Anaesthesiology Intensive Therapy, 2009,XLI,3; 120-124

Open versus percutaneous repair of abdominal aortic aneurysm

*Ewa Karpel1, Ewa Wach2, Piotr Marszołek3, Mariusz Czechowski1


1Department of Anaesthesiology and Intensive Therapy, Silesian Medical University in Katowice


2Department of Anaesthesiology and Intensive Therapy, Teaching Hospital, Silesian Medical University in Katowice


3Department of Anaesthesiology and Intensive Therapy, Paediatric Centre in Sosnowiec

  • Table 1. Intraoperative blood losses and fluid therapy
  • Table 2. Therapy with vasoactive agents

Background. The mortality in aortic abdominal aneurysm surgery remains in the 2-7% range. The aim of the study was to compare the results and safety of surgical aneurysm resection with grafting under general anaesthesia, using percutaneous insertion of a stent under local anaesthesia and intravenous analgesic sedation.   

Methods. The data from patients scheduled for elective subrenal abdominal aortic treatment was analysed retrospectively. Patients were allocated to two groups, according to their general condition, ASA status, presence of other pathologies and anatomical conditions. Patients in group I underwent open surgery with general anaesthesia; patients in group II received stents implanted using local anaesthesia and intravenous analgesic sedation.

Results. One houndred twenty-seven patients were allocated either to group I (n=87) or to group II (n=40). Blood pressure, heart rate, the need for catecholamines, blood loss and fluid replacement were all higher in group I. More than 50% of patients from this group required mechanical ventilation in the early postoperative period as well as longer hospitalization. All patients in group II survived, while 6 patients from group I died from postoperative complications. 

Conclusions. Endovascular repair of aortic abdominal aneurysms under local anaesthesia combined with i.v. sedation is a safe alternative in high-risk patients.

In 1986 Volodos [1] and in 1990 Parosi [2] performed stent-graft implantations in patients with abdominal aortic aneurysms (AAA) starting the new era of vascular surgery. For years, we continued our search for a safe method of surgical treatment of AAA patients to reduce the risk of perioperative mortality and complications. The main factors increasing this risk include coexisting cardiovascular and respiratory diseases (coronary disease with past myocardial infarction, cardiac arrhythmia, obstructive pulmonary disease), which often accompany AAA. Laparotomy and resection of AAA under general anaesthesia, which remains the basic treatment, favour the development of perioperative complications, such as cardiac infarction, arrhythmias, respiratory distress, pneumonia, renal failure, CNS ischaemic incidents, intestinal necrosis, lung embolism, haemorrhages, DIC syndrome, or liver failure. Thanks to a markedly lower extent of and trauma related to endovascular procedures, some other methods of anaesthesia may be used and thus the incidence of anaesthesia-induced complications reduced, which is of particular importance in high-risk patients [3]. In many cases, due to their general status, AAA patients are disqualified from conventional procedures with general anaesthesia, as the risk of complications exceeds the expected benefits of the procedures performed. For such patients, the endovascular method is the only method of management.

The objective of the present study was to compare the safety and efficacy of classical and endovascular method of AAA repair based on selected perioperative parameters, anaesthetic management, in particular.

METHODS

The perioperative courses of all patients scheduled for elective repairs of abdominal aortic aneurysms localized below the renal artery over the period of 2 years were retrospectively analysed. The inclusion criteria were age below 65 years and ASA III and IV physical status.

Patients were allocated to two groups: group I – undergoing classic procedures- resection of the abdominal aortic aneurysm under general combined anaesthesia and group II – undergoing endovascular procedures – stent-graft implantation under local anaesthesia with analgosedation. All patients received identical preoperative premedication (midazolam). Anaesthetic procedures were carried out by the same anaesthesiologist according to the designed management protocols.
In group I, general anaesthesia was induced with hypnomidate 0.2-0.3 mg kg-1, fentanyl 1.5 µg kg-1 and atracurium 0.3-0.5 mg kg-1 or cisatracurium 0.15 mg kg-1. After endotracheal intubation, anaesthesia was maintained with inhalation mixture of O2:N2O (1:1) and isoflurane 0.2-0.8%. Muscle relaxation was provided with atracurium 0.1-0.3 mg kg-1 or cisatracurium 0.03 mg kg-1 depending on individual needs. Intraoperative anaesthesia was provided with fentanyl 1-2 µg kg-1 repeated every 30 min.

In group II, infiltration anaesthesia was administered by the operator, 10-20 mL of 1% lignocaine into each groin. To provide sedation and increase analgesia, patients received fentanyl in fractionated doses 1-2 µg kg-1 every 30-60 min and midazolam 0.01-0.1 mg kg-1 every 30-60 min based on clinical evaluation. After the exposure of the femoral artery, the surgeon introduced the stent-graft catheter, 17 F to 24 F in diameter (3 F=1 mm). The choice of endovascular prosthesis depended on the diameter of AAA neck, width and course of iliac arteries.

In group I, 1000 mL of crystalloids were transfused over the first 0.5 h of the procedure followed by 500 mL for each successive 0.5 h; in group II – 500 mL of crystalloids were transfused every 0.5 h of the procedure. In both groups, 10% 500 mL of hydroxyethylated starch were given when blood loss reached 500 mL at blood loss =3000 mL – 1000 mL. Red cell preparations were transfused to all patients with blood loss of 1000 mL, >2000 mL – fresh frozen plasma was added.
Nitroglycerine preparations were administered when arterial pressure increased by 50% of the baseline value and did not decrease after deepening of general anaesthesia or analgosedation.

Catecholamines were used in patients with circulatory insufficiency manifesting itself in a decrease in systolic arterial pressure by 50% of the baseline value unresponsive to fluid therapy.

The criteria of operating room extubation included: procedure duration <120 min, blood loss< 600 mL, efficient respiration (f 14-20 min-1, VT 7-10 mL kg-1), circulatory stability (no vasoactive drugs), normal diuresis ( >0.5 mL kg-1 h-1), consciousness and reactions to commands. In unconscious patients with inefficient respiration, mechanical lung ventilation was used at intensive postoperative care units (IPCUs); in some patients with efficient respiration yet with consciousness disturbances, airways were artificially maintained until the extubation criteria were met.

The following parameters were analysed in all patients: the amount of intraoperative fluids, blood loss, circulatory stability, efficacy of recovery and extubation in the operating room. In the postoperative period, cardiovascular (myocardial ischaemia and myocardial infarction), respiratory and excretory (renal failure) complications and mortality were analysed in each group. Patients were transferred to the surgical ward once they were conscious, with logical contact, efficient respiration and circulation, orally fed and with normal 24 h diuresis. The postoperative analysis involved: the amount of blood preparations transfused, arterial pressure agents used, postoperative complications (myocardial infarction, renal failure, mechanical lung ventilation), duration of IPCU stay, post-procedure hospitalization, and perioperative mortality.

Hypotheses were statistically verified using the Student’s t test for independent samples, nonparametric Mann-Whitney U test, nonparametric Wald-Wolfowitz test, nonparametric c2 test of independence – for dichotomic (binary) variables, and the significance test with a small sample correction. P=0.05 was considered significant.

RESULTS

The study encompassed 127 patients, 87 in group I and 40 in group II. The majority of patients in both groups were males (74 in group I and 33 in group). Body weight and height of patients were comparable. In group I, the mean age was significantly lower compared to group II (71.24 vs 73.58; p=0.01).

All patients had various additional diseases. The incidence of coronary disease, arterial hypertension, myocardial infarction and chronic renal failure was higher in group II patients (p <0.05).

The mean duration of procedures was comparable in both groups (group I: 90-270 min, group II: 65-320 min).

In all patients, MAP drops were observed during anaesthesia and surgery. In group I, they were related to aorta unclamping; in group II, the lowest values were detected in stent-graft implantation in the aorta lumen. Incidents of elevated arterial pressure during surgery were significantly commoner in group I than in group II (52 vs 5; p=0.000), which is likely to be associated with the surgical technique used. Decreases in HR were similar in all patients; the incidence of HR increases compared to baseline values, was markedly higher in patients undergoing classical procedures (51 vs 8; p=0.000). The SpO2 values were similar in both groups.

Blood loss during procedures under general anaesthesia was markedly higher than in endovascular repairs. In patients with classical procedures, the amount of intraoperative crystalloids was substantially higher; 85% of them required additional infusions of colloid solutions. In group II, this percentage was 40%. Moreover, in group I, the number of patients transfused with red blood cells was significantly higher; fresh frozen plasma was administered to 10 patients of group I and 1 group II patient (Table 1).

To maintain haemodynamic stability, patients received intraoperatively vasodilating or vasoconstricting drugs. The demands for those agents were found to be significantly higher in classical method patients, who more often developed haemodynamic disturbances requiring correction (Table 2).

The patients in group II breathed spontaneously and did not require endotracheal intubation during stent-graft implantation procedures. In group I, as many as 17 patients had to be mechanically ventilated for 10 h to 259 h. Amongst the remaining 70 patients, 27 were extubated immediately after surgery whereas 43 were artificially ventilated for 1-24 h.

In the postoperative period, the majority of patients in both groups required blood preparations. The demands for vasoactive drugs were significantly higher in group I (46%) than in group II (7%).

Based on continuous ECG monitoring and troponin T determinations,  myocardial infarctions were diagnosed in 7 group I patients and in none of group II patients (p<0.003).

Postoperative oliguria requiring therapeutic interventions occurred in 27.6% of group I patients and only a few of group II patients (p=0.026). Patients subjected to classical procedures under general anaesthesia required longer (1-16 days) stay in the IPCUs compared to group II patients (p=0.000). Likewise, procedure-discharge hospitalization was significantly shorter in group II (p=0.011).

All patients in both groups survived procedures. In group I, 6 patients died due to postoperative complications – 5 because of circulatory and respiratory failure caused by myocardial ischaemia and 1 because of septic shock resulting from intestinal ischaemia and fecal peritonitis.

DISCUSSION

The present study is the first Polish attempt to compare perioperative courses of patients with sub-renal abdominal aortic aneurysms subjected to classical (resection) procedures or endovascular repairs. Currently, resection of sub-renal aortic aneurysms is a relative safe, yet extremely invasive method of therapy. The mortality rates in this group were initially 20% and decreased to about 5%, or even 2% in specialist centres performing many such procedures [4, 5]. However, management of high-risk patients and weighing benefits and risks of procedures are still emotive. The mortality rates in patients <65 years of age are only 2.2% and increase to 7.3% in the 80-year-old patients.

Stent-graft implantation is effective and particularly useful for patients at the risk of perioperative complications following classical aneurysm resections due to concomitant internal diseases. Its unquestionable assets include possible use of block or local anaesthesia, lack of extensive abdominal opening or necessary aorta camping, low blood loss compared to conventional procedures and shorter postoperative rehabilitation as well as hospitalization. [6, 7].

Endovascular therapy is considered suitable only for high risk patients [7, 8]. Despite marked differences in survival rates between classical and endovascular procedures, patients undergoing the latter are usually disqualified from surgery. The incidence of postoperative complications is 4% for endovascular surgery and 12.5% for conventional treatment [6]; the respective mortality rates are 1.2 % and 4.6% [9].  

Complications after first implantations (circulatory insufficiency, myocardial infarction, respiratory distress) resulted from the new method as well as the anaesthesia technique applied [10, 11, 12]. Initially, stent-graft implantations were performed under general anaesthesia, lasted long and in many cases were converted to laparotomy. With the introduction of a new, improved generation of endovascular prostheses and improved skills of operators, the procedure duration was gradually reduced and the number of complications dropped, which enabled to perform implantations under block anaesthesia. The goal was to improve short- and long-term outcomes of therapy, which was indeed demonstrated in numerous reports [13, 14].

Our paper confirmed that sub-renal aortic aneurysms can be repaired under local anaesthesia with analgosedation and that such a therapy was safe and resulted in lower incidences of perioperative complications. The findings demonstrated significant differences in the ranges of arterial pressure and heart rate changes, the incidence of which was markedly higher in AAA resections under general anaesthesia.

Moreover, the frequency of indications for intraoperative vasoactive drugs was lower during endovascular procedures. None of the patients in this group developed circulatory insufficiency requiring catecholamines and only 4 (9.5%) received nitroglycerine preparations. Surgical resections of sub-renal aortic aneurysms were characterized by higher mean blood losses compared to endovascular procedures; likewise, the amounts of crystalloids, colloids, red blood cells and fresh frozen plasma needed to maintain haemodynamic stability were much higher. Lower blood losses and resultant lower demands for fluid infusions in patients undergoing endovascular procedures compared to conventionally treated patients are relevant in those severely ill, with small reserves and adaptive capacities of the cardiovascular system [15].

Resections of sub-renal aortic aneurysms have to be performed under general anaesthesia with artificial lung ventilation. Mechanical lung ventilation favours numerous postoperative complications, which develop in 4-70% of patients and include pneumonia, respiratory failure, bronchospasm, atelectasis and exacerbation of obstructive pulmonary disease as well as chronic lung diseases with parenchymal fibrosis [16]. Moreover, the incidence of postoperative complications is correlated with the duration of general anaesthesia [16]. The commonest non-cardiac complications are acute ischaemia of lower limbs and postoperative pulmonary complications. Endovascular treatment, as less invasive, enabled to provide less burdensome anaesthesia. None of the patients subjected only to local anaesthesia with intravenous analgosedation developed postoperative respiratory distress requiring endotracheal intubation and mechanical lung ventilation.

According to the findings reported by de Virgilio and co-workers [17], the incidence of cardiac events following endovascular procedures was 6% vs 5% after resections. The authors believe that such percentages were related to general anaesthesia administered in both kinds of procedures and worse general status of patients qualified for endovascular repairs. Another study showed that amongst all patients subjected to general anaesthesia (age and ASA score comparable), myocardial infarction occurred in 1% of endovascular cases and in 5% of classical ones [18]. Furthermore, it is known that cardiac complications account for 50% of all complications following classical procedures and only for 30% after endovascular repairs [19].

In our study, myocardial ischaemia was observed in 7 (8%) patients operated on classically. Five of them died. In the endovascular group, no cases of myocardial ischaemia were noted. These results confirm that AAA resections under general anaesthesia favour additional myocardial ischaemia events compared to endovascular procedures under local anaesthesia with analgosedation.

Renal failure is a separate problem. Increased preoperative concentration of creatinine is a relevant factor increasing the risk of surgery, incidence of postoperative complications and mortality [20]. Our findings confirmed this rule as 27.6% of patients undergoing classical resection of aneurysms developed renal dysfunction manifesting itself in reduced hourly urine excretion. In this group of patients, only 2 had preoperative chronic renal failure (creatinine levels >1.2 mg dL-1). Otherwise, only 10% of patients subjected to stent-graft implantations developed oliguria requiring  pharmacological support.

The main advantage of endovascular repairs of sub-renal aortic aneurysms is their low invasiveness compared to classical resections. In patients undergoing percutaneous prosthetic procedures of abdominal aortic aneurysms, their normal activity is restored within 1-2 days, which cannot be observed after traditional procedures [21, 22].  Our literature lacks comparative analyses of both methods of therapy as only few centres perform endovascular procedures, their periods of observation are short and selection of patients varies. In Poland, the duration of hospitalization as a factor determining hospitalization costs is undervalued. Our study demonstrated that endovascular repairs of sub-renal aortic aneurysms shortened the ITU and hospital stay.

Currently, numerous vascular centres increasingly recognize endovascular treatment of abdominal aortic aneurysms as a method giving a change of success in patients with various concomitant diseases; local anaesthesia with analgosedation sufficient for such repairs reduces markedly the risk of circulatory and respiratory complications.

CONCLUSIONS

Endovascular repair of sub-renal aortic aneurysms under local anaesthesia with analgosedation is a good and safe method of therapeutic management in high-risk patients, which

– provides intraoperative haemodynamic stability,

– does not require endotracheal intubation nor depresses the respiratory efficiency,

– is associated with lower intraoperative blood losses and less invasive perioperative fluid therapy compared to classical surgical resections,

– reduces the incidence of postoperative complications and deaths in the immediate post-operative period,

– does not require long hospitalization.

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REFERENCES

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Address:

*Ewa Karpel
Klinika Anestezjologii i Intensywnej Terapii
Śląskiego UM w Katowicach
ul. Medyków 14, 40-752 Katowice
e-mail: ekarpel@sum.edu.pl

Received: 20.01.2009
Accepted: 12.05.2009