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Biomedical subjects

T Hess

Publications and source records attributed to T Hess.

At least 37 records · Page 2Linked to original sources
PubMed1999

Resulting tensile forces in the human bone-patellar tendon-bone graft: direct force measurement in vitro.

The objective of this study was to measure the resultant force in the human bone-patellar tendon-bone graft after reconstruction of the anterior cruciate ligament under various conditions in vitro. Seven fresh-frozen cadaver lower extremities were used. Force measurement was made with a quartz force transducer mounted in a specially designed load cell. The effect of passive extension movement, quadriceps pull, varus torque, and valgus torque on the resultant force in the ligament were investigated. Passive extension of the joint generated a rapid increase of force in the graft between 30 degrees and 0 degrees of flexion, reaching its maximum (128+/-25 N) at full extension. When quadriceps pull was applied to extend the joint, resultant force increased at 50 degrees of flexion and reached its maximum (219+/-25 N) at full extension. Additional resistance applied to the level of the ankle joint generated an additional load of the graft. Increase of forces in the ligament resulted from both varus and valgus applied moments.

Aged↗
PubMed1998

[Pneumococcal vaccination--yes or no?].

Invasive pneumococcal infections, defined as demonstration of Streptococcus pneumoniae in blood cultures or CSF, are frequent and associated with high mortality in risk groups. Risk groups are the over-65s, individuals with anatomic or functional asplenia, immunosuppressed patients, patients with haemotological neoplasias and HIV-infected subjects, as well as, in general, al sufferers from chronic cardiopulmonary disease, diabetics and patients with severe renal failure or nephrotic syndrome. The 23valent polysaccharide vaccine produces a reliable immune response in children aged over 2 years and adults. The immune response is diminished in severely immunocompromised subjects and in the elderly. Numerous clinical studies provide evidence of the effectiveness of pneumococcal vaccination in the he prevention of invasive pneumococcal infection. Pneumococcal vaccination is recommended for the above mentioned risk groups. It should be observed that for the group at most risk, i.e. heavily immunosuppressed and HIV-infected subjects, there are no convincing data on clinical effectiveness. Regarding non-bacteriaemic pneumococcal pneumonias there are only pointers to the possible usefulness of polysaccharide vaccines. Booster vaccination is not recommended by the manufacturers in view of the reportedly increased incidence of side effects. Studies show that side effects are not more frequent than with primary vaccination. A single revaccination is particularly indicated in status post splenectomy. The conjugate vaccines now under development will improve the efficacy of pneumococcal vaccination and will also be usable in children aged under 2 years.

Adolescent↗
PubMed1998

Herpes simplex virus encephalitis: cranial magnetic resonance imaging and neuropathology in a mouse model.

We performed a long-term magnetic resonance imaging (MRI) study in a mouse model of herpes simplex virus encephalitis. Mice were infected with herpes simplex virus type 1 (HSV-1) strain F. A 1.5-T cranial MRI scanner with standard spin-echo sequences was used. Neuropathological studies included immunohistochemistry. The presence of HSV DNA in brain tissue was determined with a polymerase chain reaction assay. Clinical assessment was performed daily: within the first 2 weeks the animals were severely affected and recovered thereafter. MRI and histopathological abnormalities corresponded well. HSV DNA was detectable initially and at 6 months. Extent and severity of structural abnormalities increased at 6 months. MRI offers a new in vivo approach for the detection of structural changes in the disease course of experimental herpes simplex virus encephalitis.

Animals↗
PubMed1998

Low specificity of the bacterial index for the diagnosis of bacterial pneumonia by bronchoalveolar lavage.

The bacterial index (BI) as defined by the sum of log10 colony-forming units (cfu) of microorganisms per milliliter of bronchoalveolar lavage (BAL) fluid, i.e., a multiplication of the single cfu/ml, has been used to distinguish between polymicrobial pneumonia (BI> or =5) and colonization (BI<5). Since many false-positive results are to be expected using this parameter, the diagnostic value of the BI was studied prospectively by obtaining bacteriologic cultures of BAL fluid in 165 consecutive unselected patients. In 27 cases the diagnosis of bacterial pneumonia was established on clinical criteria. In 133 patients pneumonia could be excluded, and in five patients the diagnosis remained unclear. Using a cut-off of > or = 10(5) cfu/ml BAL fluid, sensitivity and specificity for the diagnosis of pneumonia were 33% (9/27) and 99% (132/133), respectively. Sensitivity was mainly influenced by prior treatment with antibiotics, being 70% (7/10) in untreated and 12% (2/17) in treated patients. Applying the BI methodology at a cut-off of > or =5, however, resulted in an unacceptably high rate of 16 additional false-positive results, thus lowering the specificity to 87% (116/133; P<0.0001) while increasing the sensitivity to only 41% (11/27; P = 0.77). In conclusion, given the high rate of false-positive results, the methodology of the BI is of doubtful value for the diagnosis of bacterial pneumonia by BAL in an unselected patient group. By applying the absolute number of cfu/ml BAL fluid, however, positive bacteriologic cultures of BAL fluid are highly specific for the diagnosis of pneumonia. Their sensitivity is limited by previous antibiotic therapy.

Adolescent↗
PubMed1998

[Multiple reader analysis for evaluation of functional MR mammography].

The diagnostic impact and reproducibility of the different methods used within the concept of functional MR-Mammography (FMRM) was assessed by a multi-reader-analysis. By four experienced readers, 100 histologically confirmed cases were evaluated in six different sessions. Per session, one of the following components was analyzed: clinical history (I), static MRM (II), color-coded projection images (III), time-signal curves of contrast enhancement within a large ROI (IV) and the strongest enhancing pixel (V) obtained from the histologically confirmed lesion and the complete FMRM reading (VI). The functional methods (IV-VI) revealed significantly (p < 0.05) higher specificities than the others (I-III). The highest reproducibility between the readers was observed for (IV) phi chi = 0.80, (V) phi chi = 0.76 and FMRM (VI) phi chi = 0.63. These three methods also presented the best ROC-curves and showed the highest complementarity with respect to the false positive classifications in x-ray mammography. FMRM is a reader independent, reproducible method. The analysis of the contrast enhancement time-intensity curves with high temporal resolution allows an improved differentiation of malignant and benign findings.

Adult↗
PubMed1998

[Diagnostic imaging for therapy control of primary bone tumors].

Adjuvant chemotherapy has significantly improved the prognosis of patients with bone sarcomas. Preoperative diagnostic imaging of tumor response to such therapy has become a mainstay for the assessment of prognosis, planning of surgery and further treatment. During therapy, responding tumors show characteristic changes on conventional radiography, angiography, sonography, radionuclide studies, CT and MR. The usefulness and the limitations of each imaging modality in assessing response to therapy are reviewed. The diagnostic importance of specific changes such as tumor volume reduction, calcification and tumor vascularization is discussed.

Adolescent↗
PubMed1998

Generating and influencing Torsades de Pointes--like polymorphic ventricular tachycardia in isolated guinea pig hearts.

Torsades de Pointes (TdP) is a polymorphic ventricular arrhythmia which can degenerate into ventricular fibrillation. The most typical symptom of TdP is the ECG morphology where QRS complexes seem to rotate around the isoelectric baseline. Bradycardia and delayed repolarization are regarded as pathophysiologic predispositions. For better understanding of the pathophysiology and the evaluation of therapeutic or proarrhythmic potential of drugs, a functional experimental model is needed. In the present study, an experimental model of polymorphic tachyarrhythmias taken as TdP equivalents in isolated guinea pig hearts was developed. The hearts were perfused by the Langendorff technique. Bradycardia was induced by dissection of the sinus node, and prolongation of the QT interval by infusion of two inhibitors of the sodium channel inactivation, veratridine and DPI 201-106. TdP equivalents were triggered reproducibly by application of electrical single stimuli at the end of the T wave. Experiments with different concentrations of the channel active substances alone and in combination, with different perfusion times and mode of electrical stimulation (single pulse versus train stimulation), showed the highest incidence for TdP equivalents by means of an initial 30 min long infusion of 0.5 microM each veratridine and DPI 201-106 in combination with electrical single stimuli. After finishing the infusion with the channel active substances but still with lasting effects from them. TdP equivalents were triggered repeatedly in five of six experiments. The reasons for this increased TdP susceptibility after finishing the infusion are not known. In a separate series of six similarly arranged experiments, the incidence for TdP equivalents could be decreased from 83% to 12.5% (p < 0.001) by increasing the concentration of magnesium in the perfusate from 1.17 to 5.0 mM. With these experiments, the clinically known therapeutic effect of magnesium suppressing TdP could be demonstrated in an in vitro model for the first time. The results suggest that this model could be used as a base for further studies of clinical relevant drugs, especially antiarrhythmic agents, to obtain hints of possible risks of proarrhythmic effects or of suitability for therapeutic use at TdP attacks.

Animals↗
PubMed1998

[Digital mammography: experiences in its clinical application].

TARGET: In 1989 in the Cantonal Hospital of Lucerne conventional film-screen mammography was replaced by digital mammography. With the support of a retrospective study, it was checked whether or not digital mammography represents an equally valid diagnostic procedure in daily routine. METHODS: 1204 patients were examined using digital mammography. A reevaluation of these patients was carried out using clinical and radiological routine controls. Additionally a radiological and histological examination was performed in 127 cases in which excisional biopsies had been done, paying particular attention to detail perception. RESULTS: The sensitivity of digital mammography achieved a total of 85%, whereas the accuracy was 81%. With additional use of ultrasound and galactography the sensitivity attained 91%. By reevaluation the sensitivity amounted to 87%, the accuracy remaining at 81%. The positive predictive value was especially high with 76% and 77%. CONCLUSION: Digital mammography offers satisfactory diagnostic performance.

Biopsy↗
PubMed1998

[Experimental evaluation of dynamic MRI for quantifying liver perfusion].

Gadolinium-DTPA enhanced dynamic MR imaging is a new method for the quantification of portal bloodflow and liver perfusion. In this study we evaluated the validity of this method comparing it with thermodiffusion and dopplerflowmetry in pigs. We found a significant correlation of tissue perfusion between dMRI and thermodiffusion and of portal bloodflow between dMRI and dopplerflowmetry. Partial occlusion of the portal vene was accurately detected by dMRI. Dynamic MRI could become a valuable diagnostic method for the quantification of liver perfusion.

Animals↗
PubMed1997

[Dying and death in an acute-care medical hospital].

Nowadays, more people seem to die in hospitals or other establishments than in their own homes. The following paper reports on 50 consecutive cases of death that occurred in a clinic of internal medicine. The analysis concentrated on the circumstances, the symptoms and the treatment of the patients during the 12 h. preceding and immediately before death as well as on the opinion of the relatives and the attending staff. A questionnaire registered the different opinions. Nearly a third of these deaths occurred after a fairly short hospitalization time. Death was not always the result of a long illness and it involved also young people. Most of the patients died in their hospital room, in the presence of their relatives and/or of the attending staff. They were mostly unconscious during the moments preceding their death. Terminal symptoms such as pain, anxiety, shortness of breath or thirst were largely kept under control. The relatives and concerned people were, as far as possible, informed about the grievance and the fatal issue of the patient's illness. Their reactions were diverse. Most relatives were satisfied with the treatment and care given to the hospitalized patient. The doctors and nursing staff considered their working together as being better than usually expected. Clear therapeutical concepts, appropriate palliative care as much as optimal communication are important requirements for a good treatment of the dying. The following results allow us to question many a prejudice concerning death in a hospital surrounding, but also show us possibilities of improvement. So we should sometimes question ourselves about the sense and the need of certain nursing interventions. We should spend more time during our medical training on the question of palliative care and on the problem of the relationship of doctors to death and to the dying. We feel that establishing a "science of death" or a segregation of the dying in specialized institutions makes no sense.

Adult↗
PubMed1997

Signal generation in a non-EU country.

One of the most important objects of post-marketing surveillance is the early detection of serious, unknown and unexpected adverse events. As spontaneous reported adverse events vary considerably in their signal-generating value the Swiss Drug Monitoring Center SANZ implemented an early signal detection system in 1991. With a set of screening criteria the individual case reports are automatically checked by the system and read into a signal file. Subsequently these potential signals are processed to quantify the signal generating value of the particular case. According to the screening criteria 2072 (53%) of the reported cases were considered as potential signals. After validating and quantifying their signal value 27% (565) were drug-related and unlabelled, 8% (173) were also rated as serious. On the basis of these cases 114 labelling changes were made. Some of the most interesting cases are discussed. This computer-assisted early signal generation model in a small country with 7 million inhabitants has a high detectability of new, rare, serious and quality of life affecting adverse drug reactions (ADRs). These newly detected ADRs must be interpreted in cognizance of the limitations and restrictions of spontaneous reporting and do not allow pharmacoepidemiologic conclusions.

Journal Article↗
PubMed1997

Use of preoperative vascular embolisation in spinal metastasis resection.

Preoperative selective embolisation was carried out on 17 patients with spinal metastases from various primary tumours. There was a significant reduction in the blood loss (2088 ml) and infusion volume requirement (3500 ml) and more favourable postoperative haemoglobin (Hb) development compared with the non-embolised but otherwise identical control group. The reduced intraoperative bleeding manifested itself in the form of greater clarity and a less complicated intraoperative course. Particularly with a dorsal approach, the reduced bleeding permitted more exact preparation and more extensive tumour resection. Preoperative embolisation is thus a valuable aid in spinal metastasis resection. Given suitable indications and exact positioning of the embolising material, no significant complications should arise. The method as a whole calls for close collaboration between interventional radiologists and spinal orthopaedists.

Blood Loss, Surgical↗
PubMed1997

Drug-induced attack of bronchial asthma in inpatients: a 20-year survey of the Comprehensive Hospital Drug Monitoring Programme on adverse drug reactions, Berne/St. Gallen.

Epidemiological aspects of attacks of bronchial asthma related to drugs are prospectively studied in inpatients of three teaching hospitals in the Comprehensive Hospital Drug Monitoring (CHDM)-programme. Results are based on 34,840 individual patients (among 48,005 consecutive admissions) in the years 1974-1993. Between 1974 and 1993, every patient admitted to any of the three medical clinics in the CHDM programme was monitored for any suspicion of an adverse drug reaction (ADR); every drug exposure period during hospital stay was registered. Nineteen patients (0.05% of the 34,840 individual patients) had at least one attack of bronchial obstruction during hospitalisation, considered as probable or definite ADR. The frequency related to exposure periods in response to penicillins is 0.014%, to non-steroidal anti-inflammatories (NSAIDs) 0.0145, to acetyl salicylic acid (ASA) 0.018%, to paracetamol 0.008% and to beta-adrenoceptor blockers 0.26%. Of the 12 patients reacting to a drug with an allergic or idiosyncrasy/intolerance type of bronchial obstruction, 7 had a history of bronchial asthma (extrinsic or intrinsic), and 3 had the diagnosis chronic obstructive pulmonary disease (COPD). A history of bronchial asthma or COPD is confirmed to be a risk factor for this particular ADR. Of the seven patients with a bronchial obstruction to beta-adrenoceptor blockers, five were diagnosed with COPD, while two had neither COPD nor bronchial asthma. The relative risk for this pharmacological reaction in COPD patients was 96 (95% confidence interval 45-208) compared with non-COPD patients in the group of 3244 exposed to beta-adrenoceptor blockers.

Adrenergic Antagonists↗
PubMed1997

Creatine deficiency syndrome caused by guanidinoacetate methyltransferase deficiency: diagnostic tools for a new inborn error of metabolism.

Hepatic guanidinoacetate methyltransferase deficiency induces a deficiency of creatine/phosphocreatine in muscle and brain and an accumulation of guanidinoacetic acid (GAA), the precursor of creatine. We describe a patient with this defect, a 4-year-old girl with a dystonic-dyskinetic syndrome in addition to developmental delay and therapy-resistant epilepsy. Several methods were used in the diagnosis of the disease: (1) the creatinine excretion in 24-hour urine was significantly lowered, whereas the creatinine concentration in plasma and in randomly collected urine was not strikingly different from control values; (2) the Sakaguchi staining reaction of guanidino compounds in random urine samples indicated an enhanced GAA excretion; (3) GAA excretion measured quantitatively by guanidino compound analysis using an amino acid analyzer was markedly elevated in random urine samples; (4) in vivo 1H magnetic resonance spectroscopy (MRS) revealed a strong depletion of creatine and an accumulation of GAA in brain; (5) in vivo phosphorus 31 MRS showed a strong decrease of the phosphocreatine resonance and a resonance identified as guanidinoacetate phosphate; and (6) in vitro 1H MRS showed an absence of creatine and creatinine resonances in cerebrospinal fluid and the occurrence of GAA in urine. For early detection of this disease, we recommend the Sakaguchi staining reaction of urine from patients with dystonic-dyskinetic syndrome, seizures, and psychomotor retardation. Positive results should result in further investigations including quantitative guanidino compound analysis and both in vivo and in vitro MRS. Although epilepsy was not affected by orally administered creatine (400 to 500 mg/kg per day), this treatment resulted in clinical improvement and an increase of creatine in cerebrospinal fluid and brain tissue.

Amino Acid Metabolism, Inborn Errors↗
PubMed1996

[Is a clinical positional control for nasogastric tubes good enough? A prospective study of 43 patients].

OBJECTIVE: Nasoenteric tubes are usually introduced blindly by nursing staff, i.e. without visual or radiological control. A prospective study was undertaken to determine how often such blind procedure results in potentially dangerous tube placement and how often such faulty positioning remains undetected in a standardised clinical check. PATIENTS AND METHODS: 43 patients (23 men, 20 women; age 24-90 years) requiring the introduction by nursing staff of a nasoenteric tube were studied, 12 in an intensive care unit (seven intubated) and 31 in an ordinary ward. At most 24 hours after the customary check of the tube's position by the nursing staff (air injection with epigastric auscultation), specially experienced medical and nursing personnel determined and recorded the tube's placement in a standardised manner. Subsequent radiological examination documented the position. RESULTS: All 43 tubes lay in the gastrointestinal tract. Only one tube was in a potentially dangerous position in the lower end of the oesophagus, as had already been diagnosed by the examiners. Of four other tubes which were not optimally placed (three in the region of the cardia, one in the duodenum) three were found to be "not correctly placed" by the clinical check, and one was detected only radiologically. CONCLUSIONS: Clinical control of a nasoenteric tube's position suffices in most instances. Checking the position further by an experienced person adds to safety. The study's findings suggest that radiological control can be safely limited to cases in which there was a problem in positioning the tube or the clinical control was unclear.

Adult↗