country, as restoration of blood flow after AIS is associated with improved outcome and reduced mortality.3 Endovascular revascularization involves a variety of different therapies designed to either dissolve or mechanically retrieve the clot. Since time to revascularization is an independent predictor of good outcome in patients with AIS, the anesthesia team should be informed early about a case and be ready to respond.
As with other INR procedures, anesthetic management during revascularization includes local anesthesia, sedation or general anesthesia. In the setting of acute stroke, studies suggest that general anesthesia may be associated with poor outcome.4 This study and others like it have a common problem, however; the patients receiving general anesthesia have worse baseline stroke scores and higher rates of pre-procedural aspiration. So it is unclear how anesthesia selection affects outcome. Moreover, recent evidence suggests that in the setting of general anesthesia, systolic blood pressure less than 140 mmHg was a predictor of poor outcome.5 If general anesthesia is required, then hypotension should be avoided.
Early placement of an arterial line is essential for precise control of blood pressure during an acute stroke. However, since time to stroke treatment is critical, arterial line placement should never delay the start of the case. Arterial pressure can always be obtained from the femoral sheath during the procedure.
One outcome all of these procedures share is the possibility of an intracerebral catastrophe. If this happens, the proceduralist must communicate whether the problem is vessel occlusion or vessel rupture and hemorrhage. An occlusion can be treated with induced hypertension to try to use collateral circulation to restore perfusion. Hemorrhage would require the immediate reversal of anticoagulation. Either of these situations may ultimately require a trip to the O.R. for an emergent craniotomy. The equipment and a plan to safely transport a critically ill patient must always be ready.
At the end of an INR procedure, the surgeon or radiologist will want to perform a neurological exam. A timely emergence from general anesthesia will allow this exam to take place. The anesthesiologist should plan for this, and appropriate drugs and doses should be used. It’s important to remember that a patient with a deteriorating neurological status may emerge slowly no matter how skillfully the anesthetic is administered. Managing the expectations of the proceduralist on this issue can prevent trouble at the end of the case.
In the future, INR techniques could be used to treat brain tumors. Howard Riina, M.D., Professor of Neurosurgery at NYU Lagone Medical Center, has used a super-selective infusion of bevacizumab to treat glioblastomas.6 Dr. Riina feels it’s just a matter of finding the right chemotherapeutic agent to make this treatment viable.
Finally, working in INR will expose you to a great deal of radiation. It’s important to have a full-body lead apron, thyroid shield, eye protection and a radiation badge. Furthermore, it’s a good idea to stand behind a portable glass shield and move as far away from the radiation source as possible. There are more detailed reviews of anesthesia for INR available in the literature.7,8
John L. Ard, Jr., M.D. is Assistant Professor of Anesthesiology, New York University Langone Medical Center, New York, New York.
T. Kate Huncke, M.D. is Clinical Professor and Vice Chairman, New York University Department of Anesthesiology
1. Molyneux AJ, Kerr RS, Yu LM, et al.; International Subarachnoid Aneurysm Trial (ISAT) Collaborative Group. International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion. Lancet. 2005;366(9488):809–817.
2. Parmuk AG, Saatci I, Cekirge HS, Aypar U. A contribution to the controversy over dimethyl sulfoxide toxicity: anesthesia monitoring results in patients treated with onyx embolization for intracranial aneurysm. Neuroradiology. 2005:47(5):380-386.
3. Rha JH, Saver JL. The impact of recanalization on ischemic stroke outcome: a meta-analysis. Stroke. 2007;38(3):967-973.
4. Abou-Chebl A, Lin R, Hussain MS, et al. Conscious sedation versus general anesthesia during endovascular therapy for acute anterior circulation stroke; preliminary results from a retrospective, multicenter study. Stroke. 2010;41(6):1175-1179.
5. Davis MJ, Menon BK, Baghirzada LB, et al.; The Calgary Stroke Program. Anesthetic management and outcome in patients during endovascular therapy for acute stroke. Anesthesiology. 2012;116(2):396-405.
6. Jeo JY, Kovanlikaya I, Boockvar JA, et al. Metabolic response of glioblastoma to superselective intra-arterial cerebral infusion of bevacizumab: a proton MR spectroscopic imaging study. AJNR AM J Neuroradiol. 2012;33(11):2095-2102
7. Lee CZ, Young WL. Anesthesia for endovascular neurosurgery and interventional neuroradiology. Anesthesiol Clin. 2012;30(2):127-147.
8. Schulenburg E, Matta B. Anesthesia for interventional neuroradiology. Curr Opin Anesthesiol. 2011;24(4):426-432.
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