Thoracoabdominal Aneurysm Repair: Lessons Learned on a General Vascular Surgery Unit

Abstract

Purpose: Much has been learned in the past thirty years regarding the management of patients with thoracoabdominal aortic aneurysms (TAA), especially from the seminal contributions of Crawford and associates at Baylor. As a result of the efforts of Dr. Crawford and a few others, the management of these patients has spread from those centers specializing in the care of patients with TAAs to institutions that perform a wide breadth of general vascular surgery. This change in settings might be accompanied by a change in the morbidity and mortality expected with the repair of TAAs, and the risk factors identified by Crawford and associates might not apply to other institutions. Therefore, the authors conducted a retrospective review of their experience to analyze the surgical results obtained when repairing TAAs at an institution that performs a large breadth of general vascular surgery but does not specifically specialize in the repair of TAAs. In addition, the authors determined whether any of 207 clinical variables was statistically associated with in-hospital mortality, ischemic spinal cord injury, or renal failure and quantitated the strength of any such association by statistical analysis.

Methods: A retrospective study was conducted of all patients who had an elective or emergency repair of a TAA at The Ohio State University Hospitals from January 1979 to March 1994. All patients in this series were operated on at Grant Hospital or the University Hospital in The Ohio State University Hospitals system. Student's t test was used to determine whether any of the 207 clinical variables analyzed in this study was significantly associated with any of the following three endpoints: in-hospital mortality, (continued on next page) (Abstract continued) ischemic spinal cord injury, or renal failure. Univariate and multivariate logistic regres sion analyses were applied to those variables that were significantly associated with the three endpoints in order to quantitate the strength of their association.

Results: 110 patients underwent 112 repairs of a TAA. For the entire group, the overall in- hospital mortality rate from all causes was 26.7%. The most common underlying specific cause of death was coagulopathy. Ischemic spinal cord injury occurred in 19.6% and acute renal failure occurred in 14.4%. Univariate logistic regression analyses identified increasing aortic clamp time and intraoperative blood loss as variables that increased the risk of all three endpoints. For in-hospital mortality, multivariate logistic analyses of preoperative and intraoperative variables demonstrated an increasing risk with advancing age, a greater number of units of red blood cells transfused intraoperatively, incidental operative procedures, and coagulopathy as significant variables. When postoperative variables were included in the analysis, postoperative coagulopathy, vascular complica tions, and hemodynamic instability were significantly associated with an increased risk of in-hospital mortality. Similarly, multivariate analyses demonstrated that increasing intra operative blood loss and replacement of the distal half of the descending thoracic aorta were significantly associated with ischemic spinal cord injury. Finally, multivariate analyses demonstrated that revision of any anastomosis significantly increased the risk of developing postoperative renal failure.

Conclusions: Aortic clamp time affects in-hospital mortality, paraplegia, and dialysis. This is probably a result of the systemic effects of ischemia and reperfusion injury on the cardiac system, the coagulation/fibrinolytic system, the spinal cord, and the kidneys. Furthermore, these data indicate that the patients who develop a coagulopathy are at very high risk of dying. Additional investigations designed to identify clinical methods to prevent and control coagulopathies may help decrease the mortality associated with repair of the thoracoabdominal aorta. Finally, the distal half of the descending thoracic aorta is the most critical segment of the aorta with respect to ischemic spinal cord injury.