Endovascular grafting of abdominal aortic aneurysms

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Endovascular grafting of abdominal aortic aneurysms Karen M. Lombardo, RN, MSN Abdominal aortic aneurysm (AAA) is a common condition that vascular nurses see daily in their practice. Ruptured AAA is the thirteenth leading cause o f death in the United States. Increasingly, vascular surgeons are f a c i n g older patients with severe comorbid conditions and an AAA. Thesefactors have led to the development o f less invasive techniques f o r repairing AAAs. Endovascular grafiing is a technique currently beingpe~formed on selectedpatients. Benefits of this procedure include a small femoral incision, f e w e r cardiopulmonary risks than the traditional surgeliy, rapid recovery, short hospital stay, a n d a decrease in overall cost. Nurses are responsible f o r patient education, assessment, and evaluation o f patients undergoing this procedure. (J Vasc Nurs 199 7;15:83- 7.)

Abdominal aortic aneurysm (AAA) is a common condition. It is estimated that the incidence of AAA in the general population is approximately 60 per 1000.1 If the population sample is further limited by selecting those patients over the age of 50 and adding hypertension or evidence of peripheral vascular disease, the incidence rises dramatically. In 1951 DuBostz was the first to successfully repair an AAA surgically. Before the development of direct surgical repair, approximately 80% of patients with the diagnosis of AAA died from aneurysm rupture within a 2- to 3-year period of observation) Since 1951, there have been many improvements in the diagnosis and treatment of AAAs. Despite these advances, approximately 15,000 patients die each year in the United States from ruptured AAA, which makes this diagnosis the thirteenth leading cause of death in the United States. 2 It is widely accepted that elective surgical repair of asymptomatic aneurysms carries a low mortality of approximately 5% and offers the greatest chance of reducing the mortality associated with this condition.4 Increasingly, vascular surgeons are encountering older patients with severe comorbid conditions. These conditions can increase operative morbidity to 60%.5 These factors have led to the development of a less invasive technique for repairing AAAs. The technique currently being performed on selected patients is an endovascular approach. ENDOVASCULAR GRAFTING TECHNIQUE

New procedures that use endovascular grafts may represent an important alternative to standard surgical repair for a va-

riety of vascular disorders, including aneurysms, arterial traumatic lesions, and arterial occlusive disease. 6 The first clinical experience with the endovascular repair of AAA was reported by Parodi and colleagues in 1991 7 Since then, several systems have been developed to perform endovascular graft procedures. The endovascutar technique involves the transluminal placement and attachment of a sutureless aortic graft prosthesis across an aneurysm. Wissenlink and Hollier8 categorize the technical principles of endovascular grafting as follows: (1) preparation of the graft, (2) introduction into the access artery, (3) advancement across the aneurysm, (4) positioning, (5) anchoring, (6) prevention of continued aneurysmal dilation, and (7) maintenance of distal patency. Endovascular repair of AAA is currently indicated for patients with aortic or iliac artery aneurysms requiring repair. The diameter and length of the endovascular graft need to be individually tailored for each patient, using data obtained from sonograms, computed tomography (CT) scans, and arteriograms. Introduction of the graft/introducer assembly is advanced across the area of aneurysmal dilation. Proper positioning of the graft requires adequate imaging techniques. Intraoperatire fluoroscopy with radiographic contrast material is most commonly used. The proximal end of the graft is placed in an area of undilated, healthy aorta, adjacent to the aneurysm, avoiding occlusion of the mesenteric, renal, and celiac branches. The ability of the graft material to stretch longitudinally facilitates proper placement of the distal end. Once the graft is placed it usually cannot be repositioned or retrieved. Therefore the exact location and complete bridging of the aneurysm with the graft is essential. To prevent migration of the graft, adequate anchoring is necessary. Balloon-expandable or self-expanding stents or anchoring hooks may be used to fix the graft to the aortic wall. The ideal graft should be thin-walled, flexible, compliant, and resistant to radial forces. 8 Trials are currently taking place for a tube graft (Figure 1) and a bifurcated graft (Figure 2). These grafts are made of a lightweight, woven Dacron. Radiopaque markers are sewn into the longitudinal axis of the graft. Figure 3 shows preoperative and postoperative angiograms of a patient who had a bifurcated graft implanted. The procedure is currently done in the operating room under general or epidural anesthesia. Both the vascular surgeon and the interventional radiologist perform the procedure. INCLUSION AND EXCLUSION CRITERIA

Patients who are diagnosed with an AAA are screened for possible inclusion for the endovascular technique. Imaging

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Figure 1. Tube graft. (From• ParodiJC. Transfemoral intraluminal graft implantation for abdominal aortic aneurysm. In: Carter DC, Russell RCG, series editors. Vascular surgery. In: Jamieson C, Yao JST, volume editors. Rob & Smith's operative surgery. 5th ed. London: Chapman & Hall; 1993.)

modalities used are CT and angiography. CT permits accurate measurement of the diameter of uninvolved aorta proximal and distal to the aneurysm. The diameter of the aneurysm is also measured. Angiography provides information concerning tortuosity of the arteries, evidence of collateral mesenteric blood flow pattern, aberrant renal artery anatomy, and an accurate measurement of the length of the graft required. 9 Table I summarizes the inclusion and exclusion criteria for patients involved in the endovascular study being done by Endovascular Technologies, Inc. (Menlo Park, Calif.).

Figure 2. Bifurcated graft. (From Chuter TA, Donayre C£; White RA, editors. Endoluminal vascular prosthesis. Ist ed. Boston: Little Brown; 1995.)

a small femoral incision rather than a large abdominal incision. Recovery is more rapid, with the average post-operative length of stay in the hospital being 24 to 48 hours. ICU monitoring is not required. After recovery from anesthesia, the patient can be up and about and begin to eat. All of these benefits also result in a decrease in overall cost.

BENEFITS OF THE ENDOVASCULAR PROCEDURE

COMPLICATIONS

The endovascular procedure can be performed under local or regional anesthesia, and the need for blood products is reduced. The presence of multiple peritoneal adhesions, prior vascular reconstructive procedures, malignancy, or abdominal wall stomas can greatly increase the difficulty of surgical repair, but does not interfere with endovascular repair. This procedure places less stress on the heart and reduces pulmonary complications. The risk of postoperative impotence is decreased by the avoidance of periaortic dissection. 8 There is

The traditional surgical p r o c e d u r e requires e x t e n s i v e intraabdominal or retroperitoneal dissection, interruption of blood flow to the renal and mesenteric arteries, and general anesthesia. Cardiac and respiratory impairment; renal failure; liver, intestinal, and spinal cord ischemia; ileus; bleeding; coagulation disorders; and impotence are all potential complications that can be attributed directly to the surgical procedure. Potential complications directly related to the endovascular procedure are listed in Table II.

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Figure 3. A, Preoperative angiogram of an aortoiliac aneurysm. Rs Postoperative angiogram of an implanted bifurcated grafi.

superior a n d inferior cuffs of nonaneurysmal vessel

occlusion or ectasia

)air o f a b d o m i n a l aortic a n e u r y s m : results of t h e N o r t h A m e r i c a n EVT

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TABLE III

RESULTS TO DATE

Moore and Rutherford 9 described the results of a phase 1 trial of endovascular repair of AAAs, conducted under FDA protocol in 13 US medical centers. The trial was designed to test the safety and efficacy of an endovascular tube graft device designed by Harrison M. Lazarus and d e v e l o p e d by Endovascular Technologies, Inc. (Menlo Park, Calif.). Follow-up e x t e n d e d to 27 months. Thirty-nine implants (85%) were successful and seven attempts were unsuccessful and the patients required o p e n surgical repair. Complications of the endovascular repairs included myocardial infarction, iliofemoral arterial injury, w o u n d infection, transient unexplained fever, and minor emboli with foot petechiae. Contrast material indicating leakage outside the graft but within the aneurysm sac was detected initially in 17 grafts; in nine instances the .leakage resolved spontaneously. Of eight persistent leaks in the aneurysm sac, one was controlled with transluminal balloon angioplasty and one required surgical exploration because of aneurysm enlargement. Six patients continued to show contrast leakage but had no evidence of aneurysm enlargement. Attachment system fracture was identified in nine implants (23%), which led to one removal; the remaining eight functioned normally with no untoward sequelae. The average operating time was 194 minutes. The average hospital length of stay was 3.8 days. NURSING MANAGEMENT

Preoperatively, the nurse should ensure that baseline ankle/ brachial indices, laboratory tests, and vital signs are documented in the chart. This will assist the nurse in her postoperative evaluation of the patient. Postoperatively, pulses, Doppler tones, ankle/brachial indices, sensory motor function, and color of the extremities should be monitored every 4 hours to assess for adequate

circulation to the lower extremities and distal embolization to the foot (i.e., blue toe syndrome). Monitoring hemoglobin and hematocrit levels is important to assess for possible hemorrhage or third spacing of fluid. The incision should be checked for excessive drainage and hematoma formation. Any signs of retroperitoneal hemorrhage (Table Ill) n e e d to be reported to the physician immediately. Mesenteric ischemia is a potential complication. The patient should be monitored for abdominal distension, gut emptying with either vomiting or diarrhea, severe abdominal pain, fever, or a sudden increase in the white blood cell count. Urine output, blood urea nitrogen, and creatinine levels should be monitored to assess tissue perfusion to the kidneys. The patient's level of comfort is also important for the nurse to assess. Oral pain medication is normally given as n e e d e d and may be continued after discharge from the hospital. The patient may be discharged on oral pain medication. Patients are monitored for signs of infection including low-grade fever, elevation in white blood cell count, and change in color or increase in the amount of drainage from the wound. The vascular nurse plays a key role in the education of patients undergoing the endovascular procedure. Preoperatively, it is the role of the nurse to educate the patient about the procedure. Many of these patients are very anxious before surgery. The nurse should encourage the patient to express his or her feelings and questions. Patient education is also important in the postoperative period. These patients are monitored closely by CT, ultrasonography, abdominal radiography, blood work, and physi-

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cal examination after they are discharged from the hospital. The importance of follow-up must be stressed to the patient. There is no limitations on activity. T h e y should resume their normal activities w h e n they feel ready to do so. Some patients have returned to w o r k as early as 1 w e e k p o s t o p e r a tively. Bathing or showering are acceptable on the third postoperative day. The majority of the patients have staples in the groin, which are r e m o v e d approximately 2 w e e k s after surgery in the outpatient office. No special care of the w o u n d is necessary unless otherwise indicated. It is important that the patient understand the use of the pain medication prescribed. CONCLUSION

New procedures that use endovascular grafts m a y represent an important alternative to standard surgical repair for AAAs. The p r o c e d u r e offers m a n y benefits for high-risk patients. It has the potential of allowing a safer and less costly treatment. Preliminary results confirm that a less invasive alternative to the treatment of AAA is feasible) Nurses play a valuable part in the care of patients undergoing this procedure. Through continuing education a b o u t this n e w technique, nurses will provide quality nursing care and enhance patient outcome. I wouM like to thank Vicki Fahey, RN, MSN, and Maria Connolly, DNSc, CCRN,,for their continued encouragement, guidance~ and expertise throughout the entire process of writing this article. REFERENCES

1. Melton L, Bicherstaff L, Hollier LH, et al. Changing incidence of abdominal aortic aneurysms: a population based study. Am J Epidemiol 1984;120:379-86.

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2. DuBost C, Allary M, O e c o m o n o s N. Resection of an aneurysm of the abdominal aorta: re-establishment of the continuity by a preserved h u m a n arterial graft with result after 5 months. Arch Surg 1952;64:405. 3. Moore WS. Endovascular grafting technique: a feasibility study. In Yao JST, Pearce WH, editors. Aneurysms: n e w findings and treatments. Norwalk (CT): Appleton & Lange; 1994. p 333-40. 4. Sayers RD, T h o m p s o n MM, Bell PRF. Endovascular stenting of a b d o m i n a l aortic aneurysms. Eur J Vasc Endovasc Surg 1993;7:225-7. 5. McCombs, RP. Acute renal failure after resection of abd o m i n a l a o r t i c a n e u r y s m . Surg G y n e c o l O b s t e t 1979;148:175-79. 6. Silbersweig JE, Cynamon J, Marin ML, et al. Endoluminal therapy with endovascular grafts. Hosp Pract 1996;Jan: 123-28. 7. Parodi JC, Palmaz JCM, Barone HD. Transfemoral intraluminal graft implantation for abdominal aortic aneurysm. Ann Vasc Surg 1991;5:491. 8. Wisselink W, Hollier LH. Principles in the technique of endovascular grafting for aneurysms. In: Yao JST, Pearce, WH, editors. Aneurysms: n e w findings and treatments. Norwalk (CT): Appleton & Lange; 1994. p 317-24. 9. Moore WS, Rutherford RB. Transfemoral endovascular repair of abdominal aortic aneurysm: results of the North American EVT p h a s e 1 trial. J Vasc Surg 1996;23:543-53. 10. Dalsing MC, Sawchuk AP. Surgery of the aorta. In: Fahey VA, editor. Vascular nursing. Philadelphia: WB Saunders; 1994. p 251-90.

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