Comparison of Metal Adhesion Layers for Au Films in Thermoplasmonic Applications.

If thermoplasmonic applications such as heat-assisted magnetic recording are to be commercially viable, it is necessary to optimize both thermal stability and plasmonic performance of the devices involved. In this work, a variety of different adhesion layers were investigated for their ability to reduce dewetting of sputtered 50 nm Au films on SiO2 substrates. Traditional adhesion layer metals Ti and Cr were compared with alternative materials of Al, Ta, and W. Film dewetting was shown to increase when the adhesion material diffuses through the Au layer. An adhesion layer thickness of 0.5 nm resulted in superior thermomechanical stability for all adhesion metals, with an enhancement factor of up to 200× over 5 nm thick analogues. The metals were ranked by their effectiveness in inhibiting dewetting, starting with the most effective, in the order Ta > Ti > W > Cr > Al. Finally, the Au surface-plasmon polariton response was compared for each adhesion layer, and it was found that 0.5 nm adhesion layers produced the best response, with W being the optimal adhesion layer material for plasmonic performance.

Less is More: Improved Thermal Stability and Plasmonic Response in Au Films via the Use of SubNanometer Ti Adhesion Layers.

The use of a metallic adhesion layer is known to increase the thermo-mechanical stability of Au thin films against solid-state dewetting, but in turn results in damping of the plasmonic response, reducing their utility in applications such as heat-assisted magnetic recording (HAMR). In this work, 50 nm Au films with Ti adhesion layers ranging in thickness from 0 to 5 nm were fabricated, and their thermal stability, electrical resistivity, and plasmonic response were measured. Subnanometer adhesion layers are demonstrated to significantly increase the stability of the thin films against dewetting at elevated temperatures (>200 °C), compared to more commonly used adhesion layer thicknesses that are in the range of 2-5 nm. For adhesion layers thicker than 1 nm, the diffusion of excess Ti through Au grain boundaries and subsequent oxidation was determined to result in degradation of the film. This mechanism was confirmed using transmission electron microscopy and X-ray photoelectron spectroscopy on annealed 0.5 and 5 nm adhesion layer samples. The superiority of subnanometer adhesion layers was further demonstrated through measurements of the surface-plasmon polariton resonance; those with thinner adhesion layers possessed both a stronger and spectrally sharper resonance. These results have relevance beyond HAMR to all Ti/Au systems operating at elevated temperatures.

Comparison of risk-adjusted 30-day postoperative mortality and morbidity in Department of Veterans Affairs hospitals and selected university medical centers: vascular surgical operations in men.

BACKGROUND: In response to a Congressional mandate to compare risk-adjusted surgical outcomes from Department of Veterans Affairs (VA) hospitals with those from private-sector hospitals, the National Surgical Quality Improvement Program was initiated in the VA system and then was developed in a select group of university medical centers in the private sector. This article analyzes risk-adjusted outcomes after vascular surgical operations in men performed at VA hospitals as compared with private-sector hospitals. STUDY DESIGN: This is a prospective cohort study of a sample of vascular surgical operations in men performed at 128 VA medical centers as compared with 14 university medical centers from October 1, 2001 to September 30, 2004. Patient and operative characteristics, and both unadjusted and risk-adjusted 30-day postoperative morbidity and mortality outcomes were compared. RESULTS: Data from 30,058 vascular operations in men at VA hospitals were compared with 5,174 cases performed at private-sector hospitals. The unadjusted 30-day mortality rate was notably lower in the VA system as compared with the private-sector group (3.4% versus 4.2%, p = 0.004). After risk-adjustment, there was no marked difference in mortality between the two hospital types. The unadjusted 30-day morbidity rate was also considerably lower in the VA hospitals as compared with the private sector (17.3% versus 22.3%, p < 0.0001). After risk-adjustment, morbidity in the VA system remained considerably lower than in the private sector, with an odds ratio of 0.84 (95% CI, 0.78 to 0.92). CONCLUSIONS: In vascular surgical operations in men, the VA hospitals demonstrated a lower risk-adjusted 30-day morbidity rate than the private-sector group. There is no marked difference in adjusted mortality rates between the two types of institutions.

Identification of surgical complications and deaths: an assessment of the traditional surgical morbidity and mortality conference compared with the American College of Surgeons-National Surgical Quality Improvement Program.

BACKGROUND: Despite advances by surgeons in assessing quality and safety, the traditional surgical morbidity and mortality (M&M) conference has mostly remained unchallenged and unchanged. The goal of this study was to compare data as reported in a traditional M&M conference to data collected using the American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP) techniques. STUDY DESIGN: A retrospective study was performed comparing data from the M&M conference in a general surgery division, in which complications and deaths were identified by residents or attendings, to data compiled by a nationally audited nurse reviewer from the ACS-NSQIP from July 1, 2002, to June 30, 2003. RESULTS: Mortality rates calculated by traditional M&M conference (53 deaths in 5,905 patients), compared with the ACS-NSQIP nurse reviewer (28 deaths in 1,439 patients; 24% sample), were 0.9% versus 1.9%, respectively (p=0.001). Complication rates reported in M&M were 6.4% versus 28.9% ACS-NSQIP (p<0.0001). Subgroup analyses showed that mortality rates, as reported in conference, were substantially lower for both in-hospital and postdischarge patients, when compared with ACS-NSQIP. All subclassifications of complications, as presented in conference, were also lower, compared with ACS-NSQIP. CONCLUSIONS: Traditional surgical M&M reporting considerably underreports both in-hospital and postdischarge complications and deaths as compared with ACS-NSQIP. Approximately one of two deaths and three of four complications were not reported in the M&M conference at our institution. A Web-based reporting system based on an ACS-NSQIP platform was created to automate, facilitate, and standardize data on surgical morbidity and mortality.

The impact of the 80-hour resident workweek on surgical residents and attending surgeons.

OBJECTIVE: To assess the impact of the 80-hour resident workweek restrictions on surgical residents and attending surgeons. SUMMARY BACKGROUND DATA: The ACGME mandated resident duty hour restrictions have required a major workforce restructuring. The impact of these changes needs to be critically evaluated for both the resident and attending surgeons, specifically with regards to the impact on motivation, job satisfaction, the quality of surgeon training, the quality of the surgeon's life, and the quality of patient care. METHODS: Four prospective studies were performed at a single academic surgical program with data collected both before the necessary workforce restructuring and 1 year after, including: 1) time cards to assess changes in components of daily activity; 2) Web-based surveys using validated instruments to assess burnout and motivation to work; 3) structured, taped, one-on-one interviews with an external PhD investigator; and 4) statistical analyses of objective, quantitative data. RESULTS: After the work-hour changes, surgical residents have decreased "burnout" scores, with significantly less "emotional exhaustion" (Maslach Burnout Inventory: 29.1 "high" vs. 23.1 "medium," P = 0.02). Residents have better quality of life both in and out of the hospital. They felt they got more sleep, have a lighter workload, and have increased motivation to work (Herzberg Motivation Dimensions). We found no measurable, statistically significant difference in the quality of patient care (NSQIP data). Resident training and education objectively were not statistically diminished (ACGME case logs, ABSITE scores). Attending surgeons perceived that their quality of their life inside and outside of the hospital was "somewhat worse" because of the work-hour changes, as they had anticipated. Many concerns were identified with regards to the professional development of future surgeons, including a change toward a shift-worker mentality that is not patient-focused, less continuity of care with a loss of critical information with each handoff, and a decrease in the patient/doctor relationship. CONCLUSION: Although the mandated restriction of resident duty hours has had no measurable impact on the quality of patient care and has led to improvements for the current quality of life of residents, there are many concerns with regards to the training of professional, responsible surgeons for the future.

Laparoscopic versus open gastric bypass for morbid obesity: a multicenter, prospective, risk-adjusted analysis from the National Surgical Quality Improvement Program.

OBJECTIVE: To compare laparoscopic versus open gastric bypass procedures with respect to 30-day morbidity and mortality rates, using multi-institutional, prospective, risk-adjusted data. SUMMARY BACKGROUND DATA: Laparoscopic Roux-en-Y gastric bypass for weight loss is being performed with increasing frequency, partly driven by consumer demand. However, there are no multi-institutional, risk-adjusted, prospective studies comparing laparoscopic and open gastric bypass outcomes. METHODS: A multi-institutional, prospective, risk-adjusted cohort study of patients undergoing laparoscopic and open gastric bypass procedures was performed from hospitals (n = 15) involved in the Private Sector Study of the National Surgical Quality Improvement Program (NSQIP). Data points have been extensively validated, are based on standardized definitions, and were collected by nurse reviewers who are audited for accuracy. RESULTS: From 2000 to 2003, data from 1356 gastric bypass procedures was collected. The 30-day mortality rate was zero in the laparoscopic group (n = 401), and 0.6% in the open group (n = 955) (P = not significant). The 30-day complication rate was significantly lower in the laparoscopic group as compared with the open group: 7% versus 14.5% (P < 0.0001). Multivariate logistic regression analysis was performed to control for potential confounding variables and showed that patients undergoing an open procedure were more likely to develop a complication, as compared with patients undergoing an laparoscopic procedure (odds ratio = 2.08; 95% confidence interval, 1.33-3.25). Propensity score modeling revealed similar results. A prediction model was derived, and variables that significantly predict higher complication rates after gastric bypass included an open procedure, a high ASA class (III, IV, V), functionally dependent patient, and hypertension as a comorbid illness. CONCLUSIONS: Multicenter, prospective, risk-adjusted data show that laparoscopic gastric bypass is safer than open gastric bypass, with respect to 30-day complication rate.

Defining the high-risk patient for carotid endarterectomy: an analysis of the prospective National Surgical Quality Improvement Program database.

BACKGROUND: Carotid endarterectomy (CEA) is the gold standard for the treatment of carotid stenosis, but carotid angioplasty and stenting has been advocated in high-risk patients. The definition of such a population has been elusive, particularly because the data are largely retrospective. Our study examined results for CEA in the National Surgical Quality Improvement Program database (both Veterans Affairs and private sector). METHODS: National Surgical Quality Improvement Program data were gathered prospectively for all patients undergoing primary isolated CEA during the interval 2000 to 2003 at 123 Veterans Affairs and 14 private sector academic medical centers. Study end points included the 30-day occurrence of any stroke, death, or cardiac event. A variety of clinical, demographic, and operative variables were assessed with multivariate models to identify risk factors associated with the composite (stroke, death, or cardiac event) end point. Adjudication of end points was by trained nurse reviewers (previously validated). RESULTS: A total of 13,622 CEAs were performed during the study period; 95% were on male patients, and 91% of cases were conducted within the Veterans Affairs sector. The average age was 68.6 +/- 0.1 years, and 42.1% of the population had no prior neurologic event. The composite stroke, death, or cardiac event rate was 4.0%; the stroke/death rate was 3.4%. Multivariate correlates of the composite outcome were (odds ratio, P value) as follows: deciles of age (1.13, .018), insulin-requiring diabetes (1.73, <.001), oral agent-controlled diabetes (1.39, .003), decade of pack-years smoking (1.04, >.001), history of transient ischemic attack (1.41, >.001), history of stroke (1.51, >.001), creatinine >1.5 mg/dL (1.48, >.001), hypoalbuminemia (1.49, >.001), and fourth quartile of operative time (1.44, >.001). Cardiopulmonary comorbid features did not affect the composite outcome in this model. Regional anesthesia was used in 2437 (18%) cases, with a resultant relative risk reduction for stroke (17%), death (24%), cardiac event (33%), and the composite outcome (31%; odds ratio, 0.69; P = .008). CONCLUSIONS: Carotid endarterectomy results across a spectrum of Veterans Affairs and private sector hospitals compare favorably to contemporary studies. These data will assist in selecting patients who are at an increased risk for adverse outcomes. Use of regional anesthetic significantly reduced perioperative complications in a risk-adjusted model, thus suggesting that it is the anesthetic of choice when CEA is performed in high-risk patients.

Early outcomes of endovascular versus open abdominal aortic aneurysm repair in the National Surgical Quality Improvement Program-Private Sector (NSQIP-PS).

BACKGROUND: There remains no consensus on the appropriate application of endovascular abdominal aortic aneurysm repair (EVAR). Information from administrative databases, industry-sponsored trials, and single institutions has inherent deficiencies. This study was designed to compare early outcomes of open (OPEN) versus EVAR in a contemporary (2000 to 2003) large, multicenter prospective cohort. METHODS: Fourteen academic medical centers contributed data to the National Surgical Quality Improvement Program-Private Sector (NSQIP-PS), which ensures uniform, comprehensive, prospective, and previously validated data entry by trained, independent nurse reviewers. A battery of clinical and demographic features was assessed with multivariate analysis for association with the principal study end points of 30-day operative mortality and morbidity. RESULTS: One thousand forty-two patients underwent elective infrarenal abdominal aortic aneurysm (AAA) repairs: 460 EVAR and 582 OPEN. EVAR patients were older (74 vs 71 years, P < .0001), included more men (84.6% vs 79.6%, P < .05), and had a higher incidence of chronic obstructive pulmonary disease (25.4% vs 17.9%, P < .01). EVAR resulted in significantly reduced overall morbidity (24% vs 35%, P < .0001) and hospital stay (4 vs 9 days, P < .0001). Cardiopulmonary and renal function-related comorbidities had the expected significant impact on mortality for both procedures at univariate analysis ( P < .05). While crude mortality rates between EVAR and OPEN did not differ significantly (2.8% vs 4.0%) ( P = 0.32). After multivariate analysis, correlates of operative mortality included OPEN (odds ratio [OR], 2.44; 95% confidence interval [CI], 1.03 to 5.78; P < .05), advanced age (OR, 1.11; P < .001), history of angina (OR, 5.54; P < .01), poor functional status (OR, 5.78; P < .001), history of weight loss (OR, 7.42; P < .01), and preoperative dialysis (OR, 51.4; P < .0001). EVAR also compared favorably to OPEN (OR, 2.14; 95% CI, 1.58 to 2.89; P < .0001) for overall morbidity. CONCLUSION: Significant morbidity accompanies AAA repair, even at major academic medical centers. These data strongly endorse EVAR as the preferred approach in the presence of significant cardiopulmonary or renal comorbidities, or poor preoperative functional status.

Cryopreservation prevents arterial allograft dilation.

Historically, immune-mediated degradation and subsequent aneurysm formation have limited the usefulness of cryopreserved arterial allografts. This study tested the hypothesis that modern cryopreserved arterial allografts are protected from immune-mediated dilation. Abdominal aortas were harvested from anesthetized rats (Lewis and Brown-Norway) for immediate implantation or cryopreservation. Subsequently, Lewis rats underwent infrarenal aortic replacement with either an acutely harvested or a cryopreserved graft. There were four experimental groups: (1) acutely harvested isografts (Iso; n = 6), (2) cryopreserved isografts (C-Iso; n = 6), (3) cryopreserved allografts (C-Allo; n = 6), and (4) acutely harvested allografts (Allo; n = 6). All grafts were explanted at 8 weeks. A video camera and edge detection software were used to measure systolic and diastolic in vivo graft diameter (d). Measurement of arterial blood pressure (p) allowed calculation of compliance (Dd/Dp). Tail-cuff plethysmography was used to assess graft patency at 1 week. Graft diameter and blood pressure measurements were repeated at harvest. All harvested grafts were examined histologically. Our results showed that cryopreservation prevented immune-mediated dilation in arterial allografts in our 8-week rat implant model. Furthermore, the compliance of the cryopreserved grafts and was similar to that of controls. Further investigation is needed to delineate the exact mechanism of these potential clinically significant findings.

Surgical management of popliteal artery embolism at the turn of the millennium.

Popliteal artery embolism has been a focus of study at the Massachusetts General Hospital for over 60 years. It is a formidable vascular problem with significant limb loss and mortality. To assess the impact of advances in cardiac and vascular therapies, we reviewed our outcomes over 12 years. A retrospective review from our databases identified 66 patients with 72 popliteal artery emboli between January 1989 and October 2000. Patients undergoing nonsurgical therapy or with in situ atherosclerotic thrombosis were excluded. Demographics, comorbidities, presentation, duration, etiology, treatment, and outcomes were analyzed. Patients were classified into those with acute (AP; symptoms <7 days; 59 of 72, 82%) or delayed (DP; symptoms >7 days; 13 of 72, 18%) presentation. The presentation was typically acute ischemia (85%) in the AP group and claudication (69%), rest pain (15.5%), or gangrene (15.5%) in the DP group. The most common etiology was embolism secondary to atrial fibrillation (17 of 72, 24%). Femoral artery access (15 of 72, 21%) was more prevalent than in our prior experience. In the AP group, 9 of 59 (15%) were treated with a femoral artery approach, 44 of 59 (75%) with a popliteal artery approach, and 6 of 59 (10%) with bypass. In the DP group, 11 of 13 (85%) were treated with a popliteal approach and 2 of 13 (15%) with bypass. Completion angiography was done in 17 cases (24%). Limb salvage rate was 88% (88% AP, 85% DP); the rate was 94% with angiography and 85% without it (p > 0.1). There were seven deaths (10%). The mortality rate was 33% after amputation and 7% after limb salvage (p < 0.05). Except for a greater prevalence of femoral artery access as an etiology, the demographics of patients with popliteal embolism were similar to those of prior reports. Although a femoral approach may be appropriate in select AP cases, a popliteal approach is preferred in most patients and is necessary in DP cases. Completion angiography should be performed to ensure adequacy of the embolectomy. Outcomes are unchanged. Future therapies should aim to improve limb salvage and mortality rates.

Clinical failures of endovascular abdominal aortic aneurysm repair: incidence, causes, and management.

OBJECTIVE: Despite well-documented good early results and benefits of endoluminal stent graft repair of abdominal aortic aneurysm (J Vasc Surg 2002;35:1137-44.)(AAA), the long-term outcome of this method of treatment remains uncertain. In particular, concern exists that late effectiveness and durability are inferior to that of open repair. To determine the incidence and causes of clinical failures of endovascular AAA repair, a 7-year experience with 362 primary AAA endografts was reviewed. METHODS: Clinical failures were defined as deaths within 30 days of the procedure, conversions (early and late) to open AAA repair, AAA rupture after endoluminal treatment, or AAA sac growth of more than 5 mm in maximal diameter despite endograft repair. Endoleak status per se was not considered unless it resulted in an adverse event. If clinical problems arose but could be corrected with catheter-based therapies or limited surgical procedures, thereby maintaining the integrity of successful stent graft treatment of the AAA, such cases were considered as primary assisted success and not classified as clinical failures. RESULTS: The average follow-up period was 1.5 years. Six deaths (1.6%) occurred after the procedure, all in elderly patients or patients at high risk. Five patients (1.4%) needed early conversion (immediate, 2 days) to open repair for access problems or technical difficulties with deployment, resulting in an implantation success rate of 98.6%. Eight patients (2.2%) underwent late conversion for a variety of problems, including AAA expansion (n = 4), endograft thrombosis (n = 1), secondary graft infection (n = 2), and rupture at 3 years (n = 1). Rupture occurred in an additional two patients for a total incidence rate of 0.8%. AAA sac growth of greater than 5 mm was observed in 20 patients (5.6%), four of whom have undergone successful catheter-based treatments to date. Overall, 39 patients (10.7%) needed catheter-based (n = 45) or limited surgical (n = 4) reinterventions for a variety of late problems that were successful in 92%. CONCLUSION: In our 7-year experience, one or more clinical failures of endovascular AAA repair were observed in 31 patients (8.3%). Reinterventions were necessitated in a total of 10.7% of patients but were usually successful in maintaining AAA exclusion and limiting AAA growth. These results emphasize that endovascular repair provides good results and many benefits for most properly selected patients but is not as durable as standard open repair.

Carotid endarterectomy at the millennium: what interventional therapy must match.

OBJECTIVES: Carotid endarterectomy (CEA) is supported by level 1 evidence as the standard treatment of severe carotid stenosis in both symptomatic and asymptomatic patients. As interventional techniques are emerging for treatment of this disease, this study was undertaken to provide a contemporary surgical standard for comparison to carotid stenting. PATIENTS AND METHODS: During the interval 1989 to 1999, 2236 isolated CEAs were performed on 1897 patients (62% male, 36% symptomatic, 4.6% reoperative procedures). Study endpoints included perioperative events, patient survival, late incidence of stroke, anatomic durability of CEA, and resource utilization changes during the study. Variables associated with complications, long-term and stroke free survival, restenosis, and resource utilization were analyzed by univariate and multivariate analysis. RESULTS: Perioperative complications occurred in 5.5% of CEA procedures, including any stroke/death (1.4%), neck hematoma (1.7%), cardiac complications (0.5%), and cranial nerve injury (0.4%). Actuarial survival at 5 and 10 years was 72.4% (95% confidence interval [CI] 69.3-73.5) and 44.7% (95% CI 41.7-47.9) respectively, with coronary artery disease (P < 0.0018), chronic obstructive pulmonary disease (P < 0.00018) and diabetes mellitus (P < 0.0011) correlating with decreased longevity. The age- and sex-adjusted incidence of any stroke during follow-up was reduced by 22% (upper 0.35, lower 0.08) of predicted with the patient classification of hyperlipidemia (P < 0.0045) as the only protective factor. Analysis of CEA anatomic durability during a median follow-up period of 5.9 years identified a 7.7% failure rate (severe restenosis/occlusion, 4.5%; or reoperative CEA, 3.2%) with elevated serum cholesterol (P < 0.017) correlating with early restenosis. Resource utilization diminished (first versus last 2-year interval periods) for average hospital length of stay from 10.3 +/- 1.5 days to 4.3 +/- 0.7 days (P < 0.01) and preoperative contrast angiography from 87% +/- 1.4% to 10.3% +/- 4%. CONCLUSIONS: These data delineate the safety, durability, and effectiveness in long-term stroke prevention of CEA. They provide a standard to which emerging catheter-based therapies for carotid stenosis should be compared.

Durability of aortouniiliac endografting with femorofemoral crossover: 4-year experience in the Evt/Guidant trials.

OBJECTIVES: We evaluated mid-term results of the multicenter EVT/Guidant aortouniiliac endograft (AI) trial and ascertained the durability of this endovascular technique in patients unable to undergo standard bifurcated endografting. METHODS: From November 1996 to December 1998, 121 patients were enrolled to receive the AI device on the basis of complex iliac artery anatomy contraindicating bifurcated endografting. Clinical data were centrally collected, and radiographic data were evaluated by core facility. RESULTS: AI placement was technically successful in 113 of 121 patients. At operation, patients who underwent AI had significantly more arrhythmias, congestive heart failure, and peripheral occlusive disease (P <.05) compared with patients who underwent open aneurysmorrhaphy in the EVT/Guidant trials, indicating comorbid features in this anatomic cohort. Distal AI attachment was performed to the external iliac artery in 40 (36%) patients. Median follow-up was 38 months. In the AI group, overall aneurysm diameter decreased over the duration of study from 54.4 +/- 9.6 mm to 44.4 +/- 16.4 mm (P =.004). At 24 and 36 months after repair, reduction in aneurysm size was associated with absence of endoleak (P =.003 and P =.008, respectively). Aneurysms shrunk or remained stable in 109 (96.5%) patients. Endoleak was identified in 52.3% of patients at discharge, and at follow-up in 30.9% at 1 year, 34.8% at 2 years, 28.6% at 3 years, and 30.4% at 4 years. Type II endoleak predominated. Leak from failure to completely occlude contralateral iliac flow accounted for 8 of 58 endoleaks (13.8%) at discharge. Sixteen patients (14.2%) underwent postoperative endoleak treatment; in one of these patients open conversion was necessary at 20 months. Post-procedure thigh or buttock claudication developed in 16 patients (14.2%). Thirteen patients (81.3%) had either distal attachment in the external iliac artery or contralateral type IIA occlusion. Fifteen patients (13.3%) required intervention because of reduced limb flow; one of these patients underwent open conversion at 27 months, and another underwent axillofemoral grafting at 28 months. Device migration was confirmed in 2 (1.8%) patients, without current clinical sequelae. Whereas no femorofemoral graft thromboses occurred, graft infection developed in 3 patients (2.6%). During follow-up, aneurysm in 2 patients ruptured. Late death occurred in 41 patients (36.3%). Twenty-four patients (58.5%) died of cardiopulmonary disease; one death was endograft-related after aneurysm rupture; and one death was related to femorofemoral bypass infection. Actuarial survival was 78.4% (95% confidence interval [CI], 71%-86%) at 2 years and 63.4% (95% CI, 54%-73%) at 4 years. CONCLUSIONS: In patients with significant comorbid conditions and complex iliac anatomy unfavorable for bifurcated endografting, AI with femorofemoral bypass grafting is safe and effective. In most patients this endovascular option provides satisfactory mid-term results.