Effects of surface charge and cluster size on the electrochemical dissolution of platinum nanoparticles using COMB3 and continuum electrolyte models.

We study the site-dependent dissolution of platinum nanoparticles under electrochemical conditions to assess their thermodynamic stability as a function of shape and size using empirical molecular dynamics and electronic-structure models. The third-generation charge optimized many-body potential is employed to determine the validity of uniform spherical representations of the nanoparticles in predicting dissolution potentials (the Kelvin model). To understand the early stages of catalyst dissolution, implicit solvation techniques based on the self-consistent continuum solvation method are applied. It is demonstrated that interfacial charge and polarization can shift the dissolution energies by amounts on the order of 0.74 eV depending on the surface site and nanoparticle shape, leading to the unexpected preferential removal of platinum cations from highly coordinated sites in some cases.

There is no benefit to universal carotid artery duplex screening before a major cardiac surgical procedure.

BACKGROUND: Perioperative stroke is a devastating complication after cardiac surgery. In an attempt to minimize this complication, many cardiac surgeons routinely preoperatively order carotid artery duplex scans to assess for significant carotid stenosis. We hypothesize that the routine screening of preoperative cardiac surgery patients with carotid artery duplex scans detects few patients who would benefit from carotid intervention or that a significant carotid stenosis reliably predicts stroke risk after cardiac surgery. METHODS: A retrospective review identified 1,499 patients who underwent cardiac surgical procedures between July 1999 and September 2010. Data collected included patient demographics, comorbidities, history of previous stroke, preoperative carotid artery duplex scan results, location of postoperative stroke, and details of carotid endarterectomy (CEA) procedures before, in conjunction with, or after cardiac surgery. Statistical methods included univariate analysis and Fisher's exact test. RESULTS: Twenty-six perioperative strokes were identified (1.7%). In the 21 postoperative stroke patients for whom there is complete carotid artery duplex scan data, 3 patients had a hemodynamically significant lesion (>70%) and 1 patient underwent unilateral carotid CEA for bilateral disease. Postoperative strokes occurred in the anterior cerebral circulation (69.2%), posterior cerebral circulation (15.4%), or both (15.4%). Patient comorbidities, preoperative carotid artery duplex scan screening velocities, or types of cardiac surgical procedure were not predictive for stroke. Thirteen patients (0.86%) underwent CEA before, in conjunction with, or after cardiac surgery. Two of these patients had symptomatic disease, 1 of whom underwent CEA before and the other after his cardiac surgery. Of the 11 asymptomatic patients, 2 underwent CEA before, 3 concurrently, and 6 after cardiac surgery. Left main disease (≥50% stenosis), previous stroke, and peripheral vascular disease were found to be statistically significant predictors of carotid revascularization. A cost analysis of universal screening resulted in an estimated net cost of $378,918 during the study period. CONCLUSIONS: The majority of postoperative strokes after cardiac surgery are not related to extracranial carotid artery disease and they are not predicted by preoperative carotid artery duplex scan screening. Consequently, universal carotid artery duplex scan screening cannot be recommended and a selective approach should be adopted.

Effects of a standardized emergency department protocol on after-hours use of venous duplex ultrasound.

OBJECTIVE: Vascular laboratory (VL) venous duplex ultrasound is the "gold standard" for diagnosis of lower extremity deep venous thrombosis (DVT), which is linked to many morbid conditions. Decreasing night and weekend use of VL services in the emergency department (ED) represents a potentially viable means of reducing costs as skilled personnel must remain on call and receive a wage premium when activated. We investigated the effects of workflow changes that required ED providers to use a computerized decision-making tool, integrated into the electronic medical record, to calculate a Wells score for each patient considered for an after-hours venous duplex ultrasound study for suspected DVT. METHODS: The rate of VL use and study positivity before and after implementation of the decision-making tool were examined in addition to measures of ED throughput, rate of concomitant pulmonary embolism, disposition of examined patients from the ED, observed thrombus distribution in duplex ultrasound studies positive for DVT, and calculated personnel costs of after-hours VL use. RESULTS: A total of 391 after-hours, ED-initiated venous duplex ultrasound studies were obtained during the 4-year study period (n = 213 before intervention, n = 178 after intervention; P = .12). Whereas the period immediately after the start of the intervention saw a decrease in VL use, this was not sustained. Studies performed after the intervention were not more likely to be positive for acute DVT (12.2% vs 18%; P = .1179). The average Wells score was 2.8 (range, 0-6). VL personnel were called in 347 times during the 4-year period, with a total cost of $14,643.40. Nurse-ordered studies were significantly more likely to be positive, with 22% revealing acute DVT compared with 12% for physician-ordered studies (P = .042). The intervention resulted in significant improvements in ED throughput, with time between triage and study request falling from 226 minutes to 165 minutes (P < .001). Observed thrombus distribution revealed involvement of the most proximal external iliac system in a minority of cases (11%), whereas most thrombi (89%) were limited to the femoropopliteal, calf, and superficial venous systems. CONCLUSIONS: A requirement for ED providers to document a Wells score before obtaining an after-hours venous duplex ultrasound study resulted in only a transient decrease in VL use but improved ED throughput. Studies ordered by nurses were significantly more likely to be positive, possibly as a result of consistent protocol adherence compared with the physicians. Future studies may warrant investigation into this provider variance.

Operation Enduring Freedom: the 48th Combat Support Hospital in Afghanistan.

OBJECTIVE: To examine the experience of the 48th Combat Support Hospital (CSH) while deployed to Afghanistan, with an emphasis on trauma care. MATERIALS AND METHODS: Before redeployment, a retrospective review was performed on the medical records of all patients treated at the 48th CSH from December 6, 2002 through June 7, 2003. RESULTS: During the 6-month period, 10,679 patients were evaluated and/or treated. There were 477 hospital admissions (adults, 387; children, 90; trauma, 204) and 634 operating room procedures. The most common mechanisms of injury were land mines/unexploded ordinance (74 = 36%) and gunshot wounds (41 = 20%). Extremities were the most common site. A total of 358 cases was performed on 168 trauma patients (mean, 2 cases per patient; range, 1-12). There were 63 complications in 40 trauma patients and 11 patients died. CONCLUSIONS: The 48th CSH supported military and humanitarian operations with an ongoing process of re-evaluation, adaptation, and medical education that resulted in low morbidity and mortality rates.

Endoscopy in a deployed combat support hospital: maintaining military end-strength.

OBJECTIVE: The objective was to examine the safety and efficacy of the 48th Combat Support Hospital's use of diagnostic endoscopy in Afghanistan. METHODS: A retrospective review was performed on the medical records of all endoscopy patients treated at the 48th Combat Support Hospital in Bagram, Afghanistan, from December 6, 2002 through June 7, 2003. RESULTS: Twenty-four patients (male, 21; female, 3; mean age, 35 years) underwent 28 endoscopic procedures as follows: colonoscopy, 14; esophagogastroduodenoscopy (EGD), 13; and flexible sigmoidoscopy, 1. Four patients underwent both EGD and colonoscopy. There were no complications. Of the 18 U.S. military patients, 3 (15%) were evacuated for further evaluation and/or treatment and 1 (5%) patient underwent an elective screening colonoscopy. For 14 of 17 U.S. military personnel (82%), the endoscopic procedures obviated evacuation from Afghanistan. CONCLUSIONS: Diagnostic colonoscopy and EGD were valuable and safe adjuncts that precluded evacuations out of theater for 82% of military patients. Endoscopy should be used when U.S. military operations necessitate the deployment of large numbers of forces for protracted periods.

Interdisciplinary Quality Improvement Conference: Using a Revised Morbidity and Mortality Format to Focus on Systems-Based Patient Safety Issues in a VA Hospital: Design and Outcomes.

The Veterans Healthcare Administration (VA) has embraced patient safety and quality improvement in the quest to improve care for veterans. The New Mexico VA Health Care System introduced a new morbidity and mortality conference, called the Interdisciplinary Quality Improvement Conference (IQIC), using patient case presentations to focus on underlying systems in the clinical care environment. The revised conference design also effectively teaches the 6 Accreditation Council for Graduate Medical Education (ACGME) core requirements for resident education. A formal process was established for case selection, presentation, systems issue identification, tracking, and follow-up. The IQIC has enabled the identification of more than 20 system issues at the study institution. Outcome data show lasting improvement in system issues that were addressed by this mechanism. The VA IQIC is an effective method to both identify and correct systems issues that affect patient care and is an effective method for teaching residents the 6 ACGME requirements for residency education.

Mesenteric venous thrombosis in a patient with prothrombin 20210A mutation and antithrombin III deficiency: challenges to conventional anticoagulation--a case report.

Mesenteric venous thrombosis presents as vague abdominal pain in patients with a medical or family history suggestive of a hypercoagulable state. Classic computed tomography findings will often confirm the diagnosis, and the presence of persistent abdominal pain or tenderness will determine the need for surgical intervention. Expeditious anticoagulation is the treatment of choice. This case demonstrates the CT findings for mesenteric venous thrombosis and discusses the challenges of anticoagulation in a patient with 2 hypercoagulable disorders.

Review of standards for competence in catheter-based endovascular procedures: a resource and strategy for the interventional vascular surgeon.

The field of peripheral vascular disease management is evolving. As such, vascular surgeons can no longer be complacent and expect to be included in the rapidly expanding practice of endovascular intervention. If not engaged, vascular surgeons risk losing not only the patients who have largely driven this evolution but also their role as leaders in the management of vascular disease. Therefore vascular surgeons and vascular surgical training programs find themselves in an awkward and sometimes confrontational circumstance attempting to gain experience and training in catheter-based procedures. Individual societies, both surgical and nonsurgical, have put forth competence standards for catheter-based procedures. However these standards are not always consistent and the definition of competence is often a heated debate. In addition, combining the acquisition of endovascular skills with the multitude of available endovascular training experiences, didactic and "hands-on," is not well coordinated. The objectives of this review are to summarize the literature as it relates to catheter-based endovascular competence, including publications from nonsurgical catheter-based specialties, and to place the acquisition of basic endovascular skills in context with the available endovascular courses in a stepwise strategy. A final objective is to provide a literature-based resource that outlines specific phases in the development of interventional vascular surgeons and training programs as they advance into the arena of catheter-based endovascular therapies.

Long-term follow-up of endovascular abdominal aortic aneurysm repair in a rural veteran patient population.

BACKGROUND: The endovascular repair of abdominal aortic aneurysms (EVARs) requires follow-up to detect and treat late complications. METHODS: Two hundred eleven patients underwent EVAR for infrarenal, nonruptured abdominal aortic aneurysms from 1999 to 2010 at the Raymond G. Murphy VA Medical Center, Albuquerque, NM. A retrospective review examined patient demographics, comorbidities, the distance the patient lived from the facility, early and late complications, and the device implanted. Statistical analysis included the chi-square test for independence, the Fisher exact test, and the 2-sample Mann-Whitney U test for means. RESULTS: The mean time from the operation to the first complication was 21 months (standard deviation = 20 months) with a mean follow-up of 48 months (standard deviation = 36 months). The late complication rate was 22.8% (54 patients). Sixteen percent did not require any reinterventions, 57% were treated with percutaneous interventions, and 27% required an open surgical procedure. No single comorbidity, combination of comorbidities, distance the patient lived from the facility, or device implanted was predictive of complications. CONCLUSIONS: EVAR follow-up is essential to detect complications. When complications occur, the majority occur well after the initial treatment, and most can be treated with minimally invasive percutaneous techniques.

What imaging studies are necessary for abdominal aortic endograft sizing? A prospective blinded study using conventional computed tomography, aortography, and three-dimensional computed tomography.

OBJECTIVE: Preoperative imaging modalities for endovascular abdominal aortic aneurysm repair (EVAR) include conventional computed tomography (CT), aortography with a marking catheter, and three-dimensional computed tomography (3D CT). Although each technique has advantages, to date no study has compared in a prospective manner the reproducibility of measurements and impact on graft selection of all three modalities. The objective of this study was to determine the most useful imaging studies in planning EVAR. METHODS: Twenty patients being considered for EVAR were enrolled prospectively to undergo a conventional CT scan and aortography. The CT scans were then reconstructed into 3D images using Preview Treatment Planning Software (Medical Media Systems, West Lebanon, NH). Four measurements of diameter and six of length were made from each modality in determining the proper graft for EVAR. RESULTS: Measurements from all three modalities were reproducible with intraobserver correlation coefficients of 0.79 to 1.0 for aortography, 0.87 to 1.0 for CT, and 0.96 to 1.0 for 3D CT. Measurements between observers were also similar from each modality; interobserver correlations were 0.70 to 0.97 for aortography, 0.76 to 0.97 for CT, and 0.73 to 0.99 for 3D CT. Significant differences ( P < .01) in diameter measurements were noted at D2 with aortography compared with 3D CT, whereas differences in length measurements were found between CT and 3D CT at L4 (nonaneurysmal right iliac) ( P < .01). The correlation between CT and 3D CT for most length measurements was acceptable (0.63 to 1.0). Aortography for diameters correlated poorly (0.35 to 0.67) with 3D CT. When the endograft selected by aortography/CT or 3D CT alone was compared with the actual endograft used, there was agreement in 11 of 11 patients when adjusted for +/- one size in diameter or length. CONCLUSION: Reproducible and comparable measures of diameter and length can be obtained by each of three imaging modalities available for endograft sizing. As a single imaging modality, 3D CT appears to have the best correlation for both diameters and lengths; however, the difference is not sufficient enough to alter endograft selection. Three-dimensional CT may be reserved for challenging aortic anatomy where small differences in measurements would affect patient or graft selection for EVAR.

Contemporary management of wartime vascular trauma.

OBJECTIVE: The treatment of wartime injuries has led to advances in the diagnosis and treatment of vascular trauma. Recent experience has stimulated a reappraisal of the management of such injuries, specifically assessing the effect of explosive devices on injury patterns and treatment strategies. The objective of this report is to provide a single-institution analysis of injury patterns and management strategies in the care of modern wartime vascular injuries. METHODS: From December 2001 through March 2004, all wartime evacuees evaluated at a single institution were prospectively entered into a database and retrospectively reviewed. Data collected included site, type, and mechanism of vascular injury; associated trauma; type of vascular repair; initial outcome; occult injury; amputation rate; and complication. Liberal application of arteriography was used to assess these injuries. The results of that diagnostic and therapeutic approach, particularly as it related to the care of the blast-injured patient, are reviewed. RESULTS: Of 3057 soldiers evacuated for medical evaluation, 1524 (50%) sustained battle injuries. Known or suspected vascular injuries occurred in 107 (7%) patients, and these patients comprised the study group. Sixty-eight (64%) patients were wounded by explosive devices, 27 (25%) were wounded by gunshots, and 12 (11%) experienced blunt traumatic injury. The majority of injuries (59/66 [88%]) occurred in the extremities. Nearly half (48/107) of the patients underwent vascular repair in a forward hospital in Iraq or Afghanistan. Twenty-eight (26%) required additional operative intervention on arrival in the United States. Vascular injuries were associated with bony fracture in 37% of soldiers. Twenty-one of the 107 had a primary amputation performed before evacuation. Amputation after vascular repair occurred in 8 patients. Of those, 5 had mangled extremities associated with contaminated wounds and infected grafts. Sixty-seven (63%) patients underwent diagnostic angiography. The most common indication was mechanism of injury (42%), followed by abnormal examination (33%), operative planning (18%), or evaluation of a repair (7%). CONCLUSIONS: This interim report represents the largest analysis of US military vascular injuries in more than 30 years. Wounding patterns reflect past experience with a high percentage of extremity injuries. Management of arterial repair with autologous vein graft remains the treatment of choice. Repairs in contaminated wound beds should be avoided. An increase in injuries from improvised explosive devices in modern conflict warrants the more liberal application of contrast arteriography. Endovascular techniques have advanced the contemporary management and proved valuable in the treatment of select wartime vascular injuries.

Endovascular management of a peroneal artery injury due to a military fragment wound.

A healthy 29-year-old male suffered bilateral lower extremity fragment wounds resulting in a tense right calf shortly following a wound that required a four-compartment fasciotomy. During treatment of other injuries after medical evacuation he complained of increasing right calf pain. A peroneal pseudoaneurysm (PSA) with a concomitant arteriovenous fistula (AVF) was diagnosed. The distal one-third of the peroneal artery was not visualized, and the posterior tibial and anterior tibial arteries were normal. The patient underwent percutaneous coil embolization of the pseudoaneurysm. Completion arteriography demonstrated no evidence of the PSA and AVF. The patient's bruit and pain resolved.

Aberrant right subclavian artery syndrome: a case of chronic cough.

A young, otherwise healthy man had chronic cough of 16 months' duration. Evaluation revealed an aberrant right subclavian artery. Kommerell's diverticulum without aneurysmal degeneration was present. Imaging studies showed compression of the esophagus but not the trachea. Results of methacholine challenge test were negative for evidence of reactive airway disease, but suggested mild variable intrathoracic obstruction. While aberrant right subclavian artery syndrome most commonly involves dysphagia, our patient's only symptom was cough. Right subclavian artery to right common carotid artery transposition was performed, with oversewing of the subclavian artery stump to the left of the esophagus through a right supraclavicular incision. This treatment was curative, with complete resolution of symptoms.

Re-evaluation of carotid duplex for visual complaints: who really needs to be studied?

Amaurosis fugax (AF), Hollenhorst plaques, central retinal artery occlusion (CRAO), and nonspecific visual symptoms are all reasons for patient referral for carotid artery evaluation. This study reviews the management of patients with visual signs or symptoms based on their clinical presentation, carotid duplex results, follow-up data, and outcome. We performed a retrospective review of all patients presenting to the Vascular Surgery Clinic between June 1996 and December 2001 for carotid duplex scanning because of the indication of a visual disturbance. A total of 3560 carotid duplex examinations were performed during the study period; 98 were performed for a visual complaint or finding. A total of 11.1% of group 1 (Hollenhorst plaques), 22.2% in group 2 (CRAO), 45% in group 3 (AF), and 9.8% in group 4 (nonspecific visual symptoms) had significant carotid disease and underwent carotid endarterectomy. No patient who underwent screening carotid duplex and did not have surgically correctable disease developed significant carotid disease or symptoms from carotid disease during the study period. Hollenhorst plaques, CRAO, and nonspecific visual complaints are a poor predictor of significant carotid stenosis, while AF had a significantly higher rate of surgically correctable carotid stenosis. Patients with visual signs or symptoms need an initial screening carotid duplex examination. If this does not show surgically correctable disease, patients do not need to return for further examinations unless another indication arises.

Endovascular management of renal ischemia in a patient with acute aortic dissection and renovascular hypertension.

We report the endovascular management of a patient with a type B aortic dissection complicated by renal ischemia and resultant severe hypertension. A 69-year-old male presented with acute type B aortic dissection with proximal extension complicated by severe renovascular hypertension secondary to left renal ischemia. Endovascular management consisted of imaging with intravascular ultrasound and left renal artery stenting with balloon-expandable stents. His hypertension subsequently resolved and he was discharged on his baseline two-drug regimen. Management of the ischemic complications of type B aortic dissections may be primarily approached using endovascular methods in stable patients, with open surgery reserved for those patients refractory to these methods. Patients with evidence of decreased renal perfusion represent a select group with an increased risk of associated morbidity and mortality and should therefore be aggressively managed. Accurate information and assessment of anatomy can be obtained with intravascular ultrasound and is therefore an important adjunct to the armamentarium of endovascular specialists managing complications of aortic dissection.

Endovascular assisted in situ bypass grafting: a simplified technique for saphenous vein side branch occlusion.

The in situ bypass procedure for lower extremity limb salvage requires a long continuous incision or multiple interrupted incisions over the greater saphenous vein to ligate the saphenous vein side branches. This can result in wound complications that frequently prolong hospital stay and threaten the graft. In an effort to reduce the incidence of wound complications, alternate methods of occluding the vein side branches have been used. One method is to deliver coils under angioscopic vision into the saphenous vein side branches. This report details a simplified technique that uses widely available catheter-based equipment to perform saphenous vein side branch occlusion under fluoroscopic guidance.

Preoperative risk stratification using electron beam computed tomography in elective vascular surgery: relationship to clinical risk prediction and postoperative complications.

We studied the utility of electron beam computed tomography as a screening test for the cardiovascular risk of elective vascular surgery. In 45 patients undergoing principally carotid and aortic surgical procedures, coronary artery calcification was prevalent and severe, and related to the clinically predicted cardiovascular risk of the procedure. However, only the clinically predicted surgical risk, and not coronary artery calcification, was related to the incidence of perioperative cardiovascular complications.