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Biomedical subjects

J Mühling

Publications and source records attributed to J Mühling.

At least 19 recordsLinked to original sources
PubMed2001

[Magnetic resonance tomography for planning dental implantation].

PROBLEM: Three-dimensional imaging diagnostics are increasingly recommended before inserting dental implants in high-risk areas and in cases of severe alveolar atrophy. Since patients are exposed to considerable radiation with computed tomography (CT), the possibilities of employing magnetic resonance imaging (MRI) of the jaw as a diagnostic imaging method before inserting dental implants were examined. MATERIAL AND METHOD: Twelve patients and three volunteers were examined by MRI with T1-weighted, fat-suppressed sequences and conventional T1-weighted sequences. The patients wore a diagnostic splint including markers--in the form of capillaries filled with 0.025 x 10(-2) M gadolinium solution (1.5 mm in diameter)--in the planned implant's position and axis. RESULTS: The presentation of relevant anatomic structures and the three-dimensional accuracy of the markers were judged. Metal artefacts were evaluated in vitro. The MRI of the jaw and midface represents the mandibular canal, the maxillary sinus, and other decisive anatomic structures by detailed representation of the connective tissue surrounding the bone. Artefacts of metallic fillings reduce the image quality. CONCLUSION: Obtaining clinical findings and planning before inserting dental implants with the help of MRI can certainly be applied with toothless patients and facilitates three-dimensional planning by representing the exact location and angle of the drill tubes. Local restrictions result from metal extinction artefacts in jaws with teeth and in controls after having inserted titanium implants.

Adolescent↗
PubMed2001

Hydroxyethyl starch (HES) does not directly affect renal function in patients with no prior renal impairment.

STUDY OBJECTIVES: To examine the effects of hydroxyethyl starch (HES) on renal function. DESIGN: Randomized, controlled trial. SETTING: Operating theatre of a university hospital. PATIENTS: 60 ASA physical status I and II male patients undergoing middle ear surgery. INTERVENTIONS: Patients received either lactated Ringer's solution (LRS) or one of three HES solutions. The HES solutions were administered in a dose of 15 mL/kg bodyweight (bw), the Ringer's solution in a dose of 60 mL/kg bw, after induction of anesthesia over a period of one hour. MEASUREMENTS: Blood and urine samples for hormone and enzyme tests were obtained at defined times before, during, and after surgery. Urine excretion, glomerular filtration rate (GFR), renal plasma flow, and routine hemodynamic parameters were measured simultaneously. MAIN RESULTS: There were no significant intergroup differences regarding GFR, renal plasma flow, or tubular and glomerular integrity as measured by specific proteins and enzymes (alpha-1-microglobulin, Tamm-Horsfall-protein, immunoglobulin G, and N-acetyl-beta-D-glucosaminidase). Arginine vasopressin decreased in all groups during and following anesthesia, aldosterone and plasma renin activity decreased only in the HES groups, and angiotensin II decreased only in the HES 200/0.5 group. Central venous pressure increased during fluid administration in the LRS group and returned to baseline sooner in the HES groups. CONCLUSIONS: Hydroxyethyl starch administration appears to be risk-free with regard to renal function in patients without preexisting renal dysfunction who undergo general anesthesia. The relevance of the decrease in aldosterone following HES therapy needs further investigation.

Adult↗
PubMed2001

Effects of diazepam on neutrophil (PMN) free amino acid profiles and immune functions in vitro. Metabolical and immunological consequences of L-alanyl-L-glutamine supplementation.

The objective of this study was to determine the effects of diazepam, L-alanyl-L-glutamine (ala-gln) or diazepam combined with ala-gln on polymorphonuclear leukocyte (PMN) free amino acid profiles. In a parallel study the effects on PMN immune functions were also documented for the first time. The incubation of whole blood with diazepam led to significant changes in PMN free glutamine, aspartate, glutamate, ornithine, arginine, citrulline, taurine and methionine as well as branched chain and neutral amino acid concentrations. Ala-gln caused significant increases in PMN glutamine and alanine and asparagine, aspartate, glutamate, ornithine, arginine, serine and glycine profiles. Regarding PMN immune functions, diazepam significantly decreased superoxide anion (O(2)(-)) and hydrogen peroxide production (H(2)O(2)) and myeloperoxidase activity (MPO) while ala-gln significantly increased PMN immune functions. Ala-gln supplemented to diazepam largely reversed the changes in PMN amino acid profiles and PMN immune functions brought about by diazepam. Overall, diazepam or ala-gln lead to significant changes in PMN free amino acids. Important PMN immune functions also seem to be affected. In regards to the results, there is significant relevance to the pharmacological regimens which enhance the supply of diazepam or ala-gln in whole blood suggesting that considerable changes in PMN "labile free amino acid pool" occur. These regimens often follow beneficial nutritional therapy or maleficent pharmacological stress and may be one of the determinants in cell nutrition which influence PMN function. It is partially through its effect on PMN labile free amino acid pool that ala-gln supplemented to diazepam may maintain PMN immune functions in vitro.

Journal Article↗
PubMed2001

Reproducibility of peri-implant probing using a force-controlled probe.

The aim of the present study was to evaluate the reproducibility of probing depth (PD) and vertical attachment level (PAL-V) measurements at endosseous implants. Twenty partially edentulous patients who had received 44 Frialit-2 and 30 Astra implants between 1994 and 1996 were examined. At all teeth and implants, clinical parameters (GI, PlI, PD, PAL-V) were measured at 6 sites using the flexible plastic version of the universal explorer TPS probe. At the implants and at teeth that were in similar locations compared to the implants, PD and PAL-V measurements were repeated. For each of the 20 probes that had been used for clinical examination of the 20 patients, the probing force was assessed using a precision balance. As a measure of intraexaminer reproducibility, the following standard deviations of single PD and PAL-V measurements were calculated: Frialit-2: 0.71/0.74 mm; Astra: 0.72/0.75 mm; tooth: 0.59/0.57 mm (PD/PAL-V). Stepwise multiple regression analysis revealed implant/tooth position and GI to influence PD and PAL-V measurement error (P<0.001). At anterior teeth, a lower variability was observed than at posterior teeth (P<0.001). PD and PAL-V measurement error were higher at implants than at teeth and influenced by patients. The respective models explained 13% and 17% of the variability of the dependent variable (PD/PAL-V), respectively. Intraexaminer variability of PD and PAL-V measurements at implants tended to be higher than at teeth. Multivariate analysis of variance revealed probe and probe holder to statistically significantly (P<0.001) influence probing force. However, the differences in probing force between the various probe heads were very small. They reached a maximum of 0.054 N between probe 3 and 14 and may be looked upon as clinically irrelevant.

Adult↗
PubMed2001

Methohexital affects neutrophil (PMN) dynamic free amino acid pool and immune functions in vitro.

BACKGROUND AND OBJECTIVE: The objective of this study was to determine the dose as well as the duration of exposure-dependent effects of methohexital on neutrophil [polymorphonuclear leucocyte (PMN)] free amino acid profiles and, in a parallel study, on PMN immune functions. METHODS: Whole blood samples were taken from 20 volunteers and incubated with methohexital [0 (control), 3.6, 26, 130 and 260 microg mL-1] for 10, 30, 60 or 120 min. PMN amino acid profiles were documented using advanced PMN separation and high-performance liquid chromatography procedures. Superoxide anion (O2-) and hydrogen peroxide production (H2O2), and activity of released myeloperoxidase (MPO), were determined photometrically. RESULTS: After methohexital, significant dose (> or = 26 microg mL-1) as well as duration of exposure-dependent (> or = 30 min) increases in histidine, isoleucine, leucine, valine, methionine, serine, glycine, threonine, and decreases in glutamine, glutamate, aspartate, asparagine, arginine, ornithine, citrulline, alanine and taurine were observed (P < or = 0.05). Concerning PMN immune functions, methohexital significantly decreased O2-, H2O2 formation and MPO (> or = 26 microg mL-1, > or = 30 min, P < or = 0.05). CONCLUSIONS: Altogether, there is significant relevance to the pharmacological regimens which enhance the supply of methohexital in whole blood. In regards to our results, we suggest that considerable changes in PMN 'dynamic free amino acid pool', for example induced by methohexital, may be one of the determinants in cell nutrition adversely affecting PMN metabolism. It is partially through its effect on the PMN free amino acid pool that maleficent pharmacological stress may have an unintentional influence on PMN immune functions.

Adult↗
PubMed2001

Computer assisted oral and maxillofacial surgery--a review and an assessment of technology.

Advances in the basic scientific research within the field of computer assisted oral and maxillofacial surgery have enabled us to introduce features of these techniques into routine clinical practice. In order to simulate complex surgery with the aid of a computer, the diagnostic image data and especially various imaging modalities including computer tomography (CT), magnetic resonance imaging (MRI) and Ultrasound (US) must be arranged in relation to each other, thus enabling a rapid switching between the various modalities as well as the viewing of superimposed images. Segmenting techniques for the reconstruction of three-dimensional representations of soft and hard tissues are required. We must develop ergonomic and user friendly interactive methods for the surgeon, thus allowing for a precise and fast entry of the planned surgical procedure in the planning and simulation phase. During the surgical phase, instrument navigation tools offer the surgeon interactive support through operation guidance and control of potential dangers. This feature is already available today and within this article we present a review of the development of this rapidly evolving technique. Future intraoperative assistance takes the form of such passive tools for the support of intraoperative orientation as well as so-called 'tracking systems' (semi-active systems) which accompany and support the surgeons' work. The final form are robots which execute specific steps completely autonomously. The techniques of virtual reality and computer assisted surgery are increasingly important in their medical applications. Many applications are still being developed or are still in the form of a prototype. It is already clear, however, that developments in this area will have a considerable effect on a surgeon's routine work.

Computer Simulation↗
PubMed2001

Impairment of renal function after cardiopulmonary bypass is not influenced by dopexamine.

INTRODUCTION: The objective of this study was to evaluate the effects of dopexamine on renal function in 4 groups of patients either with or without renal dysfunction. Transient renal dysfunction is often not clinically relevant in patients with normal renal function, but it is an important clinical factor in patients with pre-existing renal failure. Dopexamine (DX) is a commonly used catecholamine which probably exerts a selective effect at the splanchnic bed. MATERIAL AND METHODS: 24 patients with normal renal function and 24 patients with impaired renal function (creatinine in serum > or = 1.5 mg/dL) were each randomly allocated to 2 groups. Group 1 (control) without renal dysfunction and group 3 (control/dysfunction) with renal dysfunction were considered as control groups, while the patients in DX and DX/dysfunction groups received 1 microg/kg/min dopexamine until the end of surgery. Kidney function was investigated using standard parameters and by investigating specific proteins and enzymes. RESULTS: All patients showed pathologic excretions of the investigated parameters during cardiopulmonary bypass (CPB) with no differences between the study groups. The distal tubule, the lysosomal regions, Henle's loop and the glomerular tuft were all damaged. Heart rate and cardiac index increased significantly in the DX-groups, first until the end of surgery, second until the start of ECC. CONCLUSION: Dopexamine at a dose of 1 microg/kg/min had no influence on renal function and protein excretion and cannot be regarded as a kidney function protecting substance.

Adrenergic beta-Agonists↗
PubMed2001

Treatment of sepsis in cardiac surgery: role of immunoglobulins.

Cardiopulmonary bypass (CPB) is associated with an injury that may cause pathophysiological changes such as systemic inflammatory response syndrome, multiple organ dysfunction syndrome, and mediator-induced multiorgan failure. Systemic endotoxinaemia, release of proinflammatory cytokines, and interactions between neutrophils and endothelium have been reported to correlate with a high incidence of organ dysfunction, infection and sepsis following cardiac surgery. This review discusses the dysregulation of the immune response as a major reason for the higher susceptibility to infections following cardiac surgery, various treatment strategies to reduce CPB-induced inflammation, and especially the prophylactic use of immunoglobulins in cardiac surgery.

Cardiopulmonary Bypass↗
PubMed2001

Pharmacokinetics of antibiotic prophylaxis in major orthopedic surgery and blood-saving techniques.

The pharmacokinetics of cefuroxime, cefotiam, cefamandole, and ampicillin/sulbactam were randomly measured in 40 patients undergoing major orthopedic surgery associated with high blood and volume turnover and intraoperative blood salvage. Serum and bone concentrations and the pharmacokinetics occurring in the context of these procedures were measured. No changes in elimination half-life relative to a normal population occurred with cefuroxime, cefotiam, and ampicillin. Serum and tissue concentrations were slightly lower with cefamandole and sulbactam, but reapplication of the initial dose was required with all antibiotics 4 hours after the first application.

Aged↗
PubMed2000

3D norm data: the first step towards semiautomatic virtual craniofacial surgery.

When planning craniofacial surgical interventions, the ideal appearance of the patient is very important. The final appearance should be as close as possible to that which the patient would have if he/she were without defects. Our first step towards achieving this is to build a database containing sets of three-dimensional CT images that allows for comparison of the shape of a patient with defects to the typical shape of an age- and sex-matched "average" person without defects. We started to collect CT data from patients without pathologies and, in co-operation with two radiology institutes (in Mannheim and Heidelberg), over 100 CT data sets have now been collected and classified according to age and sex. It is necessary to choose an appropriate statistical method to calculate the norm data from the different data sets. Based on the statistical method, an age- and sex-matched "average" model of the anatomy will be created.

Adolescent↗
PubMed2000

[Craniofacial abnormalities].

Most craniofacial malformations result from a premature fusion of skull sutures. Depending on the scope of the sutures affected, the results are more or less distinct deformations of the facial and cranial skull with substantial negative effects on functional as well as esthetic aspects. The etiopathology is still unclear. Various therapies have been developed over the past 100 years. However, Tessier's technique of fronto-orbital advancement has been an important milestone in the treatment of these malformations. Numerous adjustments have since perfected this operational technique. It is now possible to treat practically all skull malformations with the surgical techniques available today. At the same time, these techniques have also aided the advancements in tumor surgery and traumatology.

Child↗
PubMed2000

[Computer-assisted oral, maxillary and facial surgery].

BACKGROUND: Methods from the area of virtual reality are used in oral and maxillofacial surgery for the planning and three-dimensional individual simulation of surgeries. SIMULATION: In order to simulate complex surgeries with the aid of a computer, the diagnostic image data and especially various imaging modalities (CT, MRT, US) must be arranged in relation to each other, thus enabling rapid switching between the various modalities as well as the viewing of mixed images. Segmenting techniques for the reconstruction of three-dimensional representations of soft-tissue and osseous areas are required. We must develop ergonomic and intuitively useable interaction methods for the surgeon, thus allowing for precise and fast entry of the planned surgical intervention in the planning and simulation phase. SURGERY: During the surgical phase, instrument navigation tools offer the surgeon interactive support through operation guidance and control of potential dangers. This feature is already available today. Future intraoperative assistance will take the form of such passive tools for the support of intraoperative orientation as well as so-called tracking systems (semi-active systems) which accompany and support the surgeons' work. The final form are robots which execute specific steps completely autonomously. DISCUSSION: The techniques of virtual reality keep gaining in importance for medical applications. Many applications are still being developed or are still in the form of a prototype. However, it is already clear that developments in this area will have a considerable effect on the surgeon's routine work.

Computer Simulation↗
PubMed2000

The effects of thiopentone on free intracellular amino acids in polymorphonuclear leucocytes.

Previous studies have shown the inhibitory effects of thiopentone on polymorphonuclear leucocyte (PML) function. However, major biochemical mechanisms which have been involved are still unknown. The aim of this study was therefore to investigate thiopentone's effects on intracellular amino acid metabolism in PML using both advanced PML separation- and HPLC techniques, especially developed for this purpose and precisely validated in our institute. Overall, our study indicates important dose-dependent alterations of free intracellular amino acid metabolism following thiopentone treatment and draw attention to the biochemical mechanisms which may be involved in both thiopentone-induced modulation in PML function and cellular immunocompetence.

Adult↗
PubMed2000

[Bipolar irrigation forceps. Initial experiences with a new device in high frequency surgery].

PROBLEM: During most surgeries, tissues are coagulated by a high-frequency current in order to stop the bleeding. Usually, bipolar forceps are used for this procedure. Until now it could not be avoided, however, that the biotissue would adhere to the forceps ends making hemostasis more difficult to achieve. Can this negative effect possibly be avoided? MATERIAL AND METHOD: A newly developed bipolar irrigation forceps spilling out a 0.9% sodium chloride solution during the coagulation process has been designed to avoid this disadvantage. The irrigation forceps has been tested and evaluated experimentally in surgery as well as clinically. RESULTS: The irrigation liquid selected is a 0.9% sodium chloride solution. Thermal imaging during biotissue coagulation has shown that the tissue heats up more and faster with flushed coagulation, and that the tip of the forceps heats up less than with unirrigated coagulation. In both experimental-surgical as well as in clinical tests it was possible to stop the biotissue sticking to the ends of the forceps. This effect was also confirmed histologically. CONCLUSION: Since other methods of avoiding the sticking effect during tissue coagulation by a high-frequency current have not been successful until now, the bipolar irrigation electrode is a promising new development. It helps the surgeon to work more efficiently and safely without having to adapt to big changes, and, at the same time, it reduces the risk of complications.

Animals↗
PubMed2000

Dysregulation of immune response following neurosurgical operations.

BACKGROUND: Postoperative infections are common and potentially fatal complications in neurosurgical intensive care medicine. An impairment of immune function has been described after central nervous system surgery and in patients harboring malignant brain tumors. The aim of our study was to investigate whether differences in cell-mediated immunity can be found in patients undergoing craniotomy for surgery of glioblastoma or clipping of an intracerebral aneurysm. METHODS: In order to determine the influence of the underlying disease on the immune system, we measured changes in cytokine concentrations (IL-6, IL-10, TGF-beta1) and lymphocyte-subsets (CD3+, CD3+HLA-DR+, CD4+, CD8+, CD19+, and CD16+56+) in 8 patients with glioblastoma and in 8 patients with an intracerebral aneurysm before, during and after the neurosurgical procedure. RESULTS: In the comparison of glioblastoma and aneurysm patients, we could show that IL-6 plasma levels were pre- and intraoperatively higher in the aneurysm-group (P<0.05), and the plasma concentrations of IL-10 and TGF-beta were significantly elevated in the glioma-group. The lymphocyte-subsets showed a significantly lower percentage of NK-cells and activated T-cells in the glioma-group. CONCLUSION: Our results document a significant dysregulation of immune response in glioma patients. This may be induced by elevated plasma concentrations of immunoinhibiting cytokines IL-10 and transforming growth factor-beta 1.

Brain Neoplasms↗
PubMed2000

Effects of etomidate on free intracellular amino acid concentrations in polymorphonuclear leucocytes in vitro.

BACKGROUND: Previous studies have shown the inhibitory effects of etomidate on polymorphonuclear leucocyte (PMN) function. No reports exist, however, regarding free intracellular amino acid metabolism, although physiological cell metabolism and basic cell functions rely upon a balanced intracellular amino acid content and the cell membrane-mediated separation of cellular amino acids from the extracellular plasma amino acid pool. Thus, in the current study, we evaluated the effects of etomidate on free intracellular amino acid metabolism in PMN. METHODS: With ethics committee approval, blood was withdrawn from 35 healthy volunteers and incubated (1 h) either with 0 microg/ml, 0.0156 microg/ml, 0.0625 microg/ml or 0.5 microg/ml of etomidate as well as with its additives (propylene glycol and Lipofundin MCT 10%). The PMN were separated using standardized Percoll-gradient and centrifugation procedure before deep-freezing and lyophilization techniques were employed. All PMN samples were dissolved in methanol/H2O, and the concentrations of free intracellular amino acids were monitored using both novel advanced PMN-separation and high-performance liquid chromatography techniques. RESULTS: Etomidate influenced important free amino acid profiles in PMN in a dose-dependent manner, indicating complex changes of cellular amino acid turnover. Neither propylene glycol nor Lipofundin MCT 10% changed free amino acid concentrations in PMN. CONCLUSIONS: For the first time, the effects of etomidate on free intracellular amino acid metabolism in PMN have been investigated. Our results draw attention to the biochemical pathways which may be involved in etomidate-induced alterations in PMN function and cellular immunocompetence.

Adult↗
PubMed2000

A pattern catalogue of surgical interventions for computer-supported operation planning.

In this paper we present a new operation planning system which was evaluated in the clinic for Cranio-Maxillo-Facial-Surgery at the University of Heidelberg. In opposite to commercial systems our goal was, that the system considers the complete surgical intervention and not only a single procedure of it. A second goal was, that the system enables managing of complex operations, independent of which way the intervention will be intraoperatively performed (without technical support, with passive navigation support or active support by robots). Our system supports the surgeon during the preoperative planning as well as during the intraoperative execution phase. Therefore we developed a course model by which the managing of surgical interventions is possible. The focus of this paper is on this course model. At first we introduce instruction graphs and describe the structure of each activity observing its attributes and their context. Additionally, various surgical scopes will be presented which enable the surgeon to select one view among different ones of the individual operation procedures in accordance to medical and technical knowledge as well as in accordance to different degrees of abstraction. At last we demonstrate operation patterns, used as expert knowledge.

Computer Simulation↗