Interventional neuroradiology—anesthetic considerations☆

Preanesthetic considerations

The preanesthetic evaluation of a patient undergoing a potentially long diagnostic and therapeutic procedure in the neuroradiology suite expands on the routine preanesthetic examination of the neurosurgical patient. Airway evaluation should include routine evaluation of the potential ease of laryngoscopy in an emergent situation, and also take into the account the fact that, with the head and neck kept in a neutral position, sedation may compromise airway patency. Further, this patient

Monitoring and vascular access

Secure intravenous (i.v.) access should be available with adequate extension tubing to allow drug and fluid administration at maximal distance from the image intensifier during fluoroscopy. Access to i.v. or arterial catheters can be difficult when the patient is draped and the arms are restrained at the sides. Stopcocks and nonlocking tubing connections under the drapes should be minimized. Prior to covering the patient, the tightness of connections between segments of tubing should be

Radiation safety

There are three sources of radiation in the INR suite: direct radiation from the x-ray tube, leakage (through the collimators' protective shielding), and scattered (reflected from the patients and the area surrounding the body part to be imaged). A fundamental knowledge of radiation safety is essential for all staff members working in an INR suite. It must be realized that the amount of exposure decreases proportionally to the square of the distance from the source of radiation (inverse square

Anesthetic technique

Choice of anesthetic technique is a controversial area, and varies between centers. There are no data that support improved outcome with one technique or another. There appears to be a trend to move more towards general endotracheal anesthesia, but it is highly dependent on local practice and training.

Intravenous sedation

Primary goals of anesthetic choice for i.v. sedation are to alleviate pain, anxiety and discomfort, and to provide patient immobility. A rapid recovery from sedation is often required for neurologic testing.

Many neuroangiographic procedures, while not painful per se, can be psychologically stressful. This is especially true when there is a risk of serious stroke or death, particularly patients who have already suffered a preoperative hemorrhage or stroke. There may be an element of pain

General anesthesia

The primary reason for employing general anesthesia is to reduce motion artifacts and to improve the quality of images, especially in small children and uncooperative adult patients. This is especially pertinent to INR treatment of spinal pathology, in which extensive multilevel angiography may be performed. The specific choice of anesthesia may be guided primarily by other cardio- and cerebrovascular considerations. Total i.v. anesthetic techniques, or combinations of inhalational and i.v.

Anticoagulation

Careful management of coagulation is required to prevent thromboembolic complications during and after the procedures. Whether heparinization should be used for every case of intracranial catheterization is not clear to date. Generally, after a baseline activated clotting time (ACT) is obtained, i.v. heparin (70 units/kg) is given to a target prolongation of two to three times baseline. Heparin can then be given continuously or as an intermittent bolus with hourly monitoring of ACT.

Superselective anesthesia functional examination (SAFE)

SAFE is carried out to determine, prior to therapeutic embolization, if the tip of the catheter has been inadvertently placed proximal to the origin of nutritive vessels to eloquent regions, either in the brain or spinal cord [8]. Such testing is an extension of the Wada and Rasmussen test in which amobarbital is injected into the internal carotid artery to determine hemispheric dominance and language function. Its primary application is in the setting of brain arteriovenous malformation (BAVM)

Deliberate hypotension

The two primary indications for induced hypotension are (1) to test cerebrovascular reserve in patients undergoing carotid occlusion, and (2) to slow flow in a feeding artery of BAVMs before glue injection.

The most important factor in choosing a hypotensive agent is the ability to safely and expeditiously achieve the desired reduction in blood pressure while maintaining the physiological stability of the patients. The choice of agent should be determined by the experience of the practitioner,

Deliberate hypertension

During acute arterial occlusion or vasospasm, the only practical way to increase collateral blood flow may be an augmentation of the collateral perfusion pressure by raising the systemic blood pressure. The Circle of Willis is a primary collateral pathway in cerebral circulation. However, in as many as 21% of otherwise normal subjects, the circle may not be complete. There are also secondary collateral channels that bridge adjacent major vascular territories, most importantly for the long

Management of neurologic and procedural crises

Complications during endovascular instrumentation of the cerebral vasculature can be rapid and life threatening, and require a multidisciplinary collaboration. Having a well thought-out plan for dealing with intracranial catastrophe may make the difference between an uneventful outcome and death. Rapid and effective communication between the anesthesia and radiology teams is critical.

The primary responsibility of the anesthesia team is to preserve gas exchange and, if indicated, secure the

Postoperative management

After INR procedures, patients spend the immediate postoperative period in a monitored setting to watch for signs of hemodynamic instability or neurologic deterioration. Blood pressure control, either induced hypotension or induced hypertension, may be continued during the postoperative period. Complicated cases may go first to CT or some kind of physiologic imaging such as single photon emission computed tomography (SPECT) scanning; only rarely is an emergent craniotomy indicated.

Carotid cavernous and vertebral fistulae

Carotid cavernous fistulae (CCF) are direct fistulae usually caused by trauma to the cavernous carotid artery leading to communication with the cavernous sinus, usually associated with basal skull fracture. Treatment of CCF, a challenging surgical procedure, has become relatively easier with the development of detachable balloons [12]. Vertebral artery fistulae are connections to surrounding paravertebral veins, usually as a result of penetrating trauma, but may be congenital, associated with

Vein of Galen malformations

These are relatively uncommon but complicated lesions that present in infants and require a multidisciplinary approach including an anesthesiologist skilled in the care of critically ill neonates. The patients may have intractable congestive heart failure, myocardial lesions, intractable seizures, hydrocephalus, and mental retardation [13].

Spinal cord lesions

Embolization may be used for intramedullary spinal AVMs, dural fistulae, or tumors invading the spinal canal. Often, general endotracheal anesthesia with controlled ventilation is used to provide temporary apnea that may increase the ability to see small spinal cord arteries at the limits of angiography imaging resolution and exquisitely sensitive to motion artifact. For selected lesions, intraoperative somatosensory and motor-evoked potentials may be helpful in both anesthetized and sedated

Carotid test occlusion and therapeutic carotid occlusion

Carotid occlusion, both permanent and temporary, may be used in several circumstances. Skull base tumors frequently involve the intracranial or petrous portion of the carotid artery or its proximal Willisian branches. Large or otherwise unclippable aneurysms may be partly or completely treated by proximal vessel occlusion. To assess the consequences of carotid occlusion in anticipation of surgery, the patient may be scheduled for a test occlusion in which cerebrovascular reserve is evaluated in

Intracranial aneurysm ablation

The two basic approaches for INR therapy of cerebral aneurysms are occlusion of proximal parent arteries and obliteration of the aneurysmal sac. The aneurysmal sac may be obliterated by use of coils and balloons. However, obliterating the aneurysmal sac while sparing the parent vessel is still challenging [16]. Manipulation of the sac may cause distal thromboembolism and rupture. Incomplete obliteration may result in recurrence and hemorrhage. The anesthesiologist should be prepared for

Balloon angioplasty of cerebral vasospasm from aneurysmal SAH

Angioplasty may be used to treat symptomatic vasospasm with correlating angiographic stenosis refractory to maximal medical therapy [17]. Angioplasty is usually reserved for patients that have already had the symptomatic lesion surgically clipped (for fear of rerupture), or for patients in the early course of symptomatic ischemia to prevent transformation of a bland infarct into a hemorrhagic one. A balloon catheter is guided under fluoroscopy into the spastic segment and inflated to

Sclerotherapy of venous angiomas

Craniofacial venous malformations are congenital disorders causing significant cosmetic deformities, that may impinge on the upper airway and interfere with swallowing. Absolute alcohol (95% ethanol) opacified with contrast is injected percutaneously into the lesion, resulting in a chemical burn to the lesion and eventually shrinking it. The procedures are short (30–60 minutes) but painful, and general endotracheal anesthesia is used. Complex airway involvement may require endotracheal

Angioplasty and stenting for atherosclerotic lesion

Angioplasty with or without stenting for atherosclerosis has been tried in cervical and intracranial arteries with favorable results [20], [21]. Risk of distal thromboembolism is the major issue to be resolved in this procedure and methods. A catheter system that employs an occluding balloon distal to the angioplasty balloon has been proposed [22]. Carotid angioplasty and stenting may provide a therapeutic option for patients particularly at risk of surgery. However, efficacy and indications in

Thrombolysis of acute thromboembolic stroke

In acute occlusive stroke, it is possible to recanalize the occluded vessel by superselective intra-arterial thrombolytic therapy. Thrombolytic agents can be delivered in high concentration by a microcatheter navigated close to the clot. Neurologic deficits may be reversed without additional risk of secondary hemorrhage if treatment is completed within 6 hours from the onset of carotid territory ischemia and 24 hours in vertebrobasilar territory. One of the impediments in development in this

Important points and objectives

There is a rapidly expanding list of application of INR procedures in the field of the treatment of CNS disease. Anesthesiologists should be familiar with specific procedures and their potential complications. Constant and effective communication between the anesthesia and radiology teams is critical to safely carry out INR procedures and to deal with intracranial catastrophe.

Acknowledgements

The authors wish to thank Broderick Belenson, Mark Espinosa, Sabrina Larson, and Gaurab Basu for assistance in preparation of the manuscript; Van V. Halbach, MD, and Christopher F. Dowd, MD, John Pile-Spellman, MD, Lawrence Litt, MD, PhD, and Nancy J. Quinnine, RN, for development of clinical protocols discussed herein; members of the UCSF Center for Stroke and Cerebrovascular Disease, UCSF Center for Cerebrovascular Research, and the Columbia University AVM Study Group for continued support.