The impact of compliance on Stage 2 uni-ventricular heart circulation: An experimental assessment of the Bidirectional Glenn.

The Bidirectional Glenn (BDG) or cavopulmonary connection is typically undertaken to volume unload the single ventricle in an effort to preserve ventricular and atrioventricular valve function. The geometry of this surgical palliation has been shown to influence the fluid energy loss as well as the distribution of flow that enters through the superior vena cava. In-vitro and in-silico studies to date have been performed on rigid wall models, while this investigation looks at the impact of flexible thin walled models versus rigid walls. Rigid and compliant models of two patient-specific Glenn geometries were fabricated and tested under various flow conditions, within a biosimulator capable of replicating patient specific flow conditions. It was found that the compliant models exhibit greater levels of energy loss compared to the rigid models. Along with these findings greater levels of turbulence was found in both compliant models compared to their rigid counterparts under ultrasound examinations. This shows that vessel compliance has a significant impact on the hemodynamics within hypoplastic left heart syndrome.

Embolus Analog Trajectory Paths Under Physiological Flowrates Through Patient-Specific Aortic Arch Models.

Atrial fibrillation (AF) is the most common irregular heartbeat among the world's population and is a major contributor to cardiogenic embolisms and acute ischemic stroke (AIS). However, the role AF flow plays in the trajectory paths of cardiogenic emboli has not been experimentally investigated. A physiological simulation system was designed to analyze the trajectory patterns of bovine embolus analogs (EAs) (n = 720) through four patient-specific models, under three flow conditions: steady flow, normal pulsatile flow, and AF pulsatile flow. It was seen that EA trajectory paths were proportional to the percentage flowrate split of 25-31% along the branching vessels. Overall, AF flow conditions increased trajectories through the left- (LCCA) and right (RCCA)-common carotid artery by 25% with respect to normal pulsatile flow. There was no statistical difference in the distribution of clot trajectories when the clot was released from the right, left, or anterior positions. Significantly, more EAs traveled through the brachiocephalic trunk (BCT) than through the LCCA or the left subclavian. Yet of the EAs that traveled through the common carotid arteries, there was a greater affiliation toward the LCCA compared to the RCCA (p < 0.05).

The Mechanical Characterisation of Bovine Embolus Analogues Under Various Loading Conditions.

Embolus Analogues (EAs) can provide understanding of the mechanical characteristics of blood clots of cardiac origin. Bovine EAs (n = 29) were fabricated with varying concentrations of thrombin (0-20 NIHU/ml blood). Histological staining confirmed that EA composition compared sufficiently with human samples reported in literature. EAs were mechanically described under seven testing conditions: tensile, compression, shear wave ultrasound elastography (SWE), parallel plate rheometry, indentation, creep and relaxation. The Young modulus of bovine EAs in tension varied from 7 kPa (5% strain) to 84 kPa (50% strain). The compressive Young modulus increased with increasing thrombin concentration, which was in agreement with the SWE results. There was no significant difference in Young modulus throughout the clot (p < 0.05). The EAs displayed a non-linear response under parallel plate rheometry, creep and stress relaxation. The 3rd order Mooney-Rivlin constitutive equation and Standard Linear Solid model were used to fit the non-linear stress-strain response and time-dependent properties, respectively. This is the first study in which bovine EAs, with and without addition of thrombin, are histologically and mechanically described with corresponding proposed constitutive equations. The equations and experimental data determined can be applied for future numerical and experimental testing of mammalian EAs and cardiac source clots.

[Management of adult abdominal pain in the Emergency Room]. / Prise en charge des douleurs abdominales de l'adulte aux Urgences.

Abdominal pain is a commonplace reason for surgical consultation in the emergency department and is the the most common symptom which the digestive surgeon on-call must evaluate. He must understand the pathophysiologic basis of visceral pain and referred pain in order to appreciate its diverse manifestations. Abdominal pain can stem from many causes intestinal and non-intestinal, medical and surgical. Evaluation and management in the emergency department must be rapid and pragmatic; clinical history and physical examination should define the gravity of the case, direct the first diagnostic procedures and complementary examinations, and guide the therapeutic direction. Ultrasonography is a quick and effective diagnostic procedure in the diagnosis of biliary, urologic, and gynecologic pathologies; it can be useful for other digestive problems as well. The new generation spiral CT scanner gives excellent definition of digestive and vascular pathologies. The initial evaluation and management of the acute abdomen may determine the prognosis of the patient; it should lead to prompt symptomatic relief and to a well-directed treatment appropriate to the diagnosis.

3-D numerical simulation of blood flow through models of the human aorta.

A Spiral Computerized Tomography (CT) scan of the aorta were obtained from a single subject and three model variations were examined. Computational fluid dynamics modeling of all three models showed variations in the velocity contours along the aortic arch with differences in the boundary layer growth and recirculation regions. Further down-stream, all three models showed very similar velocity profiles during maximum velocity with differences occurring in the decelerating part of the pulse. Flow patterns obtained from transient 3-D computational fluid dynamics are influenced by different reconstruction methods and the pulsatility of the flow. Caution is required when analyzing models based on CT scans.

A mathematical model to predict the in vivo pulsatile drag forces acting on bifurcated stent grafts used in endovascular treatment of abdominal aortic aneurysms (AAA).

Endovascular treatment of abdominal aortic aneurysms (AAA) is a promising new alternative to the traditional surgical repair. However, the endovascular approach suffers problems such as stent graft migration, endoleaks and stent mechanism breakage. Fatigue failure is believed to be the major cause of stent graft migration and device breakage. Knowledge of the in vivo forces acting on such devices is a basic requirement for the design of a successful endovascular device. Using a Fourier series trigonometric fit of a typical pressure and flow relationship, a mathematical model, using the control volume method, was developed to predict the pulsatile drag forces acting on various bifurcated stent graft geometries. It was found that for an iliac angle of 30 degrees, a proximal diameter of 24 mm and an iliac diameter of 12 mm, the drag force varied, over the cardiac cycle, between 3.9 and 5.5 N in the axial direction. It was noted that for a specific iliac angle the drag force variation with proximal diameter approximates a quadratic fit, with an increase in proximal diameter producing an increase in drag force. The more compliant the aorta the higher the drag force. Previously published results demonstrated the axial loads (axial drag forces) required for stent graft migration for certain stents types are lower than the drag forces calculated in this study. It is believed that the results of this study can provide guidelines for the quantitative analyses of the in vivo drag forces experienced by stent grafts and could therefore be used as design criteria for such devices.

[Antibiotic prophylaxis in surgery of the esophagus]. / Antibioprophylaxie en chirurgie de l'oesophage.

Surgery of oesophagus carcinoma is a long and major procedure. Perioperative radiochemotherapy is often required. Therefore many factors favour the occurrence of local and general postoperative infection, justifying an antibiotic prophylaxis directed against oesophageal and gastric flora. In case of oesophageal stenosis, the oesophageal floral often switches to the fecal type. Antimicrobial agents diffuse to the surgical site and reach there high concentrations for the time of surgery. We recommend, just prior the induction of anaesthesia the intravenous administration of a single dose of a third generation cephalosporin (ceftriaxone 2 g) and nitroimidazole (ornidazole 1 g). The long half-life of these agents allows sufficient concentrations at surgical site to be obtained and the efficacy of this regimen has been demonstrated. Selective decontamination of the digestive tract with systemic antibiotherapy is another approach for the prevention of postoperative complications of surgery of oesophagus carcinoma.

Clinical evaluation of the CORDIS vascular access port systems: a multicenter study.

Two non-metallic vascular access port systems, the Multipurpose Access Port (MPAP) and Miniport, developed by CORDIS S.A., France, have been evaluated clinically in 78 cancer patients. During the investigational period covering a total experience of 369 treatment cycles and 1,370 infusion days, no cases of infection or septicemia were observed. Serious complications such as drug extravasation and catheter occlusion occurred, although the incidence was relatively low (+/- 1%) when compared with the number of treatment courses (cycles), but in relation to the number of patients included in this study, the procedure-related complication rate was 17.5% for the MPAP and 15.8% for the Miniport. Procedure-related complications can be avoided by proper handling and use of suitable drug combinations to minimize crystallization reactions within the port-catheter systems. The final complication rate (total minus procedure-related) in terms of termination of treatment, i.e. explantation of the port-catheter system was 12.1% for the MPAP and 12.5% for the MINIPORT, which generally confirms the results of other groups. More than 87% of both port-catheter systems were still functional at the end of evaluation.

[Hereditary deficiency of antithrombin III, protein C and protein S. A study of 31 patients from 8 unrelated families]. / Les déficits constitutionnels en antithrombine III, protéine C et protéine S. Etude de 31 sujets appartenant à huit familles non apparentées.

The families of eight unrelated patients were studied with regard to a hereditary deficiency in antithrombin III (ATIII), protein C, or protein S. These deficiencies were recognized in the course of investigations for deep-vein thrombosis (DVT) in the eight patients. A group of 31 individuals (patients and family members), mostly less than 40-year-old was explored. Two cases of AT III deficiency were discovered, as well as 21 of protein C deficiency, and seven of protein S. Ten of the 30 have had recurrent venous thrombosis at the time of bedrest, trauma, surgery, pregnancy, postpartum or during oral contraceptive treatment. Spontaneous DVT occurred in three cases. Seventeen patients had remained asymptomatic till then. Such patients need antithrombotic treatment during surgery or pregnancy. Prophylactic treatment with enoxaparin in one patient (deficiency in protein C) during her second pregnancy is discussed. It seems that low molecular weight heparin may be a safe alternative to unfractionated heparin. Oral anticoagulants are efficient in preventing reoccurring venous thromboembolism in patients with AT III deficiency. The questions of whether oral anticoagulants should be continued in the long-term in patients with protein C or protein S deficiency who have had a DVT, and whether asymptomatic deficient patients should be given any antithrombotic treatment outside circumstances likely to induce a DVT, remain as yet unanswered.

[Biological criteria for the evaluation of prophylactic treatment with a low molecular weight heparin (Kabi 2165)]. / Critères biologiques d'évaluation d'un traitement prophylactique par une héparine de bas poiids moléculaire (Kabi 2,165).

Efficacy of a low molecular weight heparin (Kabi 2165) was compared with that of non-fractionated heparin in the prevention of abdominal surgery postoperative venous thrombosis by means of a double-blind randomized trial in 79 patients. Determination of D. dimers in these patients allowed assessment of specificity of this assay for detection of postoperative venous thrombosis.

[Evaluation of the activity and quality of care in a digestive surgery department]. / Evaluation de l'activité et de la qualité des soins dans un service de chirurgie digestive.

Since 1980, details of all patients operated upon in a digestive surgery unit have been entered on record-cards with the view of obtaining information on the activity of the unit and improving post-operative care. Over a 3-year period, 2005 patients underwent surgery, 25% of them for cancerous lesions. Biliary tract operations (385 patients), fundoplication by the abdominal route for gastro-oesophageal reflux (58 patients) and curative resection of the colon for carcinoma (100 patients) were set apart for evaluation. For each of the above pathologies, morbidity, mortality and duration of stay in hospital in cases with uneventful or complicated post-operative course were analyzed. Annual audits of this kind result in accurate evaluation and periodical reappraisal of the therapeutic habits of the medico-surgical team.