Endovascular repair of abdominal aortic aneurysm does not improve early survival versus open repair in patients younger than 60 years.

OBJECTIVES: Multiple randomised trials have demonstrated lower perioperative mortality after endovascular aneurysm repair (EVAR) compared to open surgical repair for infrarenal abdominal aortic aneurysms (AAAs). However, in these trials the mortality advantage for EVAR is being lost within 2 years of repair and the patients evaluated are relatively older with no study specifically comparing EVAR and open repair for patients younger than 60 years of age. DESIGN: A retrospective analysis of prospectively collected data. MATERIALS AND METHODS: Patients younger than 60 years of age who underwent EVAR and open surgical repair for elective infrarenal AAA were identified from the 2007-09 National Surgical Quality Improvement Program (NSQIP) - a prospective database maintained at 237 centres across the United States. Univariate and multivariate analyses were performed. RESULTS: Of the 651 patients, 369 (56.7%) underwent EVAR and 282 (43.3%) underwent open repair. Thirty-day mortality for EVAR and open repair were 1.1% and 0.4%, respectively. This was not significantly different on univariate (P = 0.22) as well as multivariate (P = 0.69) analysis after controlling for other co-morbidities. On multivariate analysis, body mass index, history of stroke and bleeding disorder prior to surgery were associated with a higher 30-day mortality after AAA repair (combined open and EVAR). CONCLUSIONS: These contemporary results demonstrate that the 30-day mortality rate after open repair is similar to that after EVAR in patients younger than 60 years with infrarenal AAA.

Effects of intravenous and intra-arterial infusions of prostaglandin E1 on canine hindlimb blood flow distribution.

Prostaglandin E1 (PGE1) has been used clinically in the treatment of ischemic peripheral vascular disease. However, the preferred route of administration and its influence on the distribution of blood flow to the skin, muscle, bone, and arteriovenous anastomoses ( AVAs ) have yet to be established. Bilateral femoral arterial blood flow was measured electromagnetically in 10 anesthetized adult mongrel dogs (mean weight 16.5 kg). The distribution of femoral arterial flow to the skin, muscle, bone, and AVAs was determined with use of femoral intra-arterial injections of radioactively tagged microspheres (15 +/- 1 mu) before, during, and 1 hour after 20 minutes of intravenous and intra-arterial infusions of PGE1 at 0.1 microgram kg-1 min-1. Intra-arterial infusions caused a significant (P less than 0.003) increase in femoral arterial flow (462 +/- 58 ml X min-1), which was sustained throughout the infusion. The distribution of flow to the skin increased significantly (P less than 0.01) to 24.1 +/- 2.1%, whereas that through AVAs was significantly (P less than 0.05) decreased to 3.2 +/- 0.9%. Femoral arterial blood flow did not change during intravenous infusions; however, there was a significant (P less than 0.01) reduction in the distribution to muscle (41.1 +/- 10.5%) associated with a significant (P less than 0.02) increase in distribution through AVAs (30.8 +/- 11.5%). These data demonstrate the superiority of intra-arterial infusion over intravenous infusions of PGE1 in the canine hindlimb. There was a significant increase in femoral arterial blood flow with increased distribution to the skin and decreased shunting. Femoral arterial blood flow did not change during intravenous infusions; however, a reduction in the distribution of flow to the muscle was accompanied by an increase in shunting.

Differential patency and limb salvage for polytetrafluoroethylene and autogenous saphenous vein in severe lower extremity ischemia.

Polytetrafluoroethylene (PTFE) was compared to autogenous saphenous vein (ASV) in 133 femoropopliteal and femorotibial or peroneal bypass procedures performed in limb salvage during a 4-year period. PTFE was used as an alternative prosthesis in the absence of a suitable ASV. Sixty-nine femoropopliteal bypasses (FPBPs) were studied--36 with ASV and 33 with PTFE. Sixty-four femorotibial or peroneal bypasses were categorized as femoral distal bypasses (FDBPs)--34 with ASV and 30 with PTFE. With a 3-year clinical follow-up, cumulative function rate (CFR)--patency including thrombectomy--for FPBP with ASV was 65% as compared to 53% for PTFE (P greater than 0.05), whereas the limb salvage rate (LSR) was 75% with ASV and 56% for PTFE (P greater than 0.05). However for FDBP, the GFR was 55% for ASV and 7% for PTFE, whereas the LSR was 55% with ASV and 26% for PTFE. The cumulative patency rate (CPR)--initial thrombosis of a prosthesis as an endpoint--was not significantly (P greater than 0.05) different from CFR, suggesting that thrombectomy with or without distal anastamotic revision does not contribute to patency of the PTFE prosthesis in these limb salvage cases. PTFE was a suitable alternative to ASV for FPBP; however, PTFE is recommended for FDBP in selected cases only.

Soluble factors modulate changes in collagen gene expression in abdominal aortic aneurysms.

BACKGROUND: Although increased procollagen gene expression and synthesis have been implicated in the progression of abdominal aortic aneurysms (AAA), factors modulating this change have not been identified. Furthermore, it is not known whether the increase in AAA procollagen expression is specific to this disease or also occurs in tissue affected by atherosclerotic occlusive disease (AOD). If paracrine rather than autocrine factors are responsible for increased gene expression in AAA, this effect should be transferable to target smooth muscle cells through conditioned media. Our objectives were to determine 1 alpha (I) procollagen messenger RNA levels in AOD tissue compared with normal and AAA and to determine whether differences noted in tissue procollagen gene expression could be transferred through conditioned media from normal, AOD, and AAA tissues to target smooth muscle cells in primary culture. METHODS: Normal, AOD, and AAA tissue was used for tissue RNA extraction or was minced and washed with serum-free media (4 degrees C) x 30 minutes and the media applied to human aortic smooth muscle cells (SMC) in primary culture for 36 hours. Total RNA from tissue and SMC exposed to conditioned media was analyzed by Northern and dot blot analysis for 1 alpha (I) procollagen. RESULTS: Relative tissue 1 alpha (I) procollagen levels were not increased in AOD (0.23 +/- 0.05) as compared with normal (0.17 +/- 0.03); both were decreased compared with AAA (0.53 +/- 0.07; p < 0.01). The 1 alpha (I) procollagen levels in SMC exposed to conditioned media from AAA (1.73 +/- 0.15) were increased (p < 0.05) compared with AOD (1.10 +/- 0.12) and normal (1.16 +/- 0.16). CONCLUSIONS: There is no increase in tissue AOD procollagen gene expression. The ability to transfer the same relative patterns of gene expression from tissue to target SMC with conditioned media suggests that paracrine, rather than autocrine, factors modulate procollagen expression in AAA tissues.

Duplex scans before subclavian vein catheterization predict unsuccessful catheter placement.

Subclavian catheterization in patients with cancer is associated with up to a 38% incidence of subclavian vein thrombosis. These thrombi seldom recanalize. The persistent occlusion of the subclavian vein may hinder subsequent catheter placement. To determine the frequency of this occurrence and to determine if preoperative duplex scanning could identify these individuals, we performed preoperative duplex scanning in 22 patients who had previously had an indwelling subclavian catheter for chemotherapy. Subsequent subclavian vein catheterization was attempted without knowledge of the results of the duplex scan. Nineteen scans were normal. Of these, 18 patients underwent successful catheter placement. In one patient, catheterization was unsuccessful and an intraoperative venogram showed a focal obstruction of the proximal portion of the subclavian vein. Three scans showed noncompressibility of the vein, and catheter placement was unsuccessful in these three veins. In patients who have had previous subclavian catheters, persistent obstruction of the vein prevents subsequent catheter placement in 14%. Duplex scanning before subsequent catheter placement generally identifies these individuals.

Ultrasonic imaging and oculoplethysmography in diagnosis of carotid occlusive disease.

Pulsed Doppler ultrasonic imaging (UI) of the cervical carotid artery provides flow-dependent anatomic detail of the carotid bifurcation, while oculoplethysmography (Kartchner) (OPG-K) and ocular pneumoplethysmography (Gee) (OPG-G) reflect changes in flow and pressure resulting from hemodynamically significant lesions. We examined 66 patients prospectively with UI, OPG-K, and OPG-G to compare the relative accuracy of these techniques with contrast arteriography. Both UI and OPG-G were significantly more accurate than OPG-K. While the accuracies of UI and OPG-G were not significantly different, their combined use resulted in a significant increase in sensitivity compared with that of Doppler imaging alone. In addition, UI correctly identified 22 (85%) of 26 occlusions of the internal carotid artery. The use of UI and OPG-G together provided accurate anatomic and hemodynamic information useful in the evaluation of carotid occlusive disease.

Poststenotic flow velocity changes as a function of stenosis geometry.

We used an in vitro pulsatile flow model to examine the velocity profile distal to a variable nonaxisymmetric stenosis. Using a continuous-wave Doppler velocimeter, the peak systolic frequency was determined distal to the stenosis and in planes parallel and perpendicular to the long axis of the stenosis. In both planes, an exponential regression best describes the relationship between peak systolic frequency and reduction in cross-sectional area. Regressions at each point of insonation diverged as a direct function of reduction in cross-sectional area and as an indirect function of distance from the stenosis. At each point of insonation, regressions representing the relationship in the mutually perpendicular planes diverged in direct proportion to reduction in cross-sectional area. Slopes were greater in parallel planes of insonation. These data demonstrate that two variables, distance and geometry, may influence the results of spectral analytic studies.

Doppler ultrasound, laser Doppler, and perfusion fluorometry in bowel ischemia.

Improved accuracy and objectivity in the evaluation of intestinal viability has been reported by some investigators using Doppler ultrasound, and more recently laser Doppler velocimetry and perfusion fluorometry. To compare the sensitivity and clinical applicability of these techniques, intestinal viability was evaluated by each method in nine 15- to 50-cm loops of small bowel prepared by division of the mesenteric vasculature in five anesthetized dogs. The sensitivity of Doppler ultrasound was 86%, of laser Doppler flow velocity 85%, of laser Doppler index 94%, and of perfusion fluorometry 95%. Though the sensitivity of Doppler ultrasound is significantly less than that of laser Doppler and perfusion fluorometry, this is not unexpected since the latter two techniques are more quantitative than Doppler ultrasound. Clinically, Doppler ultrasound compares favorably with laser Doppler and perfusion fluorometry, and its low cost and simplicity suggest its adjunctive use in the operative setting.

Interpretation of Doppler segmental pressures in peripheral vascular occlusive disease.

Measurement of Doppler segmental arterial pressures in the lower extremity using narrow pneumatic cuffs has become a standard noninvasive diagnostic technique. Correlation between arteriographic and noninvasive studies was available for 345 aortoiliac segments and 326 femoropopliteal segments. If stenoses of 50% or greater and occlusions were considered hemodynamically significant, the sensitivity to aortoiliac disease was 97%, but only 67% to femoropopliteal disease. The specificity for hemodynamically insignificant disease was 50% and 68%, respectively. Accuracy was influenced by the presence of associated aortoiliac or femoropopliteal disease. The sensitivity to hemodynamically significant femoropopliteal disease was 55% if there was associated aortoiliac disease, and 89% in its absence. In the presence of significant femoropopliteal disease, specificity for the absence of aortoiliac disease decreased from 70% to 41%.

Dissections after childbirth.

The occurrence of spontaneous internal carotid or vertebral artery dissection after childbirth remains rare. To our knowledge, seven cases of arterial dissection in the postpartum period have been described in the literature as single case reports. We report four additional cases of internal carotid and vertebral artery dissection in the puerperal period, documented by angiography. Physicians should consider the possibility of arterial dissection in any young patient presenting with acute ischemic stroke, including women in the postpartum period. The availability of modern noninvasive ultrasound and imaging techniques may result in earlier diagnosis and facilitate identification of this condition.

Availability of content information does not improve performance on computerized case simulations.

BACKGROUND: A previous study evaluated repeated, serial administrations of computer-based simulations. The data demonstrated an increase in scores across rotations during the academic year, but no difference between scores in successive years. METHODS: The initial study only indirectly assessed the effect of information sharing on measured performance. To directly assess the effect of information transfer, 8 computer-based case simulations were administered over 2 consecutive years to 220 third-year students at the conclusion of 12 surgical clerkship rotations (6 per year). During the second year of administration information regarding content area, in the form of the case stem or introductory lead-in material, was provided to each rotation of students prior to the examination based on a sequential algorithm. RESULTS: The data demonstrate no increase in overall mean score for the examination over the 2 years. Scores were significantly different for 2 of the 8 cases, increasing in the one and decreasing in the other. CONCLUSIONS: The data demonstrate no evidence that prior knowledge of content area influences the scores of successive classes on computerized models of performance assessment.

Repeated use of computerized case simulations in a test format does not present a security risk.

BACKGROUND: Computer-based examination formats permit evaluation of patient care strategies in a realistic context. Because such examinations are complex and difficult to develop, the same case simulations must often be used on multiple occasions. METHODS: To determine if repeated, serial administration of computerized case simulations influences performance, 8 simulations were administered over 2 consecutive years to 252 third-year medical students at the conclusion of 16 surgical clerkship rotations (8 per year). One-way analyses of variance were used to compare scores across rotations during the year and to compare scores between 2 consecutive academic years. Scheffe pairwise comparisons were used to identify trends within each academic year. RESULTS: The data demonstrate an increase in scores across rotations during the year. There is, however, no difference between scores in successive years. CONCLUSIONS: The data are consistent with an increase in knowledge during the course of the year, without evidence that test information transfer influences the performance of successive classes.

Video-assisted, retroperitoneal approach for abdominal aortic aneurysm exclusion.

Abdominal aortic aneurysm (AAA) repair is a common procedure associated with significant morbidity and mortality. Although attempts have been made to reduce operative risk in patients with significant comorbid disease by combining aneurysm exclusion with axillofemoral bypass, the morbidity is not greatly reduced when the standard operative approach is required for exclusion. The authors describe a technique for staple exclusion of AAA using a minimally invasive, video-assisted retroperitoneal approach.

Learning style influences student examination performance.

BACKGROUND: The Kolb Learning Style Inventory (LSI) measures preference for each of four learning orientations: abstract conceptualization, concrete experience, active experimentation, and reflective observation. These orientations define four learning styles: convergence, divergence, assimilation, and accommodation. METHODS: To determine if learning style correlates with objective multiple-choice and clinical measures of performance, the learning styles of third-year medical students (n = 227) were evaluated using the LSI. Performance was assessed using the United States Medical Licensing Examination step 1 (USMLE 1), the National Board of Medical Examiners (NBME) multiple-choice surgical subject examination (MCQ), and NBME computer-based case simulations (CBX). RESULTS: The data showed a significant (P < or = 0.05) relationship between learning style and performance on the USMLE 1. There was a significant (P < or = 0.05) and direct correlation between an abstract orientation and performance on the USMLE 1 (r = 0.33) and MCQ (r = 0.20). There was no relationship between learning style and clinical performance measured using the CBX. CONCLUSIONS: These data demonstrate that performance on objective measures of academic achievement is influenced by learning style, while application of that knowledge in the management of clinical situations may require additional skills beyond those measured.

Learning preferences, computer attitudes, and test performance with computer-aided instruction.

BACKGROUND: Learning preference refers to how individuals choose to approach learning situations. Computer-aided instruction (CAI) permits the adaptation of educational content to individual student learning strategies. METHODS: To determine if learning preference and computer attitude influence the acquisition of knowledge using CAI materials, a prototype CAI program was developed that incorporated differing learning exercises. Students (n = 180) completed Rezler's Learning Preference Inventory (LPI) and a computer attitude survey (CAS). The LPI uses three sets of paired scales to characterize learning preference and choice of learning situation. The CAS assesses student attitudes toward computers in general (CAS-G), as well as the educational use of computers (CAS-E). After finishing the program students completed a program attitude survey (CAS-P). Immediate comprehension was assessed by pretests and posttests incorporated into the program. Retention was assessed by a repeat of the posttest 4 to 6 weeks after initial program review. RESULTS: Scores (mean +/- SEM) on the pretest, posttest, and late posttest were 38.1% +/- 1.35%, 70.9% +/- 1.24%, and 62.5% +/- 1.44%, respectively. There was no correlation between students' learning preferences or computer attitude and test performance. CONCLUSIONS: The data indicate that CAI provides a means of delivering educational content that results in an increase in knowledge that is not correlated with computer attitudes or learning preferences.

Rational approach to postoperative transfusion in high-risk patients.

An appropriate threshold for transfusion in patients with coronary artery disease has not been defined. Our purpose was to determine: (1) the effects of preoperative volume loading; (2) postoperative function and oxygen delivery (DO2); (3) an appropriate transfusion threshold based on observed DO2 in high-risk patients undergoing abdominal aortic aneurysm (AAA) repair, bypass of aortoiliac disease (AOD), distal bypass, or carotid endarterectomy (CEA). Preoperative volume loading increased cardiac output (CO) in all groups by 15% to 22%. Postoperative CO was unchanged from optimal preoperative values except in the CEA group, in which it decreased. Systemic vascular resistance decreased in the AAA and AOD groups. The decrease in postoperative DO2 in all groups (25% to 31%) was related to a decrease in hemoglobin. Despite marginal (less than 11 mL/kg/min) postoperative DO2 in more than a third of patients, there was no compensatory increase in CO. Thus, after optimization of function by volume loading, red cell transfusion may be the only way to increase DO2. Hemoglobin levels of 10 to 12 g/dL may be required for adequate DO2 when ventricular function is markedly impaired.

Management of synchronous renal cell carcinoma and aortic disease.

BACKGROUND: We have noted a significant incidence of renal cell carcinoma (RCC) detected during evaluation for aneurysmal and aortoiliac occlusive disease. The approach to synchronous malignancy and aortic disease (staged versus concurrent resection) is controversial, as is the management of incidental RCC (partial versus radical nephrectomy). PATIENTS AND METHODS: We reviewed our experience with incidental RCC in patients undergoing aortic reconstruction between 1991 and 1994. Ninety-seven patients underwent aortic reconstruction for aneurysmal (72), occlusive (20), or embolic disease (5) during the time frame under review. All were men. Of the 80 preoperative computerized tomographic (CT) scans obtained, 7 (9%) demonstrated renal lesions suspicious for RCC. All lesions were explored and excised by partial or radical nephrectomy before heparinization and completion of the planned aortic procedure. RESULTS: The overall mortality rate was 3%. None of the deaths occurred in patients undergoing combined procedures. Four partial and three radical nephrectomies were performed. Of the 7 renal lesions, 2 were complex cysts and 5 were RCC. Both patients with complex cysts were treated with wedge resection. One patient required surgical drainage of a wound abscess after partial nephrectomy. No significant differences were found between preoperative (1.4 +/- 0.1 mg/dL) and postoperative (1.8 +/- 0.2 mg/dL) creatinine levels following combined procedures. On follow-up CT scans done at 6-month intervals (mean follow-up 24 months), no evidence exists of recurrence, metastasis, or graft infection. CONCLUSIONS: This patient population demonstrated an unexpectedly high prevalence of incidental RCC (5 or 80 CTs, 6%). No increase in mortality was found when RCC and aortic disease were treated at the same operation. While partial nephrectomy was associated with one wound infection in this series, it is an effective treatment for small incidental RCC and may avoid unnecessary nephrectomy in patients with benign disease. Base on the high incidence of RCC in this population, we recommend exploration of all suspicious lesions. Nephrectomy can be performed safely in the same setting as aortic reconstruction. Because underlying renal dysfunction is not uncommon in patients with aneurysmal and aortoiliac occlusive disease, nephron-sparing surgery should be considered.

Femoral venous trauma: techniques for surgical management and early results.

During a 4 year period (1979 through 1983), 181 major arterial (69 percent) and 81 venous (31 percent) injuries were treated surgically. Of the venous injuries, 24 (30 percent) involved the femoral veins (9 common femoral, 15 superficial femoral). Management of these femoral venous injuries included lateral venorrhaphy in 10 cases (42 percent), venous patch angioplasty in 5 cases (21 percent), end-to-end anastomosis in 4 cases (17 percent), interposition autogenous saphenous vein grafts in 3 patients (12 percent), and ligation in 2 cases (8 percent). One case that included common femoral venous ligation and one that included a failed interposition saphenous vein graft in the superficial femoral vein subsequently were managed with in situ saphenous vein bypass. For one interposition saphenous vein graft repair of the common femoral vein we utilized the spiral vein graft technique. Excluding one early death from associated injuries and one superficial femoral venous injury managed by ligation without postoperative complications, 17 of 23 (74 percent) femoral venous repairs were judged patent postoperatively (13 confirmed by venography and 4 by noninvasive testing). The adjuvant use of intermittent pneumatic calf compression and low molecular weight dextran appears to have been beneficial in maintaining patency of the femoral venous repairs. Early clinical follow-up demonstrated the presence of edema in 6 of 8 cases (75 percent) initially treated by ligation or complicated by postoperative occlusion. Early postoperative edema, present in 4 of 17 (24 percent) patients with patent venous repairs, had resolved by the time of discharge. We recommend routine repair of femoral venous injuries. When significant edema or ischemia develop following obligatory venous ligation or postoperative occlusion of a venous repair, revision or venous bypass should be considered.

The role of real-time B-mode ultrasonography and ocular pneumoplethysmography following carotid endarterectomy.

Real-time B-mode ultrasonography and ocular pneumoplethysmography (OPG-G) were used to evaluate 41 patients (54 arteries) following carotid endarterectomy. Thirteen patients had bilateral procedures. Recurrent stenosis was observed in three (6%), and postoperative occlusion in three (6%). In one symptomatic patient, the origin of an occluded external carotid artery was the source of atheroemboli. Only two of the seven patients were symptomatic and three of the seven had hemodynamically insignificant stenoses. Of the three patients with recurrent stenosis, two had a normal OPG-G and demonstrated the value of combinate noninvasive evaluation. The noninvasive diagnosis in these two cases was based on B-mode ultrasonography. Of the three postoperative occlusions, one had a normal OPG-G. Since the OPG-G cannot distinguish stenosis from occlusion, B-mode ultrasonography was necessary to demonstrate the presence of an occluded internal carotid artery and the absence of internal carotid flow in each case. B-mode ultrasonography also permitted the identification of several characteristic postoperative findings. An intimal shelf was often observed, corresponding to the proximal limit of the endarterectomy. Seventy-four per cent demonstrated thickening of the arterial wall and 45 per cent were observed to have calcification in the area of the endarterectomy. The true incidence of recurrent disease following carotid endarterectomy is uncertain, but it probably exceeds those estimates based on symptomatic recurrence. Because of the incidence of asymptomatic and/or hemodynamically insignificant disease, we recommend the routine use of noninvasive studies following carotid endarterectomy.

Differential hyperemic responses following femoral arterial and thigh cuff occlusion in the canine hindlimb.

The hyperemic response following arterial reconstruction is variable. To further evaluate this response, arterial blood flows in the canine hindlimb were compared following isolated femoral arterial occlusion and after thigh cuff tourniquet occlusion, which also obstructs collateral circulation. Arterial occlusion and tourniquet occlusion produced significant (P less than 0.05) increases in femoral arterial flow after all intervals of occlusion, except following 30 minutes of isolated arterial occlusion. Isolated arterial occlusion and tourniquet occlusion produced comparable hyperemic responses through five minutes of occlusion. However, tourniquet occlusion produced a significantly greater increase (P less than 0.05) in femoral flow when occlusions exceeded five minutes. These data suggest that the extent of collateralization may moderate the postobstructive hyperemic response following aortic and femoropopliteal reconstruction. The collateral recruitment during isolated arterial occlusion may be responsible for a diminished hyperemic response with time, while obstruction of the collateral circulation during tourniquet occlusion may result in a greater hyperemic response.