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F Haas

Publications and source records attributed to F Haas.

At least 37 records · Page 2Linked to original sources
PubMed2000

Multistream model for quantum plasmas

The dynamics of a quantum plasma can be described self-consistently by the nonlinear Schrodinger-Poisson system. We consider a multistream model representing a statistical mixture of N pure states, each described by a wave function. The one-stream and two-stream cases are investigated. We derive the dispersion relation for the two-stream instability and show that a new, purely quantum, branch appears. Numerical simulations of the complete Schrodinger-Poisson system confirm the linear analysis, and provide further results in the strongly nonlinear regime. The stationary states of the Schrodinger-Poisson system are also investigated. These can be viewed as the quantum mechanical counterpart of the classical Bernstein-Greene-Kruskal modes, and are described by a set of coupled nonlinear differential equations for the electrostatic potential and the stream amplitudes.

Journal Article↗
PubMed1999

[Iatrogenic necrosis of the large toe after tourniquet placement--clinical course and reconstruction].

We present a necrosis of the big toe in a 20-year-old woman with an ingrowing toenail after wedge-shaped excision in the big toe. The reason for the necrosis was a tourniquet that was left in place after the operation. The ischemia, which lasted for 2 days, resulted in subtotal necrosis of the big toe. Six weeks after the operation the patient underwent microsurgical reconstruction. This is a report on the treatment of this complication from the beginning. Early surgical intervention is advocated.

Adult↗
PubMed1999

Long-term survival and functional follow-up in patients after the arterial switch operation.

BACKGROUND: For many years, the arterial switch operation (ASO) has been the therapy of choice for patients with transposition of the great arteries (TGA). Although excellent short- and mid-term results were reported, long-term results are rare. METHODS: Between May 1983 and September 1997, ASO was performed on 285 patients with simple TGA (n = 171), TGA with ventricular septal defect (VSD) (n = 85), and Taussig-Bing (TB) anomaly (n = 29). This retrospective study describes long-term morbidity and mortality over a 15-year period. RESULTS: Hospital mortality was 3.5% for simple TGA, 9.4% for TGA with VSD, and 13.8% for TB anomaly. Late death occured in 2 patients, 1 with simple TGA and 1 with TGA and VSD. The cumulative survival for all patients at 5 and 10 years is 93%, and at 15 years is 86%. Reoperations were required in 31 patients and were most common for stenosis of the right ventricular outflow tract (RVOT). However, no correlation was found between technical variations on pulmonary artery reconstruction and this type of complication. Forty-six patients underwent follow-up angiography, which revealed five cases with coronary occlusion or stenosis. Follow-up is complete in 96% of the patients from 1 to 15.2 years. Sinus rhythm is present in 97%; 88% of the patients show no limitations on exertion. CONCLUSIONS: The ASO can be performed with low early mortality, almost absent late mortality, and infrequent need for reoperation. The favorable long-term results demonstrate that the ASO can be considered as the optimal approach for patients with TGA and special forms of double-outlet right ventricle.

Cause of Death↗
PubMed1999

[The lower trapezius muscle island flap. Anatomic principles and clinical relevance].

Up to now, there is no uniform anatomic description neither of the branches of the subclavian artery nor of the pedicle of the lower myocutaneous trapezius flap. A dissection study was carried out on 140 necks in 70 cadavers. Variations of the subclavian artery and its branches, vessel diameter at different levels, the course of the pedicle under the levator scapulae muscle, the arc of rotation of the island flap, and the variations of the segmental intercostal branches to the lower part of the trapezius muscle were examined. Results of this study enable us to suggest a new nomenclature for the branches of the subclavian artery, a proper pedicle definition, and a technique for safe flap elevation. The lower trapezius island flap is a thin and pliable myocutaneous flap with a constant pedicle which ensures safe flap elevation. This flap has the potential for a wider acceptance due to minor donor site morbidity, large arc of rotation, and an ample range of clinical applications in the head and neck area as an island flap as well as a free flap.

Angiography↗
PubMed1999

99mTc-tetrofosmin SPECT for prediction of functional recovery defined by MRI in patients with severe left ventricular dysfunction: additional value of gated SPECT.

UNLABELLED: This study was designed to evaluate gated 99mTc-tetrofosmin SPECT for prediction of functional recovery proven by sequential MRI. 99mTc-labeled tetrofosmin is a recently introduced tracer for myocardial perfusion. However, its role for viability assessment is still under investigation. METHODS: 99mTc-tetrofosmin uptake in 19 patients with coronary artery disease and severe left ventricular dysfunction was correlated to regional wall thickening before and 4.5 +/- 0.8 mo after successful coronary artery bypass grafting, as derived from corresponding gated short-axis MRI. Preoperative wall thickening determined by gated SPECT was used as an additional parameter for prediction of functional outcome. Optimal threshold cutoffs to separate reversible from irreversible dysfunction were determined by receiver operator characteristic (ROC) analysis. RESULTS: The sensitivity and specificity of regional 99mTc-tetrofosmin for prediction of functional recovery was 87% and 42%, respectively (cutoff: 50% of maximum tracer retention). The area under ROC curves for prediction of functional recovery measured 0.66 +/- 0.01. Segments with > or =50% uptake and impaired but detectable wall thickening determined by gated SPECT had a significantly higher likelihood for functional improvement compared with segments with absent wall thickening (P < 0.05). There was no difference in segments with <50% tracer retention. There was good agreement for ejection fraction measurements by MRI and gated SPECT (mean ejection fraction 32 +/- 12 versus 34 +/- 11; r = 0.71, P < 0.001). CONCLUSION: Regional 99mTc-tetrofosmin uptake provided high sensitivity but limited specificity for prediction of functional recovery after revascularization, leading to fair overall accuracy. Wall thickening assessment derived from gated SPECT may improve the specificity of 99mTc-tetrofosmin uptake for prediction of functional recovery but not the sensitivity in low-flow areas. In addition to the assessment of global function, gated data acquisition can be helpful to improve the overall accuracy of 99mTc-tetrofosmin SPECT for prediction of functional recovery after bypass surgery.

Coronary Artery Bypass↗
PubMed1998

Regional myocardial wall thickening and global ejection fraction in patients with low angiographic left ventricular ejection fraction assessed by visual and quantitative resting ECG-gated 99mTc-tetrofosmin single-photon emission tomography and magnetic resonance imaging.

We investigated the use of visual and quantitative technetium 99m tetrofosmin ECG-gated single-photon emission tomography (SPET) for the assessment of regional myocardial wall thickening (WT) and left ventricular (LV) ejection fraction (EF) in comparison with gated magnetic resonance imaging (MRI) in patients with a low angiographic LVEF. Gated SPET using 99mTc-labelled flow tracers offers potential for simultaneous assessment of myocardial perfusion and LV function. Few data are available on the use of visual and quantitative gated SPET in patients with low LVEF. In this study 21 patients with low angiographic LVEF (mean 37%+/-5%) were studied. Resting gated 99mTc-tetrofosmin SPET and gated MRI were performed within 48 h. WT was assessed by visual interpretation (five point score) and quantitative analysis based on count increase. There was good agreement for EF measurements by MRI and gated SPET (mean EF: 33%+/-12% vs 35%+/-11%, r = 0.86, P<0.001). Areas under receiver operator characteristic curves (AUC) for differentiation between MRI WT score points ranged from 0.60 to 0.66 for visual SPET WT analysis, from 0.59 to 0.71 for delta count increase values and from 0.46 to 0.60 for % WT, indicating substantial overlap between WT categories. Absolute agreement for visual WT between MRI and gated SPET ranged from 25% to 57% (kappa 0.03-0.25) depending on tracer uptake, and was limited in areas with moderate to severe perfusion defects (kappa 0.03-0.13). It is concluded that gated SPET provided reliable estimates of regional WT and global function in patients with low angiographic LVEF.

Coronary Angiography↗
PubMed1998

Venous thrombosis in a replanted finger with underlying factor V Leiden mutation.

Resistance to activated protein C (APC resistance) was described recently as a cause for thrombophilia. APC inactivates coagulation co-factors Va and VIIIa. A single base-pair mutation changing Arg506 to Gln at the APC cleavage site of the factor V gene leads to a factor V Leiden variant, which is the most frequent cause of APC resistance. Recently, its role in peripheral venous thrombosis during pregnancy was described. We here report a case with thrombosis of the venous anastomoses after finger replantation with resistance to activated protein C associated with factor V Leiden mutation.

Adult↗
PubMed1998

[The posterior interosseous flap--review and personal experience].

The posterior interosseous flap was first introduced by Zancolli and Angrigiani (1985) and short time later by Penteado and Masquelet (1986). The flap is used for soft tissue reconstruction in the hand but has not gained wide acceptance due to tedious pedicle dissection and venous problems. In 1993, Angrigiani et al. published a simplified modification in the elevation of the flap. They included a constant fasciocutaneous perforating vessel in the flap to enhance the viability. We applied the modified elevation technique in twelve patients. Our experience, indications, and complications will be discussed. In contrast to Angrigiani's statement, our flaps still show a temporary mild to moderate venous congestion similar to the flaps raised in the original technique.

Aged↗
PubMed1997

Increased sarcolemmal glucose transporter abundance in myocardial ischemia.

Many clinical and laboratory studies suggest that an increase in glucose uptake and metabolism by ischemic myocardium helps protect myocardial cells from irreversible injury. We have examined whether increased sarcolemmal abundance of cardiomyocyte glucose transporters plays a role in this adaptive response. We have shown that acute myocardial ischemia in perfused rat hearts results in increased sarcolemmal abundance of the major glucose transporter, GLUT4, by causing translocation of GLUT4 molecules from an intracellular compartment to the sarcolemma. In nonischemic control hearts only 18 +/- 2.8% of GLUT4 molecules were on the sarcolemma whereas in ischemic hearts this increased to 41 +/- 9.3%. Insulin also caused translocation of GLUT4 molecules to the sarcolemma, and resulted in 61 +/- 2.6% of GLUT4 molecules on the sarcolemma. The combination of ischemia and insulin did not result in additive increases in sarcolemmal GLUT4 abundance. In more persistent or chronic ischemia, the other major myocardial glucose transporter, GLUT1, appears to play an important role. The mRNA for this transporter, which is constitutively expressed on cardiomyocyte sarcolemma, was increased 2.0-fold in regions of hibernating myocardium in humans with coronary heart disease as well as in persistently hypoxic rat neonatal cardiomyocytes in primary culture. In neither of these conditions was GLUT4 mRNA expression increased. Thus, acute myocardial ischemia increases sarcolemmal glucose transporter abundance mainly by translocating previously synthesized GLUT4 molecules from an intracellular compartment, whereas more chronic ischemia also increases GLUT1 abundance via enhanced mRNA expression. Increased GLUT1 and GLUT4 abundance may participate in the augmented glucose uptake of ischemic myocardium and therefore may help protect ischemic myocardium from irreversible injury.

Animals↗
PubMed1997

Preoperative positron emission tomographic viability assessment and perioperative and postoperative risk in patients with advanced ischemic heart disease.

OBJECTIVES: This study sought to investigate whether determination of tissue viability by means of positron emission tomography (PET) before coronary artery bypass graft surgery (CABG) affects clinical outcome with respect to both in-hospital mortality and 1-year survival rate. BACKGROUND: Patients with coronary artery disease (CAD) and severe left ventricular (LV) dysfunction are at higher risk for perioperative complications associated with CABG. Therefore, the selection of patients who will benefit from CABG is an important clinical issue. METHODS: This study retrospectively evaluated 76 patients with advanced CAD and LV dysfunction (LV ejection fraction < or = 0.35) who were considered candidates for CABG. Thirty-five patients were selected for CABG on the basis of clinical presentation and angiographic data (group A), and 34 of 41 patients were selected according to extent of viable tissue determined by PET (group B) in addition to clinical presentation and angiographic data. RESULTS: There were four in-hospital deaths (11.4%) in group A and none in group B (p = 0.04). After 12 months, the survival rate was 79% in group A and 97% in group B (p = 0.01). Postoperatively, group B patients had a less complicated recovery (p = 0.05). They required lower doses of catecholamines (p = 0.002) and demonstrated a significantly decreased incidence of low output syndrome (p = 0.05). CONCLUSIONS: This retrospective data analysis suggests that selection of patients with impaired LV function on the basis of extent of viability supplementary to clinical and angiographic data may lead to postoperative recovery with a low early mortality and promising short-term survival. Therefore, viability studies permit selection of patients who are at low risk for serious perioperative complications.

Ammonia↗
PubMed1996

Anatomic basis of the lower trapezius musculocutaneous flap.

Differences in the description of the blood supply of the lower trapezius m. and the fact that all former findings are based on very few cases caused us to reinvestigate the arterial supply of the lower trapezius m. Based on the anatomic investigation of 70 human cadavers, the trapezial branch of the dorsal scapular a. was found to be the constant vessel to the lower trapezius m. The origin of the dorsal scapular a., however, was found to be very variable. In 45% it was a direct branch of either the subclavian a. or the costocervical trunk. In the remaining 55% the dorsal scapular a. formed different trunks with the superficial cervical a. and/or suprascapular a. branching off either the subclavian a., the thyrocervical trunk, or the internal thoracic a. Additional segmental musculocutaneous perforators also supply the lower part of the trapezius m. and the overlying skin. Consequently, the lower or ascending part of the trapezius m. has a vascular pattern type V. Thus, the lower trapezius musculocutaneous flap merits consideration in head and neck reconstruction.

Back↗
PubMed1996

Mechanical unweighting effects on treadmill exercise and pain in elderly people with osteoarthritis of the knee.

BACKGROUND AND PURPOSE: People with osteoarthritis (OA) of the knee who have pain generally exhibit decreased activity and physical deconditioning. This study investigated the effects of mechanical unweighting on knee pain and exercise responses in people with OA of the knee who have pain. SUBJECTS: Four men and 23 women, with a mean age of 67.9 years (SD = 11.3, range = 50-88) and having a 12-year average duration of knee OA, participated. METHODS: A mechanical unloading device enabled subjects to perform a modified Naughton treadmill exercise test at 0%, 20%, and 40% of body weight support (BWS). Oxygen consumption (VO2), heart rate (HR), and perceived pain were measured during the last minute of each exercise stage. RESULTS: Mechanical unweighting at 20% and 40% BWS decreased the Vo2 and HR responses to treadmill exercise but did not decrease knee pain during walking in this sample. CONCLUSION AND DISCUSSION: These findings indicate that treadmill exercise accompanied by BWS permits recommended training intensities to be obtained in elderly people with OA, but may not provide pain relief in this group.

Aged↗
PubMed1995

Methicillin-resistant Staphylococcus haemolyticus on the hands of health care workers: a route of transmission or a source?

We undertook a cross-sectional study of hand carriage and environmental contamination of methicillin-resistant coagulase-negative staphylococci on three wards of a single subspeciality surgical service. Sixteen hand cultures from 15 health care workers and 32 environmental cultures were obtained. Of 49 isolates, 35 (72%) were Staphylococcus haemolyticus. This species comprised 14 of the 16 (87%) hand isolates and 21 of the 32 (66%) environmental isolates. Using restriction length polymorphism of total DNA, we identified a single clone of S. haemolyticus on the hands of four health care workers and in the environment at seven locations on two wards. The widespread dissemination of a single clone suggests transmission of S. haemolyticus on the wards and prompts further prospective studies.

Carrier State↗