Current Issue
AUGUST 2000 - VOLUME 20 - NUMBER 4
Endovascular Grafting for Repair of Abdominal Aortic Aneurysm
Mildred A. Jones, RN, PhD, CS, Leslie A. Hoffman, RN, PhD, and Michel S. Makaroun, MD
About the Authors
Mildred A. Jones, RN, PhD, CS, is a clinical nurse specialist and an assistant professor at the University of Pittsburgh School of Nursing, Pittsburgh, Pa. She is also a clinical associate at the University of Pittsburgh Medical Center and practices as a critical care nurse in the postanesthesia recovery unit.
Leslie A. Hoffman, RN, PhD, is a professor and chair of the Department of Acute/Tertiary Care, University of Pittsburgh School of Nursing. She is also a fellow of the American Academy of Nursing and a pulmonary specialist in
clinical research.
Michel S. Makaroun, MD, is associate professor of surgery, directory of endovascular surgery, and
director of the peripheral vascular laboratory at the University of Pittsburgh. He is the principal investigator for the Aneurysm Detection and Management Trial and the Endovascular Aneurysm Clinical Tube Trial at the University of Pittsburgh Medical Center.
This article originally appeared in the August 2000 issue of Critical Care Nurse, Vol 20, No. 4, pp 38-51.Reprint requests: InnoVision Communications, 101 Columbia, Aliso Viejo, CA 92656. Phone, (800) 899-1712 or (949) 362-2050 (ext 515); fax, (949) 362-2022; e-mail, ivcReprint@aol.com.
Minimally invasive surgical techniques are a revolutionary and innovative approach to the practice of surgery. These techniques are being used in an increasing number of patients with cardiovascular and pulmonary conditions. For example, minimally invasive direct coronary artery bypass grafting is used to establish revascularization in the beating heart without the need for cardiopulmonary bypass, aortic cross-clamping, and a median sternotomy. Video-assisted thoracoscopy allows resection and biopsy of the lung through a small incision.
Another recently introduced minimally invasive procedure, an endovascular grafting technique, is being used for selected patients who require repair of an abdominal aortic aneurysm (AAA). This innovative procedure may affect cardiovascular nursing, hospital length of stay and costs, and patients’ quality of life. Critical care nurses must be knowledgeable about this new procedure in order to provide education, assessment, evaluation, and quality nursing care to patients and patients’ families.
In this article, we describe endovascular repair of AAA and the implications for nursing and management of patients who have this surgery. We also address the surgical procedure; criteria for selecting patients; advantages and potential complications of the procedure; and perioperative care, including discharge and follow-up.
Background
An AAA is a weakening and dilatation of the vascular wall, primarily in the infrarenal area, between the renal arteries and the aortic bifurcation. Growth of an AAA to greater than 6 cm is associated with a 50% chance of rupture and massive hemorrhagic shock within 1 year.1 AAA is the 13th leading cause of death in the United States. It has a mortality rate of approximately 80% and accounts for 15 000 deaths annually.1,2 Traditionally, an AAA is repaired by an invasive procedure that involves creating a surgical access to the aneurysm through an incision in the midline of the body or in the flank. The aneurysmal part of the vessel is replaced with a prosthetic graft that is anastomosed to the abdominal aorta. The graft is then enclosed by the aneurysmal sac.1 After the procedure, the typical recovery period is 1 day in an intensive care unit and then 5 to 10 days in a general unit.
In contrast, with the new minimally invasive endovascular procedure, pioneered by Juan Parodi and colleagues in 1991, a sutureless vascular graft is introduced and implanted into the abdominal aorta through a femoral arteriotomy. This technique eliminates the need for an abdominal incision and associated complications. In addition, the postoperative course typically requires only 1 to 3 days of hospitalization in a general unit.3
The first device approved by the Food and Drug Administration for clinical investigation of endovascular grafting in the United States is the endovascular grafting system (EGS) manufactured by Endovascular Technologies Inc (Menlo Park, Calif).4 This device consists of a catheter delivery system with a guidewire, a compressed graft with self-expanding fixation devices at each end, and a balloon catheter for positioning and driving the hooks of the fixation device into the wall of the aorta. The graft material is the same as that used in currently marketed polyester vascular grafts. With fluoroscopic guidance, the delivery catheter of the EGS is inserted through an incision into the femoral or the iliac artery over a guidewire.
The delivery catheter is then advanced up the iliac artery into the aorta, where it is positioned across the aneurysm. The vascular prosthesis is then released and implanted in the vessel wall, creating a circumferential seal, and anchored to the vessel by several hooks. Finally, the delivery catheter is removed, leaving the deployed prosthesis. The prosthesis isolates the aneurysmal wall from intraluminal blood flow and pressure. Consequently, it prevents further expansion of the aneurysm and decreases the risk of rupture.
Three types of prostheses are available for AAA repair: a tube, a bifurcated device, and an aortoiliac device (Figure 1). The type of prosthesis selected is determined by specific anatomic criteria. A part of the aorta proximal to the aneurysm and below the renal arteries that is at least 1.5 cm long is required in all patients. This length is necessary for secure fixation of the proximal hooks. Patients with an aortic distal neck above the iliac arteries longer than 1.2 cm can be treated with a tube-type EGS.
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This length is necessary for the distal fixation system of the tube device. It is applicable for 5% of patients. A bifurcated EGS requires bilateral undilated common iliac arteries for an appropriate seal of the distal fixation system. Most patients fit the requirements of the bifurcated device, and it is used for 25% to 40% of AAA repairs. The aortoiliac EGS is used when one of the common iliac arteries is not suitable for the distal attachment system because of aneurysmal or occlusional disease. The aortoiliac EGS is used for repair of AAAs with anatomic impediments that cannot be repaired with the tube or bifurcated prostheses.2,5
Endovascular Procedure
At the University of Pittsburgh Medical Center, preoperative preparation for use of an EGS includes the same routine workup required for traditional repair of an AAA. A comparison of the 2 procedures is presented in Table 1. The endovascular grafting procedure is performed in the operating room and requires general or regional anesthesia. The patient is placed supine on an operating table equipped with a special marker board. The board has remotely controlled radiopaque cursors that are used to detect fluoroscopically proximal and distal positions for graft deployment.
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The patient may receive general anesthesia or epidural anesthesia. If epidural anesthesia is used, mechanical ventilation is available in case conversion to the traditional surgical procedure is required (eg, inability to repair the aneurysm with the EGS). A central venous catheter and an arterial catheter are inserted for hemodynamic monitoring. A Foley catheter is inserted to ensure accurate measurement of urinary output for assessment of renal perfusion and function. The patient’s abdomen and groin areas are surgically prepared and draped to allow conversion to the traditional surgical technique, if necessary.6,7
Figure 2 shows the bifurcated EGS and the steps included in implanting the device. Because endovascular grafting with a bifurcated device is more common than grafting with the tube or aortoiliac devices, use of the bifurcated EGS is briefly described here.
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Both common femoral arteries are dissected through small cutdowns. After the administration of intravenous heparin (100 U per kilogram of body weight), the right common femoral artery is clamped, an arteriotomy is performed, and an 8F sheath is introduced into the right external iliac artery. The left femoral artery is punctured, and a 12F sheath is placed into the left external iliac artery. An angioscale catheter is inserted, and an arteriogram is obtained to clearly mark the renal arteries and aortic bifurcation. The final length of the device to cover the aorta from the renal arteries to a suitable section of the common iliac arteries is chosen.
Next, a snare is introduced into the aorta through the left femoral artery, and a pull wire is introduced into the aorta via the right femoral artery. The pull wire is snared above the aortic bifurcation and retracted into the left iliac artery. This step is done to help position the limbs of the graft into the iliac arteries. The EGS device is then inserted into the right femoral artery, advanced into the proximal part of the aorta, and positioned above the aortic bifurcation. The device is exposed by retracting a covering jacket, and the graft limbs are positioned in the iliac arteries. The device is further advanced up the aorta and positioned below the renal arteries. The hooks of the graft become attached to the walls of the aorta and the iliac arteries as the attachment systems are deployed.
Finally, the balloon on the device is inflated to secure the proximal attachment system to the aorta and the contralateral and ipsilateral attachment systems to the iliac arteries. An arteriogram is obtained to confirm proper positioning and complete exclusion of the AAA. Ideally, the EGS device is positioned to occlude the inferior mesenteric artery to prevent persistent blood flow within the aneurysmal sac. After all the sheaths are removed, the wounds are typically closed with subcuticular sutures. In our experience, the average operative time is 2 hours, and blood loss is 200 to 300 mL.
After the anesthesia is reversed, the patient is usually extubated in the operating room and transferred to the recovery room. Admission to the intensive care unit is not necessary. Once the patient’s hemodynamic condition is stable, he or she is transferred to a general unit and usually is discharged from the hospital within 1 to 3 days after surgery.
Criteria for Selecting Patients and Patients’ Characteristics
According to a phase 3 protocol approved by the Food and Drug Administration, patients are considered suitable candidates for EGS repair if their general health is sufficient to qualify them as candidates for the traditional AAA procedure, should conversion become necessary. At the University of Pittsburgh Medical Center, potential candidates must be 21 years or older and able to provide informed consent. They can be men or women. Because of exposure to radiation during the procedure and follow-up, women must be postmenopausal or surgically sterile. All patients must qualify for anesthesia clearance with classifications of I to IV, which range from no physiological or psychiatric disturbance (I) to severe systemic disturbance that is life threatening with or without surgery (IV). The patient’s life expectancy should preferably exceed 2 years. Preoperative angiography must indicate that the inferior mesenteric artery is not essential for intestinal perfusion because this artery is obliterated by the EGS procedure.6 Flow in the internal iliac artery should be maintained on at least one side to preserve blood supply to the rectum.
To date, approximately 190 patients have had endovascular grafting at the University of Pittsburgh Medical Center. They include patients with histories of cardiac dysfunction (myocardial infarction, coronary artery disease), coronary artery bypass graft surgery, chronic obstructive pulmonary disease, lung transplantation, hypertension, cancer, renal disease, sleep apnea, diabetes mellitus, cerebral vascular accident, liver disease, and advanced age (>80 years old). Ninety-five percent were discharged within 3 days after the EGS procedure.
Advantages and Potential Complications of Endovascular Grafting
Endovascular repair with the EGS has a number of advantages over traditional AAA surgery (Table 2). Use of an EGS eliminates the need for an abdominal incision, thus reducing complications associated with extensive invasive surgery. Regional anesthesia can be used if needed, thus eliminating the risks of general anesthesia in patients with pulmonary disease. Use of an EGS decreases respiratory complications because postoperative pain is markedly reduced and no postoperative mechanical ventilation is required. The reported mortality rate for EGS repair is 1% to 2%, compared with 3% to 5% for traditional AAA repair.5,9
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Use of an EGS device also facilitates faster recovery because a minimal groin incision causes less pain than a full abdominal incision does. Early mobility reduces convalescence time and risks related to immobility. The hospital length of stay is 1 to 3 days when an EGS device is used and 5 to 10 days when the traditional approach is used.10 Patients who have EGS repair can be transferred from the postanesthesia recovery unit to a general unit postoperatively and do not require an admission to the more costly intensive care unit.
Although substantial advantages are associated with the EGS, the procedure does have potential complications (Table 3). Of primary concern is a potential for perigraft leaks due to incomplete endovascular graft exclusion of the aneurysm; this complication may occur in 8% to 44% of patients.3,5,6,8,11,12 Small leaks may resolve spontaneously by self-sealing. However, other leaks may require insertion of coils (beads) to promote hemostasis at the site of the leakage.
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Graft-limb thromboses may occur but can be resolved with thrombolysis or a thrombectomy.3,5,8,11 Hematomas and infections may occur at the incision site.3,8,11 Occlusion of the renal artery may occur because of improper graft placement, graft migration, and graft dislocation.3,5,8 Hemorrhage and injury of the femoral and iliac arteries have been reported.5,8,11,12
In addition, procedural complications can occur, including problems with access, malposition of the graft, deployment failure, and balloon malfunction.3,5,6,8,11-13 Complications that may occur later include shrinkage and morphological changes in the configuration of the aneurysm after exclusion that can affect healing and stability of the graft.14 Graft dysfunction may require conversion to a traditional repair.3,5,6,8,11,13
However, these potential complications have been limited in our experience.5 Of 50 patients, 47 (94%) had successful EGS repair; the other 3 had conversion to standard repair. Perigraft leaks developed in 33% of the patients. The leaks resolved either spontaneously or with insertion of coils in 73% of these patients by the 6-month follow-up examination. Three patients had graft-limb occlusions, which were treated successfully with thrombolytic therapy.
Some surgeons propose that endovascular grafting will become the accepted lower risk alternative to traditional AAA surgery, especially for high-risk patients.5 Studies are ongoing to evaluate the long-term safety and efficacy of the EGS in patients with AAA. New devices developed by other companies are also undergoing trials. The ANCURE device (Guidant Technologies, Menlo Park, Calif), the EGS used at the University of Pittsburgh Medical Center, and the AneuRx device (Medtronic Inc, Minneapolis, Minn) were approved by the Food and Drug Administration for general use in September 1999.
Perioperative Care
At the University of Pittsburgh Medical Center, the nurse’s role is to assess, evaluate, and educate patients undergoing endovascular grafting for AAA repair. As clinicians, nurses are involved in the initial assessment of potential patients in the cardiovascular clinic. In collaboration with a patient’s surgeon, a nurse performs a physical and psychosocial assessment of the patient that includes evaluating and recording the patient’s cardiopulmonary status, stressors that affect the patient and the patient’s family, coping behaviors, and support systems. As a part of the research team, the nurse is responsible for overseeing implementation of the research protocol. The nurse must know about special preoperative procedures such as aortography, determination of ankle brachial indices for assessment of blood flow, and computed tomography in order to educate the patient.
The surgeon reviews all the test results with the patient and explains the endovascular grafting procedure and its potential risks and the potential for conversion to the traditional approach. The nurse’s role now becomes that of an educator and advocate who reviews the educational booklet on the EGS with the patient, reemphasizes the physician’s explanations, provides specific preoperative instructions, and answers questions asked by the patient and the patient’s family. Once informed consent is obtained from the patient, the nurse is responsible for confirming that surgery is scheduled and for obtaining the appropriate EGS catheters.
On the day of surgery, the patient is admitted to the preoperative holding area by a postanesthesia critical care nurse who performs routine preoperative procedures. These include reviewing the operating room checklist; confirming that the patient has provided consent for surgery, anesthesia, and blood products; verifying attainment of laboratory results (ie, complete and differential blood cell counts, prothrombin time, partial thromboplastin time, platelet count, and levels of electrolytes, serum urea nitrogen, creatinine, and glucose), chest radiographs, and electrocardiograms; assessing femoral, dorsalis pedis, and posterior tibial pulses; and providing preoperative teaching. The patient is then evaluated by an anesthesiologist. Next, a nurse anesthetist establishes a peripheral intravenous access, and the patient is transferred to the operating room.
The patient is given cephalosporin prophylactically: 1 g intravenously in the operating room and then 1 g every 8 hours for 24 hours. Once the patient is transferred to the operating room, the members of the operative team (ie, the surgeon, radiologist, circulating nurse, scrub nurse, nurse anesthetist, and anesthesiologist) work collaboratively to implant the EGS successfully. The surgeon confirms placement of the EGS by obtaining an intraoperative angiogram and an intravascular sonogram. In the operating room, the anesthesia is reversed, and the patient is extubated before transfer to the postanesthesia care unit.
Immediate Postoperative Care
In the postanesthesia care unit, a critical care nurse monitors the patient’s respiratory status, including oxygen saturation as indicated by a pulse oximeter; hemodynamic status, that is, arterial pressures, systemic blood pressure, electrocardiographic findings, temperature, and posterior, tibial, and dorsalis pedis pulses. The nurse also checks for the presence of abdominal or back pain, monitors sensations and movements, assesses color and groin incisions, and palpates the abdomen for a pulsating mass. Other responsibilities of the nurse include fluid management and assessment of urinary output and laboratory findings. Pain control is maintained with morphine sulfate or oxycodone hydrochloride. Within 2 hours, the patient is transferred to a general unit.
To facilitate recovery and provide a positive transition from admission to discharge, the University of Pittsburgh Medical Center developed a clinical pathway for patients who have elective repair of AAA.15 A pathway is a collaborative care plan that serves as a guideline to promote coordination of and communication about patients’ care.16 We modified the AAA clinical pathway to meet individualized care needs of EGS patients. An advanced practice nurse can use this modified pathway (Table 4) in planning care for patients after EGS repair. Each patient’s primary care nurse is responsible for implementing the plan. Incorporated within the plan are the expected outcomes. A nursing care plan (Table 5) is developed to achieve these outcomes.
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After a patient’s condition stabilizes, he or she is transferred to a general unit. During this postoperative period, the primary care nurse continues to assess the patient for signs of bleeding or occlusion and to obtain laboratory tests and studies: complete blood cell count, levels of serum urea nitrogen and creatinine, platelet count, ultrasound examinations, computed tomographic examinations, determination of ankle brachial indices, and abdominal radiographs. The primary nurse monitors the patient for cardiovascular status: vital signs; peripheral pulses, especially of the lower extremities; color; temperature; incisional bleeding or hematoma; signs and symptoms of infection; and occurrence of pain, tingling, or numbness.
Fluid intake and urinary output are monitored to assess for impaired renal function. The patient’s respiratory status is assessed, and pulmonary toilet consisting of coughing and incentive spirometry is implemented. Pain control is maintained to facilitate adequate respiration.
The patient is assessed for bowel sounds and bowel movements indicating return of peristalsis. The patient’s diet is advanced from clear liquids to a regular diet the first evening after surgery. The patient is given nothing by mouth after midnight in preparation for an ultrasound examination; the regular diet is resumed after the examination.
Functional status is monitored to maintain mobility and independence. Patients are ambulated within 4 to 6 hours after surgery. Psychological status is monitored to assess the patient’s ability to cope with ongoing stressors such as anxiety related to an unfamiliar environment, postoperative discomfort, lack of understanding of postoperative care, and the long-term outcome of this new procedure.
Discharge teaching about signs and symptoms to report, incision care, activity level, diet, and medications (Table 6) is started when the patient is admitted to the general unit and is reinforced daily until the patient is discharged from the hospital. Follow-up procedures include a physical examination, laboratory studies, and determination of ankle brachial indices at 6 weeks and physical examination, abdominal radiography, ultrasound examination, computed tomographic scan, and determination of ankle brachial indices at 3, 6, 12, and 24 months after the EGS procedure, according to the phase 3 research protocol.
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Preliminary Research Results of Endovascular Grafting
EGS repair may profoundly affect healthcare management if long-term results of clinical trials are positive. In short-term follow-up of patients who had EGS repair, physiological and psychological results have been highly favorable. Preliminary results on the feasibility and effectiveness of endovascular grafting of AAA at the University of Pittsburgh Medical Center have been published5 (Table 7). The first 50 patients who had EGS repair were compared with a concurrent surgical cohort of 69 patients who had traditional open repair during a 24-month period. The patients were part of a phase 2 clinical trial testing the EGS developed by Endovascular Technologies, Inc. The same surgeon performed all procedures with a vascular radiologist as the first assistant. In all patients, angiograms were obtained before and after implantation of the EGS device for assessment and evaluation.
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Both groups of patients had similar baseline characteristics. The majority of patients were men. The mean sizes of the AAAs were 5.6 cm (range, 4.3-8.2 cm) for EGS repair and 5.9 cm (range, 4.0-9.0 cm) for standard repair. Both groups had similar percentages of comorbid cardiac conditions, chronic obstructive pulmonary disease, and other comorbid conditions. The EGS group had a shorter length of stay and fewer readmissions than did the traditional group. One operative death occurred in the EGS group.
Perigraph leaks, the most frequent complication in patients undergoing endovascular grafting, occurred less than previously reported (33% vs 44%).10 Despite the decreased length of stay, use of an EGS device did not markedly reduce average hospital costs because of expenses for the EGS device and interventional supplies.
The researchers5 concluded that use of the EGS was feasible and effective. Mortality rate was low (2%). Patients’ satisfaction was high because minimal discomfort occurs with this procedure, and the convalescence time was reduced, allowing earlier return to previous activity levels. Research is ongoing to determine the long-term physiological and psychological effects of this innovative minimally invasive procedure, including the impact on the caregivers of these typically elderly patients.
Conclusion
Endovascular grafting, a new minimally invasive technique for repair of AAA, provides an alternative to the traditional approach. Preliminary research results indicate that endovascular grafting is feasible and effective. Use of an EGS device is associated with minimal invasiveness and blood loss; shorter operative time, length of hospital stay, and convalescence; decreased complications; and increases in patients’ satisfaction. Nurses can be on the forefront of the evolution of this innovative technique by providing education and quality nursing care for patients and patients’ families.
Acknowledgments
This study was funded in part by grant 5 RO3 Ag1525002 from the National Institute on Aging, Bethesda, Md.
We thank Theresa Hovanec, clinical nurse III, postanesthesia recovery unit, for her contributions to this article.
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15. Painter LM, Dudjak LA, Briener K, Langford A. Abdominal aortic aneurysm pathway: outcome analysis. J Vasc Nurs. 1995;13:101-105.
16. Muluk SC, Painter L, Sile S, et al. Utility of clinical pathway and prospective case management to achieve cost and hospital stay reduction for aortic aneurysm surgery at a tertiary care hospital. J Vasc Surg. 1997;25:84-93.