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Biomedical subjects

Ralf Dittrich

Publications and source records attributed to Ralf Dittrich.

At least 37 records · Page 2Linked to original sources
PubMed2005

High level of cerebral microembolization in patients supported with the DeBakey left ventricular assist device.

OBJECTIVE: Microembolic signals detected by transcranial Doppler ultrasonography have been demonstrated to be clinically relevant in patients supported with pulsatile left ventricular assist devices. We prospectively investigated the quantity of microembolic signals in patients supported with the continuous-flow DeBakey left ventricular assist device (MicroMed DeBakey VAD; MicroMed Technology, Inc, Houston, Tex) including the refined Carmeda BioActive Surface system (Carmeda AB, Stockholm, Sweden). METHODS: Twenty-three patients (20 male) aged 14 to 62 years supported with DeBakey left ventricular assist devices (n = 6 with Carmeda) were enrolled in this study. Microembolic signal monitorings were performed twice weekly by insonating the middle cerebral artery for 20 minutes without and 20 minutes with oronasal application of oxygen (6 L/min). Evidence of clinically manifest thromboembolic events was based on regular questionnaires, clinical examinations, and results of diagnostic procedures. RESULTS: Despite a low incidence of thromboembolic complications (0.24 per 100 left ventricular assist device days), 20 patients (87%) showed circulating microemboli. Overall, microembolic signals were found in 175 of 499 transcranial Doppler ultrasonographic examinations (35.1%), with mean counts of 81.2 +/- 443 (range 0-5042 signals/h). Both microembolic signal prevalence (25% vs 34%, P = .01) and absolute signal counts (46.5 vs 104, P < .01) significantly declined with oxygen delivery. There was no significant correlation between the individual microembolic signal activity and the incidence of clinical thromboembolism or the intensity of antihemostatic treatment. Patients supported with the Carmeda device did not show reduced rates of clinical thromboembolization or cerebral microemboli. CONCLUSION: In patients with DeBakey left ventricular assist devices, a high load of clinically silent microemboli can be detected within the cerebral arteries despite a low incidence of embolic complications. It needs to be investigated whether such continuous, presumably gaseous microembolization causes cognitive or neuropsychologic deficits.

Adolescent↗
PubMed2005

Placental defence is considered sufficient to control lipid peroxidation in pregnancy.

Oxidative stress is characterized by an overweight of pro-oxidants against antioxidant forces and is associated with atherosclerosis, aging, and reproductive complications. Placenta is the major source of pro-oxidant agents, antioxidant enzyme-systems, and hormones and is able to keep the lipid peroxidation under control in normal pregnancy. As oxidation processes are increased in pregnancy, we would expect a shortening of lag phase of low density lipoprotein (LDL)-oxidation. LDL oxidation assessed by measuring conjugated diene formation is a marker for the early part of lipid peroxidation process and the balance of pro-oxidants and antioxidants influences length of lag phase. Our results show that resistance of LDL oxidation is unchanged during normal pregnancy in the second and third trimester. Only antioxidants are able to protect LDL. Estriol is an antioxidant, increases the lag-phase of LDL-oxidation in vitro, and its serum concentration raises enormous during late pregnancy. Thus the biological role of high levels of estriol during pregnancy may be part of the self-protection to limit oxidative damages.

Antioxidants↗
PubMed2005

Increased uterine arterial pressure and contractility of perfused swine uterus after treatment with serum from pre-eclamptic women and endothelin-1.

The present study was designed to examine the effects of ET-1 (endothelin-1) and serum from PE (pre-eclamptic), HP (healthy pregnant) and HNP (healthy non-pregnant) women on uterine arterial perfusion pressure and uterine contractility. Swine uteri (n = 25) were perfused for a period of up to 11 h, with the aim being to preserve a viable organ. Various concentrations of ET-1 as well as serum from PE, HP and HNP women (n = 10 per group) were administered to the perfused swine uteri and IUP (intrauterine pressure) and IAP (intra-arterial pressure) were recorded. ET-1 produced dose-dependent increases in IUP and IAP. The ET-1 concentration in serum was higher in serum from PE women than in HP and HNP women (P > 0.05). Administration of all serum samples had a contractile effect on the swine uterus, with the greatest effect being seen in HNP women (12.8 +/- 5.3 mmHg), followed by PE (9.06 +/- 4.2 mmHg) and HP (6.1 +/- 4.1 mmHg) women. Statistically significant differences were observed between HNP and PE women (P = 0.048), and PE and HP women (P = 0.021). Increases in IAP following administration of serum from PE women (48.8 +/- 20.0 mmHg) were significantly higher (P = 0.024) compared with the effect of serum from HP women (28.4 +/- 13.7 mmHg). In conclusion, the findings show that serum from PE women has significant vasoconstrictive and oxytocic effects compared with serum from HP women. In pre-eclampsia, the balance between vasorelaxing and vasoactive substances is disturbed.

Animals↗
PubMed2005

Placebo-controlled randomized comparison of vaginal with rectal misoprostol in the prevention of postpartum hemorrhage.

AIM: To compare vaginally administered misoprostol to rectally administered misoprostol and placebo in a prospective randomized placebo-controlled study. METHODS: One hundred and fifty women with singleton vaginal deliveries were randomized (50 women in each arm) to receive 400-microg misoprostol tablets (crushed and suspended in a microenema) intravaginally, or 400-microg misoprostol tablets rectally, or two placebo lactose tablets rectally. The medication was administered immediately after delivery of the placenta. Women with profuse hemorrhage and delayed placental separation (>30 min) were excluded. Our outcome measures were postpartum blood loss 1 h after administration, and change in hemoglobin and hematocrit values from baseline to postpartum day 1. Analysis of variance and chi-squared tests were used to compare the outcome variables between groups. RESULTS: One hundred and twenty-six women were available for analysis. Baseline characteristics were similar across the groups. The number of excluded subjects, the estimated blood loss, and the drop in hemoglobin and hematocrit values did not differ between the three groups (P > 0.05). CONCLUSIONS: Misoprostol administered vaginally or rectally at a dosage of 400 microg following placental separation was not effective for decreasing postpartum bleeding in women without excessive hemorrhage.

Administration, Intravaginal↗
PubMed2005

Comparison of a 1-MHz and a 2-MHz probe for microembolus detection using transcranial Doppler ultrasound.

OBJECTIVES: Clinically silent microembolic signals (MES) can be detected by transcranial Doppler sonography (TCD). There is theoretical evidence that lower ultrasound emission frequencies may lead to a higher signal intensity and thus sensitivity to detect MES. We compared a 1-MHz probe with a 2-MHz probe regarding sensitivity in the detection of MES. Moreover, embolus detection by transcranial Doppler ultrasound is very time consuming and semi-automated detection is mandatory. Therefore, we studied an on-line algorithm using the bi-gate technique and the two transmission frequencies. METHODS: After defining detection thresholds of > or = 12 dB (1 MHz) and > or = 10 dB (2 MHz) with eight normal subjects as MES-negative controls, taking into account natural fluctuations of the Doppler spectrum, we studied 36 patients with ischaemic events and five asymptomatic patients with incidental embolic sources. All patients subsequently underwent a 1-hour unilateral embolus detection from the middle cerebral artery (MCA) or the posterior cerebral artery (PCA), respectively, using 1 and 2 MHz for 30 minutes each in a randomized order. The software algorithm was compared with a blinded off-line analysis by an experienced observer as a gold standard. RESULTS: The investigator detected 198 MES (range 0-41 MES) in the recordings of 29 patients out of the 41 patients using the 1-MHz probe and 101 MES (range 0-32 MES) in the recordings of 14 patients using the 2-MHz probe (p = 0.0007). Sensitivity of the software to detect MES confirmed by the investigator was 31% using 1 MHz and 41% using 2 MHz. The positive predictive value was 6 and 30%, respectively. DISCUSSION: The sensitivity and positive predictive values of the automated algorithm to detect MES were unacceptably low for clinical practice with both frequencies. The use of 1 MHz instead of 2 MHz may, however, be useful when evaluating the recordings off-line by an experienced blinded observer.

Adolescent↗
PubMed2005

Capnography screening for sleep apnea in patients with acute stroke.

Sleep apnea syndrome (SAS) is a prominent clinical feature in acute stroke patients. Diagnosis is usually established by polysomnography or cardio-respiratory polygraphy (CRP). Both diagnostic procedures produce high costs, are dependent on the access to a specialized sleep laboratory, and are poorly tolerated by patients with acute stroke. In this study we therefore investigated whether capnography may work as a simple screening tool in this context. In addition to conventional CRP, 27 patients with acute stroke were studied with capnography provided by our standard monitoring system. The trend graphs of the end-tidal CO(2) values (EtCO(2)) were used to determine the capnography-based estimate of the apnea-hypopnea index (AHI(CO2)). Index events were scored when the EtCO(2) value dropped for > 50% of the previous baseline value. We found that the AHI(CO2) correlated significantly with the apnea-hypopnea index measured with conventional CRP (AHI(CRP)) (r = 0.94; p < 0.001). An AHI(CO2) > 5 turned out to be highly predictive of an AHI(CRP) > 10. According to our findings, routinely acquired capnography may provide a reliable estimate of the AHI(CRP). The equipment needed for this screening procedure is provided by the monitoring systems of most intensive care units and stroke units where stroke patients are regularly treated during the first days of their illness. Therefore, early diagnosis of SAS in these patients is made substantially easier.

Aged↗
PubMed2005

Can Doppler time domain analysis of microembolic signals discriminate between gaseous and solid microemboli in patients with left ventricular assist device?

OBJECTIVE: Microembolic signals (MES) can be detected by transcranial Doppler sonography (TCD). To identify gaseous microemboli the inhalation of oxygen is an established method in patients with prosthetic heart valves. Time domain analysis of sample volume length (SVL) and of frequency modulation showed promising results in the discrimination between solid and gaseous microemboli. We investigated whether these time domain analyses allow the discrimination of different types of microemboli in patients with the non-pulsatile DeBakey left ventricular assist device (LVAD). MATERIALS AND METHODS: Repeated unilateral detection of MES was performed by TCD in 20 patients supported with DeBakey LVAD. Each monitoring session consisted of 20 minutes without and 20 minutes with inhalation of 100% oxygen (6 l/min). A total of 500 MES, detected with (n=250) or without (n=250) the supply of oxygen, were randomly chosen for offline analysis. The SVL (in cm) was calculated by duration and velocity of the MES measured in the time domain mode. Additionally, frequency modulation of MES was classified into three main types: Without modulation (type I), with gradual changes (type II) and with rapid changes (type III). RESULTS: With oxygen supply, both prevalence (26.4% versus 36.2%, p<0.01) and mean counts of MES per hour (49+/-293 versus 108+/-550, p<0.001) significantly declined compared with the MES load while breathing room air. There was no significant difference in the SVL of MES under oxygen (0.85+/-0.38 cm) compared with those without oxygen delivery (0.92+/-0.37 cm, p=0.6). Furthermore, no significant differences were noted for the MES frequency modulation types in time domain analysis with regard to oxygen supply. CONCLUSIONS: The reduction of MES under oxygen delivery confirms the gaseous nature in a substantial number of circulating microemboli produced by the DeBakey LVAD. However, SVL and frequency modulation of MES did not appear to provide valuable information regarding the structural nature of the underlying microembolic material.

Brain↗
PubMed2005

High dose estrogen treatment increases bone mineral density in male-to-female transsexuals receiving gonadotropin-releasing hormone agonist in the absence of testosterone.

OBJECTIVE: To study the effect of estrogen (E) on the male skeleton in the absence of testosterone (T). DESIGN: Retrospective analyses of 40 middle-aged transsexuals treated with subcutaneous injections of gonadotropin-releasing hormone agonist every 4 weeks and oral 17-beta-estradiol-valerat 6 mg/day over two years until reassignment surgery. METHODS: The bone mineral density (BMD) in the femoral neck and lumbar spine (L2-L4) was measured with dual-energy X-ray absorptiometry at the beginning of cross-sex hormone treatment, after 12 and 24 months, and serum T, E, sex hormone-binding globulin (SHBG), calcitonin (CAL), osteocalcin (OSC), and urinary free deoxypyridinoline (DPD) were measured. RESULTS: After 12 months, a significant increase in BMD in the lumbar spine from 1.2 to 1.234 g/cm2 and after 24 months to 1.274 g/cm2 was observed. There was a significant increase in BMD in the femoral neck area from 1.068 to 1.109 g/cm(2) after 24 months. There was a significant decrease in serum T levels from 18.65 to 0.57 nmol/l after 12 months, and to 0.62 nmol/l after 24 months, a significant increase in SHBG levels from 50.09 to 125 nmol/l after 12 months, and to 130 nmol/l after 24 months, and a significant increase in serum E levels from 73.42 to 881.6 pmol/l after 12 months, and to 923.62 pmol/l after 24 months of cross-sex hormone treatment. Serum levels of CAL, OSC and urinary DPD were unchanged. CONCLUSION: We conclude that high dose E treatment is able to increase BMD significantly in the femoral neck and lumbar spine independently of serum T levels in middle-aged men. There is no risk of osteoporosis developing in male-to-female transsexuals receiving GnRHa when there is an adequate E substitution.

Adult↗
PubMed2004

Endothelial Chlamydia pneumoniae infection promotes oxidation of LDL.

The bacterium Chlamydia pneumoniae chronically infects atheromatous lesions and is linked to atherosclerosis by modifying inflammation, proliferation, and the lipid metabolism of blood monocytes. As continuous LDL modification in the vascular intima is crucial for atherogenesis we investigated the impact of endothelial infection on LDL oxidation. HUVEC were infected with a vascular C. pneumoniae strain. Supernatants of infected cells but not cell lysates increased lipid peroxidation products (6.44 vs 6.14 nmol/ml, p<0.05) as determined by thiobarbituric acid reacting substances assay. Moreover, supernatants rendered human LDL more susceptible to oxidation as shown in a copper-ion catalysed LDL oxidation assay by a 16% reduction of LDL resistance against pro-oxidative stimuli (p<0.05). Chlamydial infection of vascular endothelial cells releases acellular components that convert LDL to its proatherogenic form and reduce its resistance against oxidation. Foci of chronic endothelial chlamydial infection may thus continuously contribute to the dysregulated lipid metabolism that promotes atherogenesis.

Catalysis↗
PubMed2004

The identification of right-to-left shunts using contrast transcranial Doppler ultrasound: performance and interpretation modalities, and absence of a significant side difference of cardiac micro-emboli.

Cardiac and extracardiac right-to-left shunts can be identified by transesophageal echocardiography (TEE) as well as by transcranial Doppler ultrasound (TCD) using contrast agents that do not pass the lungs. Currently, the appropriate performance of a Valsalva manoeuvre (VM) to provoke the shunt, the use of different contrast agents and the classification of the TCD results are still under debate. In this study, we looked also at possible side effects of provoked cardiac micro-emboli in the left and right hemisphere. Seventy-one patients were investigated by both TEE and bilateral TCD of the middle cerebral arteries. The following protocol was applied in a randomized way: (1) Echovist-300 without VM; (2) Echovist-300, VM for 5 seconds starting 5 seconds after the beginning of contrast injection; (3) repetitive short VMs in between 2 and 13 seconds after the beginning of Echovist-300 injection; and (4) repetitive short VMs in between 2 and 13 seconds after the beginning of agitated saline injection. Only if one of the tests (2-4) was negative, this particular negative test was repeated. Use of Echovist-300, but not of saline yielded 100% sensitivity in the detection of TEE-proven shunts. The repetitive VM was slightly superior to the conventional VM. Introduction of a threshold of two or even three microbubbles produced less falsely positive TCD results in comparison to the TEE. There was no difference in microbubbles. TCD using Echovist-300 is a sensitive method to identify TEE-proven cardiac right-to-left shunts. Repetitive VM is an alternative to conventional VM.

Adult↗
PubMed2003

Right-to-left-shunts detected by transesophageal echocardiography and transcranial Doppler sonography.

BACKGROUND: Transesophageal echocardiography (TEE) and transcranial Doppler sonography (TCD) can identify right-to-left-shunts that predispose to paradoxical embolism. In a large cohort we compared the results of both techniques. METHODS: 222 patients were investigated by both techniques using the contrast agent Echovist-300 and performing each test once without and once with the Valsalva maneuver (VM). RESULTS: TEE-proven right-to-left-shunts were detected by TCD with a high sensitivity of 94%. In addition, TCD revealed shunts not noted during TEE in about 20% of all patients studied. These shunts are in general smaller than those concordantly identified; however, 9% of the patients without a TEE-proven shunt presented with a shunt that allows a considerable amount of contrast medium to pass. There were 12% more microbubbles detected in the right middle cerebral artery than in the left middle cerebral artery during the TCD test performed with VM, but not during the TCD test performed without VM. CONCLUSIONS: Contrast-enhanced TEE and TCD are complementary methods in the assessment of stroke and stroke-prone patients. The side difference of microbubbles may indicate a selective streaming of cardiac emboli during VM.

Adolescent↗
PubMed2003

Spontaneous normalization of ovarian function and pregnancy in a patient with resistant ovary syndrome.

We report a case of normalization of ovarian function followed by pregnancy in a young woman with hypergonadotropic ovarian failure. The change from the hypergonadotropic to the normogonadotropic state was followed by serial hormone determination and ultrasonography. It occurred within a few days and was accompanied by an increase in estradiol as well as circulating Inhibin A concentrations.

Adult↗
PubMed2003

Maillard reaction products inhibit oxidation of human low-density lipoproteins in vitro.

Dietary intake of antioxidants has been associated with a reduced risk of cardiovascular diseases, which is very likely caused by their capability of prevent oxidation of low-density lipoproteins (LDL). During food processing and storage, substances with antioxidative properties are formed by Maillard reactions. In this study, the activity of Maillard products to inhibit copper-induced oxidation of human LDL in vitro was investigated. d-Glucose was heated with an equimolar amount of glycine, l-lysine, or l-arginine, for 1 h under reflux. The increase of the antioxidative activity (AOA) of the Maillard mixtures was highly significant compared to the control mixtures. Additionally, two defined Maillard products with amino reductone structure were tested. 3-Hydroxy-4-(morpholino)-3-buten-2-one (1) and amino hexose reductone (2) showed a significant and dose dependent AOA. Compound 1 was about half as active as ascorbic acid, which served as positive control. Thus, it can be concluded that Maillard products, particularly those with amino reductone structure, have the strong potential to inhibit LDL oxidation.

Antioxidants↗
PubMed2003

On the origin of microembolic signals--a clinical and postmortem study.

BACKGROUND AND PURPOSE: Clinically silent circulating microembolic signals (MES) can be identified by transcranial Doppler ultrasound (TCD). It is not yet clear whether their occurrence is always linked to the presence of embolic sources. METHODS: 24 terminally ill patients (7 women, 17 men; mean age 68 years) were investigated by TCD of the middle cerebral arteries. These findings were correlated with a complete post-mortem examination of potential embolic pathways. RESULTS: Four patients out of the 24 under investigation showed MES, 2 of them bilaterally. All these 4 MES-positive patients had a definite embolic source, i. e. bilateral carotid artery occlusive disease, endocarditis with thrombotic valvular adhesions and severe plaques in the aortic arch, dilated left atrium and a patent foramen ovale, or severe plaques in the aortic arch and a dilated left atrium, respectively. CONCLUSION: In the investigated patient group, we could demonstrate that MES can only be found when an embolic source is present. The finding of MES justifies an extensive clinical and laboratory search for potential embolic sources including extracranial and intracranial colour-coded duplex ultrasound, ECG, Holter-ECG, and TEE.

Adult↗
PubMed2003

Microembolus detection in four patients with Fabry's disease: further support for a primarily microangiopathic origin of early cerebrovascular symptoms.

Fabry's disease is a sex-linked recessive storage disorder leading to cerebrovascular symptoms in many cases. Whether the primary origin of cerebrovascular symptoms in these patients is due to autochthonous thrombosis of small vessels or embolic infarction from large vessels is under debate. Microembolic signals (MES) indicative of an active embolic source can be recorded by transcranial Doppler sonography. We report four patients (34, 44, 62 and 66 years old) with Fabry's disease from one kindred in whom we carried out microembolus detection recordings to disclose active embolic sources. Three of the patients had had transient focal neurological deficits. Two patients had angina pectoris and one had exercise dyspnea, but no patient had clear evidence of disease of the large coronary vessels or brain-supplying arteries. No MES were found in 1-hour recordings in any patients, supporting the hypothesis that early cerebrovascular symptoms arise from small vessel occlusion and not from embolic sources as an indicator of disease of large brain-supplying arteries or cardiac embolism.

Adult↗
PubMed2002

Comparison of GnRH agonists and antagonists in unselected IVF/ICSI patients treated with different controlled ovarian hyperstimulation protocols: a matched study.

OBJECTIVES: To evaluate the results of the use of GnRH antagonist (GnRHant) and GnRH analog (GnRHa) in two matched groups of unselected IVF/ICSI patients in a retrospective matched pair analysis. STUDY DESIGN: Patients (n=52) were stimulated with human menopausal gonadotropin (hMG) and/or recombinant FSH (rFSH). In Group I (n=26) a daily dose of 0.25mg of Cetrorelix (GnRHant) was administered when follicles reached a diameter of > or = 14 mm. Patients in Group II (n=26) were first desensitized with GnRHa triptorelin long protocol, which was continued during the gonadotropins treatment until the induction of ovulation. RESULTS: In both groups, serum LH levels remained low during the stimulation. The mean length of stimulation, and the dose of FSH required per patient were similar in both groups. The mean E2 level on day of hCG administration was significantly higher in the patients of Group II (2076+/-1430 versus 1145+/-605 pg/ml), however, a progressive increase in serum E2 concentration during the cycle was noted in both groups. A median of 5.38 and 6.34 mature oocytes per patient was obtained, and the fertilization rate was 59.3% in Group I and 63.6% in Group II. Pregnancy rate (PR) were better in Group II (15 versus 5%), and no severe or moderate ovarian hyperstimulation syndrome (OHSS) occurred. CONCLUSIONS: GnRHant and GnRHa provide comparable results in unselected patients, while GnRHant allows a higher flexibility in the treatment.

Embryo Transfer↗
PubMed2002

Microembolus detection by transcranial doppler sonography.

Microembolic signals can be detected by transcranial ultrasound as signals of high intensity and short duration. These signals represent circulating gaseous or solid particles. To optimize the differentiation from artefacts and the background signal and to facilitate the clinical use, several attempts have been made to automatize the detection of microemboli. Microemboli occur spontaneously in various clinical situations but their clinical impact and possible therapeutical implications are still under debate. This article provides a review of the actual literature concerning the current state of technical and clinical aspects of microembolus detection.

Artifacts↗