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Biomedical subjects

B Pohl

Publications and source records attributed to B Pohl.

At least 19 recordsLinked to original sources
PubMed2006

Onset properties of mivacurium measured by mechanomyography depend on the twitch height of the adductor pollicis muscle.

INTRODUCTION: The influence of the twitch height of the adductor pollicis muscle during baseline measurements on the pharmacodynamic parameters of mivacurium was prospectively evaluated. PATIENTS AND METHODS: Fifty adult patients were anaesthetized with propofol and alfentanil. Neuromuscular function was monitored mechanomyographically by measuring the force of the adductor pollicis muscle following stimulation of the ulnar nerve. Following a stabilization period of 20 min, the individual twitch height of the adductor pollicis muscle was determined before a single bolus of mivacurium (75 microg kg-1) was administered. Patients were divided into two groups. The data of patients whose thumb adduction force was below the median value of all patients were the 'low force' group (9.1 +/- 1.4 N) and the data of all other patients were the 'high force' group (13.7 +/- 1.8 N). RESULTS: In the 'high force' group, maximum neuromuscular blockade of mivacurium was deeper (0.97 +/- 0.05 vs. 0.93 +/- 0.06; P < 0.05) and onset faster (2.9 +/- 1.1 min vs. 4.0 +/- 1.2 min; P < 0.05). Neuromuscular recovery did not differ between the groups. CONCLUSION: The different onset speeds reflect either different sensitivity to neuromuscular blocking agents with respect to patients' muscle power or a problem of the mechanomyographic measuring technique.

Adult↗
PubMed2006

[Depth of anaesthesia during intubation: comparison between propofol and thiopentone].

In order to study the depth of anaesthesia during endotracheal intubation, 30 patients received either thiopentone or propofol for anaesthesia induction. The BIS value as a parameter for the depth of anaesthesia and the rate pressure product (RPP) were acquired online. Patients who received thiopentone for anaesthesia induction showed significantly higher BIS values at the moment of intubation and reached BIS values >60 significantly more frequently than patients receiving propofol. The RPP in the propofol group lay significantly below that of the thiopentone patients. For all patients there was an mean increase in BIS values of 8 index points and an increase in the RPP. Therefore, BIS values around 50 should be achieved before intubation in order to avoid the critical BIS value for awareness of >60 despite the increase caused by the intubation procedure. Within 24 h of intubation all patients were interviewed for possible signs of awareness. None of the patients was able to remember the intubation or reported other experiences that indicated an unconscious awareness. Nevertheless, the progress of BIS values in a standardized intubation as performed in the normal clinical routine, shows that the use of thiopentone for initiating anaesthesia results in a very flat level of anaesthesia during intubation. The risk for patients to experience awareness should therefore, not be underestimated. Therefore, when using thiopentone it is recommended to also use a rapid acting muscle relaxant or to select a high ED95 to compensate for the flat level of anaesthesia. Alternatively, repetetive boluses of the hypnotic shortly before intubation should be considered or to revert to propofol. The dosage and pharmacokinetics of the analgesic should also be taken into consideration because an insufficient analgesia leads to a faster flattening of the depth of anaesthesia.

Adolescent↗
PubMed2006

Comparison of invasive and less-invasive techniques of cardiac output measurement under different haemodynamic conditions in a pig model.

BACKGROUND AND OBJECTIVE: Despite the introduction of various less-invasive concepts of cardiac output measurement, pulmonary arterial thermodilution is still the most common measurement technique. METHODS: This prospective controlled study was designed to compare different methods of cardiac output measurement simultaneously. Pulmonary arterial thermodilution, transpulmonary thermodilution (PiCCO), trans-oesophageal echo-Doppler probe (HemoSonic) and partial carbon dioxide rebreathing technique (NICO monitor) were evaluated against a peri-aortic transit-time flow-probe as reference method in a clinically relevant animal model. After approval from the Local Ethics Committee on Animal Research, the investigations were conducted in nine anesthetized domestic pigs. Systemic haemodynamics were modulated systematically by the application of catecholamines, caval occlusion and exsanguination. Statistical analysis was performed with Bland-Altman and linear regression. RESULTS: A total of 366 paired cardiac output measurements were carried out at a reference cardiac output between 0.5 and 7 L min(-1). The correlation coefficients for pulmonary arterial and transpulmonary thermodilution against reference were 0.93 and 0.95, for trans-oesophageal Doppler and partial rebreathing technique 0.84 and 0.77. Pulmonary arterial thermodilution and transpulmonary thermodilution showed comparable bias and limits of agreement. Where HemoSonic showed an overestimation of cardiac output at a higher precision, NICO overestimated low and underestimated higher cardiac output values. CONCLUSIONS: Our data suggest that pulmonary arterial thermodilution and PiCCO may be interchangeably used for cardiac output measurement even under acute haemodynamic changes. The method described by Bland and Altman demonstrated an overestimation of cardiac output for both thermodilution methods. HemoSonic and NICO offer non-invasive alternatives and complementary monitoring tools in numerous clinical situations. Trend monitoring and haemodynamic optimizing can be applied sufficiently, when absolute measures are judged critically in a clinical context. The use of the NICO system seems to be limited during acute circulatory changes.

Algorithms↗
PubMed2005

Detection of human hantavirus infections in Lithuania.

BACKGROUND: In Europe certain hantaviruses are known to cause hemorrhagic fever with renal syndrome of different severity. The objective of the present investigation was to study the presence of hantavirus infections in Lithuania. MATERIAL AND METHODS: Two different serum panels from cancer patients (n = 438) and blood donors (n = 299) from Lithuania were tested by monoclonal antibody capture IgG ELISA using yeast-expressed recombinant nucleocapsid (rN) proteins of Puumala virus (PUUV), Hantaan virus (HTNV) and Dobrava virus (DOBV). The reactivity of ELISA-positive sera was proven in Western blot tests using various hantavirus rN proteins. Selected serum samples were further analyzed by focus reduction neutralization assays. RESULTS: In the IgG ELISA 39 sera from the cancer patients and four sera from blood donors were found to be reactive with at least one of the rN proteins. By immunoblot using the three yeast-expressed rN proteins, the ELISA reactivity of 36 of 39 and two of four serum samples from cancer patients and blood donors, respectively, was confirmed; this corresponds to a seroprevalence of 8.2% and 0.7%, respectively. In ELISA, the majority of the samples reacted exclusively with rN proteins of HTNV and DOBV (31 of 36 and one of two in the two groups). In the group of sera selected for serotyping by focus reduction neutralization assay, this dominance was confirmed by the identification of eight DOBV but only four PUUV infections. No infection by HTNV or another hantavirus besides DOBV and PUUV was verified. Anti-hantavirus-positive human sera were detected in all seven investigated counties of Lithuania. CONCLUSION: In Lithuania at least two hantaviruses, DOBV and PUUV, circulate and cause human infections. Additional investigations are needed to study the seroprevalence more precisely and to search for clinical cases of hantavirus infections.

Antibodies, Viral↗
PubMed2004

[Feedback control of muscle relaxation with a varying on-off controller using cisatracurium].

BACKGROUND: Under clinical conditions constant neuromuscular blockade can also be maintained by a simple closed-loop system. However, delayed onset time, non-linearity of the dose-response curve and different sensitivity to muscle relaxants for each patient are limiting factors. METHODS: In 20 patients who underwent elective surgical procedures under continuous propofol/alfentanil anaesthesia and relaxation with cisatracurium, the maintenance of an electromyographically controlled cisatracurium block of 90% was achieved by a varying on-off control system. Using an own computer-aided measuring device, the course of the neuromuscular blockade and deviations from the desired neuromuscular block were registered. RESULTS: Over a period of 64.2+/-14.0 min, neuromuscular block could be controlled on average at a T(1)-level of 10% (90% block). The mean error of the deviation of the obtained neuromuscular blockade from the set-point was -1.6+/-0.9% on average. To maintain this neuromuscular blockade, a dose rate of 1.4+/-0.9 micro g x kg(-1) x min(-1) cisatracurium was necessary. CONCLUSIONS: It can be concluded that a simple closed-loop system allows the safe use of the intermediate term muscle relaxant cisatracurium for the performance of surgical procedures.

Adult↗
PubMed2003

[The syringe pump as actuator--a practical application problem of feedback control systems].

Based on a computer simulation programme, the accuracy of the Graseby 3400 syringe pump was tested for its use in a feedback control system of the neuromuscular block. Firstly, a calculation of errors to determine the difference between the target and actual flow rates was carried out. Next, the characteristic curves of the syringe pump were determined under different flow and sampling rates to correct the application software of the feedback controller with a view to obtaining the correct flow rates online. It was discovered that, particularly with short 12 s sampling rates, dose-dependent errors of almost 100% were provable. Therefore, the application of a robust controller and integration of the characteristic curves at the outlet of the controller software are required. For the adoption of syringe pumps in medical feedback control systems, definite determination of the actual infusion quantity using an exact calculation of errors is required. Especially in cases of short sampling rates in combination with low infusion quantities, the syringe pump comes almost to a standstill, which results in extreme differences between target and actual flow rates.

Computer Simulation↗
PubMed2002

[Oral and rectal premedication of children with midazolam]].

Premedication in children continues to be a problem in anaesthesiology. Apart from the application of premedication drugs, a strongly committed anaesthetist and sound psychological work are decisive prerequisites for adequate premedication. In this randomized study, 329 children aged between 1 and 14 who were scheduled for small surgical procedures were examined. Based on the results of a preliminary trial using different dosages of midazolam, the children were premedicated either orally with 0.4 mg/kg BW midazolam or with 0.3 mg/kg BW midazolam as a rectal solution and the premedication effect was recorded according to the classification of Lindgren. These reduced doses of midazolam, which were much lower than those described in the literature, led to very good premedication effects, too. Regarding cardiovascular behaviour, an increasing anxiolysis and the effect of premedication led to a significant decline in mean arterial blood pressure and heart frequency. The circulatory changes that occurred were at no time clinically relevant in any child, and therefore no treatment was needed. Based on the measured oxygen saturation, no significant respiratory changes were seen during the observation period. The frequency and extent of the registered side-effects were classified as slight. Side-effects such as singultus, salivation and ataxia/gesticulations were of no danger during the entire perioperative period.

Adjuvants, Anesthesia↗
PubMed2002

[Quantitative assessment of neuromuscular block of the orbicularis oculi muscle].

In a prospective clinical study neuromuscular block at the orbicular ocular muscle was examined qualitatively and quantitatively by an AMG approach. The signals were recorded, visualized and evaluated simultaneously under PC-support after TOF-stimulation in 20 s intervals. Fifty ASA I and II patients were included into the study. After oral premedication with midazolam 10-15 mg, anaesthesia was induced with propofol 2 mg/kg and alfentanil 0.02 mg/kg and maintained by means of propofol 6-8 mg/kg/h and alfentanil 0.02 mg/kg/h. After intubation and signal stabilization, mivacurium 0.75 mg/kg was administered and neuromuscular blockade was recorded online. The measured acceleration at the orbicular ocular muscle amounted 0.9 g on average. Maximal neuromuscular block was registered at 78.5% and the TOF-ratio of 0.8 was achieved after 14.1 min. The low values of the AMG-signals of the orbicular ocular muscle requiring very high technical demands on the measuring instrument. Additional problems arise through the considerable temporal expenditure for discovering the optimal location of stimulation. During the AMG monitoring the position dependence of the measured values of the sensors must be taken into consideration. These technical problems restrict the suitability of the AMG at the orbicular ocular muscle as a quantitative neuromuscular monitoring tool.

Adolescent↗
PubMed2001

[Clinical administration of muscle relaxants for intubation].

Muscle relaxants are used for tracheal intubation, surgical procedures and in the intensive care unit. This review describes muscle relaxants available in Germany, with special focus on their use in endotracheal intubation. We compare the advantages and disadvantages of succinylcholine (the only depolarising agent) with those of short- and intermediate-acting non-depolarising agents in an attempt to define the characteristics of the ideal muscle relaxant. The effective doses required to attain 95% neuromuscular block and maximum effect (onset time) are compared for adults and children. It is documented that, with non-depolarising agents, increasing the dose and using either the priming or timing principle possibly reduce the onset time of neuromuscular block during a rapid sequence induction. The advantages and disadvantages of using non-depolarising instead of depolarising agents are discussed using data from our studies and those of other research groups. Possible side-effects due to the chemical structure and the necessary dosage for intubation of different agents are also discussed. Two points are emphasized: firstly, the use of non-depolarising agents for intubation requires the possibility of safe ventilation of the patient via mask, and, secondly, it is important that procedures be performed by an experienced anaesthetist.

Adult↗
PubMed1999

Expression of the highly conserved RNA binding protein KOC in embryogenesis.

The human KOC gene which is highly expressed in cancer shows typical structural features of an RNA binding protein. We analyzed the temporal and spatial expression pattern of KOC in mouse embryos at different gestational ages. The expression of KOC seems to be ubiquitous at early stages. During advanced gestation highest KOC expression occurs in the gut, pancreas, kidney, and in the developing brain. The expression pattern of KOC was compared to its Xenopus homologue Vg1-RBP during frog development. Similar expression was found in these organs suggesting an important functional role of the homologous proteins in embryonic development.

Amino Acid Sequence↗
PubMed1999

Identification of genetic determinants for the hemolytic activity of Streptococcus agalactiae by ISS1 transposition.

Streptococcus agalactiae is a poorly transformable bacterium and studies of molecular mechanisms are difficult due to the limitations of genetic tools. Employing the novel pGh9:ISS1 transposition vector we generated plasmid-based mutant libraries of S. agalactiae strains O90R and AC475 by random chromosomal integration. A screen for mutants with a nonhemolytic phenotype on sheep blood agar led to the identification of a genetic locus harboring several genes that are essential for the hemolytic function and pigment production of S. agalactiae. Nucleotide sequence analysis of nonhemolytic mutants revealed that four mutants had distinct insertion sites in a single genetic locus of 7 kb that was subsequently designated cyl. Eight different open reading frames were identified: cylX, cylD, cylG, acpC, cylZ, cylA, cylB, and cylE, coding for predicted proteins with molecular masses of 11, 33, 26, 11, 15, 35, 32, and 78 kDa, respectively. The deduced amino acid sequence of the protein encoded by cylA harbors a conserved ATP-binding cassette (ABC) motif, and the predicted proteins encoded by cylA and cylB have significant similarities to the nucleotide binding and transmembrane proteins of typical ABC transporter systems. Transcription analysis by reverse transcription-PCR suggests that cylX to cylE are part of an operon. The requirement of acpC and cylZABE for hemolysin production of S. agalactiae was confirmed either by targeted mutagenesis with the vector pGh5, complementation studies with pAT28, or analysis of insertion elements in naturally occurring nonhemolytic mutants.

Animals↗
PubMed1998

[Measuring muscle relaxation with mivacurium in comparison with mechano- and electromyography].

Based on survey of the literature, methodological problems of electromyographic and mechanomyographic neuromuscular monitoring are presented. Often mechanomyography (MMG) is accompanied by mechanical problems during the registration of the contractions in the operating theatre. In contrast to mechanomyography the registration of electromyographic signals is easier whereas the processing of electromyographic signals is more difficult. In the operating theatre, registration problems can also occur with electromyography (EMG) from artefacts arising from stimulation impulses, high frequency apparatus and alternating current. During neuromuscular monitoring using MMG, a positive drift of the amplitudes of the contractions can be observed, whereas EMG leads to a negative drift of the amplitudes of the action potentials. Both observations can lead to misinterpretation of the degree of neuromuscular block measured by single twitch stimulation during the recovery period. Both the positive and negative drifts can be prevented by single twitch stimulation lasting for up to 10 minutes before the start of the neuromuscular monitoring of the effect of a given dose of a muscle relaxant. Finally, a clinical study of simultaneous registration of the MMG at the M. adductor pollicis and of the EMG at the M. interosseus dorsalis DI under total intravenous anaesthesia using propofol and alfentanil and muscle relaxation with a bolus dose of 75 mg/kg mivacurium is described. During the mechanomyographic studies, a decrease in the preload by an average of 1.2 Newton (N) with a maximum level of 4.0 N occurred. The decrease in preload was less than 25%. The mechanomyographically measured onset time of an ED95 of mivacurium amounted to 3.5 +/- 1.2 minutes on average and the degree of maximum neuromuscular block on average (95.1 +/- 5.6%) tallied very well with the expected value of 95.0%. The electromyographically measured onset time of an ED95 of mivacurium amounted to 4.3 +/- 1.2 minutes on average and the degree of maximum neuromuscular block amounted to only 91.3 +/- 8.1% on average. A comparison of the mechanomyographic values and the electromyographic values leads to the following results: the MMG showed a significantly shorter onset time (p < 0.0001) and a significantly deeper maximum neuromuscular block (p = 0.0004) than the EMG. There were also significant differences between mechanomyographically and electromyographically measured recovery values regarding T1(75) (p = 0.0007), T1(90) (p < 0.0001), TOF0.8 (p = 0.0386) and T1(25-75) (p < 0.0001). On average, an ED95 of mivacurium showed a significantly slower recovery in the mechanomyogram than in the electromyogram.

Adult↗
PubMed1996

Novel series of plasmid vectors for gene inactivation and expression analysis in group A streptococci (GAS).

Ten novel streptococcal shuttle vectors for genomic integration and allelic replacements have been constructed based on plasmid pSF152. These vectors can replicate in E. coli, but not in streptococci because of the absence of a streptococcal origin of replication. The basic vector pFW5 (2.8 kb, aad9 spectinomycin-resistance marker) carries two multiple cloning sites MCS-I and MCS-II (10 and 15 restrictions sites, respectively) to either side of the aad9 resistance gene. Each MCS is flanked by transcription termination sites for stabilization of recombinant plasmids. In vector pFW6 the transcription terminator between aad9 and MCS-II was deleted. Plasmids pFW7 through pFW10 carry resistance genes for kanamycin, chloramphenicol, erythromycin, and tetracyclin instead of aad9. Vectors pFW11 and pFW12 are pFW5/6 derivatives harboring an improved synthetic aad9 promoter. In pFW-phoA and pFW-gfp, promoterless alkaline phosphatase and green fluorescent protein boxes were integrated into MCS-I. If streptococcal DNA fragments are cloned into MCS-I and MSC-II, these vectors can be used for specific allelic replacements in streptococci via double-crossover recombinations. Depending on the vector used, this event will not lead to polar effects, facilitating mutagenesis within operons. The vectors containing reporter boxes allow in vivo studies of gene expression and promoter activity in pathogenic streptococci and potentially, also in other Gram-positive bacteria.

Alkaline Phosphatase↗
PubMed1996

[The child with minor trauma. Does observation of fasting times reduce the risk of aspiration?].

According to a literature search, it seems most unlikely based on patho-physiological requirements and physiological aspects that traumatized children benefit from preoperative waiting times aimed at achieving a 6-h fast. Irrespective of fasting, traumatized children are at risk of requiring aspiration. Many generally recommended measures for the avoidance of aspiration are neither reasonable nor effective in traumatized children. The physical and psychological benefits that can be derived from shorter preoperative waiting times can more than over-ride the organizational difficulties caused by waiting longer.

Child↗
PubMed1996

What is the size of the group A streptococcal vir regulon? The Mga regulator affects expression of secreted and surface virulence factors.

The vir regulon of group A streptococci (GAS) organizes the expression of several bacterial virulence factors under the control of the Mga regulator. Previously, the genes encoding the Mga regulator (mga), M and M-related proteins (emm, mrp, enn) and C5a peptidase (scpA) were reported to be clustered on the streptococcal genome in a core vir regulon. In the present study, the genomic regions of a serotype M49 strain upstream of mga and downstream of scpA were sequenced to assess the boundaries of the vir regulon. In the upstream region, an operon was identified that may be potentially involved in substrate transport and is independent from Mga regulation. In the downstream region, another Mga-controlled, scpA-cotranscribed gene was detected. This gene termed orfX encoded a 385-amino acid (aa) potential surface protein of unknown function. No binding of serum proteins to a recombinant ORFX was detectable and phagocytosis resistance of an orfX mutant remained unchanged. Downstream of orfX, another Mga-independent gene determined the 3' end of the core vir regulon. Utilizing the M49 wild type, a mga- mutant and comparative Northern blot hybridization, genes encoding the capsule synthesis machinery, streptokinase and streptolysin O, as well as erythrogenic toxin A and DNase C were found to be Mga independent. In contrast, expression of the genes encoding the cysteine protease SpeB, streptococcin A and the oligopeptide permease was reduced in the mga- mutant. This indicated that in addition to the core vir regulon, Mga directly or indirectly controls a number of genes dispersed throughout the GAS genome.

Amino Acid Sequence↗
PubMed1996

Molecular characterization of group A streptococcal (GAS) oligopeptide permease (opp) and its effect on cysteine protease production.

Bacterial oligopeptide permeases are membrane-associated complexes of five proteins belonging to the ABC-transporter family, which have been found to be involved in obtaining nutrients, cell-wall metabolism, competence, and adherence to host cells. A lambda library of the strain CS101 group A streptococcal (GAS) genome was used to sequence 10,192 bp containing the five genes oppA to oppF of the GAS opp operon. The deduced amino acid sequences exhibited 50-84% homology to pneumococcal AmiA to AmiF sequences. The operon organization of the five genes was confirmed by transcriptional analysis and an additional shorter oppA transcript was detected. Insertional inactivation was used to create serotype M49 strains which did not express either the oppA gene or the ATPase genes, oppD and oppF. The mutation in oppA confirmed that the additional shorter oppA transcript originated from the opp operon and was probably due to an intra-operon transcription terminator site located downstream of oppA. While growth kinetics, binding of serum proteins, and attachment to eukaryotic cells were unaffected, the oppD/F mutants showed reduced production of the cysteine protease, SpeB, and a change in the pattern of secreted proteins. Thus, the GAS opp operon appears to contribute to both protease production and export/processing of secreted proteins.

Amino Acid Sequence↗