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A Thiel

Publications and source records attributed to A Thiel.

At least 19 recordsLinked to original sources
PubMed1997

CD45RA-expressing memory/effector Th cells committed to production of interferon-gamma lack expression of CD31.

It has been considered before that human naive and memory/effector CD4+ T-cells cannot be subdivided solely according to the differential expression of CD45 isoforms. By the lack of expression of CD31 we have identified a subset of CD4+ CD45RA+ CD31- cells which show distinct features of antigen-experienced Th1 cells. Short term stimulation of highly purified human peripheral blood CD4+ T-cells with PMA/ionomycin, followed by the cytometric analysis of intracellular cytokines, showed that a minor subpopulation of CD4+ CD45RA+ CD45RO- cells is able to produce interferon-gamma (IFN-gamma) rapidly, a characteristic of antigen-experienced Th1 cells. Whereas among CD45RA+ CD4+ T-cells both CD31+ and CD31- subsets produce interleukin-2 (IL-2) upon PMA/ionomycin stimulation, only the CD31- subpopulation is able to produce IFN-gamma. Thus, our phenotypic and functional characterization of CD45RA+ CD45RO- Th cells shows that CD45RA+ CD45RO- cells do not represent a homogeneous population of antigen-unexperienced, naive T-cells. We speculate that a certain subset of human CD4+, CD45RO+ memory T-cells reverts to expression of the CD45RA isoform, and that this subset can be identified by the lack of CD31 expression.

Animals↗
PubMed1997

[Transcranial doppler sonography. Effect of sevoflurane in comparison to isoflurane].

METHODS: Using transcranial Doppler sonography (TCD), we studied the effects of sevoflurane compared to equipotent doses of isoflurane on blood-flow velocity in the middle cerebral artery (MCA) before, during, and after general anaesthesia. In random order, 30 patients received sevoflurane (n = 15) or isoflurane (n = 15) given in stepwise-increasing doses of 0.5, 1.0, and 1.5 MAC in oxygen/air (FiO2 = 0.5). Oxygen/air was then replaced by oxygen/nitrous oxide 33%/65% with decreasing doses (1.5, 1.0, 0.5 MAC) of sevoflurane or isoflurane. During each step, ventilation was controlled to provide first normocapnia (end-tidal pCO2 = 38 mmHg) and then hypocapnia (end-tidal pCO2 = 27 mmHg). MCA blood-flow velocity and pulsatility, arterial blood pressure, heart rate, and body temperature were recorded simultaneously at the end of each period. For statistical analysis, within-group comparison was made by one-way ANOVA. Differences between groups were determined by two-way analysis of variance. Age, weight, and height of the patients were compared using Student's t-test; P < 0.05 was considered significant. RESULTS: Groups were comparable regarding age, weight, and height. TCD parameters were not significantly changed by increasing doses of sevoflurane or isoflurane given in oxygen/air when compared to the awake data. However, increasing MCA blood-flow velocity was found with decreasing doses of sevoflurane or isoflurane given in oxygen/nitrous oxide (P < 0.05 for 0.5 MAC, normoventilation) without intergroup, differences. In both groups, hyperventilation always decreased MCA blood-flow velocity. CONCLUSIONS: We conclude from our TCD data that equipotent doses of sevoflurane and isoflurane comparably affect cerebral perfusion, especially when nitrous oxide is given simultaneously.

Adolescent↗
PubMed1997

Topographical analysis of the EEG effects of a subconvulsive dose of lidocaine in healthy volunteers.

BACKGROUND: The purpose of the present study was to assess the effects of intravenous lidocaine on spatial changes of electroencephalographic power and on psychomotoric status in conscious volunteers. METHODS: In 11 healthy volunteers lidocaine (2-min bolus, 100 mg; 15 min infusion, 40 micrograms.kg-1.min-1) or placebo were given intravenously in a randomized, single-blinded, two-way crossover study. Haemodynamics and lidocaine plasma concentrations were measured at baseline and within a period of 30 min following bolus injection. Vigilance and emotional status were tested using visual analogue scales (VAS). Toxic CNS effects were evaluated by a questionnaire. The raw EEG (17 leads, reference Cz) and computed power spectra were continuously recorded. RESULTS: The chosen lidocaine dosage led to nearly constant plasma concentrations (unbound lidocaine 2.5 min and 15 min after bolus 0.36 +/- 0.14 microgram/ml and 0.30 +/- 0.06 microgram/ml, respectively [mean +/- SD]). The placebo caused no symptoms, changes in VAS-scores or EEG-parameters. Lidocaine induced pronounced subjective symptoms and significant increases in delta activity for 15 min, most dominant at the frontotemporal and occipital leads (max. +219% O1). Frontal and occipital beta 1 and beta 2 power (max. +131% and +124% at O1, respectively) was immediately increased after the bolus injection. No EEG changes occurred at central region Cz, and no interhemispheric EEG differences were noted. Theta, alpha 1, and alpha 2 power remained unchanged. CONCLUSION: The current data demonstrate simultaneous changes in psychomotoric status as well as delta and beta spectral power during lidocaine infusion. These data could be an indication that the pronounced frontotemporal and occipital EEG changes are the electroencephalographic expression of subjective sensations.

Adult↗
PubMed1996

Non-invasive functional mapping of the human motor cortex using near-infrared spectroscopy.

We applied non-invasive multisite near-infrared spectroscopy (NIRS) to assess oxygenation changes during performance of a sequential finger opposition task in five healthy human adults. Oxygenation response was localized anatomically using three-dimensional high-resolution magnetic resonance imaging (3D MRI). NIRS measurements showed a localized increase in [oxy-Hb] and a decrease in [deoxy-Hb] in all subjects. The largest response was obtained when the measurement position was over the primary motor and sensory cortex hand area. Interestingly, changes in [deoxy-Hb] seemed to be more localized than changes in [oxy-Hb]. We conclude that this simple, non-invasive and flexible optical bedside method may be used for functional brain mapping.

Adult↗
PubMed1996

Volume replacement with gelatin or hydroxyethylstarch solutions does not impair somatosensory evoked potential monitoring: a haemodilution study in conscious volunteers.

The influence of haemodilution with colloids on somatosensory evoked potentials in non-premedicated volunteers is reported. In seven volunteers (randomized crossover design), blood (20 mL kg-1 within 30 min) was removed and simultaneously replaced by gelatin 3% or hydroxyethylstarch 6%. After 30 min, blood was retransfused within 30 min. Median and posterior tibial nerve somatosensory evoked potentials were recorded from the cortex, second cervical vertebra, Erb's point and 1st lumbar vertebra, respectively. One volunteer experienced a severe allergic reaction to gelatin, therefore only six gelatin trials were evaluated. Haemodilution decreased the haematocrit from 39.8 +/- 1.6% (mean +/- SD) to 31.1 +/- 2.0% (gelatin) and from 40.7 +/- 1.7% to 29.8 +/- 1.5 % (hydroxyethylstarch), respectively. Retransfusion increased haematocrit to 34.4 +/- 0.9% (gelatin) and to 34.2 +/- 1.3% (hydroxyethylstarch). Neither haemodilution with gelatin nor haemodilution with hydroxyethylstarch or retransfusion influenced evoked potentials. In conclusion, the treatment of blood loss up to 30% of estimated blood volume with gelatin or hydroxyethylstarch will not affect somatosensory evoked potential monitoring provided normovolaemic conditions are maintained.

Adult↗
PubMed1996

[Circulating cerebral microembolisms. Detection with transcranial Doppler ultrasound].

Ischaemic stroke is predominantly caused by cerebral emboli which may originate from cardiac sources or atherosclerotic lesions of the cerebral arteries. The diagnosis is primarily based on clinical symptoms and may be confirmed by typical patterns in cranial computed tomography. Echocardiography, ultrasonography of the supraaortic vessels, and angiography are additional diagnostic tools and helpful in clarifying the pathogenesis. Circulating cerebral emboli can be detected using transcranial Doppler sonography (TCD). Emboli are characterised by short-term, high-intensity ultrasonic signals with characteristic audible "chirps". Because of their acoustic impedance, gaseous emboli reflect the ultrasonic beam with a higher intensity than do formed particles. The differentiation between true embolic signals and artifacts (probe dislocation, electrocautery) requires an experienced observer. With recent developments in automatic detection systems, monitoring will become more feasible for clinical applications. During cardiovascular surgery, TCD signals implying cerebral emboli have been registered in various studies. The incidence of embolic signals during cardiopulmonary bypass varies with stage (before, after aortic declamping) and type of surgery (coronary, valve replacement) and the perfusion regime (bubble, membrane oxygenator). For carotid surgery, embolic signals are most likely to occur with carotid clamping, during shunt insertion, and after declamping. There are some studies suggesting a relation between intraoperative embolic signal count and post-operative neurologic state, but the prognostic significance of these signals is still under debate. Strictly controlled prospective studies including a large number of patients have to be conducted to answer the question whether embolic signal count indicates an increased stroke risk. The high number of patients after valve replacement showing up to 30 embolic signals per minute without suffering from neurologic symptoms raises the question whether continuous, predominantly gaseous microembolisation may cause cumulative brain damage. At present, the nature of emboli (gaseous vs. solid) cannot be easily identified by TCD in clinical settings. Future technical improvement of ultrasonic devices may solve this problem, since detection of solid rather than gaseous emboli seems more likely to be clinically relevant.

Animals↗
PubMed1996

[Effects of different kinds of ventilation and positioning measures on blood flow velocity in the middle cerebral artery].

OBJECTIVE: Aim of the present study was to quantify the influence of varying respiratory parameters and different body positionings on transcranial Doppler sonography (TCD) values. With the approval of the local ethics committee, 34 patients without neurological deficits scheduled for an operation in supine position (n = 15) and in the so-called "rabbit-position" (RP, n = 19) were chosen for a prospective randomised investigation. METHODS: Prior to induction of anaesthesia, during the study and after extubation, the systolic (Vs), diastolic (Vd) and mean (Vm) of blood flow velocities as well as pulsatility (Vs - Vd)/Vm of the middle cerebral artery were determined by TCD. In addition mean arterial pressure and heart rate were monitored. Pulmonary airway pressures were observed during anaesthesia and CO2-partial pressure and central venous pressure (CVP) were determined by central venous line and blood samples. Anaesthesia was initiated with 5 mg/kg thiopental and continued with 0.8-1.2 vol% isoflurane in N2O/O2 = 2:1. After positioning all variables were recorded at 10-minute intervals with an inspiratory:exspiratory (I:E) ratio of 1:2, positive endexspiratory pressures (PEEP) of 0 and 10 cm H2O and an I:E ratio of 1:1 with 0 and 10 cm H2O PEEP. The respirator was adjusted to maintain an endtidal pCO2 of 40 mmHg. RESULTS: Neither different positioning of the patients, nor the alteration of respiratory parameters affected TCD variables in a significant way. No significant alterations were detected between the two groups of patients. Rising PEEP resulted in a minor but significant increase in CVP by an average of 3 cm H2O in both groups. The respective positions produced different respiratory pressures. These were in the "RP-group", with and without PEEP, at an approximately 5 cm H2O higher level. All other parameters did not vary significantly. CONCLUSION: The findings of this study show that a positioning of patients in a so-called "rabbit position" during anaesthesia does not alter the rate of blood flow velocity in the middle cerebral artery. Moreover, the modification of important respiratory parameters, especially a rise of PEEP to 10 cm H2O, had no significant influence on TCD values.

Adult↗
PubMed1996

Isovolaemic haemodilution with hydroxyethylstarch has no effect on somatosensory evoked potentials in healthy volunteers.

BACKGROUND: An animal study in anaesthetized baboons demonstrated that somatosensory evoked potentials (SSEP) can be affected by extreme haemodilution. This might lead to misinterpretation and reduce the value of intraoperative SSEP monitoring when colloids are administered. In the present study, the effect of haemodilution (HD) and subsequent retransfusion of autologous blood on SSEP was determined in healthy non-premedicated volunteers. METHOD: Acute isovolaemic HD served as a model for blood loss immediately replaced with colloids. In 12 volunteers, 20 ml/kg.bw blood was withdrawn within 30 minutes and simultaneously multaneously replaced with 6% hydroxyethylstarch (HES). 30 minutes later, the autologous blood was retransfused within 30 minutes. Recording sites and parameters were: 1. Median nerve SSEP: cortical, cervical (C2), Erb's point; 2. Posterior tibial nerve SSEP: cortical, cervical (C2), lumbar (L1). In addition to SSEP latency and amplitude, median and tibial nerve central conduction times, spinal conduction time and nerve conduction velocity were determined. Serial SSEP measurements were made before, during and after HD and retransfusion every 15 minutes. RESULTS: HD consisting of a withdrawal volume of 1550 +/- 155 ml (mean +/- SD) induced a decrease in haematocrit from 42.0 +/- 3.1% to 29.6 +/- 1.6% (P < 0.001). Following retransfusion, haematocrit increased to 35.0 +/- 2.1% (P < 0.001). Neither HD nor retransfusion influenced SSEP parameters. CONCLUSION: We conclude from our data that the therapy of blood loss up to 30% of estimated blood volume with HES does not affect SSEP monitoring as long as normovolaemia is maintained.

Adult↗
PubMed1996

Mood (affective) disorders (F3). Results from the ICD-10 field trial of the Diagnostic Criteria for Research in German-speaking countries.

The present study reports results of the ICD-10 research criteria trial concerning the diagnosis of affective disorders (section F3). On the basis of written case reports and videotapes a total of 451 clinicians from 34 centres in German-speaking countries prepared 2.228 diagnostic ratings on 39 different psychiatric patients. Three of the 39 cases met the diagnostic criteria for affective disorders, and 248 of the diagnostic assessments referred to these cases. The majority of clinicians rated the reliability, the ease and the suitability of the diagnostic criteria positively. The reliability of the affective disorders was extremely good, with a kappa of 0.93 in the range of 2-character diagnoses. The reliability of the 3-character categories was much smaller: Kappa values for depressive episode (F31) and recurrent depressive disorder (F33) were 0.68 and 0.54, respectively. The lowest concordance had a kappa value of 0.22 and was found in the case report of dysthymia (F34.1). Therefore a more precise definition of the diagnostic criteria for dysthymia would be desirable.

Germany↗
PubMed1996

Neurotic and psychosomatic disorders (F4, F5). Results from the ICD-10 field trial of the Diagnostic Criteria for Research in German-speaking countries.

The concept of neurotic and psychosomatic disorders in ICD-10, chapter V (F), follows the principle of descriptive diagnosis; therefore the classical approaches with special regard to psychoanalytic terminology were abandoned. These changes were subject of a multicentric field trial in German speaking countries evaluating practicability, acceptability, feasibility, reliability and aspects of validity of the ICD-10 Diagnostic Criteria for Research: Involving 34 psychiatric, child-psychiatric and psychosomatic centres 17 video-documented cases with ICD-10 diagnoses from sections F4 and F5 were assessed independently in case conferences. On the basis of 1,116 ratings, acceptability and practicability were rated as comparatively sufficient. For 3-character diagnostic categories, the chance-corrected interrater reliability coefficients (kappa) showed a range from 0.62 to 0.95. The concordance with the independently assessed expert consensus diagnosis for the different cases showed a range between 87 and 100%.

Germany↗
PubMed1996

[Changes in somatosensory evoked potentials after sevoflurane and isoflurane. A randomized phase III study].

Monitoring of somatosensory evoked potentials (SEP) is used to identify critical phases of cerebral ischaemia by means of characteristic changes in the signal patterns. A correct interpretation of the results is possible, however, only if the influence of drugs that act on the central nervous system is known. We were able to show that volatile anaesthetics have an impact on latencies and stimulus amplitudes. In this study, we examined the influence of sevoflurane as compared with isoflurane on the conduction of SEP by the median nerve at various concentrations. In addition, we determined how the addition of nitrous oxide (N2O) influenced the stimulus response of median-nerve SEP. Both isoflurane and sevoflurane caused a dose-dependent increase in latency of the primary cortical complex, while the influence on the cervical components of the SEP with respect to increased latency was only slight. No significant difference was found between both study groups. Under the influence of N2O, there were marked reductions in amplitude of the cortical stimulus response. Thus, it can be recommended that supplementation with N2O should be avoided in the presence of low initial amplitudes. Based on our results, the use of isoflurane and sevoflurane concentrations up to 1.0 MAC seems to be compatible with intraoperative monitoring of SEP.

Anesthetics, Inhalation↗