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Biomedical subjects

H Gehring

Publications and source records attributed to H Gehring.

At least 37 records · Page 2Linked to original sources
PubMed1998

Perioperative cytokine release during coronary artery bypass grafting in patients of different ages.

Surgical interventions and cardiopulmonary bypass (CPB) induce a systemic inflammatory response with cytokine release. Ageing is perceived as a process of impaired immune functions: IL-1beta, IL-6 and tumour necrosis factor-alpha (TNF-alpha) secretion are increased while IL-2 release is reduced in advanced age. At present, little information is available about perioperative immune reactions at different stages of ageing. The aim of the present study was to compare IL-6, IL-1beta, TNF-alpha, IL-10 and soluble IL-2 receptor (sIL-2R) in younger and older patients undergoing cardiac surgery. Male patients (n = 14) undergoing elective coronary artery bypass grafting (CABG) surgery employing CPB with moderate hypothermia were divided into two groups according to their age: group 1 included seven patients < 50 years old, group 2 included seven patients > 65 years old. All patients received general anaesthesia using a balanced technique with sufentanil, isoflurane and midazolam. Blood samples were collected pre-operatively (T1); intra-operatively during CPB (T2); post-operatively on the day of surgery (T3); on the first post-operative day (T4). Blood concentrations of IL-6, IL-1beta, IL-10, TNF-alpha and sIL-2R were measured using commercially available ELISA kits and corrected for plasma cell volume. Statistical analysis was performed by non-parametric analysis of variance and Mann-Whitney U-test. Significance level was set to P<0.05. There were no statistically significant differences in the perioperative release of TNF-alpha, IL-6, IL-1beta, IL-10 and sIL-2R among the two groups. We conclude that the perioperative course of cytokine release in patients undergoing CABG surgery with CPB and comparable perioperative management does not significantly differ in the two age groups.

Adult↗
PubMed1998

Effects of propofol vs isoflurane on respiratory gas exchange during laparoscopic cholecystectomy.

BACKGROUND: Respiratory function and pulmonary gas exchange are affected in laparoscopic procedures where a pneumoperitoneum is introduced using CO2. Previous studies have shown differing results concerning pulmonary gas exchange during laparoscopic procedures: Whereas in patients undergoing isoflurane anaesthesia decreases in PaO2 are demonstrated, this factor remains unchanged in patients undergoing propofol anaesthesia. In the present study, the effects of propofol on pulmonary gas exchange were compared with those of isoflurane in patients undergoing elective laparoscopic cholecystectomy in a prospective randomised manner. METHODS: Twenty ASA patients with physical status I and II were divided randomly between isoflurane (IG) and propofol groups (PG). After induction of anaesthesia patients were moderately hyperventilated. Respirator settings remained unchanged during pneumoperitoneum (PP) until 10 min after deflation of the peritoneal cavity. Blood gas analyses were performed at 5 time points: 15 min after induction of anaesthesia (giving pre-PP values), immediately before carbon dioxide insufflation (0 min PP), after both 30 and 60 min of PP and 10 min post PP. Inspiration plateau pressure (Pplat), compliance of the respiratory system, and both ins- and expiratory gas concentrations were continuously recorded by an Ultima V monitor (Datex Corp., Helsinki, Finland). The difference between arterial and end-tidal CO2 partial pressure (P(a-et)CO2) was calculated so as to allow assessment of physiological dead space by the modified Bohr equation. RESULTS: Pulmonary gas exchange differed significantly after 30 min of PP between the IG and the PG. At this time, PaO2 was 19.5 +/- 2.9 kPa (mean +/- SD) in the IG and 23.1 +/- 1.8 kPa in the PG (P < 0.01), whereas PaCO2 was 5.5 +/- 0.37 kPa in the IG and 4.9 +/- 0.27 kPa in the PG (P < 0.01). These discrepancies remained until after carbon dioxide desufflation. At 10 min post PP, PaO2 was 18.3 +/- 2.6 kPa in the isoflurane group and 21.9 +/- 2.2 kPa in the propofol group (P < 0.01), whereas PaCO2 was 5.4 +/- 0.46 kPa in the IG and 4.8 +/- 0.22 kPa in the PG (P < 0.01). During carbon dioxide insufflation the P(a-et)CO2 increased significantly in the IG from 0.47 +/- 0.13 kPa to 0.76 +/- 0.37 kPa (P < 0.05), while the values in the PG remained constant. CONCLUSION: This study demonstrates that pulmonary gas exchange in patients with laparoscopic cholecystectomy is affected by the choice of anaesthetic procedure. During and after laparoscopic cholecystectomy using isoflurane as the anaesthetic, the PaCO2 is significantly higher and the PaO2 significantly lower than they are with propofol.

Adult↗
PubMed1998

[Measuring breath alcohol concentration during artificial ventilation. Model studies of the effect of temperature and humidity on measurements by various sampling systems].

The present paper examined the question as to the extent to which the taking of gas samples for the purpose of measuring the breath alcohol concentration (BAC) in the expired air of patients on artificial respiration is influenced by temperature and humidity. For this purpose a lung model standardized at different alcohol concentrations was used, in which the temperature (T: 25, 30 and 35 degrees C) and the relative humidity (RH: 50, 75 and 95%) were varied.

Breath Tests↗
PubMed1997

[A new probe holding device for continuous bilateral measurements of blood flow velocity in basal brain vessels].

The clinical relevance of transcranial Doppler sonography for the evaluation of cerebral perfusion and cerebrovascular regulatory mechanisms, as well as for the registration of embolic events, has increased considerably as a technique of non-invasive monitoring. The continuous measurement of blood flow velocities in two different vessel segments, either ipsilateral or contralateral, is limited by intricate probe fixation and positioning for optimal insonation of the vessel on the one hand. On the other hand probes are displaced frequently during anaesthesiological measures, so that continuous registration during induction of anaesthesia is not always guaranteed. In view of these limitations, a new probe-positioning and holding device has been developed and tested in a clinical study of patients undergoing cardiac surgery (n = 22). The newly designed probe-positioning and holding device allowed the unilateral adjustment and continuous measurement of the blood flow velocity in the middle cerebral artery (Vmca) from anaesthesia induction to endotracheal intubation in all patients (n = 9). This was possible in only 61.5% (n = 8) of the patients who were monitored via conventional mode of probe fixation (n = 13). The new method rendered possible the positioning, insonation and measurement in two vessel segments in 77.8% of the patients, in contrast to 53.8% of the patients where the conventional technique was used. The newly designed probe holding device meets all standard requirements from the anaesthesiological viewpoint, and facilitates the perioperative application of transcranial Doppler sonography for non-invasive monitoring.

Aged↗
PubMed1997

[The preparation for elective interventions--the spectrum and dissemination of somatic and psychological measures in Germany].

INTRODUCTION: The positive effects of preoperative preparation on postoperative recovery in patients undergoing elective surgery have been demonstrated. On that account, we surveyed the practice procedures of preoperative preparation for elective surgery patients at German hospitals. METHODS: During November 1994, we sent 1500 questionnaires to the directors of anaesthesiology departments in Germany. A total of 590 questionnaires (39.3%) were completed and returned. The participating hospitals range in size from 20 to 2600 beds (mean = 364; s = 334,97), totalling together more than 1.7 million surgical operations per year. RESULTS: The surveyed hospitals used one or more of the following procedures for pre-operative preparation: 573 (98.6%) of the replying hospitals used medical anxiolysis, 415 (71.3%) applied preoperative respiratory therapy. Furthermore, 222 (38.5%) of the studied hospitals trained their patients in postoperative relevant behaviour (respiratory therapy n = 167; physiotherapy n = 63 and patient-controlled analgesia n = 41). 74 (13%) offered psychological counselling, 29 (5%) made use of other psychological techniques (muscle relaxation; autogenic training, biofeedback) and 26 (4%) used other preparatory methods like video tapes (n = 13), music (n = 5), acupuncture (n = 4). DISCUSSION: Nearly all hospitals prepared their patients for surgery with a pre-op visit and anxiolytic medications. Further preparatory methods in most surveyed hospitals are only used on a case-by-case basis. At present psychological methods of preoperative preparation are not routinely used in clinical practice in Germany. CONCLUSIONS: Existing possibilities for optimising preoperative preparation in patients undergoing elective surgery are not used regularly. Preoperative preparation needs to be improved, especially in patients undergoing major surgery. Standardisation of management procedures and integration of several professional groups and regular application of known procedures for preoperative preparation may lead to cost-saving optimisation of the duration of hospital stay.

Anti-Anxiety Agents↗
PubMed1996

Molecular-dynamics simulation of domain movements in aspartate aminotransferase.

Mitochondrial aspartate aminotransferase is a homodimeric protein with 2 x 402 amino acid residues. The enzyme in solution undergoes ligand-induced and syncatalytic conformational changes which appear to correspond to shifts in the equilibrium between the crystallographically defined open and closed conformation. In the closed conformation, the small domain of each subunit has rotated as a rigid body by 13 degrees and 14 degrees towards the large coenzyme-binding domain and has closed the active-site pocket. Molecular dynamics simulations at 300 K of 120-ps duration were started from the crystal structures of the unliganded pyridoxal form (open form) of the dimeric enzyme and the 2-methylaspartate-liganded closed form in which the 2-methyl group had been removed. Both structures contained the crystal water molecules and were placed in a 5-A shell of water. The rms fluctuations of the individual C alpha atoms during the simulations agreed well with the corresponding B factors of the crystal structures. Superposition of the initial structures and the average structures of the last 20 ps showed in both simulations extensive C alpha deviations in the case of the whole subunit but much smaller changes in the individual large and small domains, indicating a movement of the two domains relative to each other. In the simulation of the open form, superposition of the large domains made evident a displacement of the small domain towards its position in the closed crystal structure, which can be described by a rotation of the small domain by about 13 degrees around the twofold symmetry (z) axis. A significantly less extensive rearrangement of parts of the small domain, i.e. a rotation of about 5 degrees around the z axis, was observed in the simulation of the substrate-liganded enzyme (closed form) which, in contrast to the open form, showed only small conformational changes around the active site. In both simulations an additional rotation of the small domain by 9 degrees around the x axis occurred. The actual domain movement is estimated to occur in a time range at least two orders of magnitude larger than the simulation time of 120 ps. Apparently, the surface tension of the unrestrained nonspherical shell of water accelerates the simulated conformational change which, however, quite closely imitates the geometric features of the extensive movement of the small domains (each approximately 130 residues).

Animals↗
PubMed1996

Stereochemical constraint in the evolution of pyridoxal-5'-phosphate-dependent enzymes. A hypothesis.

In the transamination reactions undergone by pyridoxal-5'-phosphate-dependent enzymes that act on L-amino acids, the C4' atom of the cofactor is without exception protonated from the si side. This invariant absolute stereochemistry of enzymes not all of which are evolutionarily related to each other and the inverse stereochemistry in the case of D-alanine aminotransferase might reflect a stereochemical constraint in the evolution of these enzymes rather than an accidental historical trait passed on from a common ancestor enzyme. Conceivably, the coenzyme and substrate binding sites of primordial pyridoxal-5'-phosphate-dependent enzymes had to fulfil the following prerequisites in order to allow their development toward effective catalysts: (i) the negatively charged alpha-carboxylate group of the amino acid substrate had to be positioned as far as possible away from the negatively charged phosphate group of the cofactor, and (ii) the C alpha-H bond had to be oriented toward the protein. Compliance with these two criteria implies, under the assumption that C4' is protonated by an acid-base group of the protein, the observed stereochemical feature.

Binding Sites↗
PubMed1996

[Measurement of expired alcohol concentrations with a new electrochemical sensor. A model investigation to determine interference with volatile anesthetics and clinical application].

UNLABELLED: Absorption of irrigating fluid in transurethral prostatic resection (TURP) and percutaneous nephrolitholapaxy (PNL) into veins or delayed absorption due to fluid extravasation may result in a TURP syndrome. The measurement of end-tidal breath alcohol concentration (et AC) as a monitor of absorption of irrigating fluid labelled with 2% ethanol is limited by the disturbance of infrared sensors by volatile anaesthetics and nitrous oxide (N2O) (Fig. 2). An electrochemical sensor is acceptable for this method. The aim of the present study was the evaluation of breath alcohol measurements using an electrochemical sensor device (Alcomed 3010, Envitec). The stability of the sensor in the presence of volatile anaesthetics was examined using a lung model. In a clinical investigation, the device was then applied to spontaneously breathing or mechanically ventilated patients inhaling volatile anaesthetics during endoscopic urological surgery. METHOD: A two-chamber lung model filled with water for performing noninvasive measurements at the mouth of a patient has already been introduced by Brunner et al. (Fig. 1). With the addition of different amounts of ethanol to the temperature-controlled water, a constant ethanol concentration is achievable in the air above the water that is dependent on adjustments of the ventilator. Increasing concentrations of volatile anaesthetics (isoflurane, enflurane, halothane, and sevoflurane) were added to the fresh gas flow (2 l O2/3 l N2O) and etACs were measured using the manually triggered self-absorbent electrochemical sensor. First, regression equations were established between breath alcohol concentrations and increased volatile anaesthetic concentrations. Regression equations were then established between end-tidal anaesthetic gas concentrations and vaporizer adjustments in order to rule out an influence of ethanol on the anaesthetic gas monitor Ultima V (Datex). In the clinical investigation, 53 intubated and ventilated patients (33 undergoing PNL, 20 undergoing TURP) and 48 patients breathing spontaneously (32 with inhalation anaesthesia, 16 with spinal anaesthesia) were investigated. The etAC was measured with the Alcomed 3010 and compared with gas-chromatographically registered blood alcohol concentrations (BAC). The study had previously been approved by the Ethical Committee of the Medical University of Luebeck. Patients with liver disease and a history of toxic abuse were excluded. Only one value per patient (maximum BAC) was included in the statistics in order to avoid a cluster effect. RESULTS: The lung model experiments demonstrated that the measurement of etAC with an electrochemical sensor is free of interference by volatile anaesthetics (Table 1). The slope of the regression between the measured alcohol concentration and increased concentrations of anaesthetics did not differ significantly from baseline values. The measurement of end-tidal anaesthetic concentrations was not significantly different from vaporizer adjustments in the presence of increased alcohol concentrations (Table 2). During the clinical investigation, a regression between etAC and BAC was determined for both groups. For the group of patients breathing spontaneously, the correlation coefficient was 0.961 and the regression equation revealed etAC = 0.5677*BAC-0.1303 (Fig. 5). However, in the group of ventilated patients a biphasic course was shown that was dependent on BAC (Fig. 6). At BAC < 0.4%, a similar correlation (r = 0.856) to the spontaneously breathing group could be seen (regression equation: etAC = 0.617*BAC-0.020). Above 0.4% BAC there was no acceptable correlation (r = 0.444, regression equation: etAC = 0.202*BAC+0.104). CONCLUSIONS: The tested electrochemical sensor does not interfere with volatile anaesthetics and N2O as demonstrated by a lung model. There is a good correlation between etAC and BAC measurements in patients breathing spontaneously with special regard to the slope of the regression (s = 0.57).

Anesthetics↗
PubMed1996

Apoptosis-induced concomitant release of cytosolic proteins and factors which prevent cell death.

In the course of the apoptotic cell death, cells fragment into apoptotic bodies, the elimination of which by phagocytosis is thought to avoid the release of cytosolic constituents whose occurrence is indicative for necrotic cell death. Confluent cultures of chicken embryo fibroblasts, however, show a different behaviour. After serum deprivation, they transiently released with the same time course mitogenic activity, lactate dehydrogenase and cytosolic peptidyl prolyl cis-trans isomerases into the serum-free culture medium. The release correlated in time with a decrease of the cell number which started approximately 3 h after serum removal and ceased within approximately 10 h at about half of the initial cell density. Morphological features like cell shrinkage, membrane blebbing and cell fragmentation as well as internucleosomal DNA fragmentation indicated apoptotic cell death whereas necrotic cell death could be excluded. Conditioned medium (M(r) > or = 30 kDa) from serum-deprived cultures of chicken embryo fibroblasts completely prevented chicken embryo fibroblasts to undergo apoptosis as did phorbol 12-myristate, 13-acetate and, to -60%, L-cysteine. Cycloheximide had no effect on serum deprivation-induced apoptosis. From the present results it can be concluded that chicken embryo fibroblasts and possibly other cells undergoing apoptosis release cytosolic components and endogenous survival factor(s) which prevent apoptosis.

Animals↗
PubMed1996

[Measuring pulmonary CO2 elimination--studies with the lung model using various mixed gases].

One way of determining pulmonary CO2 elimination during anaesthesia is the breath-by-breath method. With this technique, CO2 analysis is carried out using either the mainstream method (MSM), that is, directly in the expired air flow, or in samples of expired air. A disadvantage of MSM is the lack of sensor signal correction for changes in the composition of the gas mixture and barometric pressure. Sidestream systems (SSM) measure respiratory gas flow and gas concentration with adequate accuracy, and also correct the measured values for gas composition and ambient parameters. Disadvantages of breath-by-breath analysis are the SSM-system-related delay and distortion of the CO2 curves. In the present study, a computer-assisted comparative analysis of CO2 elimination measurement by the sidestream and mainstream methods was carried out using different mixtures of gases in a lung model. Under the selected conditions simulated in the lung model, evaluation of CO2 elimination using SSM and MSM is possible with an error of between 0 and 10% versus reference systems. Measuring accuracy of the MSM system in particular is found to depend directly on the composition of the gas mixture. Using the method described here, the measuring error of an SSM system in terms of delay and response time can be compensated with adequate accuracy.

Carbon Monoxide↗
PubMed1996

[Breath alcohol analyzers with electrochemical sensory--accuracy of measurements in lung model ventilation].

Absorption of irrigating fluid by blood vessels during endoscopic urological surgery may result in cardiac insufficiency, impairment of electrolyte metabolism and neurological disorders. For detection and quantification of the volume absorbed, ethanol is added to the irrigating fluid. The resulting blood alcohol concentration can be obtained by measuring the alcohol concentration in the expired air. For artificially ventilated patients receiving a general anesthetic, electrochemical sensors that remain uneffected by volatile anaesthetics are used. In the present study, the measuring accuracy of three different alcohol analyzers using electrochemical sensors was tested against an infrared reference sensor during simulated ventilation in a lung model, and the optimal trigger time point for sampling determined. All three devices tested show the same degree of accuracy as the reference. For manual endexpiratory triggering devices with short sampling times are best suitable. Portable devices powered by rechargeable batteries and usable with both spontaneously breathing and ventilated patients are recommended for clinical application.

Body Water↗
PubMed1996

[Plasma volume determination with ICG dye in changes of intravascular volume. Dye dilution method before and after autologous blood donation and after retransfusion in the human].

OBJECTIVE: The determination of the current intravascular plasma volume with the dye dilution method is of major interest in therapeutic intervention and scientific research. The use of the rapidly eliminated dye indocyanine green (ICG) allows to perform plasma volume measurements serially and to observe a time course. The following questions should be investigated in the present study: 1. Do the plasma volume (PV) values measured by the ICG method in this study agree with data of other authors with special respect to basic values for further clinical investigations, and 2. Do the measured differences coincide with the withdrawn and retransfused plasma volume? DESIGN: Prospective study (on each 20 healthy female and male volunteers). SETTING: Research laboratory of a university department of anesthesiology. PARTICIPANTS: Each 20 healthy female and male volunteers. INTERVENTIONS: Measurement of PV with ICG both before and after withdrawal of 10% of blood volume and after retransfusion. RESULTS: The plasma volume per body surface area (PV/BSA) was in the group of female volunteers 1639 +/- 198 and in male volunteers 1687 +/- 224 ml/m2 (mean +/- SD). The withdrawn amount of plasma volume (EPV) was 188 +/- 23 in the female group and 149 +/- 26 ml/m2 in the male group. Determined by the ICG method the difference for the withdrawal was in female volunteers 198 +/- 174 and in male volunteers 171 +/- 158 ml/m2 and for the retransfusion in the female group 190 +/- 169 and in the male group 142 +/- 154 ml/m2. CONCLUSIONS: The mean differences in plasma volume measured by the ICG method both before and after withdrawal and after retransfusion of autologous blood were in good agreement with the withdrawn amount of plasma volume. The large standard deviation has to be considered in clinical assessment of an individual measurement.

Adult↗
PubMed1995

Changing the reaction specificity of a pyridoxal-5'-phosphate-dependent enzyme.

The electron distribution in the coenzyme-substrate adduct of aspartate aminotransferase was changed by replacing active-site Arg386 with alanine and introducing a new arginine residue nearby. [Y225R, R386A]Aspartate aminotransferase decarboxylates L-aspartate to L-alanine (kcat = 0.04 s-1), while its transaminase activity towards dicarboxylic amino acids is decreased by three orders of magnitude (kcat = 0.19 s-1). Molecular-dynamics simulations based on the crystal structure of the mutant enzyme suggest that a new hydrogen bond to the imine N atom of the pyridoxal-5'-phosphate- aspartate adduct and an altered electrostatic potential around its beta-carboxylate group underlie the 650,000-fold increase in the ratio of beta-decarboxylase/transaminase activity.

Aspartate Aminotransferases↗