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Biomedical subjects

D Heimbach

Publications and source records attributed to D Heimbach.

At least 19 recordsLinked to original sources
PubMed2004

[Legal aspects of injuries due to positioning of the patient in urology].

Each positioning of the patient has method specific risks and risk increasing factors which depend on the type of surgery carried out. The causes of damage during positioning are pressure and strain when the protective reflexes are out of action, as well as a reduction of the shielding muscle tone through anaesthesia. The surgeon is responsible for the positioning of the patient, and the anaesthetist for the "infusion arm". For this interdisciplinary cooperation, the principles of horizontal work division are required: strict role boundaries, trust without reciprocal direction, close coordination and reciprocal respect for the specialist requirements of the partner, resolution of conflicts taking these requirements into consideration and the final decision of the surgeon. Legally, the damage caused by the positioning of the patient is considered to be fully under control. It can only be reduced by medical care but can not be eliminated. For compensation, the medical practitioner must prove that the appropriate amount of care was taken in the positioning of the patient as well as in the medical cooperation.

Anesthesiology↗
PubMed2004

The use of chemical treatments for improved comminution of artificial stones.

PURPOSE: The acoustic and mechanical properties of various stone compositions are significantly different and thus result in varying degrees of fragility. Consequently, results to shock wave lithotripsy (SWL) are influenced accordingly. We report the results of a study of fragility of various stone compositions, and the influence on each stone's baseline physical properties and fragility when exposed to various chemolytic solutions. MATERIALS AND METHODS: Before SWL artificial stones of differing compositions were irrigated with various chemolytic solutions. Calcium oxalate monohydrate (COM) stones were treated with ethylenediaminetetraacetic acid (EDTA), stones composed of magnesium ammonium phosphate hydrogen were treated with hemiacidrin, and stones made of uric acid (UA) were treated with tromethamine. Synthetic urine served as a control for all stone groups. Using an ultrasound transmission technique, longitudinal wave propagation speed was measured in all groups of artificial stones. Stone density was also measured by using a pycnometer (based on Archimedes' principle). Based on these measurements transverse (shear) wave speed (assuming a constant Poisson's ratio), wave impedance and dynamic mechanical properties of the artificial stones were calculated. Moreover, the microhardness of these artificial stones was measured, and fragility testing using SWL with and without pretreatment with the previously mentioned chemolytic solutions, was performed. RESULTS: Wave speed, wave impedance, dynamic mechanical properties and microhardness of EDTA treated COM stones and tromethamine treated UA stones were found to decrease compared to untreated (synthetic urine) control groups. The suggestion that chemolytic pretreatment increases stone fragility was verified by the finding of increased stone comminution after SWL testing. Combining this medical pretreatment and SWL, the findings demonstrate a significant impact of various solvents on stone comminution, in particular EDTA treated COM stones, tromethamine treated UA stones and hemiacidrin treated magnesium ammonium phosphate hydrogen stones. These data suggest that by altering the chemical environment of the fluid surrounding the stones it is possible to increase the fragility of renal calculi in vitro. CONCLUSIONS: These results indicate that appropriate chemical treatments may provide a useful adjunctive modality for improving the efficacy of stone comminution during shock wave lithotripsy.

Citrates↗
PubMed2003

[A new method for the evaluation of stone fragmentation after ESWL].

INTRODUCTION: Efficacy of ESWL treatment can be evaluated by determining the number and size of urinary stone fragments. However, the available methods for classification of stone fragments are inaccurate. Therefore, a method for semi-automatic determination of fragment size and number after ESWL was developed. METHODS: Artificial struvite stones (BON[N]-STONES) were disintegrated with a lithotriptor (Siemens, Lithostar plus) by application of 50 and 200 shock waves at 19 kV. The stone fragments were collected and pre-sorted on cascade sieves. Pictures taken of the fractions were digitalized and the images optimized in edge sharpness, contrast, and colour depth using an image processing software. Finally, the pixel number of each fragment was determined and the real area was calculated. Fragment size and volume were then depicted by frequency of occurrence in a histogram. RESULTS: Fragments with a diameter ranging from 0.3 - 5 mm could be determined by the system described. About 2,000 - 3,600 fragments were generated in this size range from the artificial struvite stones. With low shock-wave application, a considerable number of fragments larger than 2 mm could be observed. By increasing the impact to 200, more than 90 % of the stone volume was found in fragments smaller than 2 mm (previously 50 %). CONCLUSION: The system described enables a qualitative and quantitative description of stone fragmentation after ESWL not achieved thus far.

Humans↗
PubMed2002

Chemolitholysis and lithotripsy of infectious urinary stones - an in vitro study.

OBJECTIVES: This study was performed to look for an improvement of therapeutic strategies with regard to the treatment of infectious urinary stones using artificial stones made of struvite and apatite ('Bon(n) stones') which are comparable to their natural counterparts. MATERIALS AND METHODS: Using an experimental arrangement simulating the physiological conditions in the upper urinary tract, the efficacy of artificial urine (pH 5.7), Suby G solution (pH 3.6), mixtures of artificial urine with Suby G (pH 3.9 and pH 4.1) in dissolving artificial struvite and apatite stones (Bon(n) stones) was investigated. The dissolution of natural infectious urinary stones was also measured. Additionally, investigations on shock-wave lithotripsy (SWL) combined with initial chemolytic treatment of the stones were performed. RESULTS: The efficacy of Suby G solution in dissolving artificial stones was demonstrated. Direct comparison of chemolysis of natural and artificial stones showed no statistical difference between infectious urinary stones and Bon(n) stones of the same material. The investigations on SWL showed a significant improvement on stone comminution, especially of artificial apatite stones after initial chemolytic treatment with Suby G. CONCLUSION: New basics to improve dissolution of infectious urinary stones have been developed by performing standardized in vitro investigations. Local chemolysis with Suby G is an effective tool in the treatment of infectious stone disease. SWL can be improved by varying the physical properties of infectious stones through initial treatment with Suby G solution.

Apatites↗
PubMed2001

Chemolysis of struvite stones by acidification of artificial urine--an in vitro study.

OBJECTIVE: The aim of the study was to look for strategies that improve the clinical outcome of struvite stones. An in vitro experimental set up with artificial stones made of struvite (BON(N)-STONES) was chosen to perform standardized and reproducible analyses on various artificial urines with pH-values that may be reached by acidification with oral methionine treatment. MATERIALS AND METHODS: Artificial ball-shaped stones made of struvite (BON(N)-STONES) with a diameter of 0.8 cm were used. The investigations on chemolysis were performed using a dissolution device which simulates the physiological conditions in the upper urinary tract with computer-assisted on line measurement of data. For chemolysis of struvite BON(N)-STONES artificial urines according to Griffith at four different pH-values (pH 5.75, pH 6.0, pH 6.25, pH 6.5) were used. Furthermore natural and struvite BON(N)-STONES were treated with Suby G-solution (pH = 4.0). RESULTS: Comparing natural and artificial struvite stones after treatment with Suby G there was no significant difference regarding their dissolution rate. The dissolution rate of struvite stones in artificial urine rose with a decreasing pH-value. The diminution of the pH-value from 6.5 to 5.75 lead to an increase of the dissolution rate of more than 35%. This increase in the dissolution rate decreased with falling pH-value. CONCLUSIONS: The acidification of urine accelerated the dissolution rate of struvite stones in vitro. Considering in vivo conditions the intake of 1,500-3,000 mg L-methionine may lead to a sufficient acidification for a good dissolution of struvite stones.

Humans↗
PubMed2000

Improving cystine stone therapy: an in vitro study of dissolution.

OBJECTIVES: To perform an in vitro study analyzing the possibilities in therapeutic strategies for an effective treatment of cystine stones. METHODS: Artificial stones made of cystine [Bon(n)-Stones] with a ball-shaped size of 0.9 cm in diameter were used. Chemolysis of artificial cystine stones with different solvents (artificial urine, physiologic sodium chloride solution, acetylcysteine, tris-(hydroxymethylene)-aminomethane [THAM], and combinations of these) was investigated. An experimental arrangement with computer-assisted online measurement of data simulating the physiologic conditions in the upper urinary tract at varying pH values was used. RESULTS: All solutions showed a statistical improvement in the solubility of cystine stones compared with artificial urine and physiologic sodium chloride solution. The combination of THAM (pH 10) and 2% acetylcysteine was most effective (1 3.91 +/- 1.73 mg/hr) and demonstrated a 41 -fold higher ability to dissolve cystine calculi compared with artificial urine. CONCLUSIONS: Our data indicate that local chemolysis with special solutions is an effective treatment modality in cystine stone therapy.

Acetylcysteine↗
PubMed2000

Chemolysis of artificial cystine stones (BON(N)-STONES) in vitro using a new dissolution device: first results.

BACKGROUND AND PURPOSE: The treatment of cystine stones is a clinical problem. This in vitro study was performed to establish an experimental system that enables standardized and reproducible investigations on chemolysis of cystine stones to look for an improvement of dissolution strategies. MATERIALS AND METHODS: Artificial spherical stones made of cystine (BON(N)-STONES) with a diameter of 0.9 cm were used. A new dissolution device was developed simulating the physiological conditions in the upper urinary tract with computer-assisted online measurement of data. For chemolysis of artificial cystine stones, different solvents (artificial urine, physiologic sodium chloride solution, 2 % acetylcysteine, 8.4 % sodium bicarbonate solution, THAM, and combinations) were used. RESULTS: Chemolysis is an effective tool in the management of cystine stone disease. Statistical analysis showed significant differences (p < or = 0.05) for all solutions compared with artificial urine alone. A combination of THAM at pH 10 with acetylcysteine (2%) showed a 48-fold stronger ability to dissolve cystine calculi than did artificial urine. CONCLUSION: By performing standardized in vitro investigations, new basics to improve the dissolution of cystine stones have been developed. It is recommended to use artificial stones made of cystine and a dissolution device simulating physiological conditions for investigations on chemolysis in the future.

Acetylcysteine↗
PubMed2000

A new type of artificial urinary calculi: in vitro study by spiral CT.

RATIONALE AND OBJECTIVES: Artificial urinary calculi similar to natural stones have long been sought in urologic research. In an experimental study, the authors assessed the CT characteristics of a new type of artificially produced urinary calculus [BON(N)-STONE]. METHODS: Six different types of urinary calculi (uric acid, struvite, cystine, calcium oxalate, brushite, and apatite) were produced by a coating technique in which several layers of a suspension of pure substance were applied around a core and dried. A total of 60 stones (10 per group) were studied by spiral CT at two energy levels (100 and 120 kV, 250 mA) with 1-mm slice thickness. RESULTS: All calculi showed a small hyperdense core surrounded by a homogeneous matrix and a slightly hyperdense outer rim. From the least to the most dense, the stone types were uric acid, struvite, cystine, calcium oxalate, brushite, and apatite. Absolute CT values at 100 and 120 kV could differentiate between all groups of stones at a significance level of P < 0.001 or better. Attenuation values were in a comparable range to reported values for natural stones, with the exception of uric acid and struvite, which were notably lower. CONCLUSION: These artificially produced urinary calculi showed properties similar to those of natural stones. Thus, this seems to be a promising stone model for further investigations.

Humans↗
PubMed2000

Influence of alkaline solutions on chemolitholysis and lithotripsy of uric acid stones. An in vitro study.

OBJECTIVES: This study was performed to look for an improvement of therapeutic strategies with regard to the treatment of uric acid stones using artificial stones made of uric acid (BON(N)-STONES) which are comparable to their natural counterparts. MATERIALS AND METHODS: Using an experimental arrangement simulating the physiological conditions in the upper urinary tract the efficacy of different alkaline solutions and artificial urine in dissolving artificial uric acid stones (BON(N)-STONES) was investigated. The dissolution of natural uric acid stones was measured and investigations on shock wave lithotripsy (SWL) combined with initial chemolytic treatment of the stones were performed. RESULTS: The efficacy of alkaline solutions, especially THAM at a pH of 10, in dissolving artificial uric acid stones was demonstrated. The investigations on SWL showed a significant improvement on stone comminution of artificial uric acid stones after initial chemolytic treatment with THAM. CONCLUSIONS: New basics to improve dissolution of uric acid stones have been developed by performing standardized in vitro investigations. The suggestion was confirmed that stone fragility and thus SWL can be improved by varying the physical properties of uric acid stones through initial treatment with THAM solution.

Lithotripsy↗
PubMed2000

Acoustic and mechanical properties of artificial stones in comparison to natural kidney stones.

PURPOSE: Standardized and reproducible artificial kidney stone models are important for performing comparative studies of different lithotripsy modalities. The acoustic and mechanical properties of renal calculi dictate the manner by which stones interact with the mechanical stresses produced by shock wave lithotripsy (SWL) or intracorporeal lithotripsy modalities. We have developed a novel artificial kidney stone model that is made of natural substances found in real kidney stones. These stone models appear to be much closer in physical properties to natural kidney stones than previously used stone models. MATERIALS AND METHODS: The acoustic and mechanical properties of six groups of artificial stone models were compared to corresponding natural stones of similar compositions. Moreover, three groups of artificial stone models made of plaster-of-Paris were compared to their natural counterparts. In terms of acoustic properties, stone density was measured using a pycnometer based on Archimedes' principle, whereas longitudinal and transverse (or shear) wave propagation speeds were measured using an ultrasound pulse transmission technique. These values were used to calculate wave impedance and dynamic mechanical properties (bulk modulus, Young's modulus, and shear modulus) of the stones. The microhardness of the stones was measured and the effect of composition on stone fragility was evaluated. RESULTS: Artificial stones, when compared to natural stones of similar composition, showed similar trends in longitudinal and transverse wave speeds, wave impedance, and dynamic elastic moduli. However, values for the artificial stones were uniformly low compared to those of natural stones, suggesting that these artificial stones may be more amenable to shock wave fragmentation. The results of SWL on stone fragmentation of artificial and natural stones also revealed similar trends with the exception of artificial cystine stones which were found to be the most resistant to shock wave fragmentation. CONCLUSIONS: The results indicate that the physical properties of artificial stones made of natural stone materials are comparable to renal calculi of the same chemical composition. The data suggests that these stone phantoms are suitable for performing standardized and reproducible in vitro investigations, especially with regards to fragility of kidney stones of different chemical compositions during SWL.

Acoustics↗
PubMed1999

How to improve lithotripsy and chemolitholysis of brushite-stones: an in vitro study.

Because of their resistance to fragmentation, treatment of brushite stones is a big problem. This study was performed to look for an improvement in therapeutic strategies by using artificial stones made of brushite (Bon(n)-stones), which are comparable to their natural counterparts. Using an ultrasound transmission technique, longitudinal wave propagation speeds were measured at different time intervals during treatment with hemiacidrin. From these and density measurements, transverse wave speed, wave impedance and dynamic mechanical properties of the artificial stones were calculated. Moreover, the microhardness of artificial stones was measured and investigations on shock wave lithotripsy (SWL) combined with initial chemolytic treatment of the stones were performed. The suggestion was confirmed that stone fragility and thus SWL can be improved by varying the physical properties of brushite stones through treatment with hemiacidrin. Additionally, we demonstrated the efficacy of Suby G in dissolving artificial brushite stones using an experimental arrangement simulating the physiological conditions in the upper urinary tract. Moreover, the efficacy of four different intracorporeal lithotripsy devices (electrohydraulic, pneumatic, laser and ultrasound) was tested and it was shown that electrohydraulic lithotripsy seems to be the best system for comminution of brushite stones.

Calcium Phosphates↗
PubMed1999

Causes of phosphate stone formation and the importance of metaphylaxis by urinary acidification: a review.

The most important phosphates involved in urinary stone disease are carbonate apatite, brushite, and struvite. Overall, phosphate stones account for 12-20% of all stones, with a downward trend for struvite and an increase in carbonate apatite being observed in the last decade. The physicochemical basis for the formation of phosphate calculi is supersaturation. Once the solubility product has been exceeded, a metastable process of supersaturation begins, with slow crystalline growth. If a critical limit of supersaturation is exceeded, large-scale spontaneous precipitation of crystals occurs in a second stage. No urinary tract infection is involved in brushite stone formation. Although infection is not a prerequisite for the formation of carbonate apatite stones, infective conditions favor carbonate apatite formation. Struvite is the characteristic infection calculus, formed as a result of urinary tract infection with urease-producing bacteria. During the first episode of urinary stone disease a definitive diagnosis of the type of stone involved is very difficult without analysis of the latter by infrared spectroscopy or X-ray diffraction. In recurrent disease, appropriate treatment can be initiated on the basis of the previous stone analysis in the majority of cases. The best means of preventing recurrent disease involving any type of phosphate stone is definitive calculus removal by shock-wave lithotripsy, percutaneous stone removal, or open surgery (especially in children). Chemolysis via acidification of the urine with Suby G solution or hemicidrin supported by oral acidification, achieved by the metabolism of L-methionine, and antibiotic therapy (especially for infectious stones) are important adjuvant modalities of therapy. After therapy of phosphate stones, metaphylaxis involving controlled urinary acidification with L-methionine supports the treatment of infection and, at a pH value of less than 6.2 and urine dilution to 2.5 l/24 h, prevents the crystallization of struvite, brushite, and carbonate apatite.

Acids↗
PubMed1999

Simultaneous contralateral testicular metastasis from a renal clear cell carcinoma.

The case of a 66-year-old male with a right renal cell carcinoma and a left testicular mass is reported. Radical nephrectomy and contralateral orchidectomy were performed. Histology revealed a metastasis of the renal cell carcinoma of clear cell type into the left testis. The patient died seven months post-operatively of disseminated lung metastases. The case demonstrates the multi-ocular metastatic potential of renal cell carcinoma.

Adenocarcinoma, Clear Cell↗
PubMed1999

Hydronephrosis after aorto bifemoral graft surgery: a marker for late graft complications.

Ureteral obstructions are serious late complications after aortoiliac reconstructive vascular surgery, which lead to loss of kidney function if they remain untreated. One case report serves to describe the incidence, aetiology, clinical presentation and treatment options of an obstructive uropathy following graft surgery. Hydronephrosis due to a ureteral obstruction is considered as a "marker" of graft complication. Therefore, ultrasound examination and close follow-up beyond 1 year are recommended in all patients who undergo aortoiliac surgery.

Aorta, Abdominal↗
PubMed1999

Pharmacokinetic-pharmacodynamic modeling of the respiratory depressant effect of alfentanil.

BACKGROUND: Although respiratory depression is the most well-known and dangerous side effect of opioids, no pharmacokinetic-pharmacodynamic model exists for its quantitative analysis. The development of such a model was the aim of this study. METHODS: After institutional approval approval and informed consent were obtained, 14 men (American Society of Anesthesiologists physical status I or II; median age, 42 yr [range, 20-71 yr]; median weight, 82.5 kg [range, 68-108 kg]) were studied before they underwent major urologic surgery. An intravenous infusion of alfentanil (2.3 microg x kg(-1) x min(-1)) was started while the patients were breathing oxygen-enriched air (fraction of inspired oxygen [FIO2 = 0.5) over a tightly fitting continuous positive airway pressure mask. The infusion was discontinued when a cumulative dose of 70 microg/kg had been administered, the end-expiratory partial pressure of carbon dioxide (PE(CO2) exceeded 65 mmHg, or apneic periods lasting more than 60 s occurred During and after the infusion, frequent arterial blood samples were drawn and analyzed for the concentration of alfentanil and the arterial carbon dioxide pressure (PaCO2). A mamillary two-compartment model was fitted to the pharmacokinetic data. The PaCO2 data were described by an indirect response model The model accounted for the respiratory stimulation resulting from increasing PaCO2. The model parameters were estimated using NONMEM. Simulations were performed to define the respiratory response at steady state to different alfentanil concentrations. RESULTS: The indirect response model adequately described the time course of the PaCO2. The following pharmacodynamic parameters were estimated (population means and interindividual variability): EC50, 60.3 microg/l (32%); the elimination rate constant of carbon dioxide (Kel), 0.088 min(-1) (44%); and the gain in the carbon dioxide response, 4(28%) (fixed according to literature values). Simulations revealed the pronounced role of PaCO2 in maintaining alveolar ventilation in the presence of opioid. CONCLUSIONS: The model described the data for the entire opioid-PaCo2 response surface examined. Indirect response models appear to be a promising tool for the quantitative evaluation of drug-induced respiratory depression.

Adult↗
PubMed1998

Percutaneous chemolysis--an important tool in the treatment of urolithiasis.

Persistent residual calculi after therapy, i.e. extracorporeal shock wave lithotripsy (ESWL), percutaneous nephrolitholapaxy (PNL), as well as pyelo- and nephrolithotomy are big problems in the treatment of urolithiasis. Furthermore, the therapy of stones is problematic in patients with inadequate drainage, impaired kidney function, or with high risks against anaesthetics. Between 1991 and 1997 percutaneous antegrade chemolysis was carried out in eleven patients. In nine of them complete dissolution of stones was achieved. In two further cases, in which calcium oxalate was the main component of the stones, chemolysis was unsuccessful. Through our own cases and under consideration of the literature, we will show that percutaneous chemolysis in these cases is useful and effective in the treatment of urolithiasis.

Adult↗
PubMed1997

[Treatment of benign prostatic hyperplasia with alpha 1-adrenoreceptor antagonists].

The International Consensus Committee recommends alpha-adrenoceptor antagonists for medical therapy benign prostatic hyperplasia (BPH). This review evaluates 52 randomized, placebo-controlled, double-blind studies, including 10399 patients and, moreover, 40 clinical studies including 33600 patients undergoing treatment with alpha-adrenoceptor antagonists because of BPH. The therapeutic efficacy of all alpha-adrenoceptor antagonists is more or less the same. There is an average improvement of symptom scores of about 35% and a mean increase in maximum flow rate of between 1.8 and 2.5 ml/s. Studies investigating long-term efficacy and quality of life tend to show a long-term benefit. The introduction of selective alpha 1-adrenoceptor antagonists led to a significant reduction of side effects. These side effects are primarily caused by the vasodilatatory qualities of alpha-blockers. The development of so-called uroselective alpha 1A-adrenoceptor antagonists in the treatment of BPH possibly leads to further reduction of side effects related to vasodilatation. Medical therapy by alpha 1-adrenoceptor antagonists seems to be superior to phytotherapy or treatment with 5 alpha-reductase inhibitors, as shown in a few studies. So far, it is not clear whether there is any advantage of combination therapy. The application of alpha 1-adrenoceptor antagonists is indicated in all cases of symptomatic BPH, excluding patients who need TUR-P (e.g., middle lobe) or prostatectomy. If patients are either willing or eligible to have surgical treatment, therapy by alpha 1-adrenoceptor antagonists is a rational choice. Comparative clinical trials have to be conducted to provide additional information and to clarify which alpha-blocker may be recommended as the first choice. Until then, those alpha 1-adrenoceptor antagonists should be used for which safety and efficacy are well documented and which can be prescribed at reasonable costs.

Adrenergic alpha-1 Receptor Antagonists↗