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Biomedical subjects

F Bremer

Publications and source records attributed to F Bremer.

At least 19 recordsLinked to original sources
PubMed2006

[Pharmacodynamics of two different propofol formulations].

BACKGROUND: Propofol is nowadays available in various lipid formulations. We compared two different propofol formulations with respect to pharmacodynamics, using the EEG and clinical signs. MATERIALS AND METHODS: Ten volunteers received Diprivan 1% and Propofol 1% MCT Fresenius as a computer controlled infusion with increasing propofol target concentrations. A sigmoid E(max) model with effect compartment was estimated for the median frequency of the EEG power spectrum, based on measured arterial propofol plasma concentrations. Clinical pharmacodynamics were assessed by reaction on acoustic stimuli, eyelid reflex and corneal reflex. RESULTS: The drugs did not differ in pharmacodynamics with respect to EEG (EC(50) 2.1+/-0.6 for Diprivan and 2.1+/-0.5 microg/ml for Propofol Fresenius) and clinical signs. The pharmacodynamic model was characterized by a steep concentration effect relationship and a distinct hysteresis between propofol plasma concentration and effect (k(e0) 0.12+/-0.04 and 0.12+/-0.5 min(-1)). CONCLUSIONS: The investigated lipid formulations have no influence on the pharmacodynamics of propofol.

Acoustic Stimulation↗
PubMed2004

[Accuracy of target-controlled infusion (TCI) with 2 different propofol formulations].

BACKGROUND: Target-controlled infusion (TCI) of propofol was initially realized as a device for prefilled syringes (Diprifusor). New TCI systems can be used with any propofol formulation. We compared two different propofol formulations with respect to accuracy of TCI and pharmacokinetics. MATERIALS AND METHODS: A total of 10 volunteers received Diprivan 1% and Propofol 1% MCT Fresenius as TCI using the pharmacokinetic model of the Diprifusor. The prediction error was determined from measured arterial concentrations. A three-compartment model was fitted to the concentration data. RESULTS: The median prediction error and the median absolute prediction error were -1.4% and 23.3% for Diprivan, and -5.9% and 17.8% for Propofol Fresenius. The drugs did not differ in pharmacokinetics but showed a smaller central volume of distribution than used for infusion control. CONCLUSIONS: The pharmacokinetic model of Diprifusor can also be used for TCI of Propofol Fresenius. The large volume of distribution in this model may cause an overshoot in concentration.

Adult↗
PubMed2004

Automated EEG preprocessing during anaesthesia: new aspects using artificial neural networks.

The computer-aided detection of artefacts became an essential task with increasing automation of quantitative electroencephalogram (EEG) analysis during anaesthesiological applications. The different algorithms published so far required individual manual adjustment or have been based on limited decision criteria. In this study, we developed an artificial neural networks-(ANN-)aided method for automated detection of artefacts and EEG suppression periods. 72 hr EEG recorded before, during and after anaesthesia with propofol have been evaluated. Selected parameterized patterns of 0.25 s length were used to train the ANN (22 input, 8 hidden and 4 output neurons) with error back propagation. The detection performance of the ANN-aided method was tested with processing epochs between 1 to10 s. Related to examiner EEG evaluation, the average detection performance of the method was 72% sensitivity and 80% specificity for artefacts and 90% sensitivity and 92% specificity for EEG suppression. The improvement in signal-to-noise ratio with automated artefact processing was 1.39 times for the spectral edge frequency 95 (SEF95) and 1.89 times for the approximate entropy (ApEn). We conclude that ANN-aided preprocessing provide an useful tool for automated EEG evaluation in anaesthesiological applications.

Algorithms↗
PubMed2000

[Volumetry of pleural effusion in multi-morbidity, postoperative patients of a surgical intensive care unit. Comparison of ultrasound diagnosis and thoracic bedside image].

Aim of this study was to evaluate the importance of chest ultrasound and chest x-ray for the indication of thoracic drainage of pleural effusions in patients of an operative intensive care unit. Between December 1996 and June 1997 21 patients were included in a prospective trial in the operative intensive care unit. 26 thoracic drainages were used to drain pleural effusions. In all patients chest radiography in supine position and chest ultrasound were performed to assess the need of pleural drainage. Pleural fluid measured radiologically was categorized into 3 groups: pleural fluid less than 500 ml, 500 to 1,000 ml or more than 1,000 ml. The amount of the pleural effusion was sonographically determined by a standardized formula. After complete drainage of the pleural space the real volume of the fluid was measured and compared with the estimated value. The real amount of the fluid was correctly determined by chest radiographs in 16 cases (62%) and by chest ultrasound in 18 patients (69%). Pleural effusions less than 600 ml sonographically correlated much better with the real amount of the fluid than pleural effusions above 600 ml. In 8 cases (31%) ultrasound provided an additional information for correct indication of drainage. Considering both x-ray of the chest in supine position and chest ultrasound the correct indication to drain the pleural effusion was achieved in 25 cases (96%). In this prospective trial we compared chest ultrasound and chest radiography and demonstrated that ultrasound is more suitable to determine the amount of pleural effusions than radiography. In case of clinical and radiological suspicion on pleural effusion demanding for drainage a chest ultrasound should be performed to avoid underestimation of pleural fluid.

Adult↗
PubMed1999

Pharmacokinetics of meropenem in critically ill patients with acute renal failure undergoing continuous venovenous hemofiltration.

OBJECTIVE: Meropenem is a broad-spectrum antibiotic used for severe infections. In patients with chronic end-stage renal failure, meropenem clearance is reduced and doses must be adjusted according to the creatinine clearance. The aim of this study was to assess pharmacokinetic data of meropenem in patients with acute renal failure and to determine the amount of drug removed by continuous venovenous hemofiltration, an often-used renal replacement therapy in patients with acute renal failure. METHODS: Nine critically ill anuric patients with acute renal failure undergoing continuous venovenous hemofiltration received 500 mg meropenem 2 or 3 times daily. Plasma and hemofiltrate concentrations were determined during 1 dosing interval at steady state. Pharmacokinetic parameters were calculated for a 2-compartment open model and dose requirements were calculated. RESULTS: The total meropenem clearance was 52.0 +/- 8.4 mL/min, with a hemofiltration clearance of 22.0 +/- 4.7 mL/min and a nonrenal-nonhemofiltration clearance of 29.9 +/- 5.4 mL/min; 235.9 +/- 88.6 mg, or 47.2% +/- 17.7%, of the dose were removed through continuous venovenous hemofiltration. The terminal elimination half-life was 8.7 +/- 3.5 hours and the volume of distribution at steady state was 12.4 +/- 1.8 L. Peak and trough concentrations for a dosing interval of 12 hours were 38.9 +/- 9.7 mg/L and 7.3 +/- 1.3 mg/L, respectively. The corresponding concentrations for a dosing interval of 8 hours were 44.7 +/- 10.4 mg/L and 11.9 +/- 0.7 mg/L, respectively. CONCLUSION: Pharmacokinetic data of anuric patients with acute renal failure were similar to those of patients with end-stage renal failure. Because hemofiltration contributes significantly to meropenem elimination, the recommended dose for critically ill anuric patients receiving continuous venovenous hemofiltration should be increased by 100% to avoid potential underdosing.

Acute Kidney Injury↗
PubMed1998

[Prothrombin time and thromboplastin time. On-site measurement of the prothrombin time and activated partial thromboplastin time of surgical patients with laser photometry].

UNLABELLED: Turnaround time for analysis of prothrombin time (PT) and activated partial thromboplastin time (APTT) by standard laboratory methods ranges between 40 min and several hours. The delay in obtaining the test results limits their clinical utility for treatment of perioperative coagulation disorders and adequate anti-coagulation therapy. In this study, we compared on-site coagulation testing (OCT) of whole blood, which takes about 3 min, with standard laboratory plasma coagulation tests by our institutional laboratory (LAB) to assess the accuracy of the OCT in a clinical setting (abdominal and postcardiac surgery). METHODS: PT of 62 patients with abdominal surgery was measured intra- and postoperatively using both LAB (KC 40, Thromborel S, Centeon) and OCT (CoaguChek Plus, Boehringer Mannheim) systems. APTT was determined by LAB-(KC 40, Pathromtin, Centeon) and OCT-methods in 53 patients who underwent cardiac surgery requiring cardiopulmonary bypass. RESULTS: Linear regression demonstrated a strong and significant (p = 0.0001) correlation of OCT- and LAB-determinations both for PT (r = 0.92) and APTT (r = 0.91). For PT testing, bias analyses showed an agreement between OCT- and LAB-International Normalized Ratio (INR) (bias = 0.24; relative error = 14.6%) that was considered clinically acceptable, with 95% of the INR-differences lying between -0,26 and +0,74 (mean +/- 2 SD). Although commercial APTT-reagents usually differ in their sensitivity to heparin, we also found an acceptable agreement between OCT- and LAB-APTT values (bias = 6.7 s +/- 22 s; mean +/- 2 SD; relative error = 12%). CONCLUSION: On-site coagulation monitoring provides a rapid, convenient, and accurate assessment of coagulation that can both guide specific anti-coagulation therapy and optimize therapy control of coagulation disorders after cardiac and abdominal operations. As a consequence, OCT offers a valuable tool to reduce the inappropriate use of fresh frozen plasma and to improve cost-effectiveness.

Humans↗
PubMed1997

Pharmacokinetics of imipenem-cilastatin in critically ill patients undergoing continuous venovenous hemofiltration.

The pharmacokinetics of imipenem-cilastatin were investigated in 12 critically ill patients with acute renal failure (ARF) managed by continuous veno-venous hemofiltration (CVVH) while receiving a fixed combination of 500 mg of imipenem-cilastatin intravenously three or four times daily. No adverse drug reactions were observed. Plasma and hemofiltrate samples were taken at specified times during one dosing interval, and the concentrations of imipenem and cilastatin were determined by high-performance liquid chromatography. Pharmacokinetic variables were calculated by a first-order, two-compartment pharmacokinetic model for both substances. Total clearances of imipenem and cilastatin (mean +/- standard deviations) were 122.2 +/- 28.6 and 29.2 +/- 13.7 ml/min, respectively, with hemofiltration clearances of 22.9 +/- 2.5 and 16.1 +/- 3.1 ml/min, respectively, and nonrenal, nonhemofiltration clearances of 90.8 +/- 26.3 and 13.2 +/- 13.9 ml/min, respectively. Mean imipenem dosage requirements were approximately 2,000 mg/24 h (2,111.8 +/- 493.4 mg/24 h). They were calculated in order to achieve an average steady-state concentration of 12 mg/liter to ensure that concentrations in plasma exceeded the MICs at which 90% of intermediately resistent bacteria are inhibited (8 mg/liter) during the majority of the dosing interval. By contrast, the recommended dosage for patients with end-stage renal failure (ESRF) and infections caused by intermediately resistant bacteria is 1,000 mg/24 h. This remarkable difference may be due (i) to differences in the nonrenal clearance of imipenem between patients with ARF and ESRF and (ii) to the additional clearance by the hemofilter. Since the total clearance of cilastatin was low, marked accumulation occurred, and this was particularly pronounced in patients with additional liver dysfunction. Thus, in patients with ARF managed by CVVH, rather high imipenem doses are required, and these inevitably result in a marked accumulation of cilastatin. The doses of imipenem recommended for patients with ESRF, however, will lead to underdosing and inadequate antibiotic therapy.

Acute Kidney Injury↗
PubMed1996

[Peripheral ulcerative keratitis and a form of limited wegener's granulomatosis].

A man aged 68 years presents superior limbal infiltrates at his left eye two weeks before a marginal ulcer which quickly perforates. He has no systemic complaint. Clinical, biological, radiologic and histological evaluations disclose superior airways and lungs implications, an inflammatory syndrome, high ANCA (antineutrophiles cytoplamic antibodies) titer and vasculitis. There is no sign of renal involvement. A limited form of Wegener's granulomatosis is diagnosed. The outcome is favorable with a partial penetrating keratoplasty and systemic corticosteroid therapy in association with immunosuppressive drugs. This so called limited form of Wegener's granulomatosis is sight threatening when eye is the initial presentation. The early diagnostic and treatment will be performed by the help of ANCA in cases with subclinical systemic manifestations.

Aged↗
PubMed1993

Effects of four intravenous anesthetic agents on motor evoked potentials elicited by magnetic transcranial stimulation.

The influence of four intravenous anesthetic agents on motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (magnetic MEP) was examined in 77 subjects. The patients were anesthetized by a continuous intravenous infusion of one of the following anesthetic agents: propofol, etomidate, methohexital, or thiopental. Comparable anesthetic effects among the four agents were achieved by computing an infusion scheme for each drug. Infusion rates were increased slowly in a step-wise manner in order to reach minimal anesthetic blood concentrations within 15 minutes. During anesthesia induction, magnetic MEPs were recorded every 2 minutes from the abductor pollicis brevis muscle. The patient's level of consciousness was assessed and documented in the alternating minutes. A dose-related reduction of the MEP amplitudes was seen in all drug groups, while the latencies remained constant. Reduction of the amplitude was occasionally so prominent that the MEP was completely abolished before adequate anesthesia was achieved. MEPs were obtainable at the end of anesthesia induction in 14% of the propofol group (n = 22), 57% of the etomidate group (n = 21), 53% of the methohexital group (n = 19), and 20% of the thiopental group (n = 15). Propofol and thiopental showed significantly stronger suppression of MEP, when compared to etomidate (both P < 0.01) and to methohexital (P = 0.01 and 0.05, respectively). Etomidate was the least detrimental anesthetic agent for intraoperative monitoring of magnetic MEP. Nonetheless, the low incidence of 57% of preserved MEP in subjects without motor deficits indicated the inadequacy of this technique for intraoperative monitoring. More effective transcranial stimulation techniques are required for successful intraoperative MEP monitoring.

Adult↗
PubMed1993

[Anesthesia induction using etomidate in a lipid emulsion].

The use of etomidate as an anaesthetic induction agent has been hampered significantly by unwanted side effects such as pain on injection and thrombophlebitis. Investigations by Doenicke et al. have shown that the solubilizer propylene glycol is responsible for these side effects and that they can be avoided by the use of a lipid emulsion formulation. It was the goal of the present study to quantitate the reduction of thrombophlebitis and pain on injection following both formulations under double-blind study conditions. METHODS. In 100 patients anaesthesia was induced either with a new galenic formulation of etomidate--etomidate in lipid emulsion formulation (Lipofundin MCT 20%; eto-lip)--or with etomidate in propylene glycol 35% (eto-pg). Both groups received 0.3 mg kg-1 etomidate in double-blind randomized fashion. After the injection of etomidate the venous cannula was removed. The observing anaesthetist was unaware of the study drug used, to guarantee blinded investigation conditions. Discomfort and pain during and following injection were recorded, as was local skin irritation. Venous sequelae were assessed for 7 days following injection to register the occurrence of thrombophlebitis. RESULTS. Demographic data were not different between the two groups. For induction of anaesthesia the same dose of both preparations was necessary, and no difference in heart rate and blood pressure before, during or after anaesthesia induction was observed. Pain on injection (78% vs 14%), myoclonus (24% vs 8%) and local skin reaction (50% vs 6%) were present significantly more often in the eto-pg group (P < 0.01; P < 0.05 respectively, chi-square test) than in the eto-lip group. On the 1st and 2nd postoperative days, examination of the injected vein revealed a significantly higher incidence of symptoms of thrombophlebitis in the group treated with eto-pg (25% vs 3%). CONCLUSION. From these results it is concluded that in terms of vein compatibility the new galenic formulation of etomidate with lipofundin MCT 20% is superior to the propylene glycol preparation while pharmacodynamic properties seem not to be affected.

Adult↗
PubMed1991

[Pharmacotherapy of ventricular fibrillation. A prospective study in an emergency medical service].

This prospective study investigated the effects of standard pharmacotherapy in out-of-hospital ventricular fibrillation (VF) after i.v. or endobronchial (e.b.) administration of epinephrine and lidocaine. METHODS. Only patients presenting with out-of-hospital VF were included in this study, whereby VF of noncardiac origin was excluded. Cardiopulmonary resuscitation (CPR) was performed according to the guidelines of the American Heart Association. Basic life support was initiated by Emergency Medical Service (EMS) technicians. The first step of advanced life support was immediate defibrillation by the EMS physician. Epinephrine was given in doses of 2.5 mg e.b. or 1.0 mg i.v. If indicated, patients received 200-500 mg lidocaine e.b. or 100 mg i.v. The course of CPR was tape-recorded and 2-3 blood samples were taken from each patient for drug monitoring. Plasma levels of epinephrine and lidocaine were measured by high-pressure liquid and gas chromatography, respectively, and then correlated to the course of CPR. RESULTS. Forty-seven patients presented VF on arrival of the EMS physician. Restoration of spontaneous circulation was achieved in 64% (Table 3), and 30% of the patients were discharged from hospital without major neurologic deficits. Immediate defibrillation before initiation of pharmacotherapy produced a success rate of 15.8%, whereas defibrillation after drug therapy was successful in 61.5% of cases. Following e.b. instillation of 2.5 mg epinephrine (Fig. 1), median peak concentrations of epinephrine (40.2, range 4.0-79.8 ng/ml) were reached after 3-4 min and plasma levels greater than or equal to 10 ng/ml were seen for 20 min. After i.v. injection of 1.0 mg epinephrine (Fig. 2) maximum concentrations (71.6, range 4.7-104.2 ng/ml) were measured after 1-2 min and plasma levels decreased below 10 ng/ml after 10 min. Following e.b. instillation of 400-500 mg lidocaine mean lidocaine concentrations within the therapeutic range (2-5 micrograms/ml) were reached after 4-5 min and remained within these limits for 20-30 min. Peak concentrations were obtained after 12 min. Doses of 200-320 mg lidocaine e.b. failed to achieve therapeutic plasma levels (Fig. 3). Regarding the pharmacodynamic aspects of drug therapy, 22.5% of the initial survivors were resuscitated from VF without therapeutic epinephrine, presenting with mean endogenous epinephrine concentrations of 7.1 ng/ml, 51.6% of patients were resuscitated after epinephrine therapy with plasma concentrations greater than 20 ng/ml. In only 1 case could a relationship be demonstrated between the administration of lidocaine and resuscitation success. CONCLUSION. In CPR, the e.b. administration of epinephrine and lidocaine is a reliable alternative to the i.v. injection route of these drugs. Recommended doses are 2.5 mg for epinephrine and 400-500 mg for lidocaine. Resuscitation from VF requires immediate epinephrine therapy if initial defibrillation is not successful. Lidocaine has no effect on resuscitation from VF and therefore should be used specifically for antiarrhythmic therapy after restoration of spontaneous circulation.

Administration, Inhalation↗
PubMed1990

[The efficiency of prehospital cardiopulmonary resuscitation. Which factors determine the outcome?].

Survival rates following cardiopulmonary resuscitation differ widely with regard to the diverse rescue systems where the investigations were performed, and also with regard to the different patient populations. From 1981 to 1986, 1037 patients with out-of-hospital cardiac arrest were investigated in the city of Bonn. It was the purpose of this study to differentiate between various patient populations and to analyze factors which are responsible for CPR success. Survival rates following CPR could be increased from 8% in 1981 to 23% in 1984. Thereafter, a relatively stable survival rate of 20.1 +/- 1.7% with an initial CPR success rate of 62.5 +/- 8.1% was observed. Patients with ventricular fibrillation showed significantly higher survival rates (33.2 +/- 2.9%) when compared to asystolic victims (11.3 +/- 1.9%). The worst results were seen in these patients where CPR was initiated following trauma (8%) or in paediatric patients (8%). Factors which significantly determine survival following CPR are: initial ECG finding, therapeutic delay with regard to bystander-initiated basic life support, as well as advanced life support by emergency physicians. In addition, well standardized therapeutical strategies are of importance with early defibrillation, rapid endotracheal intubation and swift epinephrine application mostly by endobronchial administration.

First Aid↗
PubMed1978

[Bacteriemia due to acinetobacter calcoaceticus var. anitratus (author's transl)].

A serious bacteremia caused by Acinetobacter calcoaceticus var. anitratus could be observed. From the clinical point of view the most important symptoms were shivering, high tempeature up to 41 degrees C and clinical signs of acute hepatitis. There were pathological changes in the EEG. Certain signs of an outlayer damage of the heart could be seem in the ECG. The pathogenic microorganism isolated from the blood culture media was classified. Specific antibodies--agglutinines and precipitines--were demonstrated in the patient's serum. A contamination could be excluded so that the bacterium was the causative agent. The diagnostic value of finding antibodies in patient's serum having this type of bacterial infection is discussed.

Acinetobacter↗
PubMed1977

Cerebral hypnogenic centers.

Active cerebral processes can initiate and maintain sleep in mammals. Two distinct hypnogenic structures have been documented in the cat: the nucleus of the solitary tract in the medulla and a region in the basal preoptic area. Their electrical or pharmacological activation results in behavioral and EEG sleep. Both can be activated an inhibited in relation to circulatory or thermic homeostasis and to endocrine regulations, or in conditioned paradigms. Bilateral destruction or functional elimination of either hypnogenic region is followed by increased vigilance and insomnia. The tonic influence so revealed is increased by the serotonergic raphe nuclei of the pontine region, which is considered to be hypnotonic rather than hypnogenic. Postsynaptic inhibition of the ascending activating reticular system by the hypnogenic centers is involved in sleep onset and maintenance. Electrophysiological evidence is presented that indicates a mutual tonic inhibitory interaction between the brainstem arousal system and the preoptic hypnogenic center. Such reciprocal inhibitory interaction can facilitate the onset of sleep by a positive-feedback mechanism. In spite of the fact that this retroaction results in break of physiological equilibrium, it should be considered a homeostatic process aimed at maintaining the functional fitness of the forebrain neuronal circuits.

Animals↗