Anaesthesia for abdominal aortic surgery--a review (Part I)

Anesthesia for Open Abdominal Aortic Aneurysm Repair

Abdominal aortic aneurysms (AAAs) are the 13th leading cause of death in the United States 1 and approximately 40,000 patients undergo elective AAA repair each year.2 With the population aging, this number is expected to increase. Although the use of endovascular AAA repair is becoming more common, open repair, first reported by Dubost et al. in 1951 remains the gold standard.2 This chapter will review the etiology, risk factors, diagnosis, pathophysiology, operative technique, perioperative management, and postoperative complications of patients undergoing open AAA repair.

Dopexamine hydrochloride does not modify hemodynamic response or tissue oxygenation or gut permeability during abdominal aortic surgery

PURPOSE

To assess the effects of intraoperative infusion of dopexamine (a DA-1 and B2 adrenoreceptor agonist) on hemodynamic function, tissue oxygen delivery and consumption, splanchnic perfusion and gut permeability following aortic cross- clamp and release.

METHODS

In a randomised double blind controlled trial 24 patients scheduled for elective infrarenal abdominal aortic aneurysm repair were studied in two centres and were assigned to one of two treatment groups. Group I received a dopexamine infusion starting at 0.5 microg x kg(-1) x min(-1) increased to 2 microg x kg(-1) x min(-1) maintaining a stable heart rate; Group II received a placebo infusion titrated in the same volumes following induction of anesthesia. Measured and derived hemodynamic data, tissue oxygen delivery and extraction and gut permeability were recorded at set time points throughout the procedure.

RESULTS

Dopexamine infusion (0.5 -2 microg x kg x min(-1)) was associated with enhanced hemodynamic function (MAP 65 +/- 5.5 vs 92 +/- 5.7 mm Hg, P = <0.05) only during the period of aortic cross clamping. However, during the most part of infrarenal abdominal aortic surgery, dopexamine did not reduce systemic vascular resistance index, mean arterial pressure nor oxygen extraction compared with the control group. The lactulose/ rhamnose permeation ratio was elevated above normal in both groups (0.22 and 0.29 in groups I and II respectively).

CONCLUSIONS

Dopexamine infusion (0.5 -2 microg x kg(-1) x min(-1)) did not enhance hemodynamic function and tissue oxygenation values during elective infrarenal abdominal aortic aneurysm repair.

To compare general, epidural and local anaesthesia for endovascular aneurysm repair (EVAR)

OBJECTIVES

to compare general, epidural and local anaesthesia for endovascular aneurysm repair (EVAR).

METHODS

retrospective analysis of 91 consecutive patients (age 43 to 89 years) who underwent EVAR under local (LA, 63 patients), epidural (EDA, 8 patients) and general (GA, 20 patients) anaesthesia.

RESULTS

EVAR was successfully achieved in all patients without mortality or neurological, cardiac and respiratory complications. Vasopressive support as well as median fluid balance were significantly lessened in the LA group compared to GA group (p<0.0002). Stay in the Intensive Care Unit was necessary in 17 (27%), four (50%) and 14 (70%) patients, respectively, and median hospital stay was 3, 4.5, and 5.5 days, with a statistically significant difference between LA and GA group (p<0.0005).

CONCLUSION

LA is a safe anaesthetic method for the endovascular repair of infrarenal abdominal aneurysm, offering several advantages: simplicity, stable haemodynamics, and reduced consumption of ICU and hospital beds.

Retrospective review of 100 cases of endoluminal aortic stent-graft surgery from an anaesthetic perspective

One hundred cases of endoluminal aortic stent surgery were retrospectively reviewed and analysed with respect to outcome. The overall mortality rate was consistent with standard rates for open surgical repair. One hundred per cent of patients who developed multiorgan failure died (7), as did 78% of those who developed acute renal failure (9), and 55% of those who had a serum creatinine rise greater than 100 mumol/l (9). Patients given mannitol had an increased incidence of a serum creatinine rise of greater than 100 mumol/l, at 16% versus 4% for those not given mannitol. Patients with documented intra- or postoperative anaemia (Hb < or = 80 g/l) had a mortality rate of 22% compared to 5% for non-anaemic patients. The mortality rate increased from 3% to 15% if the procedure took more than four hours. The anaesthetic requirements for this new type of surgery are outlined and discussed with respect to these results. The surgical technique is summarized.

Cardiovascular responses to experimental infra-renal aortic cross-clamping. Modulating effects of isoflurane, sodium nitroprusside and milrinone

BACKGROUND

Pharmacological control of blood pressure is usually indicated during aortic cross-clamping (AXC). The aim of this study was to analyze the modulation by isoflurane (ISO), sodium nitroprusside (SNP) and milrinone (MIL) of the systemic circulatory responses to a standardized infra-renal AXC.

METHODS

Chloralose-anaesthetized pigs were exposed to AXC at control (no vasoactive drugs) and during the administration of each of the drugs.

RESULTS

During control, AXC increased mean arterial pressure (MAP, 17 +/- 4%) and systemic vascular resistance (SVR, 27 +/- 7%), but induced no significant changes in cardiac output (CO), heart rate (HR), pulmonary arterial pressures, pulmonary vascular resistance or central venous pressure. Low-dose ISO (0.7%) and investigated doses of SNP and MIL did not significantly alter this response. High-dose ISO (1.4%, attenuated the AXC-induced increase in SVR, but not in MAP. All drugs decreased non-clamp MAP levels. Therefore, with low-dose ISO and with SNP or MIL, peak MAP during AXC was not significantly different from control non-clamp levels (i.e. prior to pharmacological or surgical interventions). High-dose ISO was associated with a MAP during AXC that was below control non-clamp levels.

CONCLUSIONS

The objective that during AXC MAP should not exceed control non-clamp levels was achieveable by ISO, SNP or MIL. The modulating actions of the drugs on MAP during AXC were exerted mainly through reductions in non-clamp levels. This systemic hypotension was associated with decreased CO and SVR during ISO, and with decreased SVR and increased HR during SNP and MIL. Attenuation of the AXC-induced increase in SVR was produced only by 1.4% ISO.

Haemodynamic management in ruptured abdominal aortic aneurysm

Ruptured abdominal aortic aneurysm currently accounts for about 1 in 200 deaths and is a critical surgical emergency with an average hospital mortality of 50%. The combination of acute massive haemorrhage in an elderly patient with pre-existing medical disease is highly lethal and a major challenge for any health care system. This article outlines the general principles of management and discusses the problems of haemodynamic assessment and preclamping fluid resuscitation.

Combined epidural and general anaesthesia versus general anaesthesia for abdominal aortic surgery: a prospective randomised trial

Fifty patients undergoing elective abdominal aortic surgery were randomised to receive either combined epidural and general anaesthesia and postoperative epidural analgesia (CEGA) or general anaesthesia and postoperative intravenous morphine infusion (GA). Prospective data was collected in order to compare the two groups. This included intraoperative cardiovascular changes and postoperative complications. The use of intraoperative vasopressors was significantly higher in the CEGA group (P < 0.01) but the use of intravenous glyceryl trinitrate was significantly lower (P < 0.01). There was no significant difference between groups in regard to blood loss, volume replacement or in the number of patients requiring postoperative ventilation. Two patients in the CEGA group died postoperatively compared to one in the GA group (not significant). There was no significant difference between groups in the total number or type of postoperative complications. Combining epidural anaesthesia with general anaesthesia altered intraoperative cardiovascular management but did not affect postoperative outcome.

A review of anaesthesia for ruptured abdominal aortic aneurysm with special emphasis on preclamping fluid resuscitation

Ruptured abdominal aortic aneurysm (RAAA) remains a critical emergency with an average hospital mortality of 50%. There has been no significant improvement in survival despite advances in anaesthesia, surgery and intensive care over the last 30 years. It is believed that early diagnosis, aggressive surgical management and meticulous attention to haemodynamic status and coagulation may improve survival, but this is unsubstantiated. Mortality is closely linked to the degree of preoperative hypotension and other related factors such as massive blood transfusion and cardiac arrest. Survival depends not only on the severity of rupture, but also the ability to compensate physiologically, and is linked to the premorbid state of the patient. Management priorities are dictated chiefly by the clinical signs and symptoms at presentation. There is controversy regarding the appropriate preoperative fluid regimen for RAAA.

Abdominal aortic aneurysm repair in a patient with a cardiac transplant

We describe successful elective abdominal aneurysm repair in a patient with a cardiac transplant. In light of the unique physiology and pharmacology of the denervated heart, this presented an unusual combination of complex problems. Whereas the normally innervated heart increases cardiac output via neural stimuli, the denervated heart relies primarily on the Frank Starling mechanism which is dependent on preload and myocardial contractility. Thus, rapidly changing haemodynamic variables associated with aortic cross-clamping require scrupulous attention to the maintenance of adequate preload as well as myocardial function which can only be manipulated by direct-acting agents. We conclude that the denervated heart will readily compensate for the haemodynamic changes brought about by infrarenal aortic crossclamping if a high-normal preload is maintained and if the transplanted donor heart is free of pathology with good inherent myocardial contractility.