Martin A. Villa

Intraoperative skeletal muscle ischemia contributes to risk of renal dysfunction following thoracoabdominal aortic repair

OBJECTIVE Renal dysfunction is among the most commonly occurring morbidities following descending thoracic and thoracoabdominal aortic repair. We hypothesized that myoglobin nephrotoxicity might arise from leg ischemia caused by femoral artery cannulation, which is required for distal aortic perfusion. Lacking complete historical laboratory data on myoglobinemia, we studied somatosensory evoked potential (SSEP) changes in the leg (a functional marker of leg ischemia), as a surrogate predictor of acute postoperative renal failure. METHODS Intraoperative leg SSEP function and preoperative glomerular filtration rate (GFR - an essential covariate) were available for 299 patients. Change in SSEP was defined as 10% increase in latency or 50% decrease in amplitude. Postoperative renal dysfunction was 1mg/dl/day increase in creatinine for 2 days, clinical diagnosis of ARF or need for dialysis postoperatively. RESULTS Change in SSEP in the cannulated leg occurred in 108/299 (36%) of cases intraoperatively. All recovered normal SSEP function at decannulation. Patients with SSEP changes had 41/108 (38%) postoperative renal failure compared to 49/191 (26%) without (odds ratio 1.8, p<0.03). Modeled with GFR, aneurysm extent, and chronic obstructive pulmonary disease (COPD), SSEP changes had an adjusted odds ratio of 1.9, p<0.03. Pre-op GFR was also a highly significant predictor of postoperative renal failure (OR 0.98/ml; p<0.0001). CONCLUSION This is the first study to show a relationship between intraoperative leg ischemia and postoperative renal failure. It provides epidemiological evidence that the ischemic leg may be an important contributor to rhabdomyolysis-like renal morbidity after thoracoabdominal aortic surgery.

Serum Myoglobin and Renal Morbidity and Mortality following Thoracic and Thoraco-Abdominal Aortic Repair: Does Rhabdomyolysis Play a Role?

OBJECTIVES The intractability of renal dysfunction following thoracic and thoraco-abdominal aortic repair leads us to believe that the accepted mechanisms of renal injury - ischaemia and embolism - are incompletely explanatory. We studied postoperative myoglobinaemia and renal dysfunction following aortic surgery. METHODS Between September 2006 and February 2008, we studied serum myoglobin in 109 patients requiring thoracic/thoraco-abdominal repair for three postoperative days. Forty-two of the 109 (38%) patients were female. The median age was 67 years (range 23-84 years). As we have focussed more attention on renal function, our independent renal consultants have dialysed more aggressively. We divided dialysis into: (1) creatinine indication, (2) non-creatinine indication and (3) no dialysis. RESULTS Thirteen of the 109 (12%) patients met creatinine indication for dialysis (>4 mg dl(-1)) and an additional 28 (26%) were dialysed for other reasons. Overall mortality was 12 out of 109 (11%) cases: 11 out of 41 (27%) in dialysed patients and one out of 68 (1.5%) in non-dialysed patients. Mortality did not differ between the indications for dialysis. Predictors of mortality were baseline glomerular filtration rate (GFR), postoperative myoglobin and dialysis. The only predictor of dialysis was postoperative myoglobin. CONCLUSION A strong relationship between postoperative serum myoglobin and renal failure suggests a rhabdomyolysis-like contributing aetiology following thoraco-abdominal aortic repair. We postulate a novel mechanism of renal injury for which mitigation strategies should be developed.

Ascending and transverse aortic arch repair: The impact of glomerular filtration rate on mortality

Background:Recent studies have described the importance of renal glomerular filtration rate (GFR) as a determinant of perioperative mortality in patients with aneurysms that involve the thoracoabdominal and abdominal aorta. We studied the impact of GFR on mortality following repair of ascending and arch aneurysms. Methods:Between February 1991 and August 2006, we performed 994 repairs of the ascending and transverse aortic arch. Nine hundred twenty patients had evaluable data for this study. Sixty-two percent were men (566/920); mean age was 65 years (range 17–89). We estimated the GFR using the Cockcroft-Gault equation. Mean preoperative serum creatinine was 1.2 ± 0.9 mg/dl, mean GFR was 77 ± 37 mL/min. Renal function data were arrayed in quartiles for univariate analysis and kept continuous for multivariable analyses. Multivariable analyses assessed demographics, extent of disease, acuity of presentation, and renal function measured by both creatinine and GFR. Results:Overall 30-day mortality was 10.8% (99/920). In univariate analyses, GFR (P < 0.0001), serum creatinine (P < 0.0003), coronary artery disease (P > 0.03), acute dissection (P < 0.03), emergency presentation (P < 0.002), age (P < 0.009), pump time (P < 0.0001), cross-clamp time, (P < 0.03) and circulatory arrest time (P < 0.003) were associated with increased mortality. By multivariable analyses, only GFR (P < 0.0001), pump time (P < 0.0001), emergency status (P < 0.002) were significant independent risk factors for mortality. Conclusions:Preoperative renal function as defined by GFR was the most significant predictor of mortality during repairs of the ascending and transverse aortic arch. The use of GFR provides better preoperative risk stratification during these repairs than creatinine alone.

Endovascular Repair of Ruptured Abdominal Aortic Aneurysms: Systematic Literature Review:

Endovascular repair is increasingly used for ruptured abdominal aortic aneurysms (RAAAs). This study estimated the mortality rate for this approach. A review of 307 publications in English was performed. Thirty-four publications representing 1,200 patients with RAAA were deemed appropriate for analysis by weighted least squares regression. Of the 1,200 patients, 531 (44.3%) underwent endovascular aneurysm repair (EVAR). The average age was 74 years, and 13% were female. Aortouni-iliac grafts were used in 49.4% of patients, and 50.6% received bifurcated grafts. The technical success rate was 94.9%, with a mortality rate of 30.2%. The ratio of endovascular cases to the total number of cases strongly predicted the mortality rate (weighted coefficient −0.378, p < .0003). The mortality rate following EVAR of RAAA is 30%. A 3.8% reduction in mortality was found for each 10% increase in the percentage of ruptures repaired endovascularly at each center. These results are suggestive of a learning curve.

Effect of Patient Transfer on Outcomes after Open Repair of Ruptured Abdominal Aortic Aneurysms

Patients with ruptured abdominal aortic aneurysms (RAAAs) benefit from treatment in high-volume facilities. This study explored the effect of patient transfer on outcomes and the relationship between hemodynamic status and mortality. We performed a retrospective review of 83 consecutive patients who had open repair for RAAA at a single tertiary facility. The patients were divided into two groups based on arrival in the local emergency department, “local” (n = 44) versus “transfer” (n = 39) from an outside institution, and into three categories of hemodynamic status: (a) no obtainable blood pressure, “pulseless”; (b) requiring vasopressor support, “pressors”; and (c) no vasopressor support, “no pressors.” Thirty-day mortality was 21.4%. There was no difference in mortality between the local (18.2%) and transfer (25.6%) patients (p = .41). There were no deaths during transfer. There was no difference in the hemodynamic status of the transfer versus the local group (p = .34). The mortality by category was pulseless, 100% (3 of 3); pressors, 71.4% (10 of 14); and no pressors, 7.6% (5 of 66) (p < .0001). Actuarial survival was 66%, 64%, and 62% at 1, 3, and 5 years, respectively. Patient transfer does not adversely affect mortality after RAAA repair. Patients without a palpable pulse and those requiring hemodynamic support have a significantly higher mortality.