Aneurysms of the abdominal aorta occurring distal to the renal arteries should, in general, be replaced. This is particularly true if they are enlarging, 5.5 cm or greater in males and 5.3 cm or greater in females, producing pain or if there is evidence of impending or actual rupture. In poor-risk patients with small aneurysms less than 5 cm in diameter, observation may be the better course. Many aneurysms are corrected by endovascular techniques, but an open operative approach is acceptable and a sometime necessary alternative. Although the operation is of considerable magnitude, anticipated mortality associated with spontaneous rupture and exsanguination from an aneurysm is such as to warrant the risk of surgery in the great majority of patients. Emergency operations may offer the only chance of a patient's survival if there is evidence of leakage or rupture of the aneurysm. A past history of coronary artery disease is not a contraindication to surgery.
CT scan best defines the size and contour of these aneurysms. Transabdominal ultrasound is a good screening tool, but CT best defines size and proximal and distal extent. Aortography is carried out if there is a question about the extent of the aneurysm, if distal occlusive disease is present, and when renal vascular disease or mesenteric insufficiency is suspected. A thorough cardiac evaluation with an electrocardiogram, echocardiogram, and imaging stress test is performed.
In elective resection of an aneurysm, the preoperative preparation consists of emptying the large intestine by administering a mild cathartic. A fluid load of “crystalloid” is given at approximately 100 to 150 mL per hour beginning the evening before operation if the patient is hospitalized. Intravenous antibiotic coverage is started 1 hour before the anticipated incision. A nasogastric tube is inserted, and constant bladder drainage is initiated to follow accurately the hourly output of urine, especially during the immediate postoperative period. Catheters are placed for central venous and arterial monitoring, while a Swan–Ganz catheter may be useful in complex cardiac cases.
General anesthesia with endotracheal intubation is routine. The arterial line permits instantaneous evaluation of blood pressure changes, and blood gas sampling can be done when required. Several large-bore (16-gauge) catheters should be placed intravenously for adequate control of fluid and blood replacement, including a central venous line.
The patient is placed in a slight head-down position to aid in natural retraction of the small intestine from the region of the lower abdomen. Intravenous catheters are secured in place in both arms and adequately protected from dislodgement. The urethral catheter is connected to a constant bladder drainage bottle. Since the presence of pedal pulsations must be verified before and after the prosthesis has been inserted, some type of low support should be provided over the feet and lower third of the legs to assist in evaluating the ...