The Evolution of Anesthesia for Neuroradiologic Procedures

The Evolution of Anesthesia for N euroradiologic Procedures

HOWARD R. TERRY, JR., M.D. EDWARD F. DAW, M.D. JOHN D. MICHENFELDER, M.D. HILLIER L. BAKER, JR., M.D. COLIN B. HOLMAN, M.D.

Neuroradiologic procedures are designed to demonstrate normalities and abnormalities in the position, shape, or size of the ventricular system, subarachnoid space, and cortex as well as the arterial and venous systems of the head and neck and their relationship to bony structures. Safe anesthetic or supportive management of patients and the fulfillment of the neuroradiologic requirements, however incidental these two goals may seem, require all the care, vigilance, and resourcefulness that are applied to any major surgical procedure on the abdomen or thorax. Failure to recognize this concept has denied many patients the best care and diagnostic acumen. Indeed, some of the most desperately ill patients seen by physicians are seen for neuroradiologic procedures, for instance, geriatric and pediatric patients with expanding intracranial lesions as well as the ever-increasing number of patients having strokes or severe traumatic intracranial and spinal injuries. The role of the anesthesiologist is to maintain anesthesia of the patient and support of the patient's vital signs throughout the diagnostic precedure in the safest manner possible.· He should allow the neuroradiologist to position the patient accurately and safely in order to obtain the information sought, without danger of fire or explosion from flammable anesthetic agents. N euroradiology began with Roentgen's discovery of roentgen rays in 1895. In an effort to' improve their diagnostic success, enthusiastic physicians and surgeons soon applied the early, cumbersome x-ray apparatus 907

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to human beings. Eventually a group of interested medical scientists made the field of radiology their major interest. The crude x-ray tubes and generators, the bulky glass plates, and the slow, muddy photographic emulsions gradually were replaced by rotating anode tubes, full-wave rectifying units, stereoscopy, emulsion films, the Potter-Bucky diaphragm, intensifying screens, and, eventually, contrast media to outline cavities and hollow organs that otherwise could not be visualized. A short time after the discovery of roentgen rays, publications began to appear which were devoted exclusively to the application of roentgen rays to diseases of the skull and brain. Many times the eagerness of the early authors exceeded their knowledge of the appearance of normal radiographic anatomy. However, their efforts stimulated others and refinements in techniques for diagnosis began to multiply rapidly. From crude beginnings developed the modern science of neuroradiology which has become indispensable to neurologic, neurosurgical, and psychiatric diagnosis. In the last 25 years interested radiologists have combined their special knowledge and talents to create the subspecialty of neuroradiology, a field which has been particularly complicated by virtue of the extremely complex anatomy of the skull and spinal column. SchUller in 1918 and Naffziger in 1925 noted the fact that anteroposterior or posteroanterior x-ray views showing a shift of the pineal body away from its normal midline position usually indicated the presence of a mass. In 1898, Cannon reported roentgenologic visualization of the entire gastrointestinal tract as outlined by a mixture of bismuth introduced into the stomach and carried by peristalsis throughout the remainder of the tract. In 1913, Luckett published a reproduction of cerebral ventriculograms made possible by the spontaneous insufflation of air into the patient's ventricle through a fracture of the right frontal bone. The patient survived, so air in the ventricles obviously was not fatal. However, no one appreciated the significance of this fact until 1918 when Dandy first intentionally injected room air into the ventricular system as well as into the lumbar space. He was the first also to introduce other gases such as oxYgen, nitrogen and carbon dioxide into these spaces. In 1927 Moniz introduced cerebral angiography by injection of solutions of sodium bromide and sodium iodide directly into exposed common carotid arteries in the neck. Although these agents sometimes caused violent reactions, they were the forerunners of agents such as methylglucamine diatrizoate (Renografin) and diatrizoate (Hypaque) which are used commonly today. Loman and Myerson in 1936 successfully injected radiopaque material into the carotid arteries by needle without surgical exposure of the vessels. This procedure plus the improvement in contrast media resulted in tremendous advancement in cerebral angiography. Parallel to Roentgen's discovery of roentgen rays was the use of ether

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for anesthesia developed by Long in 1842 and further demonstrated by Morton in 1846. While the field of radiology was undergoing birth and development, anesthesia also was evolving rapidly to its present state. Unfortunately many of the first valuable anesthetic agents were flammable and explosive; they have been used and, of necessity, are probably still being used in some parts of the world for diagnostic neuroradiologic procedures. However, the safety of the patient and the medical personnel far outweighs any presently known disadvantages of nonflammable agents and techniques. Ether has been a valuable agent for anesthesia and has been used extensively, but because it is highly flammable and explosive it is exceedingly dangerous. Nitrous oxide was first introduced by Priestley in 1772, and in 1844 its weak nonflammable properties were put to clinical use. Chloroform was discovered independently by Soubeiran, von Liebig, and Guthrie in 1831. This nonflammable, portable, potent, rapid-acting agent, despite all its advantages, is not commonly used in many parts of the world because of the associated danger of necrosis of the liver. Trichloroethylene was introduced as an anesthetic agent in 1911 by Lehmann and used surgically for the first time in 1934 by Striker. Although nonflammable and nonexplosive in concentrations used for anesthesia, it lacks the required potency for certain diagnostic neuroradiologic procedures, particularly when compared to halothane, methoxyflurane (Penthrane), or chloroform. Ethylene was first used as an anesthetic agent about 1923 by Luckhardt and Carter and by Brown, and cyclopropane, in 1933 by Waters and Schmidt. Because of their flammable nature as well as their more recent development, these two agents were not used as extensively as ether in neuroradiology. Newer nonflammable agents such as halothane, which was developed in 1956 by Ravent6s and Johnstone, and barbiturates, which were developed27 in 1934, were made available. In 1960, methoxyflurane (Penthrane) was introduced as an additional nonflammable agent by Artusio and associates. Introduction of neuromuscular blocking agents also led to improved care of the neuroradiologic patient. In 1940 Bennet administered d-tubocurarine to human beings for electroshock, and in 1942 Griffith and Johnson introduced curare into anesthesia. The use of succinylcholine was described extensively by many authors 7 , 10, 17, 18, 28, 35, 36 from 1943 through 1951. d-Tubocurarine was used widely in neuroradiology for patients undergoing procedures which required general anesthesia. A long-acting muscle relaxant, it allowed insertion of an endotracheal tube as well as careful placement of topical tracheal anesthetic agents without necessitating the deep levels of anesthesia previously required. It was also used in many combinations with barbiturates, nitrous oxide, and trichloroethylene by anesthesiologists seeking to avoid the explosive combinations of ether, cyclopropane, or ethylene.

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With the introduction of halothane in 1956, the short-acting muscle relaxants combined with the rapid-acting barbiturates for induction placed anesthesia for neuroradiology on a firmer and more acceptable basis than it had known before. Over the last 25 years, these unrelated events have made it possible for neuroanesthesia to keep pace with the rapid developments in the field of neuroradiology. Proper techniques and correct interpretation probably are more closely intermingled in neuroradiology than in any other branch of diagnostic radiology. The aims of neuroradiology are:14 • 15 (1) to detect and localize a lesion, (2) to establish its nature, and (3) to assess its extension and its possible multiplicity. The anesthesiologist must assess the safety of the patient undergoing the diagnostic procedure. 5 • 12 In this clinic anesthesia usually is managed in one of two ways: by local anesthesia with mild or no sedation, or by general endotracheal anesthesia with a nonkinkable endotracheal cuffed tube (radiolucent, if possible), topically applied anesthesia to the trachea, and a nonflammable, nonexplosive anesthetic agent. When the use of local anesthesia is contemplated, the procedure must be carefully explained to the patient and every effort should be made to minimize painful stimuli. The patient should be capable of full cooperation. At present we use general endotracheal anesthesia in young children (possibly to 16 years of age) and in unduly restless or aphasic patients. Occasionally a patient who has had multiple diagnostic procedures under local anesthesia may insist on having general anesthesia. Controversy still evolves concerning the value of general anesthesia in diagnostic neuroradiologic procedures and its value in the prevention of complications. In some centers, cerebral angiography is always done with the patient under general anesthesia, presumably to reduce the incidence of cerebrovascular spasm or to increase arterial oxygen saturation. Some also use it presumably for better utilization of the Valsalva maneuver to accomplish better filling of the vessels. However, many questions remain concerning the effects of general anesthesia, spontaneous ventilation, controlled hyperventilation, hypotension, hypertension, vasodilators, and vasoconstrictors on cerebral blood flow in the presence of all the various neurologic disorders. In some other institutions angiography and pneumoencephalography are done only if the patient is under local anesthesia; sometimes the patient is not attended by any personnel trained to monitor and support vital signs. It is fairly obvious that most methods of approach have proved to be acceptable. This is particularly so if the patients are carefully evaluated beforehand by the neurologist and neurosurgeon, and carefully attended during the test by a neuroradiologist and anesthesiologist. In diagnostic neuroradiology the anesthesiologist's38 experience is desirable for the following commonly used tests: cerebral angiography, ventriculography, pneumoencephalography, and occasionally for myelography.

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ANGIOGRAPHY OF THE HEAD AND NECK

Improvement of contrast media has increased the importance of angiography of the head and neck as a diagnostic aid in neurologic and neurosurgical disorders. 2- 4 , 8,21 The characteristic concentration of contrast media in vascular abnormalities such as aneurysms, arterial venous anomalies, vascular meningiomas or hemangiomas, and certain vascular tumors, makes accurate precraniotomy diagnosis possible. Angiography also has been useful in diagnosis of displacements due to expanding intracranial lesions such as tumors or subdural or extradural hematomas. It is also useful in cases of carotid and cerebrovascular insufficiency. One advantage of cerebral angiography over pneumoencephalography, particularly with increased intracranial pressure and a surgical lesion, is that surgical treatment need not immediately follow the test. Pneumoencephalography in the presence of tumor, however, usually necessitates immediate operation, since further increase in intracranial pressure commonly follows this test. Local anesthesia usually requires a minimal dose of hypnotic, sedative or ataractic drug administered intramuscularly or intravenously on the patient's arrival in the room used for angiography. To this is added atropine or some other closely related alkaloid for its vagal blocking effect. Blood pressure, pulse, and respiration are monitored routinely, and an intravenous route is established. The neurosurgeon then carefully infiltrates 1 per cent lidocaine (Xylocaine) or a comparable local anesthetic in the skin, subcutaneous tissue, and region around the vessel to be cannulated. Parts of the cerebrovascular system may be outlined by injecting contrast medium, via percutaneous puncture, into anyone of several vessels, namely the carotid, brachial, subclavian, vertebral, and occasionally femoral arteries with the use of a catheter threaded to the arch of the aorta. The tests may be done with the patient under local anesthesia if he is cooperative, if the team is experienced in the placement of the needles or catheters, and if the neuroradiologic team is experienced in obtaining roentgenograms and uses only minimal injections, both in number and volume. There seems to be a tendency to compensate for inexperience in neuroradiology by using an increased volume of contrast medium. This action certainly increases the incidence of complications caused by the chemicals and may increase the need for general anesthesia. Many institutions use 30 ml. or more of contrast medium even for carotid injections; this amount contributes greatly to the discomfort of the patient. Injection of contrast medium produces brief pain; for example, a carotid injection causes pain in the face and supra-orbital region. The pain can be minimized by using the minimal amount of contrast medium necessary to get good diagnostic roentgenograms. Good neuroradiologic technique usually requires only 6 to 8 ml. of opaque medium in carotid or vertebral injections. Any discomfort lasts only 5 to 15 seconds and will be tolerated by a cooperative patient who understands what to expect after the injection. When large volumes

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Figure 1. Position of patient for cerebral angiography, showing difficulty anesthesiologist has in reaching patient's airway.

of dye are used, however, general anesthesia must be used because of the severe pain caused by the injection. In our opinion the use of minimal sedation and local anesthesia avoids significant alteration in the patient's normal physiology and is less apt to result in complications. Most complications that we have encountered seem to have been related directly to difficulty in introducing the needle or catheter20 (Fig. 1). They include carotid sinus reflexes, obstruction of the airway by hematomas, paralysis of vocal cords, and hemiplegia. General anesthesia is never without danger, and should be reserved for those patients who, because of age or illness, are unable to cooperate.

VENTRICULOGRAPHY

The purpose of ventriculography is to replace the ventricular fluid with air or a similar gas so that an outline of the ventricular system will be visible on roentgenograms. It may be used to determine the presence of intracranial space-occupying lesions with signs of increased intracranial pressure. Again, local anesthesia is preferable with infiltration of the scalp as well as topical application to the dura. As in cerebral angiography, the child or the uncooperative adult is best managed with general anesthesia. This method is not without hazard, since the patient must be transported from the operating room to the radiology suite in most hospitals and then

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returned. Maintenance of general anesthesia under such conditions is difficult and is further complicated by the fact that coughing or straining on the endotracheal tube must be avoided. Our present technique usually includes induction with thiopental (Pentothal) or methohexital (Brevital) followed by oxygen and succinylcholine (Anectine); the trachea is then well sprayed with a local anesthetic prior to insertion of a nonkinkable, cuffed (when possible) endotracheal tube. Maintenance of anesthesia is accomplished with halothane, nitrous oxide, and oxygen, or halothane and oxygen. Usually in ventriculography as well as in myelography and pneumoencephalography some form of a nonrebreathing system is preferable to a circle-absorber system because of its reduced bulk and greater mobility. The care of patients who have increased intracranial pressure secondary to an obstruction in the region of the third or fourth ventricle is improved if the neurosurgeon inserts a catheter into a lateral ventricle. The catheter is clamped until the neuroradiologic examination is completed. It can then serve as a means of releasing the expanding gas and thus provides a greater margin of safety to the patient during the subsequent craniotomy. While the indications for ventriculography versus pneumoencephalography vary with the type of suspected intracranial lesion, its location, and the degree of pre diagnostic intracranial pressure, it is essential that exchanges of gas and fluid be done slowly and that the contrast gas not be left under undue pressure. Also, generally a surgical lesion diagnosed by contrast gases is followed by craniotomy as soon as possible on the same day. Excessive amounts of any gas (air, or otherwise) used for a contrast medium are not only unnecessary but to be condemned. In nitrous oxide anesthesia, Saidman and Eger16 • 32 recommended that nitrous oxide be used as the contrast medium. It must be remembered by the anesthesiologist that air, being lighter than spinal fluid, will remain in the ventricles only if the head is kept in an upright position. In many instances the head is inadvertently lowered when the patient is moved, and the air passes down into the spinal column and is lost, resulting in an indeterminate test.

PNEUMOENCEPHALOGRAPHY Most pneumoencephalograms are done with air, although various hypobaric gases such as oxygen, nitrous oxide, nitrogen, and carbon dioxide have been used. Generally a puncture is made into the lumbar region with the patient in a sitting position. Cisternal punctures are used less and less because they impose greater danger on the patient than lumbar punctures and also because many physicians are no longer experienced in this technique. In certain diagnostic procedures increased use has been found for

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the injection of 6 to 9 ml. hyperbaric iophendylate (Pantopaque) instead of air to outline various portions of the ventricular system. In pneumoencephalography the indication for general or local anesthesia is the same as for angiography and ventriculography. However, when local anesthesia is contemplated for pneumoencephalography, it is imperative that a critical evaluation of the patient be done beforehand. Once the patient is in position and air has been injected, severe headache usually develops. If it is thought that the patient will not cooperate under those conditions, then general endotracheal anesthesia is indicated. To induce general anesthesia during the test may be difficult in a patient surrounded by massive radiologic equipment and it may ruin the diagnostic test by scattering air throughout the subrachnoid space. It is also extremely dangerous to add "just a touch of general anesthesia" to patients in this position. They are frequently obscured by the radiologic equipment and the main danger is that of an obstructed airway (Fig. 2). If the use of a well-managed general endotracheal anesthetic at the onset of the test could prevent loss of an airway, and cerebral damage due to hypoxia, or even death, it certainly should be provided! General endotracheal anesthesia for pneumoencephalography is difficult for everyone involved. However, the role of the anesthesiologist is twofold and of more pressing magnitude than with other tests. His primary role is to assure the patient of maximal safety while undergoing this difficult test, but he also must provide the neuroradiologist with a stationary field in order that the films necessary for diagnosis may be obtained. Experienced and competent anesthesia coverage is mandatory because of the extreme

Figure 2. Pneumoencephalography. One of many positions assumed by patient. Safety of patient, if under general anesthesia, is assured by a properly placed endotracheal tube, an intravenous route, and personnel experience in anesthesia.

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trauma to the patient, the ease of failure or nonfilling, the dangers of an indeterminate test, and the expense to the patient and the family. In patients who are awake, equipment must always be handy for supporting vital functions if necessary. A flexible styleted plastic needle should be accurately inserted intravenously for administration of drugs such as vasopressors. Likewise, equipment for support of ventilation, ventricular drainage, and cardiac resuscitation should always be available. A few pneumoencephalograms are made even with increased intracranial pressure and especially in patients in whom visualization of the third and fourth ventricles is necessary. In such instances, close cooperation between neuroradiologists, neurosurgeons, and anesthesiologists has resulted in increased use of this test with slight if any increase in danger to the patient. If nonfilling results after introduction of 15 to 30 ml. of air, usually the patient is immediately taken to the operating room for a ventriculogram. It is in such cases that the anesthesiologist must be prepared for sudden herniation of cerebellar tonsils through the foramen magnum compressing the medulla with subsequent changes in the patient's vital signs, such as apnea and hypotension, and he must be able to support the patient until surgical correction of increased intracranial pressure can be accomplished through a ventricular tap, ventricular drainage, or suboccipital craniectomy.

Figure 3. Myelography under general anesthesia. In various positions for myelography, an airway is assured with an endotracheal cuff tube. The circulatory system is monitored and an intravenous route is maintained. Cooperation between the radiologist and anesthesiologist during fluoroscopy in a darkened room is essential.

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MYELOGRAPHY

Anesthesiologists seldom need to aid in myelography. Few uncooperative patients are encountered, although an occasional child will require general anesthesia. Patients who, because of severe pain, will not be able to tolerate the various positions needed for myelography also require general anesthesia. Because of the variety of positions (supine, prone, and lateral positions in Trendelenburg or reverse Trendelenburg) and the need for a darkened room, a nonrebreathing system with an endotracheal tube, nonflammable, nonexplosive and fast-acting agents such as those mentioned previously are presently the agents of choice (Fig. 3).

CONCLUSIONS

General anesthesia and local anesthesia for neuroradiologic procedures must provide the same good operative conditions and safety to the patient that are necessary for major surgical procedures. Movement by the patient may result in distortion of the films with false results or negative surgical explorations. With the rapidly changing radiologic technology such as cine, subtraction, and stereoscopic techniques, maintenance of the patient in required positions becomes a critical and sometimes complex consideration. In cooperative patients, local anesthesia is usually adequate; in the noncooperative, general endotracheal anesthesia with a nonflammable, nonexplosive agent is necessary.

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34. Striker, C., Goldblatt, S., Warm, I. S., and Jackson, D. E.: Clinical experiences with the use of trichlorethylene in the production of over 300 analgesias and anesthesias. Anesth. & Analg. 14:68-71 (March-April) 1935. 35. Thesleff, S.: Pharmacological properties of succinylcholine iodide with particular reference to its clinical use as muscular relaxant. Acta physiol. Scandinav. 26:103129,1952. 36. Thesleff, Stephen: Pharmacologic and clinical experiments with 0.0. succinylcholine iodide. Nord. med. 46:1045, 1951. 37. Waters, R. M., and Schmidt, E. R.: Cyclopropane anesthesia. J.A.M.A. 103:975983 (Sept. 29) 1934. 38. Wylie, W. D., and Churchill-Davidson, H. C.: Neurosurgical Anesthesia: Cerebrospinal Fluid. In A Practice of Anaesthesia. Chicago, Year Book Publishers, Inc., 1961, pp. 765-798.