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Biomedical subjects

J H Beer

Publications and source records attributed to J H Beer.

At least 19 recordsLinked to original sources
PubMed2005

Shorter PFA-100-closure times in laparoscopic versus conventional hysterectomy are not caused by increased vasopressin levels.

BACKGROUND/OBJECTIVES: Bleeding problems during laparoscopic surgery are infrequent. We hypothesised that increased abdominal pressure during the application of the pneumoperitoneum would lead to an increased release of endogenous vasopressin which could then contribute to the hemostasis by increasing platelet reactivity, FVIII and von Willebrand-factor. PATIENTS AND METHODS: We compared the vasopressin levels, the platelet function as measured by the PFA-100-test, aPTT and FVIII in 39 consecutive patients who underwent elective hysterectomy (20 with the laparoscopic and 19 with the conventional, "open" method). Blood was sampled the day before surgery and 2, 4 and 72 h after the induction of anaesthesia. RESULTS: After two hours, the PFA-100 closure times with collagen/ADP decreased to lower levels in the laparoscopic group (from 93 +/- 22 to 82 +/- 20, mean +/- SD) and even further down to 65 +/- 13 s (compared to 82 +/- 20 s) (p = 0.024)) four hours after the beginning of surgery. Vasopressin levels and F VIII increased in both groups but there was no significant difference between the groups (21 vs. 17.8 pmol/l for vasopressin, differences of the mean). Bleeding was minimal, with a trend to lower Hb-levels in the laparotomy group. CONCLUSIONS: The procedural difference of laparoscopic vs. open hysterectomy appears to enhance platelet reactivity by other mechanisms than increased vasopressin levels and may contribute to an enhanced hemostatic competence in laparoscopic surgery.

Adult↗
PubMed2005

[Alpine cheese--healthy for your heart or just a lifestyle product?].

Until the 19th and the early 20th century, milk and milk products, particularly of alpine origins, seemed of special nutritional and health value and were highly recommended for the therapy resp. the therapeutic adjunct of various diseases, particularly for pulmonary tuberculosis. More recently, the association of saturated fat intake and arteriosclerosis led to the reduced use of milk and cheese resp. to the introduction of low-fat milk products. Again, alpine milk and cheese seem to differ somewhat from the others, since they appear to contain 4 times more alpha linolenic acid, three times more conjugated linoleic acid, a lower n-6:n-3 ratio, more total n-3 fatty acids and less palmitic acid as a measure of total saturated fat compared to cheese produced with silage feed in the lowlands (e.g. english cheddar). Even cheese from cows fed with linseed supplementations did not reach the n-3 concentrations of the alpine probes. Thus, alpine milk products from cows kept traditionally, and fed predominantly with alpine grass seem to have an interesting cardiovascular and possibly an economically favourable potential.

Altitude↗
PubMed2003

[Antiaggregation: aspirin].

Many randomized trials have shown aspirin as an effective antiplatelet drug for the secondary prevention of cardiovascular events. The NNT (number needed to treat) to prevent 1 vascular event is about 25. The NNH (number needed to harm) inducing one cerebral bleeding is about 1'000, to provoke one severe extracerebral bleeding about 100-200. The primary prevention can be recommended only for high risk patients for cardiovascular events (annual risk of 1-1.5% or more), calculated on the basis of the Framingham data, the Sheffield tables or in analysis of U.S. Preventive Services Task Force. The mechanisms of action, interactions and the "aspirin-resistance" are briefly discussed.

Administration, Oral↗
PubMed2002

Coagulation markers predict survival in cancer patients.

In order to prospectively evaluate the predictive value of coagulation markers such as the fibrin Ddimer for survival of cancer patients, we analyzed their role in a prospective study at a University Hospital Institute of Medical Oncology. 268 consecutive outpatients with cancer were included, 72 in remission and 196 with active disease. All cause mortality in relation to the marker levels was measured. 99/268 patients died during the observation period of 4,484 patient months (mean: 17 months). Patients with active disease had a significant, 1.5-5-fold increased marker concentration compared to patients in remission. When analyzed in quartiles, the data showed a lower than predicted death rate in the first quartile and a significantly elevated mortality in the fourth marker quartile. The odds ratio for death predicted by the fibrin monomer (FM) in the fourth vs. the first quartile was 4.1 (95% C.I.: 1.7-9.7) and p = 0.005 for the multivariate analysis of the markers. We conclude that a single determination of coagulation markers, particularly of TAT, FM, and Ddimer is sufficient to strongly predict survival in cancer patients over the following 1-3 years.

Antithrombin III↗
PubMed2001

Critical appraisal of the diagnostics of 270 consecutive cases of suspected venous thromboembolism and established consequences at a non-university center.

QUESTIONS UNDER STUDY: Diagnostic strategies in venous thromboembolism (VTE) are subject to controversy and rapid change and are dependent on the availability of the specific tests. The aim was to critically analyse the diagnostic procedures in patients with VTE at an intermediate size, non-university hospital. METHODS: The diagnostic work up of 270 consecutive patients with suspected VTE disorders was analysed prospectively and the therapeutic decisions were monitored and compared with the actually implemented new standard evaluation which consists of a sequential application of the diagnostic tools (clinical probability, D-dimer compression ultrasound V/Q lung scan or CT). The patients were followed clinically for at least three months. RESULTS: 50% of the 55 patients with suspected deep vein thrombosis (DVT) and 35% of the 215 patients with suspected pulmonary embolism (PE) were found positive and were anticoagulated. The overall number of patients being anticoagulated was not significantly changed by the new procedure but approximately 30% of the additional examinations inclusive V/Q-scans, spiral CT and compression ultrasound or phlebography could be saved. Our study and the follow up after the therapeutic decision indicate that 92% of the patients can be clearly and safely allocated, while the remainders are managed according to an essentially clinical decision. CONCLUSIONS: The vast majority (>90%) of the patients can be clearly diagnosed as positive or negative with the strategy presently used. A minority still requires an "overall decision". Our modified approach results in considerable cost savings.

Adult↗
PubMed2001

Variability in platelet responses to collagen--comparison between whole blood perfusions, traditional platelet function tests and PFA-100.

The purpose of this study was to determine if the results obtained in platelet function tests and whole blood perfusions are associated with those in platelet function analyser (PFA)-100. We used collagen type I monomers and fibrils to analyse the distinct roles of glycoprotein (GP) Ia/IIa and other collagen receptors in flowing blood under a high shear rate (1600/s) and in aggregation studies. Also, anticoagulation [citrate vs. D-phenylalanyl-1-prolyl-1 arginine chloromethyl ketone (PPACK)] was varied to enhance the functions of GP Ia/IIa, since it has been shown that the cation-poor environment of citrated blood impairs GP Ia/IIa-dependent platelet recruitment. Large interindividual variability (45-fold) was detected in deposition of platelets in whole blood perfusions over collagen monomers, whereas this variation was only fourfold in fibrils. In PFA, this variation was reduced to 2.5-fold. However, platelet deposition on monomers is associated with epinephrine-enhanced PFA (r=-.49, P<.03), whereas platelet deposition on fibrils is correlated with adenosine diphosphate (ADP)-enhanced PFA (r=-.47, P<.05), suggesting a distinct synergism between epinephrine and monomers (GP Ia/IIa) as well as ADP with fibrils (other collagen receptors). Donors with 807 C/C polymorphism of GP Ia (n=14) had longer lag phase in aggregation experiments compared with C/T (n=7) both by monomers and fibrils (P<.04), but these polymorphisms with their mild impact on GP Ia/IIa activity did not markedly differ in other tests. In conclusion, the results obtained in perfusion studies and PFA experiments correlated, but PFA fails to reveal the large-scale variability related to collagen-induced platelet responses.

Adenosine Diphosphate↗
PubMed2000

Preparation and characterization of 'heparinocytes': erythrocytes with covalently bound low molecular weight heparin.

In an attempt to create the possibility of stable, long acting, intravascular anticoagulation, low molecular weight heparin was modified by introducing a sulfhydryl group into the molecule (LMWH-SH). Human erythrocytes were covalently grafted with LMWH-SH by the use of a heterobifunctional coupling reagent which reacts with the SH group of LMWH-SH and surface exposed amino groups of erythrocytes now called 'heparinocytes' (HC). HC were morphologically indistinguishable from untreated erythrocytes and displayed identical osmotic resistance. The functionality of HC was analyzed by classical coagulation tests in which they dose dependently inhibited clot formation. HC were also functional in recalcified whole blood inhibiting thrombin formation as assessed by the cleavage of the chromogenic substrate S-2238. The system appears applicable as a potential autologous, long-term anticoagulant treatment or prophylaxis.

Blood Coagulation↗
PubMed2000

Genetics of platelet receptor single-nucleotide polymorphisms: clinical implications in thrombosis.

Several single-nucleotide polymorphisms (SNPs) of platelet receptors have been implicated to be associated with an increased risk of arterial thrombosis; this review focuses on the mechanisms and the clinical significance of two specific single-nucleotide polymorphisms, ie the GP IIIa L33P (=PlA1/2) and the GP Ia 807 C/T. Whereas the mechanism of P1A2 is thought to result from 'gain of receptor function' (and there is still considerable controversy on this subject), the collagen receptor SNP is associated with an increased number of receptors on the platelet surface, thus offering a plausible explanation for the observed increased interaction with collagen and the increased risk of thrombotic events reported in some studies but not in others. Overall, the presently available (controversial) data do still not allow the conclusion that the GPIIIa polymorphism alone represents a cardiovascular risk factor in the general population. A number of mechanisms and a series of studies suggest, however, that it may be a risk factor in certain subgroups of patients or in a number of clinical situations. The GPIa SNP discussed seems to be a mild risk factor that is particularly important in synergism with known risk factors, such as smoking, hypertension, diabetes or proteinuria, etc, which may enhance its contribution to the overall cardiovascular risk.

Angina Pectoris↗
PubMed1999

[New antiplatelet agents].

Aspirin has set the gold standard for platelet inhibition in prophylaxis and treatment of cardiovascular diseases. Invasive techniques and novel platelet-inhibitors have fundamentally changed therapeutic approaches to antithrombotic treatment and further diversification is to be expected in the future. Three trends are essentially obvious: 1) the combination of established inhibitors such as aspirin with ticlopidine or clopidogrel, 2) the use of new IIb/IIa antagonists in various molecular forms, pharmacologies and doses and 3) the combination of established platelet-inhibitors with theses novel IIIb/IIIa antagonists.

Humans↗
PubMed1999

Association of two silent polymorphisms of platelet glycoprotein Ia/IIa receptor with risk of myocardial infarction: a case-control study.

BACKGROUND: The platelet membrane glycoprotein Ia/IIa plays a major part in platelet function as a primary receptor for collagen. A previous report showed a variation of glycoprotein Ia/IIa receptor density and function associated with two silent and linked polymorphisms (807C/T and 873G/A) within the glycoprotein Ia gene. Because platelet thrombus formation is implicated in the pathogenesis of acute myocardial infarction, we investigated these polymorphisms among patients who had had a myocardial infarction. METHODS: We did a 2/1 case-control study including 177 patients (median age 57.0 [range 32-72] years) and 89 controls with same age and sex. Distributions of the 807C/T and 873G/A polymorphisms were investigated by genotyping DNA by PCR, single-strand conformation polymorphism analysis, and sequencing. FINDINGS: The prevalence of the homozygous 807T/873A genotype was 2.9 times higher among patients with myocardial infarction than among controls (16.4% vs 5.6%, p=0.022). There was an association between patients homozygous for the 807T/873A allele and myocardial infarction (odds ratio 3.3 [95% CI 1.2-8.8]), which was strongest in a subgroup of smokers. The homozygous 807T/873A genotype remained an independent risk factor for myocardial infarction (p=0.005) when age, sex, smoking, hypertension, diabetes, body-mass index, LDL-cholesterol and HDL-cholesterol, and fibrinogen were adjusted for by logistic regression. INTERPRETATION: The 807T/873A homozygosity of the platelet glycoprotein Ia/IIa gene polymorphism, associated with differences in surface collagen receptor density and activity, appears to be an independent risk factor for acute myocardial infarction. Our findings need to be confirmed in a larger, prospective study that includes patients from different populations and cardiovascular risk groups.

Adult↗
PubMed1999

Ifosfamide-induced stomatocytosis and mesna-induced echinocytosis: influence on biorheological properties of blood.

Ifosfamide is an alkylating agent which has poorly understood toxic side effects such as encephalopathy. We hypothesized that ifosfamide and concomitantly applied mesna could have an influence on the flow properties of blood, and thus carried out an in vitro study. Whole blood was incubated in vitro with increasing concentrations of ifosfamide (0-50 mg/ml), mesna (0-20 mg/ml) and combinations thereof. Chloroacetaldehyde, a major metabolite of ifosfamide, was also studied (0-5 mmol/l). Ifosfamide led to a dose-dependent stomatocytic shape transformation and mesna to an echinocytic shape transformation of erythrocytes. These shape changes were reversible upon removal of the causing agent. Both shape changes increased whole blood viscosity. Erythrocyte aggregation was decreased by both drugs at high concentration. Erythrocyte deformability, as measured with the transit time through 5-microm pores, was decreased by mesna and remained unaffected by ifosfamide. These effects were seen at concentrations which may be reached in vivo at the infusion site of the drugs into a vein and in the urinary tract. We conclude that ifosfamide and mesna interact with the lipid bilayer of the cell membrane, which may contribute to the toxicity of the compounds.

Adult↗
PubMed1999

Influence of aspirin on platelet count and volume in humans.

Platelet volume and total platelet mass are parameters of platelet activity and have become a prognostic factor in coronary heart disease. We have studied the influence of aspirin on platelet count, volume and total platelet mass in vitro and in a randomized double-blind, placebo-controlled study in 20 healthy young male volunteers in vivo. Aspirin had no influence in vitro on either platelet count, volume or mass. Repeated blood sampling during a 7-day treatment with 250 mg aspirin daily showed an increased platelet count (7.3% on day 1, 3.0% on day 2, 6.8% on day 4 and 9.3% on day 7; p < 0.01) and total platelet mass (7.2, 5.0, 8.6 and 11.5% on days 1, 2, 4 and 7, respectively, p < 0.01). Aspirin treatment without repeated blood withdrawal had no effect. These data indicate that aspirin may affect the circulating platelet mass under certain conditions.

Adult↗