Pierce A. Grace

Decreased morbidity and mortality after pancreatoduodenectomy

In two 5 year periods (1975 to 1979 and 1980 to 1984), 96 patients underwent pancreatoduodenal resection, which included 74 partial pancreatic resections and 22 total pancreatectomies. Thirty-seven of these patients had resections with preservation of the pylorus. Substantial reductions in perioperative mortality (2 percent versus 10 percent) and morbidity (26 percent versus 49 percent) (p less than 0.05) were achieved in the latter period. Pylorus preservation, with a mortality and morbidity of 3 percent and 27 percent, respectively, did not increase operative risk or compromise long-term survival in patients with malignant disease. In comparison, relatively high mortality and morbidity rates (14 percent and 59 percent) accompanied total pancreatectomy without improved long-term survival. Five year actuarial survival for nonpancreatic periampullary adenocarcinomas was 58 percent. Thus, we recommend pancreatoduodenectomy with preservation of the pylorus for resection of periampullary tumors. These patients, whose only possibility for cure is a major pancreatic resection, should not be denied this opportunity on the basis of reports from a previous era.

Vessel asymmetry as an additional diagnostic tool in the assessment of abdominal aortic aneurysms

OBJECTIVE Abdominal aortic aneurysm (AAA) rupture is believed to occur when the local mechanical stress exceeds the local mechanical strength of the wall tissue. On the basis of this hypothesis, the knowledge of the stress acting on the wall of an unruptured aneurysm could be useful in determining the risk of rupture. The role of asymmetry has previously been identified in idealized AAA models and is now studied using realistic AAAs in the current work. METHODS Fifteen patient-specific AAAs were studied to estimate the relationship between wall stress and geometrical parameters. Three-dimensional AAA models were reconstructed from computed tomography scan data. The stress distribution on the AAA wall was evaluated by the finite element method, and peak wall stress was compared with both diameter and centerline asymmetry. A simple method of determining asymmetry was adapted and developed. Statistical analyses were performed to determine potential significance of results. RESULTS Mean von Mises peak wall stress +/- standard deviation was 0.4505 +/- 0.14 MPa (range, 0.3157-0.9048 MPa). Posterior wall stress increases with anterior centerline asymmetry. Peak stress increased by 48% and posterior wall stress by 38% when asymmetry was introduced into a realistic AAA model. CONCLUSION The relationship between posterior wall stress and AAA asymmetry showed that excessive bulging of one surface results in elevated wall stress on the opposite surface. Assessing the degree of bulging and asymmetry that is experienced in an individual AAA may be of benefit to surgeons in the decision-making process and may provide a useful adjunct to diameter as a surgical intervention guide.

Fibrin: A Natural Biodegradable Scaffold in Vascular Tissue Engineering

Arterial occlusive disease remains a major health issue in the developed world and a rapidly growing problem in the developing world. Although a growing number of patients are now being effectively treated with minimally invasive techniques, there remains a tremendous pressure on the vascular community to develop a synthetic small-diameter vascular graft with improved long-term patency rates. The field of tissue engineering offers an exciting alternative in the search for living organ replacement structures. Several methodologies have emerged for constructing blood vessel replacements with biological functionality. Common strategies include cell-seeded biodegradable synthetic scaffolds, cell self-assembly, cell-seeded gels and xenogeneic acellular materials. A wide range of materials are being investigated as potential scaffolds for vascular tissue engineering applications. Some are commercialised and others are still in development. Recently, researchers have studied the role of fibrin gel as a three-dimensional scaffold in vascular tissue engineering. This overview describes the properties of fibrin gel in vascular tissue engineering and highlights some recent progress and difficulties encountered in the development of cell fibrin scaffold technology.

The need to retrieve the dropped stone during laparoscopic cholecystectomy

The effect of bile and gallstones on the peritoneal cavity was evaluated in an experimental animal study. Ninety male Sprague-Dawley rats were randomly allocated to one of six groups (n = 15). Groups 1 to 3 received an intraperitoneal injection (2 mL) of saline, sterile bile, and infected bile, respectively. Groups 4 to 6 underwent a lower midline abdominal incision (3 to 5 mm). In groups 4 and 5, a single gallstone (< 3 mm diameter) was placed in the right upper quadrant and, after closure of the wound, the animals were injected with sterile bile and infected bile, respectively. Group 6 animals underwent laparotomy alone, followed by injection of sterile saline (2 mm). All animals were killed at 4 weeks and the peritoneal cavity was carefully examined. No intra-abdominal lesions were noted in groups 1 to 3. Adhesions were noted in 11 (73%) and 10 (67%) animals of groups 4 and 5, respectively. Two intra-abdominal abscesses were noted in group 4 animals. No intra-abdominal lesions were noted in any group 6 animals. This study suggests that bile in combination with gallstones in the peritoneal cavity is associated with an increased risk of intra-abdominal adhesion formation and possible abscess formation, and that every attempt should be made to retrieve stones lost during cholecystectomy.

Prevalence and aetiology of leg ulcers in Ireland

BackgroundThe prevalence of leg ulcer disease in Ireland has been poorly documented.AimsThis study aimed to investigate the aetiology and prevalence of leg ulcers in one health district.MethodsAll patients receiving healthcare for an active leg ulcer in the Mid-Western Health Board (MWHB) region of Ireland (population: 317,069) were identified in a defined two-month period. A cross-sectional survey of all healthcare workers providing care to patients with leg ulceration was carried out. Patients with leg ulcers of uncertain cause were invited for follow-up assessment to establish the underlying cause.ResultsThere were 389 patients with leg ulcers with a mean (standard deviation [SD]) age of 72.3 (11.1) years. The prevalence was 0.12% but it was 1.03% in patients aged 70 years and over. Women were twice as likely to be affected. Venous disease accounted for 81% of ulcers, and arterial disease for 16.3%, while ulceration due to diabetic neuropathy and rheumatoid vasculitis was unusual.ConclusionLeg ulcers are an important source of morbidity in our ageing population. Effective treatment programmes could diminish the impact of this debilitating disease on the health service.

Randomized clinical trial and economic analysis of four-layer compression bandaging for venous ulcers

The aim of this study was to compare the cost‐effectiveness of four‐layer compression bandaging for venous leg ulcers with that of other available treatments.

Ultrasound guidance for difficult peripheral venous access: systematic review and meta-analysis

Background Establishing intravenous access is often vital in an acute hospital setting but can be difficult. Ultrasound-guided cannulation increases success rates in prospective studies. However, these studies have often lacked a comparative group. This systematic review and meta-analysis aimed to determine the clinical effectiveness of Ultrasound-guided peripheral intravenous cannulation compared with the standard technique in patients known to have difficult access. Methods Electronic abstract databases, trial registries, article reference lists and internet repositories were searched using the following search terms: ‘peripheral venous cannulation’, ‘peripheral venous access’. Studies meeting the following criteria were included: randomised controlled trial patients of all ages who required peripheral intravenous access; interventions were Ultrasound-guided versus standard cannulation technique; patients were identified as having difficult venous access; inclusion of at least one defined outcome (procedural success time to cannula placement; number of attempts). Results 7 trials were identified (289 participants). Ultrasound guidance increases the likelihood of successful cannulation (pooled OR 2.42; 95% CI 1.26 to 4.68; p=0.008). There were no differences in time to successful cannulation, or number of percutaneous skin punctures. Conclusion Ultrasound guidance increases the likelihood of successful peripheral cannulation in difficult access patients. We recommend its use in patients who have difficult venous access, and have failed venous cannulation by standard methods. Further randomised controlled trials (RCTs) with larger sample sizes would be of benefit to investigate if Ultrasound has any additional advantages in terms of reducing the procedure time and the number of skin punctures required for successful venous cannulation.

The biaxial mechanical behaviour of abdominal aortic aneurysm intraluminal thrombus: Classification of morphology and the determination of layer and region specific properties

Intraluminal thrombus (ILT) is present in 75% of clinically-relevant abdominal aortic aneurysms (AAAs) yet, despite much research effort, its role in AAA biomechanics remains unclear. The aim of this work is to further evaluate the biomechanics of ILT and determine if different ILT morphologies have varying mechanical properties. Biaxial mechanical tests were performed on ILT samples harvested from 19 patients undergoing open surgical repair. ILT were separated into luminal, medial and medial/abluminal layers. A total of 356 tests were performed and the Cauchy stress (σ) and tangential modulus (TM) at a stretch ratio (λ) of 1.14 were recorded for each test in both the circumferential (θ) and longitudinal (L) directions. Our data revealed three distinct types of ILT morphologies, each with a unique set of mechanical properties. All ILT layers were found to be isotropic and inhomogeneous. Type 1 (n=10) was a multi-layered ILT (thick medial/abluminal layer) whose strength and stiffness decreased gradually from the luminal to the medial/abluminal layer. Type 2 (n=6) was a multi-layered ILT (thin/highly degraded medial/abluminal layer) whose strength and stiffness decreased abruptly between the luminal and medial/abluminal layer and Type 3 (n=3) is a single layered ILT with a lower strength and stiffness than Types 1 and 2. In a sub-study, we found the luminal layer to be stronger and stiffer in the posterior than the anterior region. This work provides further insights to the biomechanical behaviour of ILT and the use of our ILT classification may be useful in future studies.

A Finite Element Analysis Rupture Index (FEARI) as an Additional Tool for Abdominal Aortic Aneurysm Rupture Prediction

Currently, abdominal aortic aneurysms (AAAs), which are a permanent dilation of the aorta, are treated surgi- cally when the maximum transverse diameter surpasses 5.5cm. AAA rupture occurs when the locally acting wall stress exceeds the locally acting wall strength. There is a need to review the current diameter-based criterion, and so it may be clinically useful to develop an additional tool to aid the surgical decision-making process. A Finite Element Analysis Rup- ture Index (FEARI) was developed. Ten patient-specific AAAs were reconstructed, and the corresponding wall stress computed. Previous experimental work on determination of ultimate tensile strengths (UTS) from AAA tissue samples was implemented in this study. By com- bining peak wall stress along with average regional UTS, a new approach to the estimation of patient-specific rupture risk has been developed. Ten cases were studied, all of which were awaiting or had previously undergone surgical AAA repair. A detailed exami- nation of these ten cases utilising the FEARI analysis suggested that there was a possibility that some of the AAAs may have been less prone to rupture than previously considered. It is proposed that FEARI, used alongside other rupture risk factors, may improve the current surgical decision-making process. The use of FEARI as an additional tool for rupture prediction may provide a useful adjunct to the diameter-based approach in surgical decision-making.

A review of the in vivo and in vitro biomechanical behavior and performance of postoperative abdominal aortic aneurysms and implanted stent-grafts.

Endovascular repair of abdominal aortic aneurysms has generated widespread interest since the procedure was first introduced two decades ago. It is frequently performed in patients who suffer from substantial comorbidities that may render them unsuitable for traditional open surgical repair. Although this minimally invasive technique substantially reduces operative risk, recovery time, and anesthesia usage in these patients, the endovascular method has been prone to a number of failure mechanisms not encountered with the open surgical method. Based on long-term results of second- and third-generation devices that are currently becoming available, this study sought to identify the most serious failure mechanisms, which may have a starting point in the morphological changes in the aneurysm and stent-graft. To investigate the “behavior” of the aneurysm after stent-graft repair, i.e., how its length, angulation, and diameter change, we utilized state-of-the-art ex vivo methods, which researchers worldwide are now using to recreate these failure modes.