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C Grosse-Siestrup

Publications and source records attributed to C Grosse-Siestrup.

At least 19 recordsLinked to original sources
PubMed2006

Thermography as potential real-time technique to assess changes in flow distribution in hemofiltration.

Flow distributions are critical determinants in the function of hemofilters. Despite their importance, however, flow distributions cannot currently be measured in filters during experimental or clinical applications. Here, we demonstrate that the thermal conduction properties of extracorporeal circuits may provide a tool to overcome this limitation. More specifically, we show that thermography provides an indirect approach to visualize differences in regional perfusion rates through temperature profiles on the filter surface. Thermograms were recorded using a TVS700 system (Ca. Goratec) during recirculating in vitro hemofiltration of porcine blood. Different test protocols were executed to characterize the contribution of thermal conduction and convection to the measurable changes in the temperature at the surface of the filter housing. For comparison and validation, these experiments were supplemented by computer tomography (CT) of filters after dye injection. Thermography enabled real-time visualization of the flow distributions in a hemofilter. Moreover, 'point' trends taken from different regions of the filter provided quantitative information about changes of flow distributions in response to changing experimental conditions. Our preliminary data suggest that thermography is a promising new approach for assessing the principles and time-related changes in flow distributions in hemofiltration. As expected, resolution is lower than that in CT measurements and further studies will be necessary to determine the smallest temperature gradient that still identifies differences in regional perfusion rates. Given its potential to develop into an inexpensive tool for the 'bedside' level monitoring of flow distributions during clinical studies, further investigation of thermography is highly desirable.

Animals↗
PubMed2004

Influence of differences in body weight and volume management on experimental results in porcine models.

BACKGROUND: In contrast to humans, young pigs naturally have a low COPpl (12-16 mmHg versus 22-26 mmHg in young humans). Thus, behavior occurring when volume management is performed similar to human medicine might be different. Potentially underestimated intra- to extravascular fluid and solute shifts could influence time course of variables investigated. That is why we studied whether differences in the basic protocol for infusion therapy and different levels of COP according to age or body weight, respectively - impair reproducibility and reliability of experimental results. METHODS: Group A [n=6, lower body weight (LBW < 22 kg)] was treated with unrestricted infusion rates (UIR) adjusted to maintain a constant blood pressure; group B [n=6, higher body weight (HBW > 28 kg)] was treated with a restricted continuous infusion rate for fluid balance (RIR); group C (n=6) combined HBW and UIR protocol. Blood pressure, plasma solutes, diuresis, and peritoneal fluid were analysed. Statistical analysis was performed using Kruskal-Wallis test and Wilcoxon test. RESULTS: UIR-treated pigs with LBW (group A) developed ascites and demonstrated time dependent decreases of plasma solute concentrations whereas in pigs of group C mainly diuresis was increased and subcutaneous edema occurred. None of the protocols enabled constant blood pressure. DISCUSSION: In young pigs (LBW), an adaptive volume substitution using crystalloids to standardize blood pressure may induce fluid extravasation; in turn data may not show statistical significance, stable hemodynamics may not be achieved and changes in plasma solute concentrations may lead to false interpretations. RIR-strategy provided reproducible, plausible results and thus should be recommended in combination with pigs >29 kg BW for the use of porcine models.

Acute Kidney Injury↗
PubMed2001

Validation of bone conversion in osteoconductive and osteoinductive bone substitutes.

Bone reconstruction can be performed with an autogeneic graft from various donor regions. Osteoconductive and osteoinductive bone substitutes originate from substances of diverse chemical and morphological types and can have a synthetic or a biological derivation. Alongside autogeneic bone transplants and allogenic and xenogeneic bone implants, alloplastic bone replacements of synthetic or semi-synthetic origin are being used for defect reconstruction. In an animal model in rabbits five bone substitutes and one autogeneic graft were surgically incorporated into identical bone defects (10times 10 mm in size) in six anatomically defined regions of the skull. With scintigraphic and histological methods, the metabolic dynamics of the bone is examined as it reacts to the transplantation of autogeneic bone or to implanted bone replacement material.The different autogeneic, xenogeneic and alloplastic bone replacement materials can be differentiated according to the functional quality of the new tissue and the dynamics of the bone conversion thus induced. In the comparison of mineralized, osteoconductive bone subsitutes (TCP, HA, calcium carbonate ceramics) with demineralized, osteoinductive implants (DBM new, DBM old) and autogeneic bone grafts, the bone inducing matrices show the largest quantity of new bone formation, making possible a volume-constant reconstruction.

Journal Article↗
PubMed2001

Isolated hemoperfused heart model of slaughterhouse pigs.

A model of hemoperfused slaughterhouse pighearts is described providing a wide range of applications which leads to a reduction in animal experiments. The size of a pigheart, heart rate, coronary perfusion, metabolism, etc. are more comparable to conditions in patients than those in hearts of small laboratory animals. Global heart function can be assessed either by measuring stroke volume, ejection fraction, Emax etc. in the working model or by measuring intraventricular pressure with balloon catheters in the isovolumetric model. Regional cardiac function can be measured by sonomicrometry and ischemic and non-ischemic areas can be compared. Local metabolic changes are measurable as well with microdialysis. Cardiac function can be kept on any given functional level by infusion of norepinephrine in spite of the fact that functional parameters are lower without adrenergic drive in vitro than in vivo. Stable heart function can be maintained for several hours with only 500 to 1000 ml of blood because the blood is permanently regenerated by a special dialysis system. This model can be applied in many research projects dealing with reperfusion injuries, inotropic, antiarrhythmic or arrhythmogenic effects of certain drugs, immunological rejection, evaluation of imaging systems (NMR, echocardiography etc.) or cardiac assist devices.

Abattoirs↗
PubMed2000

Haemodilution improves organ function during normothermic cardiopulmonary bypass: investigations in isolated perfused pig kidneys.

We investigated the effects of haemodilution on kidney function during normothermic cardiopulmonary bypass (CPB) by performing in vitro haemoperfusion of pig kidneys for 90 min after cold preservation. We compared two groups (n = 14 each) with respect to rheologic and haemodynamic parameters and glomerular and tubular function. Group 1 was perfused at a haematocrit of 0.33 +/- 0.01, group 2 at 0.21 +/- 0.01. Blood flow was adjusted according to blood pressure. Blood viscosity and vascular resistance were reduced in group 2. Comparison of group 1 versus group 2 revealed a metabolic rate of oxygen 3.4 +/- 1.7 versus 4.3 +/- 1.8 ml/min/100 g, sodium transport 1.2 +/- 1.2 versus 1.8 +/- 1.2 mmol/min/100 g, and creatinine clearance 9.9 +/- 9.1 versus 15.6 +/- 11.9 ml/min/100 g, p < 0.05. We conclude that haemodilution leads to an overproportional decrease in blood viscosity and improves the properties of flow and kidney function. In the ongoing discussion about the optimal extent of haemodilution in CPB, the importance of viscosity and blood flow should be further emphasized.

Animals↗
PubMed1999

Histologic evaluation of a natural permanent percutaneous structure and clinical percutaneous devices.

The longevity of percutaneous devices (PD) is often hampered by exit-site infection. The babyrussa tusk, the only permanent natural percutaneous structure, was histologically studied and the implant-tissue interface of 11 continuous ambulatory peritoneal dialysis (CAPD) catheters that had been implanted in humans was evaluated histologically. Attachment of the epidermis to the tusk surface was observed. All the CAPD catheters showed varying degrees of epidermal downgrowth. These results demonstrate that the epidermis is capable of adhering closely to a percutaneous structure. Regarding the CAPD catheters, no steady state at the epidermis-implant interface was achieved, so the risk of infection still remains.

Adult↗
PubMed1998

Effect of a silver device in preventing catheter-related infections in peritoneal dialysis patients: silver ring prophylaxis at the catheter exit study.

Catheter-related infections remain a significant cause of method failure in chronic peritoneal dialysis (PD) therapy. Given the increasing antibiotic resistance, such nonpharmacological strategies as local silver devices attract more interest. To establish whether a silver ring device (designed by Grosse-Siestrup in 1992) mounted onto the PD catheter and placed at the exit site at skin level is effective in preventing exit-site and other catheter-related infections, a prospective 12-month, multicenter, controlled study stratified by diabetes status was conducted. The study subjects were assessed by an extensive structured inventory, including a broad spectrum of control variables, such as age, body mass index (BMI), Staphylococcus aureus carrier status, catheter features, mode and quality of PD therapy, comorbidity, and psychosocial rehabilitation. Ten experienced German outpatient dialysis centers (seven adult, three pediatric) participated in the trial. All eligible patients (n=195) from the study area without catheter-related infections during the ascertainment period were included (incidental subjects undergoing PD therapy for at least 3 months). The main outcome measures were the occurrence of first exit-site infections (primary study end point), sinus tract/tunnel infection, and peritonitis. Ninety-seven patients were assigned to the silver ring and 98 patients to the control group. Baseline characteristics of age, sex, proportion of pediatric and incidental patients, S aureus carrier status, and other variables were similar in both groups. The incidence of infections in the silver ring group versus the control group was as follows: 23 of 97 versus 16 of 98 patients had exit-site infections, 12 of 97 versus 12 of 98 patients had sinus tract/tunnel infections, 16 of 97 versus 18 of 98 patients had peritonitis, respectively. Kaplan-Meier analysis for the probability of an infection-free interval showed no statistical difference (log-rank test) between the two groups. Displacement of the silver ring contributed to study termination in 6% of the study group patients, including two patients with catheter loss. Univariate analysis and multiple logistic regression identified younger age (<50 years), low serum albumin level (<35 g/L), number of previously placed PD catheters, short cuff-exit distance (<2 cm), and S aureus nasal carriage as risk factors for the development of exit-site infections. In conclusion, our study does not show any benefit of the silver ring in preventing catheter-related infections in PD patients. Thus, prevention of infection-related method failure in PD still has to rely on conventional antibiotic treatment strategies and less so on alternative methods.

Adult↗
PubMed1998

Microbicidal activity of a new silver-containing polymer, SPI-ARGENT II.

The survival of three bacterial species and Candida albicans was studied on SPI-ARGENT II. The immediate recovery from silver-impregnated polymer and control polymer (1 cm2) was approximately 10(6) to 10(7) microorganisms. After incubation (37 degreesC) and neutralization of silver with horse serum (5%), surviving organisms were recovered. The survival of the microorganisms on the polymer was not found to be influenced by the silver implantation.

Anti-Infective Agents↗
PubMed1998

[Effect of blood viscosity on the function of isolated perfused porcine kidney after cold preservation].

With the new method of gas exchange and dialysis carried out simultaneously with a standard dialysis module, for the first time normothermic ex-vivo whole blood perfusion of pig kidneys becomes practicable under nearly physiological conditions. To show the possibility of animal experiment replacements we use slaughter house kidneys to investigate functional abilities of the perfusion method. Slaughter house kidneys show a state of acute ischemic renal failure due to the unavoidable time of ischemia and cold preservation. Nevertheless they show a specific functional metabolism up to 4 hours of perfusion time. For the future, the new perfusion model seems suitable to investigate acute organ rejection and perfusion phenomena on pig kidneys, which are most interesting for xenotransplantation.

Animals↗
PubMed1997

A computer-assisted in-vitro biomaterial test for percutaneous devices using human keratinocyte cultures.

The aim of this study was to assess the suitability of a computer-assisted in vitro test system to evaluate candidate biomaterials used for percutaneous devices. Silicone rubber (Silastic) and five different polymers from the Eurobiomat concerted action, polyetherurethane, polyvinylchloride with plasticizer, di-ethylhexylphthalate (PVC-DEHP), polyvinylchloride with plasticizer, tri-ethylhexyltrimellitate (PVC-TEHTM), polyethylene and polypropylene were examined with respect to their qualities to facilitate keratinocyte attachment. HaCaT-cells, a spontaneously transformed non-tumorigenic human keratinocyte cell line, were cultured on the different materials for 3 days. Cellular behaviour was examined morphologically by phase-contrast and scanning electron microscopy throughout the 72 h incubation period. For the computer-assisted measurement of the cell-covered substrate surface and subsequent statistical analysis the cells were fixed after 3 days of incubation, stained, photographed and the images then digitally transformed. Of the different polymers examined silicone rubber showed the most favourable results with respect to the quantitative analysis of the cell-covered substrate surface as well as concerning cytomorphological findings. The results of this study indicate that the in vitro test system described is a sensitive screening method for evaluating candidate biomaterials used for percutaneous devices in a fast and reproducible manner, thus reducing number of animal experiments.

Journal Article↗
PubMed1997

[A new method of ex vivo whole blood perfusion of isolated mammalian organs, exemplified by the kidney of swine].

A new method for the ex vivo perfusion of organs from large mammals is described. Gas exchange and dialysis are carried out simultaneously with a low-flux polysulfon dialysis module. The dialysate (e.g. Tyrode solution) is aerated with a mixture of oxygen and carbon dioxide to ensure gas exchange with the blood. Dialysis is carried out in a closed thermostatically controlled system. Monitoring of ultrafiltration is maintained by continuously weighing the blood reservoir and adjusting an afferent and efferent blood pump. Initial results obtained with isolated pig kidneys demonstrate the suitability of the new method for use as a model for the replacement of animal experiments. Theoretically, clinical application in the area of in vivo regional organ perfusion may also be possible.

Animals↗
PubMed1994

Biocompatibility of silver-coated polyurethane catheters and silver-coated Dacron material.

The local effects of silver-coated polyurethane catheters and Dacron material were compared to uncoated polyurethane catheters and Dacron material in a long-term implantation test using rabbits. The tissue-implant interaction was analysed by investigating the type and number of inflammatory cells, capillaries, fat tissue, the extent of fibrosis, thickness of the fibrous capsule, number and distribution of silver particles, and the size of giant cells. Silver-coated and uncoated materials displayed comparable signs of inflammation and tissue reaction.

Animals↗
PubMed1991

A new method to evaluate the CAPD-catheter-exit and other percutaneous devices.

A method that has proved to be the most sensitive approach for the early diagnosis of infection of the oral mucosa around dental implants has been used to monitor the exit-sites of percutaneous devices. For three months the state of the skin-catheter interface of 13 CAPD-patients was examined every four weeks. This examination included the measurement of pocket depth with the aid of a periodontal probe, the measurement of SFFR (sulcus-fluid-flow-rate) using standardized filter paper strips and a bacteriological swab of the exit-site. The results obtained demonstrated that SFFR can be measured around percutaneous implants. The measurement of SFFR appeared to be more useful in the monitoring of exit-sites of percutaneous devices than the measurement of pocket depth or the use of bacteriological swabs. Further studies for prolonged periods are necessary to determine whether measurement of SFFR can reliably predict onset of exit-site infection before clinical signs become evident.

Adult↗
PubMed1990

Totally implantable catheter system in the dog.

Four totally implantable catheter systems for arterial and venous access were implanted for a maximum of 17 months. Hematological and bacteriological tests were performed. The platelets remained normal. Occasionally observed bacteremias were successfully treated. The morphological and SEM results show that in comparison to the standard externalized catheter the totally implantable catheter system has a longer functional lifetime and less problems with sepsis while the well-being of the experimental animal is improved.

Animals↗