Chapter 37: Anesthesia for Interventional Neuroradiology

INTRODUCTION

Interventional neuroradiology (INR) is rapidly supplementing and in some cases replacing traditional neurosurgery. Endovascular access is utilized to deliver therapeutic drugs and devices to the brain. Anesthetic considerations of INR procedures are similar to those for neurosurgery, such as patient selection and complications, and come with the advantages of decreased pain and faster recovery time.

PREOPERATIVE ASSESSMENT

Following routine preoperative evaluation, patients require a detailed neurological assessment, Glascow Coma Scale score, and level of consciousness assessment. Signs of increased intracranial pressure should be noted.

The presence of renal insufficiency is important to determine dye load tolerance. Baseline coagulation profiles should be conducted to prepare for intraoperative anticoagulation. Allergies, including protamine, iodine, shellfish, latex, and contrast should be documented. For female patients of childbearing age, pregnancy status should be confirmed. Arthritis of the neck and back may compromise the patient’s ability to tolerate supine positioning.

TESTING

Carotid Occlusion Test

The carotid occlusion test assesses carotid artery patency and confirms adequate collateral circulation before elective carotid artery occlusion. Typically required for tumors involving the internal carotid artery, or for giant (> 24 mm) internal carotid and vertebrobasilar aneurysms, carotid occlusion requires consciousness for continuous neurological evaluation. Common complications include bradycardia, hypertension, and loss of consciousness.

Wada Test

The Wada test consists of behavioral testing after an anesthetic agent, such as sodium amobarbital or sodium methohexital, injection into the internal carotid artery. This is conducted in conscious patients to determine the dominant side for vital cognitive functions, namely speech and memory, in advance of epilepsy surgery or otherwise.

Superselective Anesthesia Functional Examination (SAFE)

The SAFE is an extension of the Wada test. It is carried out before therapeutic embolization to exclude an inadvertent catheter tip placement proximal to the origin of normal vessels supplying important regions in the brain or spinal cord. Sodium amytal is injected into the vascular territory planned for occlusion and repeated neurological examination is conducted to exclude functional involvement.

ANESTHETIC CONSIDERATIONS

Interventional radiologists often treat patients who cannot tolerate open surgery. However, procedures done in the IR suite are not necessarily less dangerous.

Monitored Anesthesia Care (MAC) Versus General Anesthesia (GA)

GA produces optimal mapping with digital subtraction angiography by providing control of mobility, respirations, and the hemodynamic profile. Elevated ICP and intraoperative neurological emergencies are better controlled with GA. Finally, GA provides improved airway control in patients at risk for aspiration. However, tracheal intubation during GA induction may acutely increase BP, increasing aneurysm transmural pressure, consequently risking rupture. Additionally, MAC more easily allows for intraoperative neurological assessment, and avoids the risk of intracranial hypertension with emergence by avoiding extubation.

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