Search PubMed⌕ Search

Biomedical subjects

H Stoeckel

Publications and source records attributed to H Stoeckel.

At least 19 recordsLinked to original sources
PubMed1992

[Systematics and concept of a future integrated anesthesia device].

On the grounds of the more than one hundred years lasting development of the anaesthesia machine the systematics of the components of a future integrated anaesthesia machine is described. The new generation of today's anaesthesia machine incorporates four main functions: dosing, ventilation, monitoring and data management. Given the achievements of the last 15 years in the fields of data and signal analysis, of the clinical pharmacology of intravenous anaesthetics, of measurement and evaluation of anaesthetic drug action, the four main functions are only partially realized in today's anaesthesia machines. Especially lacking are the integration of smart dosing devices for intravenous anaesthetics, the so-called "therapeutic monitoring" which monitors the efficacy of anaesthetic drug action, and a data management system which does not only manage data but interprets them in terms of "smart alarms" and maybe in the future also by expert systems. The concept of a future integrated anaesthesia machine is investigated via a study model and on the basis of a real model composed of already existing devices.

Anesthesiology↗
PubMed1992

Influence of the pulmonary circulation on adrenaline pharmacokinetics during cardiopulmonary resuscitation.

The influence of the pulmonary circulation on the pharmacokinetics and -dynamics of endogenously released, and intravenously injected (10 micrograms kg-1), and endobronchially (e.b.) administered (100 micrograms kg-1) adrenaline was investigated in an animal cardiopulmonary-resuscitation (CPR) model. During resuscitation 80% of endogenously released and i.v. adrenaline was eliminated before reaching the arterial circulation, whereas arterial availability of adrenaline was higher than mixed-venous availability in the e.b.-medicated animals. Success of resuscitation seemed to depend on maximum adrenaline concentrations and drug availability in arterial blood. Although the average amount of endogenously released adrenaline was calculated to be equivalent to an i.v. bolus of 8 micrograms kg-1, additional i.v. or e.b. adrenaline medication resulted in higher arterial plasma concentrations, improved circulation during CPR, and better resuscitability. It is concluded that, even without a specific pulmonary metabolism, a drastic decrease in blood flow can lead to significant arterio-venous gradients in plasma concentrations and availability of a drug with a very high clearance like adrenaline.

Administration, Inhalation↗
PubMed1991

[O2 uptake and CO2 production during total intravenous propofol-alfentanil anesthesia under steady-state conditions. Is O2 uptake a parameter for assessing the depth of anesthesia?].

Depending on surgical and anaesthesiological procedures, anaesthesia leads to a reduction of O2 uptake (VO2), CO2 production (VCO2) and resting energy expenditure (REE). A controversial discussion on the degree of metabolic depression has continued in the literature fueled by a lack of studies in patients under standardised conditions. The goal of this study was to evaluate whether O2 consumption and/or CO2 production can be correlated to various depths of anaesthesia and whether VO2 could be a parameter to control narcosis. 12 patients (ASA I-II) scheduled for urological surgery of the lower abdomen, were given total intravenous anaesthesia with propofol and alfentanil. During a 60 minutes period the patients were first anaesthesized with an ED50 and then titrated to a dosage correlating with an ED95. The premedicated but awake patients each showed a REE which was about 10% below the calculated basal metabolism. Steady-state general anaesthesia led to an approximately 30% reduction of VO2, VCO2 an REE. Patients with adequate anaesthesia revealed no changes in oxidative metabolism with increased or decreased depth of anaesthesia. VO2 as a leading parameter proves to be problematic. It is useful as a measure for insufficient depth of general anaesthesia but fails to indicate overshooting anaesthesia depth.

Adult↗
PubMed1990

Effective therapeutic infusions produced by closed-loop feedback control of methohexital administration during total intravenous anesthesia with fentanyl.

A combined pharmacokinetic and pharmacodynamic model of methohexital was used to establish and evaluate feedback control of methohexital delivery during total intravenous anesthesia with fentanyl in 11 surgical patients. The median frequency of the EEG power spectrum served as the pharmacodynamic variable constituting feedback. Based on previous investigations a median frequency from 2-3 Hz was chosen as the desired EEG set point. In addition to methohexital, patients were given a 10-min loading infusion of 0.5 mg of fentanyl followed by a constant-rate infusion of 0.22 mg/h. In agreement with an earlier similar study in volunteers given only methohexital and aiming at the same set point, identical distribution of EEG power was achieved in the current study. The decrease of median EEG frequency to 2-3 Hz was primarily induced by an increase in fractional power in the 0.5-2- Hz frequency band to 46 +/- 4%. The average requirement of methohexital during the first 2 h was 675 +/- 250 mg. The authors conclude that model-based feedback control of intravenous methohexital delivery can help establish and quantitate methohexital requirements during total intravenous anesthesia with fentanyl.

Adolescent↗
PubMed1990

[Interdisciplinary computerized evaluation of perioperative risk factors].

The identification and assessment of perioperative risk factors combined with interdisciplinary management may lead to minimized risk for the patient. The numerous medical and administrative data should be collected by a computer. This was done in a preliminary study at the university of Bonn, where 9772 anaesthesias given for general surgery were evaluated. The necessary outcome studies should be based on statistical evaluation of the data (factor analysis) and their interpretation should be an interdisciplinary concern.

Adolescent↗
PubMed1990

[Electrophysiologic studies in polyneuropathy of intensive care patients].

Polyneuropathy of the critically ill patient has gained attention in recent years. The symptoms of muscle weakness and impaired somatosensory perception are more obvious for the observer and recognizable for the conscious patient, if heavy long-term sedation is avoided. The cause of polyneuropathy remains unclear and diagnostic findings are still rare and partly controversial. In five of our patients with multiorgan failure and clinical signs of muscle weakness, cortical somatosensory evoked potentials (SEP) and the evoked electromyogram (EMG) were recorded simultaneously after the stimulation of mixed peripheral nerves to test the functional integrity of the efferent and afferent neuronal pathways. We observed different degrees of SEP and EMG alterations, which were more pronounced in the lower than in the upper extremities and which may be explained by an axonal degeneration. Such a process may be caused by multiple factors and pathophysiological mechanisms. An influence of neostigmine on a reduced EMG response could not be found.

Aged↗
PubMed1990

[Perioperative morbidity and mortality of geriatric patients. A retrospective study of 3905 cases].

3905 patients of more than 60 years of age who underwent surgical, urological, orthopaedic or opthalmologic interventions, were retrospectively investigated with respect to preoperative condition, intraoperative peculiarities and postoperative complications. Only 3.2% of the old patients (of more than 75 years of age), but 7.2% of elderly patients (between 60 and 74 years of age) had no coexisting disease. Preexisting diseases were myocardial (54.5%) and respiratory diseases (41.3%), hypertension (32.6%), dysrhythmia (30.8%) and diabetes mellitus (17.6%). From the old patients, 58.1% were classified into ASA physical status III to V but only 43.2% from the elderly patients. Peculiarities during anaesthesia and recovery period were (in total): dysrhythmia (8.3%), blood pressure decrease (5.9%) and increase (1.6%) that were significantly more often seen in old than in elderly patients whereas bleeding (4.5%) in the old was not different from the elderly. Independent of age, 11.6% of patients were monitored postoperatively on an intensive-care unit. 47.3% of all patients did not develop any postoperative complication. The incidence of postoperative cardiac, respiratory, central nervous, and lethal complications was not significantly higher in old than in elderly patients. However, the incidence of complications increased significantly with ASA physical status. Mortality of elderly and old patients after emergency interventions was 17.8% and 24.7% respectively and about 10 times that high as after elective surgery (2% in both groups.)

Aged↗
PubMed1990

[The pharmacokinetics of lidocaine in resuscitation conditions. Results of experimental studies on swine].

To re-evaluate dosage requirements for i.v. and endobronchial (e.b.) lidocaine therapy under the conditions of cardiac arrest, we investigated the pharmacokinetics of lidocaine after i.v. and e.b. administration in an animal cardiopulmonary resuscitation (CPR) model. METHODS. We induced cardiac arrest by ventricular fibrillation in 16 normoventilated pigs under i.v. anesthesia. Resuscitation started after 3 min with resumed ventilation and internal cardiac compressions. Simultaneously, 8 animals received 10 micrograms epinephrine/kg and 2 mg lidocaine/kg via peripheral i.v. injection and another 8 received 100 micrograms epinephrine/kg and 2 mg lidocaine/kg via e.b. instillation. During CPR and the 1st hour of restored spontaneous circulation the ECG, heart rate, and mean arterial pressure were continuously recorded. Plasma concentrations of lidocaine were measured by gas chromatography in venous blood, which was collected automatically at intervals of 30 s. RESULTS. All animals were resuscitated successfully after 3.7 +/- 1.6 min (i.v.) and 3.8 +/- 1.1 min (e.b., means +/- SD). With no differences during CPR, the hemodynamic situation of the e.b. medicated animals was characterized by higher arterial pressures from 10-15 min and higher heart rates from 10-60 min of restored spontaneous circulation. Median maximum concentrations of lidocaine after i.v. (3.2 range 1.3-9.6 micrograms/ml) and e.b. administration (3.1 range 1.1-8.6) were measured after 5.5 min (range i.v. = 4-10 min, e.b. = 3-7 min). Mean concentrations within a therapeutic range of 2-5 micrograms/ml were reached after 2-3 min and remained within these limits for 20-25 min after both routes of administration. Individual lidocaine concentrations below the therapeutic level of 2 micrograms/ml were measured in one experiment after i.v. application and in three experiments after e.b. administration. The individual time concentration profiles were mathematically approximated using an open two - compartment model with first-order absorption. The absorption half-life of e.b. lidocaine was 3.9 min, and mean bioavailability was 90%. Elimination pharmacokinetics of i.v. and e.b. lidocaine were nearly identical, with elimination half-lives of 25 min (e.b.) and 42 min (i.v.). Total body clearances were 401 ml/min (e.b.) and 362 ml/min (i.v.). CONCLUSION. An i.v. bolus of lidocaine during CPR should not exceed 2 mg/kg. During CPR without i.v. access the e.b. instillation of lidocaine can be recommended, but to ensure therapeutic concentrations a minimum dosage of 2 mg/kg is suggested.

Animals↗
PubMed1989

Closed-loop feedback control of propofol anaesthesia by quantitative EEG analysis in humans.

Propofol was administered for 2 h to 11 volunteers by an adaptive feedback control algorithm based on quantitative EEG analysis. Median EEG frequency served as the control variable. The range 2-3 Hz was chosen as the target range of control. During the feedback period, volunteers did not respond to commands and eyelash reflex was abolished. An average median frequency of 2.5 (SD 0.3) Hz was obtained by administering propofol 1452 (262) mg within 2 h. Time to recovery was 17.9 (8.0) min. Compared with a study with methohexitone using the same approach, the relative potency of propofol was 0.72. The mean recovery time was less than half that observed after methohexitone.

Adult↗
PubMed1989

Comparison of intravenous and endobronchial atropine: a pharmacokinetic and -dynamic study in pigs.

In an experimental animal study using adolescent pigs we compared the pharmacokinetics and -dynamics of atropine following intravenous injection (0.25 mg, n = 6) or endobronchial instillation (2 mg, n = 6). Results showed that endobronchial atropine is rapidly absorbed by the pulmonary circulation, resulting in a peak plasma concentration of 48.8 +/- 25.9 ng ml-1 (mean +/- SD) after 2 min, compared to 46.3 +/- 16.7 ng ml-1 in the first min after intravenous injection. A first increase in heart rate could be observed within 1 min after both routes of drug administration. Significant changes in heart rate were found 9-30 min after endobronchial and 12-15 min after intravenous medication, with a maximum after 9 min (+57%) and 12 min (+24%), respectively. Mean bioavailability of atropine following the endobronchial route reached only 23% during the first 6 h when compared to intravenous administration. In light of this reduced bioavailability, we suggest an adult dosage in humans of atropine 2 mg diluted in 5-10 ml of saline administered endobronchially to attain a reliable increase in heart rate during a cardiac emergency when, in an intubated individual, no intravenous line is readily available.

Animals↗