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T Bein

Publications and source records attributed to T Bein.

At least 37 records · Page 2Linked to original sources
PubMed2000

Inspired oxygen fraction after cardiopulmonary bypass: effects on pulmonary function with regard to endothelin-1 concentrations and venous admixture.

Twenty consecutive patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) were allocated at random to group 1 (n = 10, high inspired oxygen fraction (FIO2) after CPB), or group 2 (n = 10, moderate FIO2 after CPB). The effects of each FIO2 on arterial and mixed venous concentrations of endothelin-1 (ET-1) and its precursor, Big ET-1, were measured. Venous admixture was calculated to assess the efficiency of pulmonary gas exchange. Patients whose lungs had been ventilated with a FIO2 of 1.0 (exposure time 70 min) after weaning from the CPB machine had significantly greater arterial and mixed venous Big ET-1 concentrations and venous admixture than patients whose lungs were ventilated with a FIO2 of 0.35. In contrast, ET-1 concentrations in the two groups were not significantly different. A reduction of FIO2 from 1.0 to 0.6 reduced venous admixture without lowering endothelial peptide concentrations. On the first postoperative day all peptide concentrations were similar in the two groups, whereas venous admixture remained non-significantly higher in group 1. A short period of high FIO2 immediately after CPB increases endothelin concentrations and pulmonary venous admixture.

Aged↗
PubMed1999

Electron Microscopy Reveals the Nucleation Mechanism of Zeolite Y from Precursor Colloids.

The growth of nanoscale crystals of zeolite Y from colloidal aluminosilicate gel particles has been investigated with high-resolution electron microscopy. Each amorphous gel particle nucleates only a single zeolite crystal, with nucleation beginning at the gel-solution interface (see scheme). Further growth of these nanocrystals is possible through the solution-mediated transport of framework building blocks.

Journal Article↗
PubMed1999

Combinatorial Methods for the Synthesis of Aluminophosphate Molecular Sieves.

Automatic dispensing of reagents into autoclave blocks followed by synthesis, isolation, and automated structure analysis with X-ray diffractometry represents an efficient methodology for the combinatorial synthesis of microporous materials. The figure shows a typical diffractogram of as-synthesized AFI-type molecular sieves taken with a CCD camera.

Journal Article↗
PubMed1999

Mechanism of zeolite A nanocrystal growth from colloids at room temperature.

The formation and growth of crystal nuclei of zeolite A from clear solutions at room temperature were studied with low-dose, high-resolution transmission electron microscopy in field emission mode and with in situ dynamic light scattering. Single zeolite A crystals nucleated in amorphous gel particles of 40 to 80 nanometers within 3 days at room temperature. The resulting nanoscale single crystals (10 to 30 nanometers) were embedded in the amorphous gel particles. The gel particles were consumed during further crystal growth at room temperature, forming a colloidal suspension of zeolite A nanocrystals of 40 to 80 nanometers. On heating this suspension at 80 degrees C, solution-mediated transport resulted in additional substantial crystal growth.

Colloids↗
PubMed1998

Jugular bulb monitoring of cerebral oxygen metabolism in severe head injury: accuracy of unilateral measurements.

To investigate the accuracy of unilateral jugularvenous monitoring, we performed bilateral jugularvenous monitoring in 22 comatose head injured patients. Fiberoptic catheters were placed upstream in both internal jugular veins and advanced into the jugular bulbs. Arterial and bilateral jugularvenous blood samples were obtained simultaneously for in vitro determination of jugularvenous oxygen saturation (SJO2), arterial minus jugularvenous lactate content difference (AJDL) and modified lactate-oxygen-index (mLOI). Ischemia was assumed, if one of the following pathologies occurred at least unilaterally: SJO2 < 55%, AJDL < -0.37 mmol/L, mLOI > 0.08. The mean and maximum bilateral SJO2 differences varied between 1.4% to 21.0%, and 8.1% to 44.3% respectively. The bias and limits of agreement (mean differences +/- 2SD) between paired samples were -0.4% +/- 12.8%. Regarding AJDL bias and limits of agreement were -0.01 mmol/L +/- 0.18 mmol/L. At best 87% of defined ischemic events could be evaluated by monitoring at the side of predominant lesion or, in diffuse injuries, at the side of the larger jugular foramen in CT scan (CT approach). We conclude, due to the wide limits of agreement in bilateral SJO2 and AJDL the reliability of unilateral jugularvenous monitoring in patients with intracranial pathology is questionable. For diagnosing ischemia the CT approach has the highest sensitivity and is therefore recommended.

Brain↗
PubMed1998

Acute effects of continuous rotational therapy on ventilation-perfusion inequality in lung injury.

OBJECTIVE: To investigate ventilation-perfusion (VA/Q) relationships, during continuous axial rotation and in the supine position, in patients with acute lung injury (ALI) using the multiple inert gas elimination technique. DESIGN: Prospective investigation. SETTING: Eighteen-bed intensive care unit in a university hospital. PATIENTS AND INTERVENTIONS: Ten patients with ALI (PaO2/FIO2 ratio < 300 mm Hg) were mechanically ventilated in a pressure controlled mode and placed on a kinetic treatment table. MEASUREMENTS AND RESULTS: Distributions of VA/Q were determined 1) during rotation (after a period of 20 min) and 2) after a resting period of 20 min in the supine position. During axial rotation, intrapulmonary shunt (19.1 +/- 15% of cardiac output) was significantly reduced in comparison with when in the supine position (23 +/- 14%, p < 0.05), areas with "low" VA/Q were not affected by the positioning maneuver. General VA/Q mismatch (logarithmic distribution of pulmonary blood flow) was decreased during rotation (0.87 +/- 0.37) in comparison with when the patient was in the supine position (0.93 +/- 0.37, p < 0.05). Arterial oxygenation was significantly improved during continuous rotation (PaO2/FIO2 = 217 +/- 137 mm Hg) as compared with in the supine position (PaO2/FIO2 = 174 +/- 82 mm Hg, p < 0.05). The positive response of the continuous rotation on arterial oxygenation was only demonstrated in patients with a Murray Score of 2.5 or less, indicating a "mild to moderate" lung injury, while in patients presenting with progressive ARDS (Murray Score > 2.5), the acute positive response was limited. CONCLUSIONS: Continuous axial rotation might be a method for an acute reduction of VA/Q mismatch in patients with mild to moderate ALI, but this technique is not effective in late or progressive ARDS. Further studies including a large data collection are needed.

Adult↗
PubMed1998

Lung aeration and pulmonary gas exchange during lumbar epidural anaesthesia and in the lithotomy position in elderly patients.

We investigated a total of 36 subjects with a mean (SD) age of 65 (13) years, during baseline conditions (supine, before any anaesthesia), and then during one of the following protocols: (1) lithotomy positioning (n = 12), (2) epidural anaesthesia (n = 12), (3) general anaesthesia in the supine position (n = 12). Lung aeration, ventilation/perfusion matching, gas exchange and functional residual capacity were measured. Lung aeration was normal during baseline assessment with almost no regions with poor aeration and no substantial dependent densities. Shunt and perfusion of poorly ventilated regions were minor. Lithotomy positioning did not reduce functional residual capacity and did not affect aeration of the lung or ventilation/perfusion matching. Epidural anaesthesia, in general, had no effect on aeration, ventilation/perfusion matching or gas exchange, regardless of whether the patient was in the supine or lithotomy position. General anaesthesia, however, caused significant increases in poorly aerated lung regions and in dependent densities (interpreted as atelectasis). In conclusion, no or little impairment of lung aeration and ventilation/perfusion matching was caused by the lithotomy position and/or epidural anaesthesia, contrary to the effects seen during general anaesthesia. However, our findings also suggest that being overweight is a factor that may cause impairment of lung aeration.

Aged↗
PubMed1998

Monitoring of cerebral oxygen metabolism in the jugular bulb: reliability of unilateral measurements in severe head injury.

To investigate the reliability of unilateral jugular venous monitoring and to determine the appropriate side, we performed bilateral jugular venous monitoring in 22 head-injured patients. Fiberoptic catheters were placed in both jugular bulbs. Arterial and bilateral jugular venous blood samples were obtained simultaneously for in vitro determination of jugular venous oxygen saturation (SJO2), arterial minus jugular venous lactate content difference (AJDL), and modified lactate-oxygen index (mLOI). Ischemia was assumed if one of the following pathologic values occurred at least unilaterally: SJO2 <54%, AJDL <-0.37 mmol/L, mLOI >0.08. The sensitivity of calculated unilateral monitoring in detecting ischemia was evaluated by comparing the incidence detected unilaterally with that disclosed bilaterally. The mean and maximum bilateral SJO2 differences varied between 1.4% and 21.0%, and 8.1% and 44.3%, respectively. The bias and limits of agreement (mean differences +/- 2 SD) between paired samples were 0.4% +/- 12.8%. There was no significant variation in bilateral SJO2 differences with time. Decreasing cerebral perfusion pressure (r = -0.559, P < 0.001) and arterial PCO2 (r = -0.342, P < 0.001) were associated with increasing bilateral SJO2 differences. Regarding AJDL, the maximum bilateral differences varied between 0.04 mmol/L and 1.52 mmol/L. The bias and limits of agreement were -0.01 +/- 0.18 mmol/L. At best, 87% of ischemic events were disclosed by monitoring on the side of predominant lesion or, in diffuse injuries, on the side of the larger jugular foramen (computed tomographic [CT] approach). We conclude that in severe head injury, even calculated unilateral jugular venous monitoring has an unpredictable risk for misleading or missing data. Therefore, the reliability of unilateral jugular venous monitoring appears suspicious. For diagnosing ischemia the CT approach is recommended.

Adult↗
PubMed1996

"Coulomb Staircase" at Room Temperature in a Self-Assembled Molecular Nanostructure

Double-ended aryl dithiols [alpha,alpha'-xylyldithiol (XYL) and 4,4'-biphenyldithiol] formed self-assembled monolayers (SAMs) on gold(111) substrates and were used to tether nanometer-sized gold clusters deposited from a cluster beam. An ultrahigh-vacuum scanning tunneling microscope was used to image these nanostructures and to measure their current-voltage characteristics as a function of the separation between the probe tip and the metal cluster. At room temperature, when the tip was positioned over a cluster bonded to the XYL SAM, the current-voltage data showed "Coulomb staircase" behavior. These data are in good agreement with semiclassical predictions for correlated single-electron tunneling and permit estimation of the electrical resistance of a single XYL molecule (approximately18 &plusmn; 12 megohms).

Journal Article↗
PubMed1996

Effects of extreme lateral posture on hemodynamics and plasma atrial natriuretic peptide levels in critically ill patients.

OBJECTIVE: To quantify the hemodynamic effects of turning critically ill, mechanically ventilated patients to the extreme left and right lateral postures. DESIGN: Prospective investigation. SETTING: Eight-bed intensive care unit in a university hospital. PATIENTS: Twelve consecutive patients presenting with severe respiratory failure and requiring continuous positive inotropic support. INTERVENTIONS: All patients were mechanically ventilated and placed in a kinetic treatment system. They were positioned in the supine, left dependent, and right dependent postures, resting for 15 min in each position. MEASUREMENTS AND RESULTS: Hemodynamic measurements, assessments of right ventricular function, and determinations of intrathoracic blood volume were performed in three different positions. Concentrations of atrial natriuretic peptide in plasma were quantified. In three patients, the findings were controlled by transesophageal echocardiography. Cardiac index [median (range) 5.5 (3.2-8.1) vs 4.3 (3.2-7.5) l/min per m2, p < 0.01], intrathoracic blood volume [1125 (820-1394) vs 1037 (821-1267) ml/m2, p < 0.01], and right ventricular end-diastolic volume [130 (83-159) vs 114 (79-155) ml/m2, p < 0.05] increased significantly in the left dependent position compared to supine. Mean arterial pressure did not change. Atrial natriuretic peptide levels rose from 140 to 203 pg/ml. In the right dependent position, we found a marked decrease in the mean arterial pressure [85 mmHg (supine) to 72 mmHg (right dependent), p < 0.01]. Cardiac index and intrathoracic blood volume were unchanged, but right ventricular end-diastolic volume decreased from 114 to 102 ml/m2 (p < 0.05). Additionally, atrial natriuretic peptide levels decreased significantly (median delta value: 37 pg/ml). In echocardiographic controls we found an increase in right ventricular end-diastolic diameters in the left dependent position and shortened diameters in the right dependent position. CONCLUSIONS: Extreme lateral posture affects the cardiovascular system in critically ill, mechanically ventilated patients: in the left dependent position a "hyperdynamic state" is reinforced, while the right decubitus position impairs right ventricular preload and predisposes to hypotension. Echocardiography and changes in plasma atrial natriuretic peptide values indicate that these findings are due to altered distensibility of the right ventricle caused by regional intrathoracic gravitational changes. We conclude that the duration and the angle of lateral posture should be restricted in hemodynamically unstable patients.

Acute Disease↗
PubMed1996

[Ventilation-perfusion ratio in patients with acute respiratory insufficiency].

UNLABELLED: Acute respiratory failure is characterised by mismatch of ventilation with perfusion (VA/Q). The multiple inert gas elimination technique (MIGET) is a complex method which allows the description of a virtually continuous distribution of VA/Q ratios. We investigated VA/Q relationships in patients admitted to the intensive care unit due to acute respiratory failure and thus requiring for mechanical ventilation. METHOD: Eight patients (mean APACHE 11 = 22 +/- 4) who suffered from acute pneumonia (n = 4), traumatic lung contusion (2), toxic lung failure (1) or massive bilateral atelectasis (1) were investigated by MIGET within 3 days after the begin of mechanical ventilation. A mixture of six inert gases, dissolved in isotonic saline, was infused continuously. Arterial and mixed venous blood samples and expired gas samples were obtained and analysed by gas chromatography. Blood-gas partition coefficients were determined, and the ratios of retention and excretion were calculated. The data were transformed in a 50-compartment model of blood flow and ventilation against VA/Q ratio. We assessed the amount of intrapulmonary shunt (VA/Q = 0), low VA/Q regions (VA/Q = 0.005-0.1), normal VA/Q regions (VA/Q = 0.11-10), high VA/Q regions (VA/Q = 11-100) and dead space ventilation (VA/Q > 100). Furthermore, we calculated the logarithmic standard deviation of pulmonary perfusion distribution (logSDQ). RESULTS: In all patients we found moderate to severe intrapulmonary shunt and VA/Q mismatching. The data are expressed as median values and ranges. Inert-gas-measured shunt was 21% (3-45.5%), whereas low VA/Q regions were little affected. Normal VA/Q regions ranged from 41.5% to 96.0% (median 76.8%). The amount of alveolar dead space ventilation was 28% (19.7-41.8%). Median logSDQ (normal range 0.3-0.6) was calculated to be 0.855 (0.540-1.490). In patients presenting with moderate lung injury (Murray score < 3), a moderate increase in shunt and a moderate VA/Q mismatch were observed. In contrast, patients with severe lung failure and critically decreased oxygenation (Murray score > 3) were characterised by massive shunting and VA/Q mismatching. Additionally, low VA/Q and high VA/Q compartments and an increase in dead space ventilation was found in these patients. CONCLUSIONS: The impairment of oxygenation in patients with acute respiratory failure is due to several pathophysiological mechanisms: increase in intrapulmonary shunt, VA/Q-mismatching and dead space ventilation, according to the severity of lung failure. We conclude from our results that the prevention and/or reduction of non-ventilated lung areas (atelectasis) is an outstanding therapeutic strategy in the treatment of patients with acute respiratory failure. From this point of view, several techniques of systemic changes in body position should be integrated as supportive therapeutic strategies.

APACHE↗
PubMed1996

Cardiovascular and pulmonary effects of aerosolized prostacyclin administration in severe respiratory failure using a ventilator nebulization system.

We investigated the effects of aerosolized prostacyclin (PGI2) administration on hemodynamics and pulmonary gas exchange in 8 patients with severe respiratory failure and acute pulmonary hypertension. Nebulization of epoprostenol (5 ng/kg body weight for 15 min) decreased mean pulmonary blood pressure from 41.2 +/- 6.7 mm Hg (mean +/- SD, before administration) to 36.1 +/- 6 mm Hg < or = 15 min (p < 0.05). The effect was reversed 10 min after discontinuation of PGI2 (40.9 +/- 6.3 mm Hg). Pulmonary vascular resistance index (339 +/- 138 dynes.s.cm-5.m2, before administration) was significantly (p < 0.05) reduced < or = 15 min (260 +/- 89 dynes.s.cm-5.m2) and increased again after discontinuation of PGI2 (341 +/- 142 dynes.s.cm-5.m2). The ratio of arterial oxygen to the fraction of inspired oxygen (PaO2/FiO2) increased from 119 +/- 34 mm Hg (before administration) to 163 +/- 76 mm Hg (15 min after initiation of administration p < 0.05) and was reduced after PGI2 discontinuation (116 +/- 35 mm Hg). Heart rate, mean blood pressure, central venous pressure, and pulmonary arterial wedge pressure remained unchanged, whereas cardiac index was slightly reduced. We assume that PGI2 aerosolization is a beneficial technique, applied with a ventilator nebulization system. The beneficial effect might be caused by selective pulmonary vasodilatation in well-ventilated areas of the lung.

Aerosols↗
PubMed1996

Moderate hypothermia in patients with severe head injury: cerebral and extracerebral effects.

Cerebral and extracerebral effects of moderate hypothermia (core temperature 32.5 degrees C-33.0 degrees C) were prospectively studied in 10 patients with severe closed head injury (Glasgow Coma Scale score < 7) in the intensive care unit of a university hospital. Hypothermia was induced by cooling the patient's body surface with water-circulating blankets. Before cooling, a conventional intracranial pressure (ICP) reduction therapy was applied, which remained unchanged throughout the study. Cerebral blood flow (CBF), cerebral metabolic rates for oxygen (CMRO2) and lactate (CMRL), and ICP were simultaneously measured prior to inducing hypothermia, after obtaining hypothermia, after 24 hours of hypothermia, and after rewarming. With respect to extracerebral effects, supplemental investigations were conducted 24 and 72 hours after rewarming. The median delay between injury and induction of hypothermia was 16 hours. Hypothermia reduced CMRO2 by 45% (p < 0.01), whereas CBF did not change significantly. Before cooling, six patients had elevated CMRL indicating cerebral ischemia. Cooling normalized CMRL in all patients (p < 0.01). The intracranial hypertension present prior to cooling declined markedly during hypothermia (p < 0.01) without significant rebound effects after rewarming. Cardiac index decreased by 18% after hypothermia was reached (p < 0.05), recovered at 24 hours of hypothermia, and surpassed baseline values after rewarming. Platelet counts dropped continuously up to 24 hours after rewarming (p < 0.01). Plasma coagulation tests did not show significant worsening. Creatinine clearance decreased during cooling (p < 0.01) and recovered by 24 hours after rewarming. Twenty-four hours after cooling had begun, eight patients had elevated serum lipase activity (p < 0.01) and four of them acquired pancreatitis. Rewarming normalized both pancreatic alterations. Seven patients made a good recovery; one survived severely disabled; and two patients died. Moderate hypothermia is effective in preventing secondary brain damage while reducing cerebral ischemia. However, there are potentially hazardous side effects that require additional monitoring.

Adolescent↗
PubMed1995

The predictive value of four scoring systems in liver transplant recipients.

OBJECTIVE: To compare 4 general severity classification scoring systems concerning prognosis of outcome in 123 liver transplant recipients. The compared scoring systems were: the mortality prediction model (admission model and 24 h model); the simplified acute physiology score; the acute physiology and chronic health evaluation (Apache II) and the acute organ systems failure score. DESIGN: Retrospective, consecutive sample. SETTING: Adult intensive care unit in a university hospital. PATIENTS: 123 adult liver allograft recipients after admission to the intensive care unit. MEASUREMENTS AND MAIN RESULTS: The scoring systems were calculated as described by the authors to classify the severity of illness after admission of the allograft recipients to the intensive care unit. The mean and median values of survivors and the group of patients, that died during hospital stay were compared. Receiver-operating characteristics were plotted for all scoring systems and the areas under the curves of receiver-operating characteristics were calculated. The predictive value of the 4 scoring systems was tested using a variety of sensitivity analyses. The mortality prediction model (24 h model) was found to have a high significance (p < 0.001) in predicting mortality and showed the greatest area under the curve (0.829). Simplified acute physiology score (p < 0.001) and acute physiology and chronic health evaluation (Apache II) (p < 0.01) had a high significance as well, but did not hit the level of prognosis of mortality prediction model, as shown in the area under the curves. Accordingly, sensitivity was highest in MPM-24 h (83%), followed by SAPS (72%) and Apache II (71%). MPM-24 h had a total misclassification rate of 22% (SAPS = 32%, Apache II = 33%). MPM-admission failed in predicting mortality (sensitivity = 52%). Organ systems failure score seemed not to be useful in liver transplant recipients. CONCLUSION: General disease classification systems, such as the mortality prediction model, simplified acute physiology score or acute physiology and chronic health evaluation are good mortality prediction models in patients after liver transplantation. We suggest that there is no need for improvement of a special scoring system.

Adolescent↗
PubMed1995

[Comparison of APACHE-II AND APACHE-III for classification of disease severity of intensive care patients].

The Acute Physiology and Chronic Health Evaluation model (APACHE II, APACHE III) is used to describe the severity of illness and predict the outcome in critically ill patients. APACHE III, introduced in 1991, has not yet been validated in Europe. We calculated APACHE II and APACHE III scores in patients after admission to the intensive care unit (ICU) and compared the prognostic value on hospital mortality. METHOD. One hundred fifty patients with stay of over 24 h were enrolled in the study and prospectively and consecutively investigated. APACHE II and III scores were calculated as described by the authors. The mean and median values of the survivors were compared with the non-surviving group (Mann-Whitney U test). Receiver operating characteristics (ROC analysis) and the areas under the ROC curves were plotted. RESULTS. Of the 150 patients, 34 died during their hospital stay (22.7%). The mean and median APACHE II and III scores were significantly higher (P < 0.001) in the non-surviving group. The area under the ROC curve was higher for APACHE III (0.899) compared to APACHE II (0.847). CONCLUSIONS. APACHE II and APACHE III were both found to have good prognostic value in general ICU patients. Our results suggest that the APACHE III version includes a more precise prediction of hospital mortality than APACHE II. A new aspect of APACHE III is an expanded modification of the Glasgow Coma Scale to assess neurologic derangements.

APACHE↗