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Biomedical subjects

H Stoeckel

Publications and source records attributed to H Stoeckel.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1989

[Return of motor and mental functions following enflurane-nitrous oxide anesthesia of 1.3 MAC in various age groups].

Recovery of motor and mental functions we investigated in 60 patients at different age ranges (Group 1: 20 young patients between 20 and 35 years; Group 2: 20 middle-aged patients between 40 and 55 years) after nitrous oxide-oxygen anaesthesia in combination with enflurane of 1.3 MAC for lumbar nucleotomy. The following parameters were investigated before and up to 80 minutes after anaesthesia: simple and discriminating motor activities, the vigilance and the short and long term memory. In simple motor actions we noticed no significant differences between the three groups. By examination of discriminating motor activity, the functional capacity of Group 3 was significantly reduced in comparison to Groups 1 and 2. Nevertheless the efficiency in Group 2 was also decreased in comparison to Group 1. The postoperative vigilance was especially impaired in the elderly patients. Only 50% of the old patients were able to satisfy the asked requirements 60 minutes after extubation. The vigilance in Group 2 showed a better improvement compared to the elderly patients but was in comparison to the young patients significantly decreased. The long term memory of the old patients pointed out a considerable reduction after this kind of anaesthesia. While no distinct differences could be found between Group 1 and 2 40 minutes after extubation, a significant difference could be observed between Group 1 and 3 even after 60 minutes. The short term memory of the elderly and the middle-aged patients was considerably reduced 60 minutes after extubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Flumazenil (Ro 15-1788) and physostigmine.

The pharmacologic effects of benzodiazepines may be counteracted either by functional antagonists like physostigmine acting via cholinergic mechanisms or by competitive antagonists like flumazenil (Ro 15-1788) acting via GABAergic mechanisms (GABA = Gamma-AminoButyric Acid). The lipophilic choline esterase inhibitor physostigmine adjusts a relatively or absolutely decreased concentration of acetylcholine at central cholinergic synaptic sites. As the neuronal network is very complex, many lipophilic compounds may cause a central anticholinergic syndrome even if they primarily do not affect cholinergic but, like benzodiazepines, GABAergic synaptic sites. Prolonged and/or adverse effects of such drugs may therefore be treated with 1-2 mg physostigmine at a maximal rate of 1 mg/min. The onset of physostigmine action can be expected within 2-20 min. Furthermore, the benzodiazepine action can very effectively be counteracted by the specific antagonist flumazenil. It could be demonstrated in volunteer and clinical studies that the hypnotic effect of benzodiazepines could be antagonized within 1-2 min. However, the minimal duration of action proved to be about 2 h as could be demonstrated by clinical observations, EEG-studies and psychometric tests. In clinical practice, a flumazenil dose of 0.3-0.8 mg proved to be the optimal dose range. The indication to treat unwanted central effects of benzodiazepines either with flumazenil or with physostigmine after anaesthesia should be restricted to cases of distinctly prolonged sedation after adequate dosage or adverse side effects. In intensive care, special indications for flumazenil and/or physostigmine may result after high benzodiazepine dosage or to differentiate a coma of undefined origin if centrally acting drugs including benzodiazepines are involved.

Awareness↗
PubMed1988

Total intravenous anaesthesia with propofol and alfentanil by computer-assisted infusion.

The combination of propofol and alfentanil was administered to 20 patients for total intravenous anaesthesia during general surgery. The infusion rates for both drugs were controlled by microprocessors in order to institute constant blood levels adapted to the patients' varying needs. The mean blood level of propofol required for adequate hypnosis during anaesthesia was 2.42 micrograms/ml (SD 0.43). Awakening occurred 7.9 minutes (SD 3.4) after the end of the infusion, at a propofol blood level of 1.59 micrograms/ml (SD 0.34). The plasma level of alfentanil was 285 ng/ml (SD 72) during major noxious stimulation and 148 ng/ml (SD 56) during minor stimulation. The computer-assisted infusions showed a measured/predicted ratio of 1.01 (SD 0.28) for alfentanil and 0.88 (SD 0.22) for propofol. This indicates that the administration device used in this study is reasonably reliable. The technique of total intravenous anaesthesia was characterised by a smooth induction without significant haemodynamic alterations, by good control during anaesthesia and by a very fast recovery without major side effects.

Adolescent↗
PubMed1988

[Pharmacokinetics and dynamics of endogenously released and therapeutically administered adrenaline in resuscitation. A comparative animal experimental study].

In this study, catecholamine plasma levels and hemodynamic response were measured to compare the effects of endogenously released (group A; n = 8), intravenously injected (group B; 10 micrograms/kg; n = 8), and endobronchially instilled (e.b.) epinephrine (group C; 100 micrograms/kg; n = 8) on resuscitation. Although the endogenous release of epinephrine produced peak plasma concentrations of 214 +/- 86 ng/ml (mean +/- SEM) during cardiac massage, only 5 animals were successfully resuscitated in group A. Mean arterial pressure and cardiac output were significantly lower in the first hour of restored spontaneous circulation compared to groups B and C. Endobronchial and intravenous epinephrine administration proved equally effective with regard to resuscitability and hemodynamic response during cardiac massage. All animals in groups B and C were successfully resuscitated and peak plasma concentrations of epinephrine were achieved with comparable onset times (317 +/- 53 ng/ml after 2.5 min in group B, 634 +/- 202 ng/ml after 3 min in group C). The tenfold epinephrine dose administered endobronchially was able to generate only a twofold increase in peak plasma epinephrine concentrations. The mean bioavailability with this route of administration, however, was 40% (5-71%). The ongoing absorption and therefore significantly longer half life of e.b. epinephrine compared to i.v. administration improved the hemodynamic situation of group C animals during the early postresuscitation period. More extensive use of e.b. epinephrine administration can be recommended, especially in out-of-hospital resuscitation, when intubation is achieved before an intravenous line can be established.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

[Instrumental monitoring in anesthesia. Results of a rapid electronic data processing survey at the time of the 1987 Central European Congress in Munich].

During the ZAK 1987 in Munich we performed a poll concerning monitoring during anaesthesia. 200 questionnaires could be evaluated. A majority of 2/3 rd monitored regularly blood pressure, ECG, FiO2, minute ventilation and ventilation pressure. These quantities were monitored independent of a presumably increasing anaesthesia risk associated with three clinical cases. Only blood pressure and ECG were considered as mandatory by a majority of 2/3 rd. Monitoring variables related more to the anaesthesia machine lide FiO2, minute ventilation, and ventilation pressure did not reach a 2/3 re majority. 78% detected at least once in their business life time a life threatening complication by monitoring devices earlier than by so called clinical signs. EEG and capnometer were the most frequent quoted monitors. Monitoring of neuromuscular blockade and intraoperative awareness was considered as a relevant problem only by 22%. 20% agreed to additional monitoring on the general ward while 2/3 rd disagreed.

Adult↗
PubMed1987

Determination of atropine in plasma by a direct radioreceptor assay.

A highly sensitive radioreceptor assay for the anticholinergic atropine was developed and could be applied directly to plasma samples obtained from mini-pigs without any clean-up. Plasma samples were collected during 6 h after atropine was administered intravenously or endobronchially. The endobronchial plasma concentration-time curves were characterized by a very rapid rise of the concentration but with a subsequent much slower decrease than after intravenous administration. This indicates an initially high as well as prolonged uptake from the lungs.

Animals↗
PubMed1987

Voltage-activated potassium, but not calcium currents in cultured bovine aortic endothelial cells.

The electrophysiological properties of cultured bovine aortic endothelial cells were characterized using the patch clamp technique. Resting potentials were measured on passing to the whole cell recording configuration and were close to--65 mV in healthy cells. In cell-attached recordings with a high potassium pipette solution, inward single channel currents were observed with zero applied pipette potential. A linear slope conductance of 25 pS was found for a wide range of hyperpolarizing patch potentials and also for depolarizing patch potentials of up to 50-60 mV. A pronounced inward rectification was apparent as no reversal of these currents was seen for larger depolarizations. Whole cell recording in physiological solutions revealed the presence of a hyperpolarization-activated inward current with strong inward rectification and no voltage-dependent ionic current was observed upon depolarization in this subset of cells. Substitution of potassium for external sodium resulted in a shift in the zero current potential consistent with potassium being the main permeant ion. Together with the characteristic voltage-dependent blocking actions of external sodium ions and low concentrations of barium and caesium ions, our results indicate that this current is very similar to the classical inward rectifier as originally described in skeletal muscle and in tunicate eggs. In a second population of cells, a depolarization-activated outward current displaying characteristics of the fast transient A-type potassium current as first reported in molluscan neurones was also observed. No evidence for inward voltage dependent sodium or calcium currents was found.

Animals↗
PubMed1987

Threshold hypnotic concentration of methohexitone.

Methohexitone was administered to 8 healthy adult volunteers as a microprocessor controlled infusion that generated 3 cycles of linearly increasing plasma levels with an anticipated slope of 0.2 microgram.ml-1.min-1. When a deep unconscious state was obtained, as indicated by burst suppression in the EEG, the infusion was stopped and then restarted when the volunteer was fully orientated. Frequent venous blood samples were obtained during and after the infusions to evaluate the threshold concentration at induced sleep and the return of orientation, at the loss and return of the eye lid reflex and corneal reflex, and the appearance and disappearance of EEG burst suppression patterns. From the first to the third infusion cycle only a slight and insignificant increase in the mean threshold concentrations was observed so the plasma levels were averaged over all three infusion cycles. The concentrations (microgram/ml) found were: asleep 3.39 and orientated 3.35, loss 4.42 and recurrence 4.32 of eye lid reflex, loss 6.51 and recurrence 5.18 of corneal reflex, and appearance 10.7 and disappearance 9.3 of burst suppression. Acute tolerance that would have led to a significant increase in threshold concentration from the first to the last infusion cycle was not demonstrated. If induced sleep and the appearance of EEG burst suppression are considered as clinical endpoints of anaesthesia, the therapeutic window of methohexitone covers a mean venous serum concentration range of 3.4 to 10.7 micrograms/ml.

Adult↗
PubMed1987

[Endobronchial administration of adrenaline in cardiopulmonary resuscitation: pharmacokinetic and dynamic studies in the dog].

The present animal study was designed to investigate the pharmacokinetic behavior of epinephrine after endobronchial (e.b.) and intravenous (i.v.) administration and its correlation to pharmacodynamic measurements. We found the effectiveness of e.b.-epinephrine (100 micrograms/kg BW) to be in the same magnitude as i.v.-epinephrine (100 micrograms/kg BW) with only a slight delay in the pharmacodynamic onset of a few seconds. The bioavailability of e.b.-administration of epinephrine was in the range of 80-85%. The therapeutic effect of e.b.-epinephrine (100 micrograms/kg BW) lasted much longer (30 min) when compared to i.v.-epinephrine (10 micrograms/kg BW) where the pharmacodynamic effect was terminated after 3 to 5 min. For the clinical situation of cardiopulmonary resuscitation a dose of 2-3 mg epinephrine in 5-10 ml of physiological saline instilled deeply into the bronchial system should be considered as alternative administration technique with fast onset and good effectiveness.

Animals↗