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Endovascular treatment of abdominal aortic aneurysms: is there a benefit regarding postoperative outcome?

Bertrand, M.*; Godet, G.*; Koskas, F.; Cluzel, P.; Fléron, M.-H.*; Kieffer, E.; Coriat, P.*

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European Journal of Anaesthesiology: April 2001 - Volume 18 - Issue 4 - p 245-250

Abstract

Introduction

Cardiac, pulmonary and renal failure, and infection, is particularly feared after major vascular procedures in high-risk patients. Recently, the endovascular treatment of aorto-iliac aneurysms has raised major interest among vascular surgeons. However, the superiority of these results after surgery over those after open surgery is questioned. The aim of this study was to compare the postoperative morbidity and mortality rates of patients undergoing the endovascular treatment with those undergoing open surgery.

Patients and methods

Patients' characteristics

From January 1997 to June 2000, 425 consecutive patients with aorto-iliac aneurysms were referred to us for vascular surgery. Thirty-nine patients who needed visceral (7) or renal (27) artery revascularization, or both (3), or a nephrectomy (2) were excluded. The 386 remaining patients were studied in a prospective manner.

Enquiry was made of any history of congestive heart failure or pulmonary oedema. Coronary artery disease was defined on a clinical history of angina, and/or a previous myocardial infarction, and/or coronary stenosis >70% demonstrated by coronary arteriography. Chronic obstructive pulmonary disease was defined according to normal clinical and radiological criteria. A serum creatinine concentration >120 μmol L−1 for more than 6 months was used to define chronic renal failure.

Surgical procedure

Patients scheduled for aortic aneurysm surgery were evaluated with spiral computerized tomography (CT) scanning and calibrated aortography. After informed consent, patients whose arterial anatomy was deemed suitable underwent endovascular treatment (n = 193). All other patients underwent open surgery and are considered as a control group (n = 193).

Endovascular treatment proved possible for patients with aortic aneurysms when the length of the proximal aortic neck was >15mm and the length of the distal aortic neck was >15mm. This form of surgery was also possible for aorto-iliac aneurysms when the length of the distal common iliac neck was >5mm. All endovascular treatment was performed via a femoral or iliac retroperitoneal route. All stent-grafts were made to measure by one of us (F.K.), using auto-expandable stainless-steel stents covered with a standard polyester prosthetic graft. A short segment of the common femoral artery was surgically exposed, with or without extension towards the external iliac artery depending upon the size and morphology of the latter. Fluoroscopy was used to position an introducer so that the stent-graft could be pushed towards the planned site of implantation. At this time, correct positioning was checked by arteriography, generally using a catheter introduced through the left brachial artery to a few centimetres above the planned site of implantation. Combined endovascular/conventional treatment of abdominal aortic aneurysms was applied when the iliac arteries had to be reconstructed. In this case, surgical reconstruction of the iliac arteries may be needed prior to endovascular aortic aneurysm repair [1]. In case of complicated bifurcation lesions, the second limb was revascularized using a crossed femoral or iliac bypass.

Anaesthetic management

All patients received the same anaesthetic management. Monitoring included use of direct measurement of radial arterial pressure and computerized ST-T segment analysis (Marquette 7010 monitor, Milwaukee, WI, USA). Premedication consisted of oral midazolam (5mg). Anaesthesia was induced by propofol (2mg kg−1), sufentanil (0.5 μg kg−1), and muscular relaxation was achieved by atracurium (0.5mg kg−1). Anaesthesia was maintained using sufentanil and isoflurane. Mechanical ventilation of the lungs was applied using a mixture of 50% N2O in O2. Intravascular volume replacement was accomplished with gelatine and hydroxyethyl starch solutions. Red cell transfusion included homologous and autologous packed cells. Furthermore, during open surgery, the shed blood was collected, washed and reinfused as packed cells, using a Cell-Saver IV or V autotransfusion system (Haemonetics, Irvine, CA, USA). Haemoglobin plasma concentration was maintained above 9 g 100 mL−1.

At the end of surgery, uncomplicated patients were extubated when their body temperature rose to 36°C. Haemodynamic events such as hypertension (> 130% of control value) were treated with a bolus of nicardipine 1 mg, or titrated using esmolol when associated with an increased heart rate (>85 beats min−1). Postoperative myocardial ischaemia - defined as an ST depression >1 mm at 60 ms after the J point - was treated with β- adrenoceptor blocking drugs or diltiazem, or nitrates when left ventricular function was poor. Hypovolaemia was treated using gelatine or hydroxyethyl starch solutions. Paracetamol (acetoaminophen), and morphine administered by a patient-controlled system, were used to provide pain relief after surgery. Patients were discharged from the intensive care unit on postoperative day 1 (POD1) in the absence of any complications.

Clinical outcome analysis

Postoperative complications were diagnosed as previously reported [2,3]. Postoperative cardiac complications were congestive heart failure, pulmonary oedema, supraventricular or ventricular dysrhythmia, development of a new Q-wave or ST-T depression longer than 48h assessed by twice-daily 12-lead electrocardiography (ECG), development of new akinesia by echography or cardiac death. In addition, cardiac troponin I (cTnl) was titrated at recovery and at postoperative days, 1, 2 and 3, using an immunoenzymofluorometric assay on a Stratus autoanalyser (Dade-Behring, Massy, France). Normal values were 0-0.5ng mL−1; values >1.5ng mL−1 were diagnostic of myocardial infarction. Postoperative respiratory complications were defined as the occurrence of atelectasis, pneumonia or acute respiratory failure (prolonged ventilatory support or need for tracheal reintubation). Acute renal failure was defined as either a postoperative serum creatinine concentration >150 μmol L−1 in patients with normal preoperative renal function or an increase in postoperative serum creatinine concentration >30% in patients with preoperative chronic renal failure. Mortality was defined as death occurring within 30days after the surgical procedure. Causes of death were related to the first intervening major complication. The follow-up for this study ended at the patient's discharge.

Statistical analysis

Statistical analysis was performed using the Student's non-paired t-tests and X2-test when appropriate; P<0.05 was considered significant.

Results

The age of the patients and the incidence of coronary disease were significantly higher in patients in the endovascular treatment group (Table 1). Six patients in the endovascular treatment group needed to be converted to open surgery (during the same operation) because of a rupture of the iliac bifurcation (1 patient), a large endoleak, i.e. the absence of complete exclusion of the aneurysm (2 patients), blocking of the stent-graft in its carrier (2 patients), or because of underevaluation of the extent of the disease in the iliac arteries (1 patient).

Table 1
Table 1:
Clinical characteristics of the patients

Tables 2 and 3 compare the main intraoperative characteristics and postoperative outcome in both groups. Data are reported using an intention-to treat analysis.

Table 2
Table 2:
Intraoperative characteristics
Table 3
Table 3:
Postoperative data

Blood loss and the need for blood products were significantly lower in the endovascular treatment group. The need for transfusion of patients in the endovascular treatment group was significantly less for any kind of blood product (110 vs. 35, P<0.001) or homologous blood products (129 vs. 56; P<0.001). The need for reoperation was more frequent (P<0.05) in the open surgery group: surgical bleeding (endovascular group = 2; open surgery group = 5), lower limb ischaemia (1 vs. 4), intestinal occlusion (1 vs. 2), gastrointestinal bleeding (0 vs. 2), colonic ischaemia (1 vs. 6), acute pancreatitis (0 vs. 1), local infection (1 vs. 2), prosthesis thrombosis (4 vs. 0), prosthesis infection (0 vs. 1), or an endoleak (1 vs. 0).

There were no significant differences with respect to cardiac complications and mortality between the two groups. Nevertheless, the patients in the endovascular treatment group showed a reduction in the number requiring reoperation; there was also a lesser incidence of pneumonia, acute respiratory and renal failure and their stay in the intensive care unit and the hospital was shorter than patients in the control group. Despite a high preoperative comorbidity, the overall mortality remained low, with no difference between the groups.

Discussion

Despite early complications associated with a learning curve, exclusion of large abdominal aortic aneurysms using unilimb stent-grafts is feasible [4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]. Strict inclusion criteria are necessary in order to improve mortality among non-surgical candidates and minimize the morbidity and mortality of endovascular treatment [17]. However, to determine whether the endovascular treatment is any better than the conventional open surgical method it was necessary to compare two groups of patients undergoing similar operations. In contrast with numerous other reports [18,19,20], our study did not suffer any recruitment bias as the patients included had not been previously selected for serious comorbidity precluding open surgery.

Despite the absence of randomization, one must note that there are almost no differences between either group concerning the preoperative status of our patients except for their age and the incidence of coronary disease. During the period of study, 39 patients needed an intraperitoneal approach to reattach renal (27) or visceral arteries (7), or both (3), or needed a nephrectomy (2) for a carcinoma. The remaining 386 patients were surgically evaluated as eligible or ineligible for the endovascular treatment, solely through consideration of their relevant vascular anatomy.

The main finding of this study is the high feasibility of endovascular treatment using this made-to-measure stent-graft, with 50% of patients eligible, in contrast with the 20-30% generally described [18,19].

In the open surgery group, respiratory complications resulted from the pattern of restriction as well as the ventilation-perfusion abnormalities induced by upper abdominal surgery. The lack of laparotomy or retroperitoneal approach and the absence of diaphragmatic dysfunction may explain the significantly lower incidence of respiratory complications in the endovascular treatment group, despite a delay for tracheal extubation that was comparable between the groups.

In both groups the low incidence of cardiac complications should be emphasized, confirming pertinent preoperative evaluation and perioperative management, although aortic cross-clamping is usually considered detrimental to left ventricular function. However, many authors report a high incidence of myocardial infarction after surgery, even after endovascular treatment; this complication is probably underestimated because of the use of insensitive markers (one patient out of 30 in Yusuf and his colleagues' study [18]).

Blood loss, and thus the need for blood and synthetic colloid products, was significantly lower in the endovascular treatment group. A significantly higher number of patients in the endovascular treatment group did not require transfusion in the perioperative period in contrast to those of the open surgery group. However, the fact that six patients in the endovascular group needed to be converted to the open surgical technique during surgery is an argument to include future patients in predonation protocols. A further study is needed to determine the accuracy of the predonation protocol in the subgroup of patients with minimal bleeding, e.g. patients needing a tubular prosthesis only.

Despite the administration of quite large amounts of radiocontrast agents (240±90 mL) the incidence of acute renal failure was significantly lower in the endovascular treatment group, confirming the major role of aortic cross-clamping in causing this complication. In the open surgery group, 10 patients required a suprarenal cross-clamp. However, other factors may play a major role in the development of renal failure, for example bleeding, hypovolaemia and septic shock.

Our results need to be confirmed by a randomized trial but demonstrate that endovascular treatment, when technically feasible, provides a smoother postoperative outcome than open surgery. The long-term results of endovascular treatment remain to be assessed. The economics of the two approaches also remains to be studied.

References

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Keywords:

ANEURYSM; aortic; SURGERY; PROSTHESIS; vascular; postoperative complications

© 2001 European Society of Anaesthesiology