1/f neural noise and electrophysiological indices of contextual prediction in aging.

Prediction of upcoming words during reading has been suggested to enhance the efficiency of discourse processing. Emerging models have postulated that predictive mechanisms require synchronous firing of neural networks, but to date, this relationship has been investigated primarily through oscillatory activity in narrow frequency bands. A recently-developed measure proposed to reflect broadband neural activity - and thereby synchronous neuronal firing - is 1/f neural noise extracted from EEG spectral power. Previous research has indicated that this measure of 1/f neural noise changes across the lifespan, and these neural changes predict age-related behavioral impairments in visual working memory. Using a cross-sectional sample of young and older adults, we examined age-related changes in 1/f neural noise and whether this measure predicted ERP correlates of successful lexical prediction during discourse comprehension. 1/f neural noise across two different language tasks revealed high within-subject correlations, indicating that this measure can provide a reliable index of individualized patterns of neural activation. In addition to age, 1/f noise was a significant predictor of N400 effects of successful lexical prediction; however, noise did not mediate age-related declines in other ERP effects. We discuss broader implications of these findings for theories of predictive processing, as well as potential applications of 1/f noise across research populations.

Correlates of frailty phenotype and frailty index and their associations with clinical outcomes.

OBJECTIVES: Frailty is a predictor of adverse health outcomes and can be measured across the life course, including among people living with HIV. The purpose of this study was to examine two commonly used measures of frailty - the frailty index (FI) and frailty phenotype - to assess common characteristics and to describe associations with multimorbidity, falls, and disability in people aging with HIV. METHODS: This was a cross-sectional observational study including 482 consecutive HIV-infected patients (mean age 53.9 ± SD 6.9 years; 75% male) attending the multidisciplinary metabolic clinic at the University of Modena, Italy. Frailty was measured with the frailty phenotype and a 37-item FI. RESULTS: The mean FI score was 0.28±0.1 and frailty phenotype categories were: 3.1% frail, 51.9% pre-frail, and 45% robust. The duration of antiretroviral therapy was significantly different across levels of frailty as measured by both frailty tools (P < 0.01), but the nadir CD4 count was only significant for the FI (P = 0.01); current CD4 count was not significantly different across frailty levels using either tool. Both frailty measures were associated with multimorbidity; the FI was associated with Instrumental Activities of Daily Living impairment and falls history, whereas the frailty phenotype was not. CONCLUSIONS: The frailty phenotype and the FI demonstrated similar characteristics in patients at a tertiary-level HIV clinic. The FI had a stronger association with age, nadir CD4 count, comorbidities, falls, and disability. Integrating frailty assessments in clinical practice will be crucial for the development of interventions in age-related conditions, including disability and falls, in older persons living with HIV.

Size and albedo of Kuiper belt object 55636 from a stellar occultation.

The Kuiper belt is a collection of small bodies (Kuiper belt objects, KBOs) that lie beyond the orbit of Neptune and which are believed to have formed contemporaneously with the planets. Their small size and great distance make them difficult to study. KBO 55636 (2002 TX(300)) is a member of the water-ice-rich Haumea KBO collisional family. The Haumea family are among the most highly reflective objects in the Solar System. Dynamical calculations indicate that the collision that created KBO 55636 occurred at least 1 Gyr ago. Here we report observations of a multi-chord stellar occultation by KBO 55636, which occurred on 9 October 2009 ut. We find that it has a mean radius of 143 +/- 5 km (assuming a circular solution). Allowing for possible elliptical shapes, we find a geometric albedo of in the V photometric band, which establishes that KBO 55636 is smaller than previously thought and that, like its parent body, it is highly reflective. The dynamical age implies either that KBO 55636 has an active resurfacing mechanism, or that fresh water-ice in the outer Solar System can persist for gigayear timescales.

A novel methodology to explore the viscoelasticity of spider major ampullate silk.

Even before material science was a recognized discipline, the amazing mechanical properties of spider silk were documented and became the object of much study. In addition to the exceptional material properties of spider silk and the reported low immunogenicity, its concatenated amino acid motif arrangement facilitates a distinct possibility of manipulating the silk to create a designer biomaterial for medical applications. Crystalline protein regions imbedded in a mobile protein matrix give it a distinct set of viscoelastic abilities. Consequently, elasticity cannot be simply quantified by only measuring extensibility. To understand how the sequence of the major ampullate proteins affects elasticity, the hysteresis of single fibers from two different species, Argiope aurantia and Nephila clavipes, were examined using cyclic loading and unloading. The yield point that discriminates a transition from elastic extension to a plastic extension was analyzed by examining three different properties: Young's modulus, energy recovery and slack in the fiber after recovery. Young's modulus remained relatively constant regardless of the cycle. However, the energy recovered decreased as the slack and cycle number increased. Large standard deviations masked any quantitative differences between species and substantiated the necessity of developing synthetic silk to harness the amazing mechanical properties of spider silk.

Filling of the aneurysmal sac with DEAC-glucosamine in an animal model of abdominal aortic aneurysm following stent-graft repair.

AIM: The aim of this study was to present the preliminary results of a technique of abdominal aortic aneurysm (AAA) sac filling in an attempt to obliterate the sac in a swine AAA model, using deacetylated-poly-N-acetyl glucosamine (DEAC-poly-N-acetyl glucosamine). METHODS: Eleven Yucatan pigs, 6 months of age, 40 kg -60 kg, were used to create an AAA with a Dacron pouch implanted surgically and left to mature for 2 weeks. One animal was used to establish the AAA creation procedures. Eight animals were used for AAA sac filling; of the 8 subjects 2 were used for acute studies, and 6 for longer-term studies. Two additional animals were used as controls without polymer sac filling. Two weeks after the AAA creation, a 13 mmx5.5 cm straight tube AneuRx stent-graft was placed to exclude the aneurysm. The aneurysmal sac was filled with a polymer, DEAC-poly-N-acetyl glucosamine at 1.5%, 70% deacetylated, mixed with iohexol. There was filling of a lumbar artery by the polymer in 2 animals. Endpoints were at 1, 2, 4, 6, 12 and 24 weeks, in the chronic study animals and 6 and 12 weeks in the control subjects, procedures consisting of aortography followed by necropsy and pathologic examination. RESULTS: The AAA creation and aneurysm sac filling was successful in all animals. An organized thrombus layer of about 2 mm in thickness was observed in all subjects along the Dacron aneurysm wall. All aneurysms were angiographically patent at the time of treatment, but fresher thrombus within the sac was seen in 4 subjects before the polymer injection. The stent-graft placement excluded the AAA sac and the polymer injection filled all AAA sacs. The AAA sac had acquired a firm rubbery consistency at the time of necropsy. There was mild inflammatory reaction to the Dacron material in the surrounding tissues and within the sac, to a lesser extent. Two animals developed paralysis of the hind limbs following treatment, most likely related to spinal ischemia, and were used as acute subjects. There was no recanalization of the aneurysm sac, during the follow-up time, ranging from 1 to 24 weeks in the treatment or control subjects. There was a 25% shrinkage of the AAA sac at 6th, 40% at 12th week and 75% by the 24th week. The 2 control subjects showed shrinkage of less than 25% at 6 and 12 weeks. There was replacement of the polymer/thrombus complex by connective tissue, fat tissue with capillary neovascularization in the treated subjects. Fibrosis and calcifications were also detected within the sac, mostly around the stent-graft and in contact with the aortic wall starting at 4 weeks. Control subjects did not show replacement of the thrombus by connective tissue or neovascularization. CONCLUSION: The results of this preliminary study support the aneurysm sac filling as a potential tool to exclude the aneurismal sac, promoting shrinkage of the AAA. DEAC -poly-N-acetyl glucosamine promotes clotting within the AAA sac with progressive replacement by connective tissue and neovascularization and may have a potential to prevent endoleaks. The polymer is easy to use, and it seems to have adequate gradual long-term replacement properties, preventing aneurysm sac recanalization.

Contemporary analysis of outcomes following lower extremity bypass in patients with end-stage renal disease.

This study was designed to compare outcomes following infrainguinal bypass between patients with end-stage renal disease (ESRD) and patients with normal renal function (NRF). Sixty-three patients with ESRD undergoing 78 infrainguinal bypasses from 1990 to 1999 were compared with a concurrent group of 132 age-, race-, and gender-matched patients with NRF undergoing 148 bypasses. Limb salvage and survival were calculated using Kaplan-Meier analysis. Markov decision analysis was used to calculate expected quality-adjusted life years (QALY) with intervention. Mean follow-up was 25 months (range 1-116). The results of our study show that infrainguinal bypass in patients with ESRD and tissue necrosis appears to provide a measurable, but marginal, degree of improvement in quality of life.

Quantitative real-time RT-PCR detection of breast cancer micrometastasis using a multigene marker panel.

Real-time RT-PCR is a relatively new technology that uses an online fluorescence detection system to determine gene expression levels. It has the potential to significantly improve detection of breast cancer metastasis by virtue of its exquisite sensitivity, high throughput capacity and quantitative readout system. To assess the utility of this technology in breast cancer staging, we determined the relative expression levels of 12 cancer-associated genes (mam, PIP, mamB, CEA, CK19, VEGF, erbB2, muc1, c-myc, p97, vim and Ki67) in 51 negative-control normal lymph nodes and in 17 histopathology-positive ALNs. We then performed a receiver operating characteristic (ROC) curve analysis to determine the sensitivity and specificity levels of each gene. Areas under the ROC curve indicated that the most accurate diagnostic markers were mam (99.6%), PIP (93.3%), CK19 (91.0%), mamB (87.9%), muc1 (81.5%) and CEA (79.4.0%). mam was overexpressed in 16 of 17 lymph nodes known to contain metastatic breast cancer at levels ranging from 22- to 2.8 x 10(5)-fold above normal mean expression, whereas PIP was overexpressed from 30- to 2.2 x 10(6)-fold above normal in 13 lymph nodes. Real-time RT-PCR analysis of pathology-negative LN from breast cancer patients revealed evidence of overexpression of PIP (6 nodes), mam (3 nodes) and CEA (1 node) in 8 of 21 nodes (38%). Our results provide evidence that mam, PIP, CK19, mamB, muc1 and CEA can be applied as a panel for detection of metastatic and occult micrometastatic disease.

Symptoms of chronic arterial insufficiency correlate with absolute ankle pressure better than with ankle: brachial index.

BACKGROUND: Doppler-based measurement of the ankle: brachial index (ABI) has long been regarded as the standard by which to objectively quantify the degree of lower extremity arterial occlusive disease, but this method fails to account for the contribution of systemic blood pressure to actual limb perfusion. We hypothesized that the absolute blood pressure would be a better predictor of the severity of symptoms of chronic occlusive disease than the ABI. EXPERIMENTAL DESIGN: retrospective comparative study. SETTING: university inpatient/outpatient vascular laboratory. PATIENTS: 1396 evaluable patients out of 2436 total consecutive patients referred with suspected lower extremity arterial occlusive disease. MEASURES: comparison of absolute ankle and digital pressures and ABI according to severity of symptoms of chronic lower extremity ischemia using three-way analysis of variance (ANOVA), likelihood ratios, and receiver operator characteristic (ROC) curves. RESULTS: The symptoms of tissue ulcer/gangrene, rest pain, and gangrene were characterized by differences in absolute pressures in the great toe (47 +/- 42 mmHg vs 55 +/- 40 mmHg vs 62 +/- 33 mmHg [mean +/- SD], F = 19.05, p < 0.001) and ankle (92 +/- 53 mmHg vs 98 +/- 44 mmHg vs 106 +/- 37 mmHg, F = 12.91, p < 0.001), but not by the ABI (0.71 +/- 0.33 vs 0.68 +/- 0.34 vs 0.71 +/- 0.28, F = 1.24, p > 0.05). ROC curves confirmed absolute digital pressure (area under curve [AUC] = 0.628) and absolute ankle pressure (AUC = 0.607) to be superior to ABI (AUC = 0.572). CONCLUSIONS: The severity of symptoms for peripheral vascular disease correlate better with absolute pressure measurement than with ABI.

Justification of intervention for limb-threatening ischemia: a surgical decision analysis.

Intervention for vascular occlusive disease of the distal lower extremity in elderly patients will inevitably be scrutinized as medical resources decline. The authors applied surgical decision analysis to three treatment options: revascularization, amputation and expectant management. The appropriate outcome probabilities were derived from our experience with revascularization to the tibial and pedal vessels, and utility scores were obtained by formalized patient assessment. Revascularization was predicted to improve patient outcome by 1.10 quality-adjusted life-years compared with primary amputation and by 1.16 quality-adjusted life-years compared with expectant management. To gain one additional quality-adjusted life-years, revascularization would cost $5280 more than expectant management, but $33,900 less than primary amputation. Sensitivity analysis predicted revascularization to be the least costly treatment per quality-adjusted life-years as long as 1-month patency exceeds 11%. Revascularization for limb-threatening ischemia of the distal lower extremity is justified and can be performed at a reasonable cost.

Diabetes mellitus is the major risk factor for African Americans who undergo peripheral bypass graft operation.

OBJECTIVE: African Americans, especially African American women, have a greater risk of lower extremity ischemia that necessitates an infrainguinal bypass graft operation and amputation. Because the prevalence of diabetes mellitus is proportionally greater in this ethnic/racial group, the relative contribution of diabetes was compared with other potential risk factors. METHODS: This study was designed as a retrospective case control study at the University and Veterans Hospitals. In a 5-year period, 764 consecutive patients who required infrainguinal revascularizations were compared with a statewide population that was described by the 1995 Behavior Risk Factor Surveillance System database. The main outcome measure was the requirement for infrainguinal revascularization. RESULTS: Diabetes mellitus was more common among African American women who underwent bypass graft operation (70%; odds ratio [OR], 24.9; 95% confidence interval [CI], 20.3 to 30.4) than African American men (46%; OR, 11.6; 95% CI, 8.9 to 15.2), white women (49%; OR, 15.9; 95% CI, 13.0 to 19.5), or white men (42%; OR, 14.8; 95% CI, 12.5 to 17.4). Overall, bypass graft operation was associated more strongly with diabetes mellitus for all groups (OR, 15.7; 95% CI, 13.5 to 18. 3) than with smoking (OR, 4.5; 95% CI, 3.8 to 5.2) or hypertension (OR, 4.6; 95% CI, 4.0 to 5.3). Life-table analysis revealed limb salvage to be worse at 3 years among African American patients (64% vs 75%; P <.005) despite similar primary and cumulative secondary graft patency rates. CONCLUSION: Diabetes mellitus is the dominant risk factor that contributes to the need for bypass graft operation, especially among African American women. A greater prevalence of diabetes mellitus may account for the higher incidence of tissue necrosis and the increased requirement for distal bypass grafting and may contribute to the reduction in long-term limb salvage that was observed with these women.

Magnetic resonance imaging differentiates between necrotizing and non-necrotizing fasciitis of the lower extremity.

BACKGROUND: Distinction between uncomplicated infective fasciitis and early necrotizing fasciitis can be extremely difficult without operation, yet the management and prognosis of both conditions depend greatly on early recognition and assessment of the extent of involvement. STUDY DESIGN: This was a prospective review of the utility of magnetic resonance imaging (MRI) in nine patients with suspected infective or necrotizing fasciitis treated at an academic medical center or a Veterans Administration hospital. RESULTS: Magnetic resonance imaging documented fascial inflammation, characterized by low intensity on T1-weighted images and high intensity on T2-weighted images, in all nine patients. Absence of gadolinium contrast enhancement on T1-weighted images reliably detected fascial necrosis in all six patients who required operative debridement. Magnetic resonance imaging was extremely useful in defining the extent of fasciitis and was more accurate in predicting necrosis or pyomyositis than was myoglobinuria or elevation of serum creatine kinase or lactate dehydrogenase. Operation was avoided in two patients without evidence of necrosis on MRI. One patient without evidence of necrosis, explored because of contradictory clinical findings, was confirmed at operation to have cellulitis without necrosis. CONCLUSIONS: Magnetic resonance imaging with gadolinium contrast accurately determines the presence of necrosis and the need for operation in patients with fasciitis of the lower extremity. Preoperative determination of the extent of involvement facilitates operative planning.

Occlusive disease associated with popliteal aneurysms: impact on long term graft patency.

OBJECTIVE: Correlate graft patency and limb salvage outcomes following popliteal aneurysm repair with the extent of tibial occlusive disease. EXPERIMENTAL DESIGN: Retrospective study with a mean follow-up of 36 months (range, 2-96 months). SETTING: Institutional teaching hospital. PATIENTS: Of 20 popliteal aneurysms among 16 patients undergoing repair, 75% were associated with preoperative tibial vessel occlusion. Normal, three vessel infrapopliteal runoff was present in 5 patients, two vessels in 7 patients, and one or no vessels in 8 patients. Fifty percent of limbs were asymptomatic, while the remainder suffered from a variety of ischemic symptoms. INTERVENTIONS: Eighteen of the 20 aneurysms were repaired with femoropopliteal bypass grafts, and two femoral-tibial bypasses were performed. Autogenous saphenous vein was used in 18 cases (10 in situ, 8 reversed) and PTFE in two short segment femoral-popliteal bypasses. MEASURES: Graft patency was determined by presence of a palpable pulse, the re-establishment of normal ankle-brachial indices, or duplex scanning. Patency and limb salvage rates were estimated using life table analysis by the Kaplan-Meier method. RESULTS: Preoperative symptoms did not correlate with tibial runoff, except in two patients presenting with acute thrombosis and ischemia. Cumulative graft patency by life table analysis was not different for either good (2-3 vessels, N-12) or poor (0-1 vessels, N-8) runoff. Overall primary patency at 60 months was 73%, and cumulative secondary patency was 100% with no limbs lost at 60 months. CONCLUSIONS: Concomitant distal arterial occlusive disease is frequently associated with popliteal aneurysms, yet did not appear to substantially impact either long-term graft patency or limb salvage.

Iliac and femoral artery occlusion by thromboemboli from an abdominal aortic aneurysm in the setting of blunt abdominal trauma.

The abdominal aorta is injured infrequently in blunt trauma to the abdomen. When injury does occur, aortic rupture, dissection, and traumatic aneurysm most commonly result. An aneurysmal abdominal aorta would appear to be at increased risk for injury from blunt abdominal trauma. This case report appears to be the first description of iliac and femoral artery occlusion by thromboemboli dislodged from an atherosclerotic abdominal aortic aneurysm at the time of a motor vehicle accident. We believe that this peripheral embolization was caused by direct compression of the abdominal aortic aneurysm by a seatbelt.

Preoperative thromboxane A2/prostaglandin H2 receptor activity predicts early graft thrombosis.

PURPOSE: This study was carried out to determine whether early failure of infrainguinal bypass grafts is associated with increased expression of platelet thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptors. A prospective correlation of preoperative platelet TXA2/PGH2 receptor-mediated activity with lower extremity graft patency was sought. METHODS: Twenty-five patients who underwent infrainguinal bypass surgery for limb salvage were studied at an inpatient academic tertiary referral center and Department of Veterans Affairs Medical Center. Outcome measures were primary graft patency rate at 3 months, platelet TXA2/PGH2 receptor activity by equilibrium binding with 125I-BOP, and aggregation to the TXA2-mimetic U46619. RESULTS: Preoperative platelet TXA2/PGH2 receptor density was higher (Bmax, 3100 +/- 1300 vs 1500 +/- 1100 sites/platelet [mean +/- SD]; p = 0.004) in the five patients who had graft thrombosis within 3 months. The EC50 for U46619 was lower (26 +/- 6 nmol/L vs 57 +/- 30 nmol/L; p < 0.05) in these patients as well, confirming the functional effect of the increased receptor density. Early graft thrombosis was more likely in patients with a platelet TXA2/PGH2 receptor density greater than 3000 sites/platelet (odds ratio, 76; 95% confidence interval, 3.9 to 1500) or an EC50 for U46619 less than 30 nmol/L (odds ratio, 16; 95% confidence interval, 1.4 to 180). CONCLUSIONS: Elevated platelet TXA2/PGH2 receptor levels and enhanced sensitivity of platelet aggregation to TXA2 predict early arterial graft thrombosis. Specific TXA2/PGH2 receptor antagonism may prevent one of the mechanisms that contributes to early graft occlusion.

Abdominal aortic aneurysm treatment: preliminary results with the Talent stent-graft system.

PURPOSE: To evaluate the treatment of abdominal aortic aneurysm (AAA) with use of the endoluminal Talent stent-graft (TSG). PATIENTS AND METHODS: In 10 men, AAA treatment was attempted with use of the TSG. All patients presented significant surgical risk, with chronic obstructive pulmonary disease and coronary arteriopathy. The mean age was 65.5 years (range, 57-82 years). The mean proximal neck diameter was 25.8 mm (range, 21.6-34 mm). Five of the TSGs were straight tubes and five were bifurcated systems. The main body of the TSG is made of a polyester graft material mounted on a self-expandable nitinol frame. The bifurcated system uses polytetrafluoroethylene (PTFE) material for the legs and extensions mounted on a self-expandable nitinol frame. The bifurcated grafts used a 22 to 27-F introducer and the extensions, a 18-F introducer through a surgical cutdown technique. RESULTS: The TSG system was successfully implanted in nine patients and failed in one because of dislodgment after deployment, which required conversion to surgery. Four leaks occurred initially. One was sealed off with balloon dilation at the end of the procedure, one leak was treated with an additional extension, another leak disappeared spontaneously in 30 days, and the other leak required embolization 4 weeks after discharge. Seven patients were discharged on the third day after the procedure, and two patients were discharged at 1 and 2 weeks, respectively. Blood transfusion was necessary in three patients because of hematoma at the incision site in two patients, which required surgical revision for hemostasis, and because of transoperative bleeding in one patient. Follow-up time ranged from 2 to 15 months. The only death occurred 5 days postoperatively as a consequence of ischemic colitis and multisystem organ failure in the only patient who required surgery. CONCLUSION: Treatment of AAA with the TSG system is effective for aneurysm exclusion. This device seems to provide a good alternative to surgery in patients who are otherwise considered to be at high risk for complications after direct surgical repair, but it is not without risk of complications.

Outcome after laparoscopic cholecystectomy for chronic acalculous cholecystitis.

Patients with typical symptoms of biliary tract disease but no gallstones on ultrasonography may benefit from cholecystectomy for presumed chronic acalculous cholecystitis. We retrospectively analyzed the outcome of 50 patients with a preoperative diagnosis of chronic acalculous cholecystitis based upon history (chronic or recurrent, postprandial right upper quadrant abdominal pain), the absence of acid-peptic disease, and normal biliary sonography treated with laparoscopic cholecystectomy (LC) and transcholecystic cholangiography from 1991 to 1996. All patients had preoperative cholecystokinin-stimulated hepatobiliary scintigraphy (CCK-HBS). There were 42 women and 8 men with a mean age of 43 years. CCK-HBS was abnormal in 45 patients (< or = 35 per cent gallbladder ejection fraction or nonfilling of the gallbladder). There was no postoperative mortality and one morbidity (urinary retention). All patients had microscopic evidence of chronic cholecystitis. At mean follow-up of 30 months, (range, 7-62 months) 39 patients (78%) were free of abdominal pain. Thirty-five of 45 patients with abnormal CCK-HBS were pain free (positive predictive value, 0.78). Four of five patients with normal CCK-HBS were pain free (negative predictive value, 0.20). The positive and negative likelihood ratios for CCK-HBS were 0.99 and 1.13, respectively, confirming that this test was not useful for predicting benefit from LC. Seven patients with persistent right upper quadrant pain had abnormal postoperative sphincter of Oddi manometry; they improved after endoscopic sphincterotomy. Patients with symptoms typical of biliary colic with normal gallbladder sonography and absence of acid-peptic disease benefit from LC in the majority of cases. Those who remain symptomatic after LC may benefit from endoscopic retrograde cholangiopancreatography with sphincter of Oddi manometry and endoscopic sphincterotomy when manometry is abnormal.

Relevance of quality improvement methods to surgical practice: prospective assessment of carotid endarterectomy.

Continuous quality improvement methods are increasingly being applied to health care systems, yet demonstration of outcome and cost benefits for surgical patients remains sparse. We used continuous quality improvement principles to specifically identify potential opportunities to reduce patient charges for carotid endarterectomy in our academic vascular surgery practice without compromising results. The targeted opportunities included: 1) limitation of laboratory examination, 2) selective cardiac stress testing, 3) discharge on 1st postoperative day, and 4) substitution of outpatient carotid duplex imaging for inpatient angiography. After 1 year, reductions in the average patient charge ($7700 versus $13,900, P < 0.001) and increases in payment/charge ratio (1.2 versus 0.8; P < 0.001) were observed. These changes were primarily due to a reduction in length of stay (2.2 versus 5.7 days; P < 0.001). No significant difference in patient morbidity occurred. Reductions in charges occurred within the targeted areas of laboratory (-77%), cardiac testing (-73%), hospital room (-60%), and radiology (-81%) utilization. Attention to the four factors identified by continuous quality improvement methods significantly reduced total patient charges without detrimental effects on patient outcome.

Racial differences in operation for peripheral vascular disease: results of a population-based study.

Operation for non-coronary atherosclerotic peripheral vascular occlusive disease may vary among race and gender groups. Using a state-wide registry, the authors identified all operations performed for infrarenal peripheral vascular disease over a 12-month period in a single south-eastern state. Procedures performed included reconstruction for aortoiliac (n=641) and infrainguinal (n=1129) disease and major amputation (n=1077). The incidence for patients over age 50 was calculated using census data. Operation for aortoiliac disease was significantly more likely for white patients (relative risk 3.79, 95% C.I. 2.84-5.15), but less likely for infrainguinal peripheral vascular disease (relative risk 0.64, 95% C.I. 0.56-0.73) and amputation (relative risk 0.17, 95% C.I. 0.15-0.19). Trends toward lower operative mortality in blacks with aortoiliac disease (10.6% versus 12.0%), PVD (3.2% versus 3.5%), and amputation (5.5 versus 8.7%) failed to attain statistical significance. Patient race was associated with the type and location of operation performed for peripheral vascular disease.

Thromboxane A2 receptor density increases during chronic exposure to thromboxane A2 receptor antagonists after porcine carotid bypass.

Domestic swine (n=12 in each group) were randomized to daily treatment with the thromboxane A2 (TXA2) receptor antagonist BMS-180291 (group I), aspirin (group II), or no drug (group III) prior to prosthetic carotid graft implantation. Platelet and arterial wall receptor density were measured by equilibrium binding using 125I-BOP. At 6 weeks, means (s.e.m.) platelet receptor density (pmol/mg) had increased in groups I (3.3(0.6) versus 1.8(0.3); P<0.05) and II (2.6(0.6) versus 1.7(0.2); P<0.05), but not in group III (1.3(0.3) versus 1.2(0.2)). Aortic membrane TXA2 receptor density (fmol/mg) was significantly greater (P<0.05) in groups I (150(50)) and II (68(10)) compared with group III (39(6)). Chronic exposure to a TXA2 receptor antagonist or aspirin is associated with increased platelet and aortic receptor density in pigs.