CHAPTER 104 Open Repair of Abdominal Aortic Aneurysms and Postoperative Assessment
Open repair of an AAA involves attaching a tube or bifurcated graft within the aneurysm sac. Occasionally, however, the native AAA is excluded from the graft and remains intact posterior to the aortic graft. The transperitoneal or the retroperitoneal approach may be used. In one study, there was no significant difference in mortality rates between the two procedures, and although retroperitoneal repair was associated with less frequent respiratory failure, it was also associated with more frequent wound complications.1
There are no strict anatomic contraindications to open repair of an AAA. However, there are many anatomic variations that must be taken into account. Coexisting aneurysms of the common iliac artery, especially if larger than 3 cm, should undergo exclusion during AAA repair. Attention should also be given to possible aneurysms of the hypogastric and external iliac arteries. The common and external iliac arteries may be severely affected by atherosclerotic disease, and may require arterial bypass grafting.2 Many pararenal aortic aneurysms are now repaired via the open surgical technique because of the frequent lack of a proximal implantation site sufficient for endovascular repair. These aneurysms require greater exposure than infrarenal aneurysms, and are technically more demanding. Repair of juxtarenal, pararenal, or suprarenal aneurysms require suprarenal clamping, which are associated with increased risk for renal damage because of ischemia.
POSTOPERATIVE ASSESSMENT
Early Postoperative Complications
On the first postoperative day after open repair of an AAA, hypotension and cardiac and respiratory dysfunction are the most likely complications to occur. Between days 1 and 3, the most common complications are congestive heart failure, pulmonary embolism, and respiratory failure. Pneumonia occurs most commonly between 4 and 7 days following surgery. The incidence of renal failure peaks within the initial 3 days following surgery and between 1 and 4 weeks postoperatively.2 A midline transabdominal incision is associated with higher postoperative rates of pulmonary complications, persistent ileus, and incisional hernias.
Overall, perioperative complications occur in up to 30% of patients. The organs most commonly affected are the heart, lungs, and kidneys. Cardiac-related complications, including arrhythmia, infarction, and congestive heart failure, occur in about 10% to 15% of patients after elective aneurysm repair. Perioperative renal dysfunction predicts a poorer prognosis and correlates with poor preoperative renal function. Insufficient management of pulmonary disease is also associated with a poorer prognosis.2
Early postoperative complications also include groin infections (in 2% to 3%), thromboembolism to the kidneys and lower extremities, and hemorrhage. Peripheral ischemia develops in less than 1% of patients postoperatively, but may occur because of damage to diseased arteries during cross clamping, iliac dissection, or peripheral embolization from aortic plaque. Spinal cord ischemia, which may result in paralysis, can occur secondary to a variety of differing factors. The artery of Adamkiewicz may arise below L3 in a minority of patients and ligation of a lumbar artery in the aneurysm sac in such a patient may lead to spinal cord ischemia. An additional cause is suprarenal or supraceliac cross clamping that compromises the spinal cord circulation. Small bowel infarction and colonic ischemia occur in 0.15% and 1% of patients undergoing elective AAA repair, respectively. Colonic ischemia most commonly develops because of ligation of the inferior mesenteric artery.2
Because of the course of the ureter over the iliac vessels, the ureter may be injured during open repair of AAAs. The ureter may have a variant course in patients with renal anomalies such as horseshoe kidney, further raising the likelihood for its injury. Ureteral fistulas with resulting urinomas may occur. Options for repair of ureteral injury include placement of a stent and reimplantation of the injured ureter into the bladder.2
Late Postoperative Complications
A common late postoperative complication is sexual dysfunction, including impotence and retrograde ejaculation. Erectile dysfunction may occur because of poor flow through the internal pudendal artery as a result of narrowing or occlusion, ligation of the internal iliac artery, an embolus or emboli in the distal pudendal arteries, or injury to the sympathetic nerves in the fascia surrounding the aorta. Other late complications include pseudoaneurysm formation, graft thrombosis, infection, aortoenteric fistula, aneurysm rupture, colonic ischemia, and peripheral embolism. These complications may affect up to 10% of patients.2
Postoperative Mortality and Survival
The postoperative mortality rate for elective open repair is approximately 5%; it is lower in younger healthier patients and higher in older at-risk patients. Risk factors that increase a patient’s risk of mortality following open aneurysm repair include advanced age, female gender, and any associated comorbidities. Additional factors include the experience of the operating surgeon, need for urgent (rather than elective) repair, and hospital volume (hospitals with higher surgical volumes generally have a lower mortality rate than those with lower volumes).2
Five-year survival of patients after successful elective open AAA repair is 60% to 70% and the 10-year survival rate is approximately 40%. These survival rates are lower than those of matched patients without AAAs, and the increased mortality is mostly to the result of manifestations of atherosclerosis, especially coronary artery disease.3
The few published reports of pararenal aortic aneurysm repair describe mortality rates that vary from 0% to 15.4%. Renal morbidity rates are high in such patients.4 In one study, there was a higher risk of overall perioperative mortality for patients who underwent open repair of juxtarenal and pararenal aortic aneurysms compared with those who underwent open repair of infrarenal aortic aneurysms (12% and 3.5%, respectively; P < .02).5
The mortality for ruptured AAA ranges from 15% to 50%, often caused by hemorrhagic shock, acute renal failure, myocardial infarction, respiratory insufficiency, or multiorgan failure.6 Mortality following open repair of a ruptured AAA is 30% to 40%.
Surgical Conversion from Endovascular Repair
Conversion from endovascular to open repair may be required for a number of reasons (Table 104-1).7 Older age, presence of chronic obstructive pulmonary disease (COPD), wider infrarenal necks, and larger aneurysms have been associated with a higher rate of conversion. In one study, the mortality rate of patients who underwent emergency conversion operations was 40%.8
TABLE 104-1 Reported Reasons for Conversion from Endoluminal Graft (ELG) to Open Repair
| Primary Conversion | Secondary Conversion |
|---|---|
| Inability to gain access | Persistent endoleak |
| Aortic rupture | Aortic rupture |
| Failed deployment | Sealed endoleak with continued AAA expansion |
| Irreversible twisting of a nonmodular ELG | Apparently successful repair with continued expansion |
| Migration of ELG causing obstructed flow | Infection in the ELG |
| Endograft thrombosis | Renal arteries covered by the endograft |
From Myers K, Devine T, Barras C, Self G. Endoluminal versus open repair for abdominal aortic aneurysms 2009. Available at: http://www.fac.org.ar/scvc/llave/interven/myers/myersi.htm. Accessed October 6, 2009.
Clinical Presentation
Aortic Graft Infection
In cases of aortic graft infection occurring within 4 months of surgery, the patient may present with fever and a high white blood cell (WBC) count. Associated septicemia, wound infection, and graft dysfunction from thrombosis or hemorrhage from the anastomotic site may occur. Infections that occur more than 4 months postoperatively may present with more subtle signs and symptoms, and a fever may be absent. Such patients have a higher likelihood of presenting with signs of complications from their aortic graft infection, such as pseudoaneurysm, aortoenteric fistula, hydronephrosis, or osteomyelitis.9
Anastomotic Pseudoaneurysms
An anastomotic pseudoaneurysm is a potential late complication after repair of an AAA. It does not contain all the layers normally present in an arterial wall and are at risk for rupture. Anastomotic pseudoaneurysms most commonly result from arterial degeneration or infection.10 They may be aortic, iliac, or femoral. Degenerative anastomotic pseudoaneurysms may present in 0.2% to 15% of patients after AAA repair.11–13 One study10 found the most common manifestations of such pseudoaneurysms to be bleeding caused by rupture (30%) and sequelae of chronic limb ischemia (25%). Pseudoaneurysms may also manifest with symptoms caused by compression of adjacent structures or acute limb ischemia, or as an asymptomatic pulsatile mass.
Imaging Indications and Algorithm
Abdominal Ultrasound
Abdominal ultrasound is often used for screening but also for preoperative and postoperative evaluation of AAAs. On ultrasound, the size of an AAA can be measured; this serves as a good method to follow patients with smaller AAAs that do not meet the size criteria for surgery. If performed by trained personnel, ultrasound has a high sensitivity (approaching 100%) and specificity (approximately 96%) for the detection of infrarenal AAAs.14
Conventional X-Ray Catheter Angiography
Select patients with AAAs, such as those with suspected mesenteric ischemia, peripheral vascular occlusive disease or peripheral vascular aneurysms, renovascular hypertension, renal anomalies such as horseshoe kidney, or thoracoabdominal aneurysms, should undergo conventional angiography. Angiography may also be performed prior to planned endovascular repair to evaluate tortuous proximal aneurysm necks and tortuous iliac arteries.15
