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Biomedical subjects

Frank Weber

Publications and source records attributed to Frank Weber.

At least 55 records · Page 3Linked to original sources
PubMed2004

Importance of adrenal incidentaloma in patients with a history of malignancy.

BACKGROUND: Adrenal incidentaloma presents a frequent finding in patients with a history of malignancy. This study was carried out to determine whether imaging techniques can discriminate between a malignant and a benign adrenal tumor and subsequently select candidates for adrenal surgery. METHODS: Beginning in July 1995, oncologic patients with adrenal incidentaloma underwent abdominal ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), and [ 18 ]fluoro-2-deoxy-D-glucose positron emission tomography (18-FDG-PET). Consecutively in all patients adrenalectomy was performed. Histologic findings were compared with the imaging results. RESULTS: In 42 patients, 33 to 79 years old (mean age, 58 years), 44 adrenal lesions were detectable. Two patients presented with bilateral adrenal masses. At operation, 43 adrenal resections and 3 biopsies were performed. Histologic examination revealed 31 metastases (71%) and 13 adrenal adenomas (29%). In metastases the sensitivity of ultrasonography, CT, MRI, and 18-FDG-PET was 66%, 81%, 100%, and 100%, respectively. For adrenal adenoma, the sensitivity of ultrasonography, CT, MRI, and 18-FDG-PET was 46%, 39%, 100%, and 54%, respectively. CONCLUSIONS: In oncologic patients with indeterminate adrenal tumors MRI and 18-FDG-PET provide accurate differentiation between metastases and benign adenomas. Positive results of these 2 imaging modalities are highly suggestive for metastatic disease. In cases of negative MRI and 18-FDG-PET results the adrenal lesion corresponds to a benign adenoma that needs no surgical intervention.

Adenoma↗
PubMed2004

Evaluation of the Alaris Auditory Evoked Potential Index as an indicator of anesthetic depth in preschool children during induction of anesthesia with sevoflurane and remifentanil.

BACKGROUND: Autoregressive modeling with exogenous input of middle latency auditory evoked potentials (A-Line autoregressive index [AAI]) has been proposed for monitoring depth of anesthesia in adults. The aim of this study was to evaluate the performance of the AAI during induction of anesthesia with sevoflurane and remifentanil in pediatric patients. METHODS: Twenty preschool children were anesthetized with sevoflurane and remifentanil. AAI, heart rate, and mean arterial pressure were compared for their ability to distinguish between different hypnotic states before inhalation induction and during sevoflurane anesthesia with and without remifentanil infusion. The prediction probability was calculated for discrimination between the predefined case milestones Awake, Spontaneous Eye Closure, and insertion of a laryngeal mask airway during general anesthesia (Laryngeal Mask Insertion). RESULTS: The AAI (mean +/- SD) in Awake children was 79 +/- 10, declining to 59 +/- 22 at Spontaneous Eye Closure and 34 +/- 13 when anesthetized. AAI values significantly overlapped between anesthetic states. For the AAI, the prediction probabilities regarding the ability to discriminate the hypnotic state at the case milestones Awake versus Spontaneous Eye Closure and Awake versus Laryngeal Mask Insertion were 0.77 and 0.99, respectively. In terms of prediction probability values, heart rate and mean arterial pressure were not indicative for anesthetic states. Remifentanil did not influence the AAI. CONCLUSION: During induction of pediatric patients with sevoflurane, the AAI is of higher value in predicting anesthetic states than hemodynamic variables and reliably differentiates between the awake and anesthetized states. However, individual AAI values demonstrate significant variability and overlap between different clinical conditions.

Anesthesia, General↗
PubMed2004

S-ketamine and s-norketamine plasma concentrations after nasal and i.v. administration in anesthetized children.

BACKGROUND: It has been suggested that nasal administration of s-ketamine may be used to improve sedation or premedication in combination with nasal midazolam in pediatric patients. In this study we measured and compared plasma concentrations of s-ketamine and its main metabolite s-norketamine after nasal and i.v. administration in preschool children. METHODS: During sevoflurane anaesthesia, 20 children, aged 1-7 years, weight 11-25 kg, received s-ketamine 2 mg x kg(-1) either intranasally (Group IN, n = 10), or i.v. (Group IV, n = 10). Six venous blood samples were obtained up to 60 min after drug administration for measurement of s-ketamine and s-norketamine plasma concentrations. RESULTS: Plasma concentrations [mean +/- sd] of s-ketamine in group IN peaked at 355 +/- 172 ng x ml(-1) within 18 +/- 13 min vs. 1860 +/- 883 ng x ml(-1) within 3 +/- 1 min in group IV (P < 0.01). Plasma concentrations of s-norketamine in group IN peaked at 90 +/- 128 ng x ml(-1) within 50 +/- 11 min vs. 429 +/- 277 ng x ml(-1) within 40 +/- 16 min in group IV (P < 0.01). One child in group IN experienced rapid and high level s-ketamine absorption with a peak plasma concentration of 732 ng x ml(-1) after 2 min, which decreased to 274 ng x ml(-1) after 60 min. Systolic blood pressure and heart rate remained unaltered in both study groups after s-ketamine administration. CONCLUSIONS: Nasal administration of s-ketamine 2 mg x kg(-1) results in a wide spread of plasma concentrations and absorption times. Rapid and high level drug absorption after nasal drug administration is possible. The use of a pulse oximeter and continuous observation after nasal administration of s-ketamine for pediatric premedication is recommended.

Administration, Intranasal↗
PubMed2004

Optimal reduced-set vectors for support vector machines with a quadratic kernel.

To reduce computational cost, the discriminant function of a support vector machine (SVM) should be represented using as few vectors as possible. This problem has been tackled in different ways. In this article,we develop an explicit solution in the case of a general quadratic kernel k(x. x') = (C + D xT x')2. For a given number of vectors, this solution provides the best possible approximation and can even recover the discriminant function if the number of used vectors is large enough. The key idea is to express the inhomogeneous kernel as a homogeneous kernel ona space having one dimension more than the original one and to follow the approach of Burges (1996).

Artificial Intelligence↗
PubMed2004

Intentional occlusion of the left subclavian artery during stent-graft implantation in the thoracic aorta: risk and relevance.

PURPOSE: To examine the clinical consequences and/or potential need for postinterventional transposition after stent-graft occlusion of the left subclavian artery (LSA). METHODS: The records of 171 consecutive patients (128 men; mean age 60.2+/-13.2 years, range 20-83) undergoing elective stent-graft repair in the thoracic aorta were reviewed to identify intentional endograft coverage of the ostial LSA, as documented by transesophageal echocardiography and/or aortography. Patients were treated for subacute type B dissection, true aneurysm, pseudoaneurysm, or previously operated type A dissection with persistent false lumen flow in the descending aorta. Among the 171 cases, 22 (12.9%) patients were identified with stent-graft occlusion of the LSA. RESULTS: A systolic blood pressure differential existed between the right (138.4+/-14.0 mmHg) and the left (101.8+/-21.0 mmHg; p<0.05) arms after occlusion of the LSA. No patient showed a malperfusion syndrome during postinterventional hospitalization. During a mean follow-up of 24.0+/-15.8 months, 15 (68.2%) patients remained completely asymptomatic, with no functional deficit or temperature differential between the arms, while 7 patients reported mild symptoms of a subclavian steal syndrome. However, no patient required any secondary surgical intervention. CONCLUSIONS: Stent-graft-induced occlusion of the ostial LSA was tolerated by all patients without chronic functional deficit. In the absence of stenotic vertebral and/or carotid arteries and with a documented intact vertebrobasilar system, prophylactic transposition of the LSA is not required prior to intentional stent-graft occlusion of the LSA.

Adult↗
PubMed2004

Cranial MRI as a screening tool: findings in 1,772 military pilot applicants.

BACKGROUND: Beginning 1 January 2000, during the selection process, the German Air Force Institute of Aviation Medicine screens all applicants for flying duty using cranial MRI to rule out relevant intracranial abnormalities. Type and frequencies of abnormalities and aeromedical consequences are described. METHODS: An intracranial MRI is done on every applicant regardless of the findings of the physical examination. RESULTS: From 1 January 2001 to 31 December 2002 we investigated a total of 1,772 applicants with cranial MRI. All of these had normal findings in both the general medical and neurological examinations. We found that 81.7% (1,452) were normal, 9% (160) had variations of the norm, 8.4% (148) had findings of unknown significance (e.g., arachnoid cysts, white matter lesions, etc.), and only 0.7% (12) had definite abnormal findings (arteriovenous malformations, cavernomas, tumors). CONCLUSION: Evident pathological cases are rare. However, cranial MRI screening adds substantial new information, increasing the value of the initial examination and making it possible to extend the examination according to the clinical indications. This leads to a highly individualized appraisal of the applicant, thus increasing flight safety.

Adolescent↗
PubMed2003

Percutaneous endovascular repair of aneurysm after previous coarctation surgery.

BACKGROUND: Formation of aortic aneurysm late after surgical repair of coarctation carries a significant risk of rupture and lethal outcome, and repeat surgery is associated with a 14% in-hospital mortality rate and morbidity from paraplegia, injury to the central nervous system, or from bleeding. The potential of nonsurgical endovascular repair by the use of stent-grafts in lieu of repeat surgery for postcoarctation aneurysm is unknown. METHODS AND RESULTS: The concept of postsurgical endovascular stent-graft placement was evaluated with respect to feasibility and safety in 6 consecutive patients with late aneurysm formation after coarctation repair. All patients had aneurysm formation late after patch aortoplasty; placement of an elephant trunk during surgical repair of secondary type I dissection preceded formation of a local aneurysm in 2 cases. Patient age was 49+/-12 years, ranging from 31 to 68 years. Transluminal placement of customized stent-grafts was successful, with no 30-day or 1-year intervention-related mortality or morbidity. Follow-up survey of 11 to 47 months revealed optimal reconstruction of the thoracic aorta; 1 patient died 11 months after endovascular repair from cancer. CONCLUSIONS: Nonsurgical aortic reconstruction of postsurgical thoracic aneurysms forming late after coarctation repair is safe and feasible; interventional stent-graft placement has the potential to avoid repeat surgery of postsurgical aortic aneurysm.

Adult↗
PubMed2003

A PERIOD inhibitor buffer introduces a delay mechanism for CLK/CYC-activated transcription.

We investigated the functions of clock genes period (per) and timeless (tim) in establishing negative feedback on circadian transcription factors clock/cycle (Clk/cyc) in Drosophila. We show that PER protein persists for several hours after rapid degradation of TIM in the morning. We observed in cell culture that isolated PER inhibits CLK/CYC-activated transcription in the absence of TIM and we further demonstrated for the first time in vivo that PER accumulation in a tim loss-of-function mutant background causes efficient inhibition of CLK/CYC-dependent transcription. These results identify PER to be the main inhibitor for CLK/CYC and they suggest a delay mechanism during early morning, when PER protein, after degradation of TIM, forms an inhibitor buffer for CLK/CYC that attenuates the restart of the next cycle of CLK/CYC-activated transcription. While TIM likely enhances the inhibition of CLK/CYC by PER in the dark, our results suggest a reduction of PER-mediated inhibition by TIM in light.

Animals↗
PubMed2003

Clinical profiles and outcomes of acute type B aortic dissection in the current era: lessons from the International Registry of Aortic Dissection (IRAD).

BACKGROUND: Clinical profiles and outcomes of patients with acute type B aortic dissection have not been evaluated in the current era. METHODS AND RESULTS: Accordingly, we analyzed 384 patients (65+/-13 years, males 71%) with acute type B aortic dissection enrolled in the International Registry of Acute Aortic Dissection (IRAD). A majority of patients had hypertension and presented with acute chest/back pain. Only one-half showed abnormal findings on chest radiograph, and almost all patients had computerized tomography (CT), transesophageal echocardiography, magnetic resonance imaging (MRI), and/or aortogram to confirm the diagnosis. In-hospital mortality was 13% with most deaths occurring within the first week. Factors associated with increased in-hospital mortality on univariate analysis were hypotension/shock, widened mediastinum, periaortic hematoma, excessively dilated aorta (>or=6 cm), in-hospital complications of coma/altered consciousness, mesenteric/limb ischemia, acute renal failure, and surgical management (all P<0.05). A risk prediction model with control for age and gender showed hypotension/shock (odds ratio [OR] 23.8, P<0.0001), absence of chest/back pain on presentation (OR 3.5, P=0.01), and branch vessel involvement (OR 2.9, P=0.02), collectively named 'the deadly triad' to be independent predictors of in-hospital death. CONCLUSIONS: Our study provides insight into current-day profiles and outcomes of acute type B aortic dissection. Factors associated with increased in-hospital mortality ("the deadly triad") should be identified and taken into consideration for risk stratification and decision-making.

Aged↗
PubMed2003

Prophylactic thyroidectomy in multiple endocrine neoplasia: the impact of molecular mechanisms of RET proto-oncogene.

BACKGROUND: Multiple endocrine neoplasia (MEN) type 2, a cancer syndrome inherited in the dominant fashion, is defined by the occurrence of medullary thyroid carcinoma (MTC), either as a singular lesion (familial medullary thyroid carcinoma, FMTC) or with the variable expression of pheochromocytoma, hyperparathyroidism (MEN 2A), ganglioneuromas, buccal neuromas and Marfanoid-like phenotype (MEN 2B). DISCUSSION: Germline mutations of the RET proto-oncogene, localized on chromosome 10q11.2, have been identified as the underlying genetic cause of the disorder. In the majority of patients with MEN 2A/FMTC missense mutations at exon 10 or exon 11 are identifiable. Cysteine to arginine exchange at codon 634 is the mutation most frequently found. In MEN 2B approximately 95% of patients present with a mutation at codon 918 (exon 16). Additionally, less frequent mutations in other codons have been found in both syndromes. The DNA-based genotype analysis enables the identification of gene carriers at risk of developing MTC and offer them prophylactic thyroidectomy prior to development of any thyroid pathologies. Prophylactic surgery is generally recommended for MEN 2A/FMTC gene carriers at the age of 4-6 years. Due to the aggressiveness of the MEN 2B syndrome gene carriers should be operated by the age of 1 year. Presumably some less virulent mutations allow postponement of the prophylactic treatment to the second to fourth decade of life. CONCLUSIONS: Compared to standard presymptomatic biochemical screening, genetic testing and consecutive prophylactic treatment contribute to better outcome of individuals at risk for MTC.

Genotype↗
PubMed2003

Premedication with nasal s-ketamine and midazolam provides good conditions for induction of anesthesia in preschool children.

PURPOSE: To evaluate the efficacy and safety of intranasally administered s-ketamine and midazolam for premedication in pediatric patients. METHODS: Ninety children were randomly allocated to receive intranasally administered s-ketamine 1 mg.kg(-1) and midazolam 0.2 mg.kg(-1) (Group K1, n = 30), s-ketamine 2 mg.kg(-1) and midazolam 0.2 mg.kg(-1) (Group K2, n = 30), or midazolam 0.2 mg.kg(-1) (Group M, n = 30) as premedicants, using a double-blind study design. Sedation and anxiolysis were evaluated using a sedation and cooperation scale and recorded at several time points. RESULTS: Acceptable conditions (K1: 23; K2: 26, M: 19) for parental separation were not different between groups. Induction conditions were acceptable in 26 patients in K2 (P < 0.05 vs M) (K1: 23; M: 19). Compared to baseline values individual conditions significantly improved in groups K1 and K2 from 2.5 min after premedication until induction of anesthesia (P < 0.003), in group M conditions improved only five minutes after premedication (P < 0.05). Adverse effects observed in this series were within an acceptable range and similar for the three groups. CONCLUSION: Intranasal administration of s-ketamine and midazolam is an appropriate premedication in preschool children.

Adjuvants, Anesthesia↗
PubMed2003

Interferon-beta-1 b decreased matrix metalloproteinase-9 serum levels in primary progressive multiple sclerosis.

Recent reports have shown that matrix-metalloproteinases (MMPs) facilitate T-cell migration into the CNS and play a role in disruption of the blood-brain-barrier and myelin break-down. An increase of MMP-9 serum levels predicts disease activity in relapsing remitting multiple sclerosis (RRMS). Interferon-beta (IFN-beta), which is an established treatment for RRMS, inhibits T-cell migration in vitro in parallel with the downregulation of MMP expression. Only limited data are available for primary progressive multiple sclerosis (PPMS) which differs in demographic and immunological aspects as well as in MRI criteria from RRMS. In this study, 19 patients with laboratory-supported definite PPMS were treated with 8 x 10(6) IU IFN-beta1b (Betaferon) subcutaneously every other day. Serum was collected before treatment and on months 1, 2, 3, 6 and 9 during treatment. Levels of MMP-9 and of its natural inhibitor known as tissue-inhibitor of matrix-metalloproteinase-1 (TIMP-1) were quantified by ELISA. In addition MMP-2 serum levels were determined by zymography. 19 healthy volunteers served as controls. Before treatment serum levels of MMP-9 were elevated in patients with PPMS compared with controls, whereas there was no difference in TIMP-1 serum levels. During treatment with IFN- beta1b the concentration of MMP-9 in the serum of 18 out of 19 PPMS patients decreased,whereas serum levels of MMP-2 and TIMP-1 remained nearly unaffected. Our results demonstrate that the MMP-9 to TIMP-1 ratio in patients with PPMS is elevated in comparison with healthy controls. The suppression of MMP-9 by IFN-beta1b indicates that this drug is immunomodulatory active in PPMS patients. Further studies are necessary to test if IFN-beta exerts a beneficial effect in PPMS.

Adjuvants, Immunologic↗
PubMed2003

Caudal bupivacaine and s(+)-ketamine for postoperative analgesia in children.

BACKGROUND: The aim of this study was to evaluate whether caudal s-ketamine would prolong analgesia together with caudal bupivacaine. METHODS: Thirty children, ASA I-II, 1 month-9 years, scheduled for minor inguinal or penile surgery, were randomly assigned in a prospective, double-blind fashion to receive single shot caudal blockade by either bupivacaine 0.125% 1 ml.kg(-1) (group B, n = 15) or a mixture of bupivacaine 0.125% 1 ml.kg(-1) and preservative-free s-ketamine 0.5 mg.kg(-1) (group K, n = 15). Postoperative pain was assessed by means of an observational 10-point scoring system and analgesia was administered if the pain score exceeded a value of 3. RESULTS: Within 24 h after caudal block 10 patients (67%) in group K and three patients in group B (20%) did not require additional analgesic medication (P < 0.01). There were no significant differences between the groups for incidence of haemodynamic changes. We did not observe any negative side-effects attributable to the caudal block or s-ketamine. CONCLUSIONS: Addition of preservative-free s-ketamine 0.5 mg.kg(-1) to caudal bupivacaine 0.125% 1 ml.kg(-1) provides significant prolongation of analgesia without producing negative side-effects.

Analgesics↗
PubMed2003

[CSF Filtration as Experimental Therapy in Therapyresistant Psychoses in Borna Disease Virus-Seropositive Patients]

According to previous investigations, mild Borna disease virus encephalitis may underlie a subgroup of affective or schizophrenic type psychoses. And virus-induced immune pathology may underlie even a larger subgroup of psychoses. We treated BDV seropositive patients suffering from therapy resistant schizophrenic or affective spectrum psychoses by cerebrospinal fluid filtration (CSFF) in an experimental add-on treatment. CSFF was shown previously to be an effective immune modulatory treatment in autoimmune neurological disease, Guillain-Barré syndrome. CSFF appears to be an effective treatment in therapy resistant psychosis also, but only 4 patients were treated yet.

Journal Article↗
PubMed2003

Elevated bilirubin and visual perception in pilots.

BACKGROUND: A fatal aircraft accident of a Bo-105 helicopter on May 20, 1996 led to the suspicion that the pilot's raised serum bilirubin level could have contributed to the accident. It was suspected that an increase of bilirubin beyond 20.52 micromol x L(-1) could disturb visual perception. METHODS: In 1998 and 1999, 101 pilots with functional hyperbilirubinemia, diagnosed as Gilbert's syndrome, were subjected to perceptual-psychological testing (signal detection test) during their periodic medical examinations at the German Air Force Institute of Aviation Medicine. The results of the psychophysiological testing were compared with a control group. RESULTS: Reaction time and perception range increased with age and were independent of serum bilirubin level. CONCLUSION: There is no evidence that raised serum bilirubin levels can diminish visual perceptional performance.

Accidents, Aviation↗