Popliteal venous aneurysm: report of two cases and review of the world literature

Two new cases of popliteal venous aneurysm are reported and added to the 22 other cases of popliteal venous aneurysm available for review. Both patients were first seen with acute pulmonary embolism and were treated with thrombolytic therapy followed by anticoagulation. Each had recurrent venous thromboembolism before discovery of the popliteal venous aneurysm. One popliteal venous aneurysm was diagnosed with phlebography and the second with venous duplex imaging, confirmed with phlebography. Both were surgically corrected with tangential aneurysmectomy and lateral venorrhaphy. Twenty-four cases of popliteal venous aneurysm are now available for review. Seventy-one percent (17 of 24) presented with pulmonary embolism, 88% (21 of 24) were saccular, and 96% (23 of 24) were located in the proximal popliteal vein. All but two were diagnosed by ascending phlebography. Three patients received no treatment: in two of these the outcome was not documented and the third had occasional pain. Two patients received anticoagulation without subsequent operative repair and both died of recurrent pulmonary emboli. Operative correction resulted in a 75% patency rate with 21% complications, most of which were related to postoperative anticoagulation. No patient who was operated on had subsequent pulmonary embolism, and there were no operative deaths. We suggest that all patients who have pulmonary embolism have lower-extremity venous duplex imaging. All popliteal venous aneurysms should be surgically repaired, inasmuch as nonoperative therapy results in recurrent thromboembolism and an unacceptably high mortality rate. Tangential aneurysmectomy with lateral venorrhaphy is the recommended procedure.

Registry of laparoscopic cholecystectomy and new and evolving laparoscopic techniques

To collect information on the rapid application of laparoscopic surgery, the National Laparoscopic Surgery Registry surveyed more than 4,000 of the 16,000 currently practicing laparoscopic surgeons. Preliminary analysis of the data has revealed that most of the respondents had been trained in general surgery, but a small percentage were certified only in surgical subspecialties. Surgeons acquiring skills in laparoscopic surgery had various levels of experience ranging from less than 1 year to more than 38 years in surgical practice. Nearly 90% of the respondents attended a laparoscopic cholecystectomy course with hands-on training. In those courses, an average of 16 hours was devoted to animal laboratories for acquisition of skills. Additional training in the form of a preceptorship is being undertaken by an increasing number of surgeons. The future of minimally invasive surgery is being supported by rapid advances in technology. New video systems capable of displaying three-dimensional images and miniaturized fiberoptic scopes are now available. Computer enhanced three-dimensional ultrasound images provide the surgeon with the ability to examine the content and consistency of tissues in addition to their appearance. Advances in mechanical retraction may eliminate the need for carbon dioxide insufflation of the abdomen. Tissue repair using tissue glues or laser-mediated processes may reduce the need for endocavitary suturing. These advances in technology and techniques may reduce the morbidity and mortality of these surgical procedures and, ultimately, improve the standard of care for surgical patients.

Structural analysis based on state-space modeling

A new method has been developed to compute the probability that each amino acid in a protein sequence is in a particular secondary structural element. Each of these probabilities is computed using the entire sequence and a set of predefined structural class models. This set of structural classes is patterned after Jane Richardson's taxonomy for the domains of globular proteins. For each structural class considered, a mathematical model is constructed to represent constraints on the pattern of secondary structural elements characteristic of that class. These are stochastic models having discrete state spaces (referred to as hidden Markov models by researchers in signal processing and automatic speech recognition). Each model is a mathematical generator of amino acid sequences; the sequence under consideration is modeled as having been generated by one model in the set of candidates. The probability that each model generated the given sequence is computed using a filtering algorithm. The protein is then classified as belonging to the structural class having the most probable model. The secondary structure of the sequence is then analyzed using a "smoothing" algorithm that is optimal for that structural class model. For each residue position in the sequence, the smoother computes the probability that the residue is contained within each of the defined secondary structural elements of the model. This method has two important advantages: (1) the probability of each residue being in each of the modeled secondary structural elements is computed using the totality of the amino acid sequence, and (2) these probabilities are consistent with prior knowledge of realizable domain folds as encoded in each model. As an example of the method's utility, we present its application to flavodoxin, a prototypical alpha/beta protein having a central beta-sheet, and to thioredoxin, which belongs to a similar structural class but shares no significant sequence similarity.

Adventitial elastolysis is a primary event in aneurysm formation

PURPOSE

Adventitial elastin degradation is a hallmark of abdominal aortic aneurysm (AAA) formation in human beings, although the quantitative relationship between elastin loss and AAA formation and growth is unknown. This study was undertaken to quantitate the reduction of adventitial elastin for small AAA, to determine whether the loss of this structural component parallels aneurysm growth, and to examine the ultrastructure of the remaining elastin elements.

METHODS

Longitudinal strips of anterior aneurysm wall were taken from 12 patients having elective repair of small (diameter < 5 cm, n = 4), moderate (diameter < 5 to 7 cm, n = 4), or large (diameter > 7 cm, n = 4) AAA and from six normal control subjects at autopsy. Specimens were prepared with elastin and collagen stains for histologic examination or formic acid for scanning electron microscopic evaluation of elastin architecture. Adventitial elastin content of aneurysmal and control aortas was quantitated with video microscopy and compared by aneurysm diameter.

RESULTS

The inner portion of adventitia of normal aortic wall was composed of densely compacted alternating lamellae of elastin and collagen, which were grossly disrupted in all aneurysms. The remaining elastin fibers were disorganized and tortuous. There was an 81.6% +/- 2.1% reduction in elastin lamellae and an 85.7% +/- 4.2% reduction in fibers per lamellae compared with the number in control aortas (p < 0.001). Size of the aneurysm made no difference in adventitial elastin content.

CONCLUSION

These data strongly suggest that elastolysis is a primary event in AAA formation that occurs before over loss of adventitial structural integrity and the development of small aneurysms.

Hemodynamic deterioration in chronic venous disease

Clinical deterioration of patients with chronic venous disease (CVD) has been well described and a standardized classification has been proposed. The progressive hemodynamic deterioration producing these clinical findings is less well appreciated. This study examines and correlates venous hemodynamics with clinical severity in patients with CVD. Two hundred seventy-four extremities from 149 patients with varying degrees of CVD and 56 extremities from 28 symptom-free volunteers were evaluated clinically and hemodynamically. Each limb was assessed for functional venous volume, degree of valvular insufficiency, efficiency of the calf muscle pump, and noninvasive estimate of ambulatory venous pressure. In addition, exercise venous pressures were recorded in 56 extremities from 36 patients and 9 extremities from 6 volunteers. As CVD progresses from class 0 to class 2, venous volume expands, valvular function deteriorates, the calf muscle pump becomes inefficient, and ambulatory venous hypertension develops. However, once extremities develop brawny edema or hyperpigmentation, further deterioration of limb hemodynamics does not occur. Patients with deep venous obstruction have more severe valvular insufficiency, calf muscle pump dysfunction, and ambulatory venous hypertension than have patients without evidence of obstruction. Residual volume fraction offers a reliable noninvasive estimate of ambulatory venous pressure (r = 0.76), although its correlation was significantly better for patients without venous obstruction (r = 0.86) than for those with obstruction (r = 0.40; p < 0.05). Deterioration in venous hemodynamics parallels clinical severity through class 2. Once brawny edema and hyperpigmentation occur, ulceration develops without additional deterioration of venous hemodynamics.

Why does prophylaxis with external pneumatic compression for deep vein thrombosis fail?

External pneumatic compression (EPC) devices are increasing in popularity for deep vein thrombosis (DVT) prophylaxis. Patients who have these devices applied postoperatively are assumed to have effective prophylaxis, although a number of extensive postoperative DVT complications have been observed. This study evaluates the proper application of EPC devices in patients in intensive care units and regular nursing floor units and assesses whether dedicated in-service instruction can improve proper use. In a prospective study of 138 patients with 2 or more risk factors for postoperative DVT, it was found that patients on routine nursing units had properly functioning EPC devices during 48% (306 of 636) of the visits compared with 78% (312 of 398) of the visits in the intensive care unit (ICU) (p less than 0.0001). Follow-up of patients transferred from an ICU to a regular nursing unit showed that functional application decreased from 82% (129 of 157) to 33% (40 of 122) (p less than 0.005). The compression sleeves were not applied in 84% of the nonfunctional devices and were properly in place but the pump nonfunctional in 16%. Unfortunately, dedicated in-service instruction did not improve the proper use of EPC. Although proper application of EPC is better in the ICU compared with regular nursing units, improper use is frequent and failure of DVT prophylaxis with EPC devices may be due to improper use, rather than failure of the method itself.

An approach to nutrition screening for older Americans

The Nutrition Screening Initiative suggests an adaptable, tiered approach to screening for poor nutritional status in older Americans. The first level of screening is a checklist to be completed by elderly individuals or their caregivers. This checklist, which will be widely disseminated, describes the warning signs of poor nutritional status. It is anticipated that individuals will approach their physicians on the basis of scores on this checklist. Also included are two screening tests designed to help clinicians more easily detect poor nutritional status, or risk factors for poor nutrition, in their patients. The level I screen is to be completed by a social service or health care professional, or by other trained personnel. The level II screen focuses on additional information to be obtained following referral to a physician or other qualified health care professional.

Risk factors for poor nutritional status in older Americans

Inappropriate dietary intake and chronic disease or disability place a substantial number of older adults at high risk of malnutrition. Malnutrition often results in considerable dysfunction and disability, reduced quality of life and, in some instances, premature or increased morbidity and mortality. Nutrition screening should prevent nutrition-related problems or allow early intervention. The elements that contribute to nutritional problems in the elderly must be clearly identified and prioritized. The desired goal of nutrition screening is a more vigorous older population able to maintain optimal nutrition, resulting in improved health and quality of life.

Effect of dietary protein on functional, morphologic, and histologic changes of the kidney during compensatory renal growth in dogs

Two diets similar in caloric density and mineral content, but markedly different in protein content, were used to study the effects of dietary protein on renal function and morphologic and histopathologic changes in dogs that had functional renal tissue reduced by seven-eights nephrectomy. The effects of moderate protein intake (MPrI = 15% protein; dry-matter basis) and high-protein intake (HPrI = 31% protein; dry-matter basis) were studied for the initial 7 months (period 1 [P1]) after renal mass reduction. Diets were then switched between groups during the following 7 months (period 2 [P2]) to evaluate the effects of increased or decreased protein intake. The HPrI caused significantly (P less than 0.05) greater glomerular filtration rate (GFR) and renal growth than did MPrI during P1. Dogs that maintained HPrI during P1 and MPrI during P2 (group 1) had significant (P less than 0.05) reduction in GFR during P2. Dogs that maintained MPrI during P1 and HPrI during P2 (group 2) had significant (P less than 0.05) improvement in GFR and renal growth during P2. At the end of the study, renal reserve was evaluated in both groups of dogs before and after group 1 was returned to HPrI for 2 weeks. During this 2-week feeding trial, group-1 dogs had marked improvement in renal reserve, relative to group 2, and GFR increased to the terminal P1 values. Results indicate a possible residual benefit from HPrI during the early phase of compensatory renal growth in the form of functional compensatory memory to HPrI. The severity of renal lesions was indistinguishable between dogs of dietary groups during both study phases.(ABSTRACT TRUNCATED AT 250 WORDS)

Consensus of the Nutrition Screening Initiative: risk factors and indicators of poor nutritional status in older Americans

Dietetics professionals must become even more proactive in taking the lead in the nutritional screening and assessment of older Americans. They can do so by encouraging all health care providers to become familiar with each older American's circumstances and needs. In addition, as individuals and as a professional health care association, we should urge our colleagues and institutions to establish regular longitudinal surveillance and continuity of care in nutrition services delivery. The timely, appropriate, and cost-effective delivery of nutritional screening, assessment, and care will improve the health and well-being of this valued segment of the US population. Dietetics professionals are a vital part of this process.

The architecture of adventitial elastin in the canine infrarenal aorta

Although the artery wall consists of three distinct layers, only the structures of the intima and media have been well characterized. The adventitia has generally been overlooked. Our examination focused on the organization of elastin and collagen which are the major components of this tunic. Canine infrarenal aortas were excised, stretched to their in vivo length, then pressure fixed in formalin. Transverse, longitudinal, and frontal sections were prepared with specific elastin and collagen stains. Areas of adventitia in these sections were examined with LM, and interconnections between collagen and elastin were photographed at various magnifications. Subsequently, the slides were fractured for attachment to SEM stubs, and the coverslips were demounted. The identical areas were then examined with SEM using the LM micrographs as a guide to identify elastin and collagen. Whole mount aortic ring preparations were digested in formic acid for 72 and 96 h at 45 degrees C to confirm adventitial elastin architecture. The adventitia was organized in alternating lamellae of collagen and elastin. The elastin lamellae consisted of continuous sheets of elastin with a longitudinal fibrillar substructure. Finer circumferential elastin fibers were also identified. These attached to both longitudinal elastin and adjacent collagen lamellae. Collagen lamellae were arranged in broad corrugated bands of fibrils. The unique architecture of the adventitia may explain some of the visco-elastic properties of the aorta in both normal and pathologic states.

Beneficial effects of dietary mineral restriction in dogs with marked reduction of functional renal mass

Although studies in partially nephrectomized rats have identified a progressive nephropathy that is altered by dietary restriction of phosphorus intake, the response of dogs to similar perturbations has not been established. Functional renal mass was reduced by 15/16 in dogs to determine its long-term effects on renal function and to evaluate the effects of two levels of dietary mineral (calcium and phosphorus) intake (0.44% phosphorus/0.57% calcium versus 1.50% phosphorus/1.91% calcium). Following a 3-month stabilization period, dogs were fed either the lower mineral diet (group 1, N = 12) or the higher mineral diet (group 2, N = 12) for 24 months. Loss of renal function with the passage of time was observed in 10 of 12 dogs maintained on the higher mineral diet, with an average decrease in exogenous creatinine clearance of 11.1 +/- 6.3%/month, leading to a survival rate of 33% in this group. Restriction of dietary mineral intake slowed (P less than 0.05) the rate of decline of exogenous creatinine clearance in group 1 to 2.6 +/- 1.1%/month and improved 24-month survival to 75% (P less than 0.01). Deterioration of renal function was associated with renal calcium accumulation and histologic evidence of nephrocalcinosis, tubular atrophy and dilatation, and interstitial fibrosis. These events were more readily apparent in female than in male dogs. A role for glomerulosclerosis was not apparent, and neither glomerular pathology nor glomerular volume was related to the observed decrements in renal function.

Preparation of the calcified tibial artery for bypass grafting

This method of preparation of calcified tibial arteries for bypass grafting produces softening of the arterial wall to permit vascular control and the construction of a technically precise anastomosis. The presence of the inflated intraluminal balloon during compression of the arterial wall inhibits violent cracking of the calcific skeleton and displacement of calcium plates into the lumen. This results in fewer intimal flaps and the preservation of an undisrupted outflow tract.

Percutaneous ablation of gallstones

The purpose of this study was to determine if gallstones could be safely and effectively ablated in the pig using a proprietary percutaneous rotor-tipped catheter, the Kensey-Nash Lithotrite (KNL). All gallstones in a single human gallbladder were defined as a gallstone set. Human gallstone sets not meeting current treatment criteria for extracorporeal shock wave lithotripsy (ESWL) were placed in the gallbladder (GB) of male pigs (N = 8; 80-100 kg). A percutaneous transhepatic guide wire was put into the GB and the abdomen closed. The KNL was then introduced under fluoroscopy using the Seldinger technique and activated. Gallstone ablation was monitored by tactile and auditory feedback to the operator and by fluoroscopy. Once completed the device was withdrawn, the GB irrigated, and the 9F sheath removed. Animals were sacrificed immediately (Group 1, N = 4) and at 28 +/- 5 days (Group 2, N = 4). Gallstones were ablated in 26 +/- 8 min. No pig had significant hemorrhage, GB perforation, or pancreatitis. One acute animal had stone fragments greater than 2 mm in the gallbladder. No other animals had any fragments greater than 1 mm present in the GB, cystic duct, common duct, ampulla, or duodenum. Histologic examination of the GB showed acute hemorrhagic mucosal injury in Group 1 and extensive mucosal regeneration with some stone fragment granulomata and mural fibrosis in Group 2. We conclude that percutaneous gallstone ablation with the KNL is safe and effective in this short-term pig model and appears to be a safe procedure for gallstone ablation. Long-term safety and effectiveness remain to be demonstrated. This device should be useful for treatment of symptomatic gallstones in patients not treatable by ESWL.

The preoperative diagnosis of the ulcerated carotid atheroma

Arteriography and carotid duplex imaging accurately quantify the degree of stenosis caused by carotid atheroma. Since arteriography is inconsistent in identifying carotid ulceration, and controversy exists regarding the diagnostic accuracy of carotid B-mode imaging, a prospective study was performed comparing the two techniques to 126 carotid endarterectomy specimens. Sixty percent (76/126) of specimens contained ulcers. The diagnostic sensitivity for B-mode imaging and arteriography was 47% (36/76) and 53% (40/76), respectively (p = NS). Importantly, the degree of stenosis caused by the plaque significantly affected diagnostic sensitivities. B-mode sensitivity was 77% (10/13) in plaques less than or equal to 50% and 41% (26/63) for plaques greater than 50% (p = 0.03). Arteriography likewise detected 77% (10/13) of ulcers in plaques less than or equal to 50% stenosis and 48% (30/63) in plaques with greater than 50% stenosis (p = 0.07). In patients with focal symptoms, 100% (10/10) of plaques with less than or equal to 50% stenosis contained ulcers, whereas in plaques with greater than 50% stenosis 63% (36/57) contained ulcers (p = 0.02). These data indicate that the diagnostic sensitivity for carotid ulceration is not significantly different between B-mode carotid imaging and arteriography. Since most B-mode errors occur with high-grade stenoses this short-coming is unlikely to adversely affect patient care. Previous studies investigating the ability of carotid B-mode imaging to detect ulceration failed to address quantitative aspects of the carotid plaque. These data appear to resolve the previously existing controversy.

Free vascularized tissue transfer for limb salvage in peripheral vascular disease

In patients with tissue necrosis, higher limb salvage rates can be accomplished with free tissue transfers performed by a vascular and plastic surgeon team. We treated 10 patients with severe ischemic soft tissue defects in their legs with radical debridement and free tissue transfer alone (two patients) or after revascularization (eight patients). Arteriography was performed to plan revascularization to evaluate bypass results, and to identify appropriate recipient vessels for free tissue transfer. Soft tissue defects treated with free tissue transfer included nonhealing amputation sites in five patients and proximal skin and muscle necrosis in the remaining patients, one of which resulted in an exposed in-situ graft in one leg. One patient underwent a distal bypass specifically to provide arterial inflow for free tissue transfer, whereas seven other patients received free tissue transfers following bypass due to persistently nonhealing wounds. The remaining two patients had diabetes mellitus with necrosis near a major joint with nonhealing amputation sites. Free tissue transfers were taken from the latissimus dorsi in six patients, and from the gracilis, rectus abdominis, rectus femoris, and scapula flaps in other patients. Recipient vessels for free tissue transfers were the external iliac artery (one patient), saphenous vein bypass grafts (two patients), popliteal artery (one patient), posterior tibial (three patients), and dorsalis pedis vessels (three patients). Eight of the 10 flaps were viable at follow-up (four months-six years), with a mean follow-up of 20 months. One patient underwent above-knee amputation 15 months after operation and one underwent below-knee amputation three years later due to central flap necrosis. The remainder achieved functional limb salvage allowing patients to resume ambulation. Vascular surgeons should consider free tissue transfer in patients with nonhealing soft tissue defects following optimal revascularization to further extend our ability to salvage the threatened limb.

Laser assisted fusion of the rat stomach: preliminary studies

The purpose of this study was (1) to determine whether rat gastrotomies could be securely closed without sutures by CO2 laser-induced tissue fusion alone and (2) to compare some characteristics (physical, biochemical, histological) of laser-fused gastrotomies with sutured gastrotomies. Following pentobarbital anesthesia a 1.5-cm longitudinal anterior gastrotomy was made in the forestomach of male Sprague-Dawley rats. This wound was closed using either a sutureless tissue weld created by a microscope-mounted CO2 laser (153 W/cm2) (Group I, N = 61) or with a running 6-O polypropylene suture (Group II, N = 58). Animals were sacrificed on Postoperative Days 1, 2, 4, 7, and 11 and the wounds were studied. Survival to scheduled sacrifice was 95% in Group I and 93% in Group II. Although bursting pressure of laser-fused gastrotomies was significantly lower than that of sutured controls on Postoperative Day 1, measurement on subsequent days showed comparable wound strength between the laser and suture groups. Wound hydroxyproline content was significantly higher on Postoperative Day 1 and lower on Postoperative Day 11 in the laser group. Histologic examination of the laser-fused wounds revealed less inflammation and earlier reepithelialization than the sutured wounds, giving the microscopic appearance of a "neater" healing wound. These results suggest that laser-induced fusion is a feasible method of gastrointestinal wound closure which may complement standard suture techniques.