An experimental study of eight current arterial prostheses

Eight currently used arterial prostheses with differing constructions and materials were implanted in the descending thoracic aorta of mongrel dogs. The prostheses were Gore-Tex (polytetrafluoroethylene), DeBakey Woven, Cooley Woven, Meadox Woven Double Velour, Cooley Knitted Double Velour, Microvel, Vasculour II, and Bionit II. Five series of these eight prostheses were serially implanted in heparinized subjects. During the 40 implantations, attention was focused on three major characteristics: preclotting efficiency, surgical handling characteristics, and healing. Gore-Tex is impervious to blood. The DeBakey and Cooley woven grafts are nearly so. The remaining prostheses required preclotting. The Meadox Woven Double Velour became impervious after two preclotting steps, the Cooley Knitted Double Velour and the Bionit II required three, and the Vasculour II and the Microvel required four. The surgical handling characteristics of the knitted prostheses clearly surpassed those of the DeBakey and Cooley woven and Gore-Tex prostheses. Although the Meadox Woven Double Velour prosthesis had better conformability than the nonveloured woven, the tendency of its cut edge to fray was more pronounced. Healing was much more advanced in the knitted and woven prostheses than in the Gore-Tex.     

An integrated approach to reduced-order control theory

Linear-Quadratic-Gaussian (LQG) theory generally requires the use of a full-order dynamic observer whose dimension is often prohibitive in applications so that reduced-order controller design techniques are needed. A general formalism is presented here for the optimal design of controllers of arbitrary prescribed order with the usual quadratic cost functionals. The gradients of the cost functional are obtained in explicit form and involves Liapunov equations. A fundamental aspect of this paper is a unifying formalism; direct output feedback and reduced-order controllers, stochastic and deterministic systems, infinite-time and finite-time problems and time-invariant and time-varying problems are considered. Optimization of sensor and actuator locations and parameter-variation-insensitive controller design are also considered within this framework. Examples are treated.     

An integrated approach to team assessment in head injury

The development of multidisciplinary teams for the assessment and treatment of traumatic brain injury has not seen a parallel development in methods of coordinating and collating the information gathered by different professions. The team at the Head Injury Rehabilitation Centre (HIRC), Sheffield uses a process of assessment that encouragesthe coordination of such information, particularly across the areas that do not fall neatly into the remit of specific disciplines. The framework of the assessment is presented, together with discussion of methods of gathering information and of sharing that information. The advantages of this approach are discussed in terms of benefits for the client, for the professionals involved in the assessment and for other services that might be involved with the client.     

Seeding endothelium onto canine arterial prostheses. The effects of graft design.

To identify prosthetic characteristics that support the proliferation of an endothelial lining, 14 different graft designs were studied in dogs. The grafts were prepared by the use of a technique of endothelial seeding that we described previously. They were studied two and four weeks after their implantation. Weft-knit Dacron grafts (water porosity from 1,400 to 1,650 mL/min/sq cm) were the most successful. A velour index (velour stitch frequency times velour loop height) was computed. When the internal velour index (IVI) was greater than 60,000 loop-mu/sq cm, the percentage of clot-free surface was 17.2 +/- 14.5%, compared with 62.0 +/- 26.9% when the IVI less than 60,000 loop-mu/sq cm. Endothelium could be detected on 61.5% of the grafts when the IVI less than 60,00 loop-mu/sq cm, compared with 0% when the IVI greater than 60,000 loop-mu/sq cm. The cells that formed the outer capsule were better organized and more adherent to the graft when an external velour was present, but external velour did not affect the inner lining. We conclude that weft-knit Dacron grafts with water porosities from 1,400 to 1,650 mL/min/sq cm and with limited internal velour (IVI less than 60,000 loop-mu/sq cm) are suitable substrates for single-staged endothelial-cell seeding.     

Poststroke neuropsychiatric illness: An integrated approach to diagnosis and management

Opinion statement Patients who have had stroke are at significant risk for various neuropsychiatric illnesses. The most common and important of these are poststroke depression and poststroke dementia (attributable to vascular dementia, Alzheimer’s dementia, or a combination of mechanisms). Poststroke neuropathology may lead some patients to experience concurrent and ‘overlapping’ mood and cognitive symptoms. Less frequently, poststroke anxiety disorders, psychosis, isolated pathologic expressions of emotions, and apathy or fatigue may be encountered. The authors review the current literature on poststroke neuropsychiatry and offer an integrated approach to pathophysiologic concepts and clinical surveillance, screening, diagnosis, and evidencebased pharmacologic and nonpharmacologic intervention for these clinical problems on the clinical boundary between neurology and psychiatry.     

Direct union of coronary arteries after excision of short segments—An approach without arterial sutures,prostheses, or adhesives

Ten dogs underwent excision of a short segment of the diagonal branch of the left anterior descending coronary artery, the distal left circumflex coronary artery or one of its branches. Hemostasis was secured by suturing the overlying epicardium except in two animals in which the addition of a pericardial patch was necessary to control bleeding. Arterial sutures, prostheses, or adhesives were not used. Two animals died in the first 36 hr after surgery, one of massive pulmonary atelectasis, the other of bleeding. Arteriograms in the eight surviving animals showed healing of the divided coronary arteries with excellent distal filling in seven of them. Vascular union was noted as early as the fifth postoperative day and as late as the end of the 3-month follow-up period.The possibility of applying this simple surgical technique to certain instances of coronary arterial occlusive disease is discussed.     

An integrated neuropsychiatric approach to diagnosis and management of patients with epileptic seizures

Opinion statement In patients who present to neurology settings with history of epileptic seizures, psychiatric disorders may be the sole manifestation of apparent neurologic symptoms, or they may coexist. Current challenges for clinicians include distinguishing between two disorders and making the correct diagnoses, interpreting test results, and (co-) managing the disorder(s). Our goal is to provide the clinician with an integrated neuropsychiatric approach for the triage, assessment (history, screening tools, examination, diagnostic tests), and treatment (neurologic and/or psychiatric) of these challenging patients. In particular, use of schemata, tables, and algorithms will offer step-by-step approaches and guidelines for the clinician. Recommendations are made for the indications for psychiatric consultation, and co-management is recommended for patients with emergencies, those who fail routine psychiatric treatments, and those with complex presentations or multiple comorbid conditions.     

Renal masses in children. An integrated imaging approach to diagnosis

In view of the continuing technologic advancements in the development and availability of diagnostic imaging modalities, it is appropriate to assess periodically the currently accepted approaches to the evaluation of renal masses in children. The roles, advantages, and disadvantages of plain film, intravenous urography, ultrasonography, radionuclide scintigraphy, computed tomography, angiography, and magnetic resonance imaging in the approach to the evaluation of renal masses in children are discussed. An integrated imaging approach that provides the most accurate and necessary information for diagnosis and treatment is recommended.     

An integrated approach to care for patients with chronic kidney disease

Although the Kidney Disease Outcomes and Quality Initiative (K/DOQI) guidelines serve to integrate the multiple stages of chronic kidney disease (CKD), in practice, the treatment of kidney disease over its progressive course may be somewhat fragmented. Because the provision of integrated care across the stages of kidney disease, is likely to be advantageous for both patients and care providers, a conceptual framework which graphically depicts the complex and chronic nature of kidney disease may prove useful. The Life Options Rehabilitation Advisory Council (LORAC) proposes a cycle diagram to reflect the chronicity and complexity of kidney disease and to emphasize a holistic perception of kidney disease from its inception to the worst-case scenario outcome of kidney failure [corrected]. The kidney disease cycle conceptualization can serve as a patient teaching aid and as a reminder of the communication, collaboration, and cooperation that are required among primary care physicians and practitioners in each of the specialty areas that address the spectrum of kidney disease.     

The preclotting of porous arterial prostheses.

A four-step preclotting method is presented for use with porous filamentous Dacron prostheses in the fully-heparinized patient. The method employs controlled fibrin formation within graft interstices, heparin neutralization of all thrombin remaining in the graft wall, and delay of systemic heparin neutralization until 15--20 minutes after clamp release. The resulting flow surface is impervious, smooth and hypothrombogenic. Experimental data are presented which support the rationale of this four-step preclotting method. Four years of clinical experience with the method are summarized, involving 300 prosthesis limbs used in aortic bifurcation, aortofemoral, femorofemoral, axillary-femoral and femoropopliteal positions in 192 patients. A clinical perspective of preclotting techniques is presented in which the proper use of this new method is suggested.     

Small-caliber arterial prostheses: influence of porosity

Thirty-two pyrolytic carbon coated Weavenit dacron grafts and 32 human umbilical vein segments treated with glutaraldehyde were implanted in the carotid arteries of 32 dogs. Prosthesis samples were removed after periods varying from 10 to 120 days, and sections examined by optical microscopy. Internal surfaces were studied by scanning electron microscopy. Overall permeability was 93.7 p. cent for the dacron prosthesis and 84.3 p. cent for human umbilical vein sections. Fundamental stages of the pseudointimal organization process were compared for the two types of prosthesis.     

Use of modified heterologous arterial prostheses in reconstructive arterial surgery]

Results with modified heterologous artery prostheses in reconstructive artery surgery.