Catherine Mc Caig, RN

Embolization of cerebral arteriovenous malformations

The treatment of arteriovenous malformations (AVM) of the brain by embolization was first introduced in 1960 by Alfred J Luessenhop, MD, a t Georgetown University Hospital Medical Center in Washington, DC. Embolization is the therapeutic introduction of a substance into the circulation to occlude vessels, usually for carotid cavernous fistula or arteriovenous malformations. It has become the procedure of choice for certain AVMs that are either very large or inoperable due to anatomical inaccessibility. Also, it is useful as a preliminary to direct excision for the elimination of some of the large arterial vessels that feed the AVM. AVMs of the brain occur mostly in the

Catherine McCaig, R N , is a staff nurse, operating room, Georgetown University Hospital, Washington, DC. She is a diploma graduate of Credit Valley School of Nursing, Mississauga, Ontario, Canada.

232

cerebrum and involve the middle cerebral artery. They are the result of the absence of capillaries between major arteries and veins causing fistulae. Direct results of this include increased intravascular pressure transmitted from the arteries to the veins, enlargement of the involved arteries and veins, and increased collateral circulation to the sites of the fistulae. Surrounding normal brain tissue can become ischemic because of the large amounts of blood that preferentially feed the AVM. The sites of the fistulae become a conglomeration of dilated vessels. The enlarged feeding arteries pass into this abnormal vasculature of multiple small channels with venous characteristics. The vessels in this mass respond by becoming torturous and coiled. The feeding arteries and draining veins involved in an AVM are those that would normally supply that area of the cerebrum. An AVM is found during the embryonic stage of cerebral development. Thereafter, its growth is parallel to that of the brain. In an adult, a n AVM can be small in size or large enough to occupy an entire cerebrum (Figs 1 , 2 , and 3). On arteriograms, an AVM appears quite diffuse during childhood. Comparative films of the adult show slight changes involving just a few more vessels. The only other changes seen are the result of small hemorrhages. Patients with AVMs may experience symptoms of frequent small hemor-

AORN Journal, August 1978, Vol28, No 2



Int. Frontal Branches



e~ I Ant.

Mid. Post.

1

/Para-central

I

I

Calloso-margina

Precuneal

-occinital I

cc

Y

Front.

Polar

Fig 1. Normal cerebral arteries. (Reproduced from Luessenhop, A J, Gennarelli, T A. “Anatomical grading of supratentorial arteriovenous malformations for determining operability,” Neurosurgery 7 [79771.)

Fig 2. An arteriovenous malformation involving the rolandic artery. [Reproduced from Luessenhop, A J, Gennarelli, T A. “Anatomical grading of supratentorial arteriovenous malformations for determining operability,” Neurosurgery 7 [7977].)

Fig 3. In comparison, a much larger arteriovenous malformation involving the three rolandic arteries and the posterior parietal artery. (Reproduced from Luessenhop, A J, Gennarelli, T A. “Anatomical grading of supratentorial arteriovenous malformations for determining operability, Neurosurgery 7 [7977].) ”

AORN Journal, August 1978,Vol.28, No 2

233

ARTERIOVENOUS MALFORMATION

TO NO BRAIN

TO NORMAL

Fig 4. Passage of emboli from vascular origin to arteriovenous malformation. (Reproduced from Luessenhop, A J, Gennarelli, T A. “Anatomical grading of supratentorial arteriovenous malformation for determining operability, Neurosurgery 7 [7977].) ‘I

rhages. The peak age of the first occurrence of bleeding is between the ages of 35 and 40 years. By the age of 4472% of all patients have had a t least one hemorrhage.’ Hemorrhage can be intracerebral or subarachnoid. The second most common symptom is focal seizures. A small percentage of patients experience headaches that are usually unilateral or migrainoid. Some patients present with objective bruit, complaining of not being able to sleep at night because of the switching noise in their heads. Depending upon the size and location of the AVM, neurological deficits can occur. These symptoms can occur independently or in combinations at any time, and diagnosis is usually not made until they appear. If untreated, bleeding episodes continue and the symptoms get

234

progressively worse. There is also a possibility that an aneurysm will form from the walls of one of the feeding arteries. Surgical excision of an AVM is the treatment of choice and is done in about 50%of all cases. For the other 50%,half are suitable for embolization.2 The object is to decrease blood flow through the fistulae in the AVM, thereby diverting blood flow to adjacent brain tissue and decreasing the size of the involved veins, which compress neural t i ~ s u e . ~ This is accomplished by occluding the vessels within the AVM and the large feeding arteries proximal to it with Silastic emboli. The abnormally enlarged arteries that feed the AVM have an increased blood flow and provide a direct channel from the internal carotid artery or vertebral artery to the cerebral arteries where the AVM is situated. Silastic emboli that are introduced pass through these enlarged feeding arteries to the AVM, rather than traveling through the smaller arteries to normal brain tissue (Fig 4). The success of the procedure is based on the fact that the emboli will flow preferentially through the abnormal arteries. Size of the emboli is important. They must be smaller than the feeders t o the AVM and larger than the normal arteries. The emboli should always enter the feeders if the diameter of the feeders is three times larger than the normal of the arteries is a r t e r i e ~ Angulation .~ also a consideration. At Georgetown University Hospital, Dr Luessenhop uses the carotid or vertebral arteries as sites for direct introduction of the emboli. Other hospitals have reported using catheters introduced via the femoral arteries. Angiography is the single most important aid in diagnosis (Figs 5 and 6). Thereafter, it is used throughout the course of treatment. An AVM will ap-

AORN Journal, August 1978, Vol28, No 2

Figs 5 and 6. Left, anterior posterior view of arteriovenous malformation. Right, lateral view of arteriovenous malformation.

pear on angiogram even before any symptoms are present. Preoperatively , a series of angiograms are taken to include vertebral and bilateral carotid injections. These studies must show all the feeding and draining vessels in relation to the AVM. They also provide a comparison between normal and abnormal vessels. Intraoperatively, angiograms show the location of the AVM, evidence of occlusion to normal arteries in the brain, and the disappearance of preferential arterial flow to the AVM. Postoperative angiograms indicate the degree of success in blocking flow to the AVM, displacement of emboli, and evidence of collateral circulation t o the

AVM. At Georgetown University Hospital, t h e embolization procedure is done under general anesthesia. Situation of the scrubbed team depends on whether a right or left arterial approach is used. For example, if a right carotid or verte-

bral artery is used, the surgeon, assistants, and scrub nurse will stand on that side also. The right arm must be carefully tucked in a t the patient’s side. The anesthesiologist and the x-ray machine would be situated on the left side of the patient. After intubation, an x-ray cassette holder that holds the cassette in the lateral projection is placed under the patient’s head and shoulders (Fig 7). The holder must be padded with towels t o avoid any pressure points. The use of t h i s holder is essential because the x-ray cassette must be placed as close to the head as possible so that magnification of the arteries is no greater than 10%.5 The patient is prepared and draped as for a carotid endarterectomy. The common carotid artery and its bifurcation are exposed and clamped proximally and distally with bulldog clamps. The surgeon chooses a Silastic catheter of

AORN Journal, August 1978. Vu128, Nu 2

235

Fig 7. X-ray cassette is placed close to the head so magnification of arteries is no greater than 10%.

Fig 8. Emboli pass through catheter to carotid artery.

236

AORN Journal, August 1978, Vol28, No 2

Figs 9 and 10. Left, anterior posterior view poskmbolization. Right, lateral view postern bolization.

appropriate size, one that is just large enough to accommodate the emboli, but not occlude the arterial blood flow. The carotid artery is incised, the catheter is inserted and passed into the lumen. Then it is securely sutured to the arterial wall. At this point, the bulldogs and retractors are removed and the wound is covered with a towel exposing only the end of the catheter. The emboli are placed in the end of the catheter with forceps. They are then flushed through the catheter with a syringe containing saline (Fig 8). After the embolus is flushed through the catheter, the catheter is clamped and an x-ray is taken. If the embolus has gone through the feeding artery to the AVM, the surgeon usually proceeds with more emboli. He can inject as many as ten emboli a t one time. The object of the procedure is to place many small emboli within the AVM. The surgeon attempts to place the larger emboli proximal to

the feeding arteries a t the origin of the AVM.6 Once this is accomplished, the procedure is ended, the catheter withdrawn, and the artery is closed. The emboli used are Silastic spheres impregnated w i t h b a r i u m sulfate. Usual sizes for cerebral AVMs range from 2.5 mm to 4.0 mm in diameter.7 The scrub nurse separates the sizes the surgeon has selected in medicine cups. The embolization tray is stocked with ample numbers of each different size emboli. However, there should be a back up supply that can be flashed if necessary. The procedure usually requires the use of 20 to 70 emboli, although as many as 200 have been used in some cases (Figs 9 and The circulating nurse has responsibilities relating to the intraoperative angiography. Preoperative angiograms must be available to the surgeon. He or she must arrange for the x-ray technician to arrive when the surgeon is ready

A O R N Journal, August 1978, Vol28, No 2

237

Fig 7 1. Embolization tray used at Georgetown University Hospital, Washington, DC.

for the initial films to be taken. Since x-rays are taken frequently throughout the procedure, the circulator must ensure that sterility is maintained at the field by guiding the x-ray technician in placement of the cassette. Also, he or she watches the scrubbed team for possible contamination as they have to leave and enter the room while x-rays are taken. The circulator marks the x-ray films consecutively as they are taken and indicates the number of emboli injected. There must be an ample supply of radiopaque medium available. At Georgetown University Hospital, an embolization tray is used (Fig 11). It consists of: Ten test tubes containing various sizes of emboli or barium-impregnated spheres ranging in size from 0.5 mm to 6.0 mm 0 Nine Silastic catheters in incremental sizes Three medicine cups

238

Four bulldog clamps One metal syringe tip adapter Two 20 cc plain tip syringes. Other necessary instrumentation and equipment includes: a basic instrument set for soft tissue dissection and exposure of the artery umbilical tapes to isolate surrounding veins a graduate pitcher with 500 cc of intravenous saline. Vital signs are monitored postoperatively. The incision is checked for bleeding. A good nursing assessment done preoperatively will benefit in observation of neurological status. Follow-up angiograms are taken when the patient is stable. Complications associated with embolization have been rare. Occasionally an embolus will pass through an AVM to the lungs, but this does not cause significant pulmonary complicati~ns.~

AORN Journal, August 1978, Vol28, No 2

T h e m a j o r complication arises when, at t h e e n d of t h e procedure, there i s proximal arrest o f an embolus in one of t h e arteries l e a d i n g t o n o r m a l brain tissue causing infarction. L o n g - t e r m studies i n d i c a t e that t h e presence o f e m b o l i within t h e cerebral arteries does n o t cause problems. S u r g i c a l e m b o l i z a t i o n o f AVMs proves t o be a significant means o f t r e a t m e n t f o r c e r t a i n inoperable cases where excision i s impractical. However, t h e AVM w i l l s t i l l b e present t o some e x t e n t d u e t o collateral circulation. In a 1 5 - y e a r s t u d y , L u e s s e n h o p h a s observed that embolization has been successful in a l l e v i a t i n g associated headaches, r e d u c i n g chances of seizures, and stabilization o r reversal of neurological deficits. A l t h o u g h t h e poss i b i l i t y of hemorrhage i s n o t reduced, if a p a t i e n t h a s n o t had a hemorrhage p r i o r t o embolization, t h e chance o f one f o l l o w i n g e m b o l i z a t i o n i s 5% in f o u r years.'O Notes 1. G Perret, H Nishioka, "Report of the cooperative study of intracranial aneurysms and subarachnoid hemorrhage: VI arteriovenous malformations," Journalof Neurosurgery 25 (1966) 467-498. 2. A J Luessenhop, Operative Treatment of Arteriovenous Malformations of the Brain: Current Controversies in Neurosurgery, T P Morley, ed (Philadelphia: W B Saunders, 1976) 203-209. 3. A J Luessenhop, J H Presper, "Surgical embolization of cerebral arteriovenous malformations through internal carotid and vertebral arteries," Journal of Neurosurgery 42 (1975) 443-45 1. 4. B Roushay, K Kricheff, N Chase, "The value of cerebral angiography in the embolizationtreatment of cerebral arteriovenous malformations," Radiology 97 (1970) 65-70. 5. A J Luessenhop, "Artificial embolization for cerebral arteriovenous malformation," Progressive Neurosurgery 3 (1969) 320-362. 6. Luessenhop, "Surgical embolization of cerebral arteriovenous malformations," 443-451. 7. A J Luessenhop,ArteriovenousMalformations of the Brain and Spinal Cord, Practice of Surgery (Hagerstown,Md: Harper and Row, Inc, 1973) 1-32. 8. Luessenhop, "Surgical embolization of cerebral arteriovenous malformations," 443-451. 9. Luessenhop, "Artificial embolization for cere-

bral arteriovenous malformation." 320-362 10. Luessenhop, "Surgical embolization of cewbra1 arteriovenous malformations. 443-451

New criteria help predict ALL remission Three new physical and clinical criteria may help predict the chances of sustained remission for children with acute lymphoblastic leukemia (ALL). Denis R Miller, MD. head of pediatrics, Memorial Sloan-Kettering Cancer Center. New York City, reported on the criteria at a National Cancer Institute symposium on protocol design for controlled clinical trials He is vice-chairman of the Childrens Cancer Study Group, which developed the indicators through a two-year study. Dr Miller's report appeared in Medical World News (May 15). According to Dr Miller, more reliable predictions of remission for ALL patients can be made using the following criteria. 0 Serum immunoglobulins. Dr Miller reports that patients with normal A, G, and M immunoglobulin levels did better than patients with impaired immunity in the study by the Childrens Cancer Study Group. 0 Rapidity of remission induction. Patients who responded to remission therapy by the 14th day of treatment had better remission rates than those whose remission induction took longer, Dr Miller said. 0 Lymphoblast morphology. Dr Miller reported that a study group of American, French, and British hematologists developed a system for classifying lymphoblasts by cytologic features in 1976. After analyzing leukemic cells from 200 patients according to size, shape, and content of their nuclei and amount and content of cytoplasm, the hematologists divided ALL lymphoblasts into three types-Ll, L2, and L3. In Dr Miller's study, those patients with LI morphology had a lower rate of bone marrow relapse than those with Lz. There were too few patients with L3 morphology for inclusion in the study.

AORN Journal, August 1978, Vol28, N o 2

239

Embolization of cerebral arteriovenous malformations.

Catherine Mc Caig, RN Embolization of cerebral arteriovenous malformations The treatment of arteriovenous malformations (AVM) of the brain by emboli...
4MB Sizes 0 Downloads 0 Views