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M Engelhardt

Publications and source records attributed to M Engelhardt.

At least 19 recordsLinked to original sources
PubMed2006

An optical evaluation of the phenomenon of red out in neuroendoscopic surgery: what is the physical background?

BACKGROUND: The loss of visualization in neuroendoscopy due to intraoperative bleeding is called "red out". Although red out is a well-known problem during endoscopy, clear physical descriptions of this phenomenon are lacking. OBJECTIVE: The aim of this study was to investigate the optical properties of red out. In particular, the attenuation coefficient, comprising scattering, and absorption, of various blood/Ringer solutions was quantified and measured spectrally resolved. Small amounts of blood virtually preclude neuroendoscopic visualization. In blood/Ringer solutions with a dilution of 1:101, it was not possible to distinguish characters (font size 10, Arial) at a distance of 5 mm. We have concluded, from our physical investigations, that the problem of red out is dominated by scattering rather than by absorption. Accordingly, technical developments aimed at increasing information acquisition under red out conditions should be based on optical measurement concepts for scattering media.

Blood↗
PubMed2006

[Origin and role of aneuploidy in cancer].

Genetic aberrations of cancer cells have a profound impact for prognosis in several malignant neoplasias. The understanding of their origin is the basis for the development of new therapeutic options. Aneuploidy is observed in a large variety of premalignancies and tumors. Aneuploid cells harbor less or more than 46 chromosomes. The exact role of aneuploidy in tumorigenesis is still not clear. It has long been debated, whether aneuploidy directly contributes to tumorigenesis or reflects nonspecific changes during tumor progression. Several mechanisms are thought to be responsible for the generation of aneuploid sets of chromosomes: these comprise failure in cell division, such as defective chromosome separation caused by compromised mitotic checkpoint signaling or centrosome aberrations. Moreover, telomere shortening and defective DNA-damage signaling appear to be powerful driving forces of genomic instability. The loss of telomere sequences at the end of each chromosome and DNA double-strand breakage accompanied by compromised damage signaling favor fusion of chromosomes and generation of aneuploidy. Furthermore, aneuploidy arises to a much higher degree from a tetraploid state when compared to diploid cells. The frequent observation of the described defects in pre- and malignant cells supports the hypothesis that aneuploidy contributes to tumorigenesis.

Aneuploidy↗
PubMed2006

High-dose chemotherapy and autologous peripheral blood stem cell transplantation in adult patients with high-risk or advanced Ewing and soft tissue sarcoma.

PURPOSE: Despite the availability of combined-modality treatment for Ewing sarcoma (ES) and soft tissue sarcomas (STS), results from independent groups still indicate a poor prognosis for high-risk and metastasized patients. The benefit of high-dose chemotherapy (HDCT) with autologous peripheral blood stem cell transplantation (ASCT) as compared to standard treatment is not defined. METHODS: Here, we report of HDCT in 35 consecutive adult patients with poor-risk ES or rhabdomyosarcoma (n = 11) and STS (n = 24) undergoing ASCT between July 1992 and March 2003. At a median follow-up of 100.6 months after ASCT, 11 patients are alive, with nine in sustained complete remission (CR) and each one in partial remission (PR) and stable disease. Median overall survival (OS) from ASCT was 17.1 months. Response to pretreatment, Karnofsky index > 80%, R (0) resection and first-line ASCT were associated with long-term OS (p < 0.05). CONCLUSION: These data indicate that (1) patients achieving a CR or PR following induction, with preserved performance status and R (0) resection may benefit from ASCT and (2) that this can be an useful therapeutic modality in a subset of patients, in some achieving remarkable responses.

Adult↗
PubMed2006

Improvement of quality of life six months after infrageniculate bypass surgery: diabetic patients benefit less than non-diabetic patients.

OBJECTIVES: The aim of the study was to assess the change in health related quality of life (HRQoL) after infrageniculate bypass grafting in patients with critical limb ischaemia (CLI). DESIGN: Observational, prospective clinical study. MATERIALS AND METHODS: In total, 86 patients (72% male; age 71 (IQR, 64-78) years) undergoing infrageniculate bypass grafting for limb salvage were assessed by the short form (SF)-36 questionnaire before and 6 months after surgery. In subgroup analysis, the influence of diabetes mellitus, age, gender, and stage of peripheral arterial occlusive disease on HRQoL-outcome were assessed. RESULTS: Following revascularization HRQoL significantly improved in all eight dimensions of the SF-36. While baseline HRQoL-values of diabetic and non-diabetic patients did not differ significantly, postoperative improvement was significantly less in the diabetes group. CONCLUSIONS: An aggressive approach towards infrageniculate bypass surgery for limb salvage is justified by quality of life improvement. However, this improvement tends to be less in patients with diabetes mellitus.

Aged↗
PubMed2006

Neurosurgical operations with the patient in sitting position: analysis of risk factors using transcranial Doppler sonography.

BACKGROUND: One major risk factor of the sitting position for neurosurgery is air embolism, especially in patients with persistent foramen ovale (PFO). The first aim of this prospective study was to evaluate a bedside method for detecting PFO using transcranial Doppler sonography (TCD) with contrast medium. A second aim was to address intraoperative monitoring, patient positioning and the occurrence and clinical relevance of air embolism. METHODS: Ninety patients with a mean age of 56.5 yr (range 14-81 yr) undergoing surgery in sitting position were investigated by TCD with contrast agent to detect functional PFO, that is PFO that can be provoked with a Valsalva manoeuvre. In patients in whom TCD was not possible, transcranial duplex sonography, duplex sonography of the carotid artery at the neck or transoesophageal ECG was performed. RESULTS: In 26 patients PFO was detected. Thirteen of them presented a persistent PFO with high-intensity transient signal in both middle cerebral arteries without Valsalva manoeuvre. The intraoperative positioning in these patients was adapted to the risk for a paradoxical air embolism, although, after surgical recommendations, three patients with a persistent PFO underwent surgery in sitting position. Intraoperative air embolisms were seen in 8 of 80 patients in sitting or semi-sitting position with air aspirable through the central venous catheter. CONCLUSION: To address the risk of a paradoxical air embolism, especially in patients undergoing surgery in sitting position, preoperative detection of PFO is advisable. If surgery is performed in seated PFO patients, additional monitoring and special care are warranted.

Adolescent↗
PubMed2006

[Minimally invasive unicondylar knee replacement with computer navigation].

METHODS: From January 2003 to July 2005 a total of 50 St Georg medial knee monosleds with metal-backed tibial components in stably seated form and Uniglide prostheses (Alphanorm/Corin) with mobile bearing onlays were implanted in minimally invasive operations. Postoperatively the alignment-especially of the tibial components-was investigated, to check whether we had achieved the dorsal slope we had been aiming at, i.e. 5-7 degrees , in the region of these knee replacements. RESULTS: Before surgery there were initial malalignments of up to 10 degrees varus and 3 degrees valgus. All leg axes were restored to between -3 degrees and +3 degrees . The desired dorsal slope of 5-7 degrees for the knee monosleds relative to the tibial component was realized, the average slope being 5.3 degrees . The a-p alignment of the tibial component and of the femoral component was correct. CONCLUSIONS: Use of the navigation system leads to more accurate and reproducible results in terms of tibial dorsal slope, which is extremely important when these monosleds are used. Overcorrection of the leg axis is generally avoided. The use of too-high medial onlays is also reliably avoided by the navigation system's monitoring of the level of the cut.

Adult↗
PubMed2006

Effects of 5-aza-2'-deoxycytidine on proliferation, differentiation and p15/INK4b regulation of human hematopoietic progenitor cells.

The demethylating agents 5-azacytidine and 5-aza-2'-deoxycytidine (DAC) have been shown to induce differentiation and inhibit growth of leukemic myeloid cells at low concentrations. However, the effect of DAC in changing the differentiation and proliferation behavior of normal human myeloid progenitors has rarely been investigated. Therefore, we established an in vitro model of normal hematopoietic differentiation, using CD34+ cells from mobilized peripheral blood, to study proliferation and colony formation, expression of several myeloid maturation markers and of the inhibitor of cyclin-dependent kinases p15/INK4b. Upon DAC treatment, cell growth was significantly decreased in a dose-dependent manner, without an increase in cytotoxicity. DAC treatment also resulted in a substantial increase of lysozyme-positive cells, which could be enhanced by G-CSF, a modest increase of myeloperoxidase+ and CD15+ cells, as well as an increase of colony-forming cells (CFU-GM) compared to control cells. p15/INK4b protein expression was strongly upregulated upon myeloid maturation, and additional DAC treatment did not change p15 expression or the methylation status of the p15 promoter at the noncytotoxic concentrations used. Taken together, these data indicate a role of DAC in changing myeloid progenitor cell expansion and differentiation. This model appears suitable also for global analyses of multiple differentially methylated genes.

Antigens, CD34↗
PubMed2006

[Experimental principles of the V.A.C.-therapy -- pressure values in superficial soft tissue and the applied foam].

OBJECT OF THE STUDY: Measurement of the pressure during V.A.C.(R)-therapy in superficial parts of the affected soft tissue as well as at the soft tissue/foam-interface, measurement of pressure values along bigger distances in the foam and the comparison of pressure transfer between polyurethane and polyvinyl-alcohol foams. MATERIAL AND METHODS: A multi-channel electronic transducer-tipped catheter system based on the piezo-resistant principle was used. Measurement was performed on a plain table surface, at a bovine muscle as well as in human tibial anterior muscle of a patient after fasciotomy. Applied pressure values by V.A.C.(R)-therapy-units were 50 to 200 mm Hg (continuous suction modus). RESULTS: 100 % pressure transition through vacuum-therapy-foams to wound surface, almost 100 % pressure transition even along 60 cm in very large polyurethane-foams using only one trac-pad connector. Pressure values > 125 mm Hg using polyvinyl-alcohol-foams showed a reduction of up to 25 % in distances > 15 cm from trac-pad-connector. On the surface of the affected soft tissue there are negative and positive pressure values (25 % quartile: - 25 mm Hg; 75 % quartile: + 15 mm Hg). DISCUSSION: Pore walls of the foam can produce positive pressure conditions resulting in soft tissue compression and consecutively hypoperfusion or ischemia. V.A.C.(R)-therapy seems to produce an heterogeneity of pressure distribution at the wound ground leading to pressure gradients and facilitating drainage of interstitial fluid. This mechanism could explain the anti-edema effects of V.A.C.(R)-therapy resulting indirectly in an increased nutritive perfusion.

Animals↗
PubMed2006

Analysis of surgical management of calvarial tumours and first results of a newly designed robotic trepanation system.

This study was performed to evaluate the surgical strategy in patients with calvarial tumours, in order to design and modify a robot-assisted trepanation system. A total of 75 patients underwent craniectomy for the treatment of calvarial tumours during the 10-year period from 1993 to 2002. The patients' complaints, the size, location and histology of the tumour, and the various cranioplasty techniques used were analysed retrospectively. In a second procedure several craniectomies at typical locations according to the study's results were performed in a laboratory setting using a hexapod robotic tool, constructed at the Helmholtz-Institute, RWTH Aachen University, and plastic model heads. The workflow was documented and the reproducibility and the accuracy of the procedure were registered. A total of 83 surgical procedures were performed on 75 patients. The majority (87 %) of lesions treated surgically were located in the frontal, temporal and anterior parts of the parietal region. Histological examination revealed benign lesions in 66 % of the patients and dural involvement in 46 %. According to these results craniectomies were performed using the robotic system. Mean positioning accuracy of the robotic system while milling was 0.24 mm, with a standard deviation of 0.04 mm, and maximum error under 1 mm. Craniectomies leaving a 1-mm layer of the tabula interna intact to ensure a healthy dura were performed in several regions successfully. The majority of calvarial tumours, requiring surgical treatment in our patients, were located in cosmetically relevant areas in which drilling can be carried out with the robotic trepanation system. Consequently, the surgical approach had to be planned carefully in order to achieve a good cosmetic outcome.

Adolescent↗
PubMed2006

Dynamic cerebral autoregulation in patients with ruptured and unruptured aneurysms after induction of general anesthesia.

INTRODUCTION: Blood pressure management in patients undergoing surgery for clipping of aneurysms is demanding. More information about the ability of cerebral vessels to normally regulate cerebral blood flow may have a direct influence on the intraoperative management. In patients with subarachnoid hemorrhage (SAH) a disturbance of cerebral autoregulation has been reported and it correlated with the severity of the bleeding in these studies. The impairment of autoregulation was demonstrated using static measurements of cerebral pressure autoregulation. However, the dynamic component of the autoregulatory capacity seems to be of importance in the acute setting after SAH. The aim of this study was to evaluate dynamic pressure autoregulation in patients undergoing surgery for intracranial aneurysms. PATIENTS/MATERIAL AND METHODS: 36 patients with a mean age of 45 years were evaluated, 26 patients with acute SAH, 10 patients with unruptured aneurysms. Cerebral autoregulation in normocapnia was tested using thigh cuffs to alter arterial blood pressure and continuous registration of the blood flow velocities with transcranial Doppler sonography. After the induction of general anesthesia under normocapnia the autoregulatory index (ARI) was calculated (values between 0-9). Patient groups were compared using Wilcoxon- and Spearman's rank test. RESULTS: The two patient groups were comparable with regard to gender, age, PaCO(2), blood flow velocities and blood pressure. In patients with SAH mean ARI was 3.1/3.3 (right/left side) compared to 4.7/4.6 (right/left side) in patients without SAH. The difference was statistically significant (Wilcoxon p = 0.0399). The degree of impairment of the autoregulatory capacity increased significantly (p = 0.006) with the severity of the SAH (Hunt&Hess and Fisher scale). CONCLUSION: Dynamic pressure autoregulation is impaired in patients after SAH compared to patients without SAH and correlates with the severity of the SAH. We propose that autoregulation should be measured in all patients with SAH or that an impaired autoregulation should be taken into account in patients with SAH undergoing surgery in the acute phase.

Adult↗
PubMed2005

[Innovative antibody-therapies for malignant lymphomas].

Non-Hodgkin s lymphoma (NHL) includes a group of malignant lymphoproliferative disorders, that particularly occur in the elderly and have an continuously increasing incidence. Because of the age distribution new treatment options with low toxicity and minor side effects - apart from "conventional" therapies like standard or high dose chemotherapy - are needed. Within these novel therapeutic modalities the use of the monoclonal antibody rituximab has been widely established. Other monoclonal antibodies, such as the anti-CD52-antibody alemtuzumab, are available for the treatment of chronic lymphatic leukemia (CLL) and T-cell-lymphomas and are being tested in clinical trials. Furthermore the option of combining targeted therapies, in which antibodies are used with radiotherapy, has led to the development of radio-immunotherapies that are now becoming available for clinical use. Current results in the treatment of advanced indolent lymphomas are promising, and their use in high-grade lymphoma and as first-line therapy is under investigation. This article summarizes the application of these novel immunotherapies and reviews the results of recent clinical trials, with particular emphasis on indications and practical aspects in everyday clinical life.

Alemtuzumab↗
PubMed2005

[Spinal intramedullary tumors. When is surgical treatment indicated?].

OBJECTIVE: Timing of surgery in patients with intramedullary tumors is the subject of controversy. The aim of this retrospective study is to evaluate whether patients with intramedullary ependymomas and astrocytomas have a better postoperative prognosis without or with slight preoperative deficits than those with severe preoperative neurological disturbances. PATIENTS AND METHODS: During a period of 8.5 years (January 1992-August 2000), 34 patients with intramedullary tumors underwent surgery in our Neurosurgical Department. Among them there were five astrocytomas WHO grade II and ten ependymomas WHO grade II. Recurrences were observed in two patients with astrocytomas and one patient with ependymoma. Pre- and postoperative functional performance was classified according to the McCormick scale in grade I-IV (grade I: neurologically normal or mild focal deficit and grade IV: severe neurological deficits and without functional independence). The follow-up period varied from 4 to 76 months (mean: 27.9 months). RESULTS: All seven grade I patients remained unchanged after surgery. Two of four grade II patients improved to grade I; two deteriorated to grade III. Two of three grade III and IV patients remained unchanged and another one deteriorated from grade III to IV. CONCLUSION: At the best, intramedullary astrocytomas and ependymomas should be operated when symptoms are mild. Early surgery can achieve good functional outcome.

Adolescent↗
PubMed2005

[Injuries and response to overload stress in running as a sport].

Running is rarely associated with acute injuries (muscle injuries, ankle sprain, ruptures of the Achilles tendon). More than 80% of the complaints are due to overuse injuries, mainly concerning knee, foot and Achilles tendon. Risk factors are high-performance sports, high training quantity, rapid increase of training intensity, previous injuries, and skeletal axis malalignment. Running is not suitable for severely overweight people and those with significant skeletal malalignment, dysplastic hips, spondylolisthesis, or cartilage damage.

Ankle Injuries↗
PubMed2005

Duplex scanning criteria for selection of patients for internal carotid artery endarterectomy.

BACKGROUND: The value of carotid endarterectomy for stroke prevention depends on reliable identification of patients at higher risk for stroke from their internal carotid artery (ICA) occlusive disease than from surgery. This selection of patients is based on the degree of ICA stenosis. Therefore, preoperative diagnostic measures should strive for a prevalence independent probability for disease of 100%. Aim of this prospective study was to obtain clinically applicable duplex scanning criteria for ICA stenosis > or = 70% with a probability for disease of 100%. PATIENTS AND METHODS: In 124 ICA in 62 patients (79% male) angiography and duplex scanning were performed. Degree of stenosis was classified in 4 categories: I < 50%; II 50%-69%; III 70%-99%; IV 100%. Cohen's kappa statistic was used to estimate agreement between both methods within categories. To improve accuracy post-test likelihood for disease was calculated for each point on the receiver operating characteristics (ROC)-curve for peak systolic (PSV) and end-diastolic velocity (EDV), and cut-off points for velocity criteria were set at a positive likelihood of 100%. RESULTS: Diagnostic agreement was good with kappa = 0.77 (95% CI, 0.64-0.90; p < 0.001). For EDV a criterion of > or = 150 cm/sec was associated with a post-test likelihood for disease of 100%. For PSV no appropriate criterion could be detected. CONCLUSIONS: A probability of 100% for ICA stenosis > or = 70% can be achieved by mere preoperative duplex scanning. Vascular laboratory specific validation of duplex scanning criteria should consider prevalence independent post-test likelihood for disease to ensure the value of CEA for stroke prevention.

Aged↗
PubMed2005

Risk factors for survival in patients with end-stage renal disease undergoing infrainguinal bypass surgery.

BACKGROUND: A poor longevity and high perioperative morbidity make lower extremity revascularization questionable in patients with end-stage renal disease (ESRD). Therefore, careful selection of patients for surgery is essential. Aim of this study was to assess negative predictors of survival in patients with ESRD undergoing infrainguinal bypass grafting for critical limb ischemia (CLI). PATIENTS AND METHODS: We reviewed the records of 49 consecutive patients with ESRD who underwent infrainguinal bypass grafting for limb salvage. Rates were computed with life-table analysis and compared by log-rank test. Effects of demographic and disease variables on the survival rate were evaluated by Cox proportional hazard regression model. RESULTS: Indications for surgery were rest pain in two (4.1%) and tissue loss in 4 7 patients (95.9%). Median follow up was 7.8 months (IQR, 2.43 to 16.23). Perioperative (30-day) morbidity and mortality for all patients were 6.1% and 12.2%, respectively. Primary and secondary patency at two years both were 81.4%. Cumulative survival rate at two years and four years were 24.9% and 9.3%, respectively Limb salvage rate and amputation-free survival rate at two and four years were 80.4%, 53.6%, 21.8% and 14.6%, respectively. Myocardial infarction and congestive heartfailure in the patients medical history both had an adverse effect on survival rate with a hazard ratio of 5.52 (95% CI, 1.94 to 15.69) and 3.12 (95% CI, 0.99 to 9.81), respectively. CONCLUSIONS: In the presence of myocardial infarction or congestive heart failure in the medical history survival rate is especially poor for patients with ESRD undergoing infrainguinal revascularization. Therefore, bypass surgery for CLI is hardly indicated in this group of patients.

Aged↗