Evaluation of a novel electrosurgical sealing mode in an ex vivo and in vivo porcine model.

BACKGROUND: Bipolar vessel sealing has been successfully introduced in a variety of procedures like prostatectomy, hysterectomy, and nephrectomy. In this study, we evaluated a new sealing mode-the thermoSEAL® mode (TSM)-operated with the VIO3 generator in an ex vivo and in vivo animal study and compared the results with the commercially available BiClamp mode (BCM), operated with the VIO300D generator. Two different instruments were used in combination with both modes, BiCision® and BiClamp® 201T (Erbe Elektromedizin GmbH). METHODS: In the ex vivo experiment, the sealing of renal arteries was evaluated using both instruments and modes. For the in vivo study, different types of arteries and veins were sealed using both modes and instruments in a side-by-side comparison for acute complications in a total of four animals. RESULTS: Mean burst pressure was in all cases significantly above 360 mmHg (p < 0.001). Sealing time during the ex vivo setting was significantly shorter for TSM compared to BCM: BiCision® (3.7 ± 0.4 vs. 7.1 ± 0.3 s; p < 0.0001); BiClamp® 201T (3.9 ± 0.3 vs. 5.1 ± 1.1 s; p < 0.0015). Lateral thermal damage was more pronounced for BCM: BiCision® (TSM 1.4 ± 0.3 mm vs. BCM 1.9 ± 0.2 mm; p < 0.0001); BiClamp® 201T (TSM 1.9 ± 0.6 mm vs. BCM 3.1 ± 0.6 mm; p < 0.0001). The sealing time during the in vivo study was significantly shorter for TSM in combination with BiCision® for arteries [TSM 3.0 ± 0.7 s vs. BCM 6.5 ± 1.3 s, (p < 0.0001) and veins 3.2 ± 1.1 vs. 5.8 ± 1.8 s, (p < 0.0001)]. No significant differences were seen for the two modes used with BiClamp® 201T [artery: TSM 3.3 ± 0.7 s vs. BCM 3.4 ± 0.9 s, (p = 0.891)]. High sealing rates for arteries (100%) and veins (>90%) were noted for both instruments and modes. CONCLUSIONS: While both modes used with two different instruments reveal high safety characterized by a high burst pressure, low thermal damage (ex vivo) zones, and high sealing rates (in vivo), the thermoSEAL® mode convinces by its fast sealing speed probably helping to reduce operation time.

Finite-element-modeling of egg white as a substitute for tissue coagulation during bipolar radiofrequency-induced thermofusion.

Radiofrequency-induced thermofusion is a frequently used electrosurgical procedure for the sealing of blood vessels. A disadvantage of vessel sealing instruments is that the generated thermal energy spreads to the surrounding tissue and may irreversibly damage it. This is particularly problematic when operating close to sensitive structures such as nerves. Given their advantages, there is nonetheless a lot of interest in using bipolar vessel sealing for surgical procedures. To select instruments that may be safely used in such cases, it is important to reliably quantify the thermal spread to the surrounding tissue. Mathematical models can help to evaluate the transient behavior, that is the evolution of the thermal spread over time, more precisely. A finite element model allows for a detailed analysis of inhomogeneities in the spatial temperature distribution. As a first step towards a finite model of the bipolar vessel sealing process, a model of the coagulation of chicken egg white is presented here. Egg white has thermal and electrical properties that are very similar to tissue, making it suitable as a substitute for the analysis of the coagulation process. It has the additional advantage, that the spatial and temporal evolution of the thermal spread can be visually gauged. The presented model describes the experimentally observed spatial temperature distribution, the shape of the coagulated egg white, and the formation of hotspots. Furthermore, it is shown that the model can correctly predict the shape of the coagulated egg white in further experiments.

A mathematical model of bipolar radiofrequency-induced thermofusion.

Bipolar radiofrequency-induced thermofusion has become a widely accepted method successfully used in open and particularly in minimally-invasive surgery for the sealing of blood vessels and tissue of up to several millimeters diameter. Despite its wide-spread application, the thermofusion process itself is not well understood on a quantitative and dynamic level, and manufacturers largely rely on trial-and-error methods to improve existing instruments. To predict the effect of alternative generator control strategies and to allow for a more systematic approach to improve thermofusion instruments, a mathematical model of the thermofusion process is developed. The system equations describe the spatial and temporal evolution of the tissue temperature due to Joule heating and heat transfer, and the loss of tissue water due to vaporization. The resulting effects on the tissue properties, most importantly the electrical resistivity, heat capacity and thermal conductivity, are considered as well. Experimental results indicate that the extent of the lateral thermal damage is directly affected by Joule heating of the lateral tissue. The experimental findings are supported by simulation results using the proposed mathematical model of thermofusion.

Experimental investigation of the magnetic configuration dependence of turbulent transport.

The dependence of turbulent transport on magnetic field properties is measured in detail on a plasma in a stellarator configuration. Pronounced poloidal asymmetries of fluctuation amplitudes and turbulent transport are observed. The transport maximum is located in regions where normal curvature of the magnetic field is negative and simultaneously the geodesic curvature has positive values. A major role of the local magnetic shear cannot be confirmed. The results can have important implications for the optimization of stellarators and the power influx into the scrape-off layer.

Generation of intermittent turbulent events at the transition from closed to open field lines in a toroidal plasma.

Turbulent transport at the transition from closed to open field lines has been investigated in the stellarator experiment TJ-K. It is found that drift-wave turbulence in the confined region is responsible for the generation of intermittent structures (so-called blobs) in the unconfined region. There the character of turbulence changes and a decoupling of density and potential fluctuations is observed. The poloidal propagation of the intermittent events can be understood in the framework of background flows caused by gradients in the equilibrium plasma pressure and potential profiles.

Relevance of allergens from cats and dogs to asthma in the northernmost province of Sweden: schools as a major site of exposure.

BACKGROUND: The prevalence of asthma in the northernmost region of Sweden has been estimated at 6% to 8% in spite of the very dry climate. The causes of the increase in asthma are not clear, but conditions are unfavorable for dust mite growth, and domestic animals are thought to be the primary source of indoor allergens. OBJECTIVES: We sought to investigate the relationship between asthma, exposure, and sensitization in Northern Sweden, with a focus on the role of schools. METHODS: Serum was collected from 110 asthmatic children, 55 children with symptoms of asthma but no established diagnosis, and 63 control children (age, 7 and 8 years). Total IgE and specific IgE to 7 allergens were measured. Dust samples were collected from the classrooms of 7- and 8-year-old children in 22 schools from Kiruna and Luleâ, Sweden. For comparison, dust was also collected from 24 homes in Kiruna and 2 schools in Virginia in the United States. RESULTS: Serum IgE antibody assays on 165 children with respiratory symptoms confirmed that there was a high degree of sensitization to cat, dog, and birch in Northern Sweden. Cat and dog allergens were present in almost all of the school samples in Sweden. By contrast, dust mite and cockroach allergens were generally unmeasurable. The highest levels of cat and dog allergens were found in samples from desks and chairs. Cat and dog allergen levels in the schools were comparable with but higher than those in the homes without pets. The schools in Virginia had similar allergen levels, except that samples from this humid region also had significant mite allergen. CONCLUSIONS: In this climate the primary sensitization associated with asthma is to cat dander and dog dander but also to birch pollen. Mite and cockroach allergens were not present in the dust samples, and sensitization to these allergens was not significant. The schools appear to be a major site of exposure to cat and dog allergens. These results are relevant both to an understanding of the reasons for the increase in asthma in this region and to any proposal to reduce exposure to allergens.

Infectious hepatitis in California; a community-wide epidemic.

In an epidemic of infectious hepatitis in a rural California community during 1961, 514 cases were reported among 8,166 residents. A sample of the 396 cases reported up to 1 September was studied, and only about a third of these cases could be confirmed in retrospect. A community survey indicated that the attack rate for the first eight and a half months of 1961 was slightly over 3 per cent. Unusual epidemiologic features of what was thought to be a contact epidemic included a summer peak, a preponderance of young and middle-aged adults, a relative sparing of lower socioeconomic groups and mildness of the illness with jaundice appearing in a minority of cases. Secondary cases were rarely observed within the expected 10- to 50-day incubation period.