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Biomedical subjects

H Stoeckel

Publications and source records attributed to H Stoeckel.

At least 55 records · Page 3Linked to original sources
PubMed1987

Quantitative EEG analysis during anaesthesia with isoflurane in nitrous oxide at 1.3 and 1.5 MAC.

In 14 patients undergoing elective surgery the EEG was studied during anaesthesia with isoflurane and nitrous oxide (in oxygen) at 1.3 and 1.5 MAC. The distribution of spectral EEG indices of the baseline EEG, during the intraoperative and recovery periods were established and compared. Median frequency exhibited the most clear separation between the distributions during recovery and the intraoperative period. During anaesthesia, the median values were found to be lower than 5 Hz; when the patient was conscious, the EEG median frequency values were greater than 6 Hz. Time to recovery was 13.4 +/- 2.9 min and 30.0 +/- 8.5 min for the groups treated with 1.3 and 1.5 MAC, respectively. Burst suppression was observed during the loading period in all patients treated with 1.5 MAC and in five patients out of seven receiving 1.3 MAC. The average duration of the period of burst suppression was markedly greater in the group receiving 1.5 MAC than in the group receiving 1.3 MAC. It is concluded that devices designed for EEG trend monitoring during anaesthesia should preferably depict a frequency measure, and allow for burst suppression recognition before spectral analysis.

Adult↗
PubMed1987

Closed-loop feedback control of methohexital anesthesia by quantitative EEG analysis in humans.

A combined pharmacokinetic and pharmacodynamic model of methohexital was used to establish and evaluate feedback control of methohexital anesthesia in 13 volunteers. The median frequency of the EEG power spectrum served as the pharmacodynamic variable constituting feedback. Median frequency values from 2-3 Hz were chosen as the desired EEG level (set-point). In 11 volunteers, the feedback system succeeded in maintaining a satisfactory depth of anesthesia (i.e., unresponsiveness to verbal commands and tactile stimuli). During feedback control, 75% of all measured median frequency values were in the preset range of 2-3 Hz. This distribution of median frequency was obtained by applying random stimulation (six different acoustic and tactile stimuli) to the volunteers approximately every 1.5 min. The decrease of median frequency from baseline to anesthetic values was primarily induced by increasing the fractional power in the frequency band of 0.5-2 Hz from 12.6 +/- 4.5% (mean +/- SD) to 46.0 +/- 2.5%. The median time to recovery (as defined by opening eyes on command) after cessation of the feedback control period was 20.6 min (10.7-44.5 min) when median EEG frequency was 5.2 Hz (4.7-8.4 Hz). The average requirement of methohexital (mean +/- SD) during the 2 h was 1.02 +/- 0.16 g. It is concluded that pharmacokinetic-pharmacodynamic models of intravenous anesthetics established previously may be used to form a suitable background for model-based feedback control of anesthesia by quantitative EEG analysis. This approach gives a possible solution to the problem of adapting pharmacokinetic and pharmacodynamic data to individuals when using population mean data as starting values for drug therapy.

Adult↗
PubMed1987

Endobronchial instillation of epinephrine during cardiopulmonary resuscitation.

We used a standard animal CPR model to study the effectiveness and hemodynamic response of 100 micrograms/kg epinephrine administered endobronchially and to compare the findings after conventional iv administration. Results showed that the endobronchial and iv epinephrine medication improved the survival rate by 100% compared to that of a control group receiving no medication. Although the hemodynamic conditions during cardiac compression were not significantly different after both routes of drug administration, endobronchial instillation produced a prolonged drug action during the first hour of restored spontaneous circulation. A more extensive use of this type of drug administration, especially in out-of-hospital resuscitation, is suggested.

Animals↗
PubMed1987

[Endobronchial administration of adrenaline in preclinical cardiopulmonary resuscitation].

The present clinical study was designed to investigate the effectiveness of epinephrine when administered endobronchially (e. b.) in patients undergoing out-of-hospital cardiopulmonary resucitation (CPR). Plasma catecholamine measurements during and following CPR in 30 patients revealed plasma levels of epinephrine and norepinephrine with tremendous variations and elevated, sometimes, for nearly 1,000 fold when compared to normal resting levels. In patients with ventricular fibrillation (VF) native epinephrine concentrations (23.5 +/- 20.4 ng/ml) were significantly different from asystolic victims (2.1 +/- 1.2 ng/ml). This finding once more supports the importance of early defibrillation as main therapeutical step in VF. When epinephrine (2-3 mg) was instilled endobronchially shortly after endotracheal intubation therapeutic concentrations of more than 10 ng/ml of epinephrine were measured when the first venous access was achieved. In 7 patients with successful CPR e. b. epinephrine was the only pharmacological therapy provided to support the cardiovascular system. Under these circumstances plasma epinephrine levels remained within the therapeutic range of 10-20 ng/ml for about 30 minutes. By these clinical findings it becomes clear that e. b. epinephrine (2-3 mg in 5-10 ml of NaCl 0.9%) instilled deeply by a catheter following intubation is the pharmacological therapy of choice in asystolic patients.

Administration, Inhalation↗
PubMed1987

Differences in lymphocyte mitogenic stimulation pattern depending on anaesthesia and operative trauma: I. Halothane-nitrous oxide anaesthesia.

Cell-mediated immunity (investigated by in vitro mitogen/antigen induced lymphocyte proliferation) is known to be depressed in the post-operative period. In the present investigation, performed with halothane/nitrous oxide inhalational anaesthesia in healthy patients without trauma (eye surgery) and with operative tissue trauma (gynaecological operations), only the combination of major surgery with halothane/nitrous oxide anaesthesia was associated with a depression of lymphocyte reactivity to phytohaemagglutin (PHA-P), Concanavalin A (Con A) and pokeweed mitogen (PWM). This lasted for 3-10 days post-operatively.

Adult↗
PubMed1987

Differences in lymphocyte mitogenic stimulation pattern depending on anaesthesia and operative trauma: II. Combined neuroleptanaesthesia.

In this study, neuroleptanaesthesia reduced the reactivity of lymphocytes to phytohaemagglutin (PHA-P) and pokeweed mitogen (PWM) in patients in a manner similar to that seen with halothane/nitrous oxide and enflurane/nitrous oxide inhalational anaesthesia. These findings began 4 h post-operatively, lasted throughout the first post-operative day and were similar in both operative trauma groups (eye surgery/gynaecological surgery). However, unlike the situation with the inhalational agent, Concanavalin A (Con A)-induced proliferation did not alter. It was also noted that, on the third post-operative day in both trauma groups, PHA-P- and PWM-induced proliferation ratios were significantly higher than were the pre-operative values. These findings could be the result of a specific effect of neuroleptanaesthesia.

Adult↗
PubMed1987

[New aspects of drug therapy in cardiopulmonary resuscitation].

Reevaluation of current concepts in drug treatment during CPR was followed by some new recommendations concerning indication or dosage of drugs for CPR: While epinephrine remains the catecholamine of choice for cardiac resuscitation, application of buffer solutions should be performed with care. Routine calcium administration is not longer considered useful. When intravenous application of drugs is not possible within time the endobronchial instillation of epinephrine, lidocaine and atropine is considered as effective as their intravenous injection.

Acid-Base Equilibrium↗
PubMed1987

[Organization of the emergency physician and rescue service with special reference to mass injuries].

When a large number of casualties has occurred due to accidents or other medical disasters the normal individualized emergency physician and rescue service has to be rearranged within a short period of time. It is essential to achieve informations as detailed as possible about the number of victims and the kind of the disaster situation. A physician especially trained for such instances should be informed immediately and take over the responsibility as leading emergency physician for the management of the large scale emergency situation. After proper screening has been performed to sort out these patients who have high treatment priority the leading emergency physician has to coordinate the medical treatment of the victims provided by the other emergency physicians. The location where the accident occurred has to be structured and the transportation of the patients into the hospitals has to be arranged. In addition back-up facilities are to be activated to gain a large number of personNel l and ambulance transportation facilities. By following these logistical scheme it becomes possible to handle large scale accidents within a reasonable period of time.

Disasters↗
PubMed1987

[Hypnotically active blood level of midazolam].

Midazolam was administered to seven healthy adult volunteers by microprocessor controlled infusions that generated 3 cycles of lineary increasing plasma levels with an anticipated slope of 20 ng ml-1 min-1. When a deep unconscious status was obtained as indicated by no response to loud verbal stimuli, the concentrations were kept constant at that plateau for 30 min. Thereafter, the infusions were stopped and restarted when the volunteers were again fully responsive to acoustic stimuli of normal intensity. Frequent venous blood samples were obtained during and after the infusions to evaluate venous threshold concentrations of induced sleep and recurrence of orientation, loss and recurrence of eyelid-reflex (and corneal reflex), and unconsciousness and recovery of responsiveness to loud verbal stimuli. From the first to the third infusion cycle a slight, but not significant increase of mean threshold concentrations could be observed. Hence, they were averaged over all infusion cycles. In detail, the following concentrations (in ng/ml; mean +/- SD) resulted: asleep: 251 +/- 110 and oriented: 277 +/- 107, loss: 543 +/- 173 and recurrence of eye-lid reflex: 532 +/- 120, unconsciousness: 575 +/- 128 and recovery to responsiveness: 555 +/- 151. In all but one volunteer, the corneal reflex could be triggered at any time. Hence, a mean threshold concentration of that, observation could not be obtained. Phenomena of acute tolerance that should lead to significant increases of threshold concentrations from the first to the last infusion cycle could not be demonstrated.

Adult↗
PubMed1986

[Effectiveness of the benzodiazepine antagonist Ro 15-1788 following anesthesia induced by flunitrazepam].

The competitive benzodiazepine antagonist Ro 15-1788 proved efficacious after general anaesthesia induced by flunitrazepam. It showed a quick onset of action within 1-2 min. After antagonisation, the heart rate, blood pressure and respiratory rate remained stable. No increased demand for analgesics could be demonstrated postoperatively. A transient anxiety that could be observed in 7 of 38 patients after doses between 0.5 and 2.0 mg seemed of minor clinical importance but may indicate that Ro 15-1788 acted not only as a pure antagonist but as a partially inverse agonist as well. Recurrence of sedation could be observed in 6 out of 38 patients after 2 h of Ro 15-1788 dosage. Careful observation of the patients for at least 2 h is therefore recommended even if antagonisation seemed successful. It was possible to reverse the benzodiazepine action successfully with doses between 0.3 and 0.8 mg. After these doses the patients will awake gently and gradually and unwanted side effects will be avoided. In our experience, Ro 15-1788 is a useful improvement in benzodiazepine application after surgical anaesthesia.

Anesthesia, General↗
PubMed1986

Pharmacological models and their use in clinical anaesthesia.

Intravenous agents used in anaesthesia belong to a variety of chemical classes and cover a number of different pharmacodynamic responses. Compared to inhalational anaesthesia the combined administration of intravenous agents offers a greater degree of freedom because different pharmacodynamic effects can be controlled separately. This greater degree of freedom, however, requires a more detailed insight into the pharmacology of the drugs to allow control of drug administration and to meet the therapeutic optimum. This review considers the combination of pharmacokinetics and pharmacodynamics as a pharmacological model. The general principles of these two subunits relevant for dosing of intravenous agents are reviewed. In establishing a model of the non-linear system relating dosing to effect, pharmacokinetics introduces an intermediate step which describes the time course of drug concentrations as a function of dosing. It is thought that incorporating the entire dependence of the effect upon time is, in most cases, linear. Pharmacodynamics relate concentration to effect in a non-linear but time-independent manner. It embodies the entire non-linearity of the system, but is assumed to be a static relation. Special attention is given to those principles which apply to any intravenous agent irrespective of its particularities. The impact of distribution and elimination, hysteresis, and ceiling on the induction, maintenance and recovery of anaesthesia, and on improving anaesthesia techniques and drug delivery are considered.

Anesthesia↗
PubMed1986

[Methods of automatic feedback regulation for anesthesia. Concepts and clinical use].

Dosing of drugs used in general anaesthetic practice is largely based on experience and trial-and-error. From the very beginning, anaesthesiological research has always attempted to supply a rational description of the rules governing the dose-response relationship. During the last few decades it became possible to identify pharmacokinetics as a main constituent of the relationship, since the rate of efficacy is primarily governed by the kinetics of the drug and the dose. On the other hand, the complete nonlinearity of the dose-response relationship can be demonstrated by means of a pharmacodynamic model. Control of anaesthesia by pharmacokinetic-dynamic models may be considered satisfactory as long as there is no pronounced scatter of the model parameters within a given population. Closed-loop feedback control is contrasted to feedforward control that attempts to monitor a given variable within a preset range by feeding back a measured signal to the drug delivery system. The present article reviews the experience and application of automatic feedback control systems used in anaesthesia. It was shown in all cases that adaptive, model-based feedback control is superior to non-adaptive methods. Pharmacokinetic and/or pharmacodynamic models were successfully applied to the servocontrol of volatile anaesthetics, intravenous hypnotics and neuromuscular blocking agents. Over and above these three applications, directly related to anaesthesia, the impact of feedback control on the regulation of blood pressure and blood glucose is reviewed.

Anesthesia, General↗
PubMed1986

[Dangers in the use of high-frequency surgical instruments in anesthesiologic monitoring].

Although the use of high-frequency units is routine in all surgical disciplines, there is still a justification for reminding users of the attendant risks. The most common injuries sustained by patients are burns caused by fault currents. Such risks increase when a combination of several electric devices is used, and in particular when the operation is performed with simultaneous anesthesiologic monitoring. All electrically conductive, direct or indirect contacts between the patient and the ground lead potential, and all connections resulting in a low resistance or a shorter distance between the active and "neutral" high-frequency electrode than the correct current pathway, may become competing "neutral" electrodes with high current densities. It is therefore imperative that all those involved should strictly observe the safety rules. The systematization of problem points is intended to introduce greater clarity into the relatively long list of admonitions, and to indicate possible organizational solutions.

Anesthesia, General↗
PubMed1985

[Anesthesia as a prerequisite for success in surgery].

After a relatively slow development until World War II anaesthesia converted rapidly from an entirely empirical and technically oriented application to an independent clinical and scientific discipline. Statistics confirm safety of today's anaesthesia in spite of the enormous spread of indications for surgery. Further progress is necessary. As an outlook the new method of closed-loop feed-back control of depth of anaesthesia has been described which may be expected to be introduced clinically in the near future.

Anesthesia, General↗
PubMed1985

The effects of a benzodiazepine antagonist Ro 15-1788 in the presence of stable concentrations of midazolam.

The benzodiazepine antagonist Ro 15-1788 was administered in a 10-mg intravenous bolus dose to seven healthy young adult volunteers to evaluate the drug's efficacy and duration of action against midazolam. A steady state serum concentration of midazolam was obtained by an initial fast infusion rate of 6.0 mg/min (duration: 10 min) and a maintenance infusion rate of 0.275 mg/min. After administering the antagonist, all subjects opened their eyes without any command in a median time of 36 s (range: 28-48 s). Their personal, temporal and local orientation was reestablished within 54-120 s (median time: 65 s). The subjects fell deeply asleep, again in a median time of 145 min (range: 115-150 min), which was interpreted as an indication of the returning action of midazolam, which was infused for a total period of 210 min. Ro 15-788 deserves further study as an antagonist, since it could prove useful in the management of benzodiazepine overdosage and in the reversal of benzodiazepine action following surgical anesthesia and in the intensive care.

Adult↗