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Biomedical subjects

I Pichlmayr

Publications and source records attributed to I Pichlmayr.

At least 19 recordsLinked to original sources
PubMed1995

[Changes with age in EEG during anesthesia].

The number of older persons who have to undergo surgical procedures is steadily growing. For these patients the risks of anaesthesia are often increased because of their past medical history and their restricted physiological resources. Apart from parameters of the cardiovascular system, the electroencephalogram (EEG) represents a supplementary method for intraoperative monitoring, because cerebral alterations caused by anaesthetics or narcotics are directly reflected in the EEG. In routinely conducted registrations of the EEG in the operating theatre it appeared that the EEG of older persons differed from the EEG of younger patients. The aim of the present study was to further investigate the effect of patients' age on the EEG during anaesthesia. METHODS. Three data sets from different EEG registrations were analysed. The first data set consisted of inductions of anaesthesia with 7 mg/kg body weight thiopental in 43 patients from 17 to 80 years of age (mean 53.6 +/- 16.7 years) using derivations C3-P3 and Cz-A1. The second data set included 69 EEG registrations of general anaesthesia induced with barbiturates and maintained with enflurane in patients from 16 to 83 years (mean 51.4 +/- 17.7 years). The third data set comprised inductions of anaesthesia with 2 mg/kg body weight propofol. EEGs of the second and third data set were recorded with the EEG monitor 'Narkograph' using derivation C3-P3 and derivations C3-P3/C4-P4, respectively. Classification of the EEGs was performed according to the proposals of Kugler [12]. The basis for the statistical analysis of all data sets was formed by parameters from the power spectra of the EEG recordings. RESULTS. The data from inductions of anaesthesia with thiopental and propofol showed EEG patterns from alpha-EEG to burst suppression activity, whereby periods with burst suppressions could more often be observed in the EEG of older people. Under thiopental burst suppression activity occurred in 20% of patients up to 50 years, in 47% of those between 50 and 70 years and in 89% over 70 years. The corresponding figures for propofol were 0%, 5% and 54%, respectively. Figure 2 depicts the correlation between age and power for the thiopental data. The power decreases with increasing age of the patients. This result led to further investigations of the effect of patients' age on the power in different EEG stages. Of special interest were deep stages of anaesthesia, because especially in these stages visual inspections revealed smaller amplitudes of the EEG signal for older patients than for younger persons. Figure 3 shows the power in the delta frequency band in deep stages of barbiturate-induced enflurane anaesthesia for patients of different age groups. The power in the delta frequency band distinctly decreases for geriatric patients. The same effect could be observed for the propofol data (Fig. 4). CONCLUSIONS. The EEG represents an important method for effective intraoperative monitoring and contributes to an individually adjusted course of anaesthesia, especially for geriatric patients. In these patients, clinical signs such as parameters of the cardiovascular system, which are usually used to judge the depth of anaesthesia, are often altered by the patient's past medical history or by drugs. Furthermore, geriatric patients show a reduced need for narcotic agents. However, the variation of the required dosage is greater in older than in younger persons. The results of the present study show that with regard to an automatic classification of the EEG during anaesthesia, alterations of the EEG with age have to be taken into account.

Adolescent↗
PubMed1995

[Channel selection for EEG-monitoring in anesthesia].

The conventional multichannel electroencephalogram is quite inconvenient for long-term monitoring in the operating theatre or intensive care unit. Recording of the EEG would be easier if a small number of channels was sufficient. Aiming at reduction of channels, leads from different regions of the scalp were analysed visually and with regard to their spectral content. METHODS. Electrode placements corresponded to the International 10/20 System (Fig. 1). EEG recordings were made with a conventional device (ES 12,000), a personal computer, and a spectral analyser. TWO-CHANNEL RECORDINGS. Retrospective analysis was performed on data from 392 patients (age 14-90 years) whose anaesthesia was induced with various anaesthetics/narcotics, for instance thiopental, ketamine, etomidate, halothane, and enflurane. The EEG was recorded using C3-P3 and Cz-A1. For each patient the changes of spectral parameters during the course of the induction were plotted and visually analysed. For statistical analyses a 30-s epoch of each patient was randomly selected from the first few minutes after the beginning of induction. TEN-CHANNEL RECORDINGS. In ten gynaecological patients (age 26-55 years) EEG recordings were performed during induction of anaesthesia with thiopental in combination with fentanyl, N2O and O2. The set of channels consisted of Fz'-Cb1, F3'-Cb1, Cz-Cb1, C3-Cb1, P3-Cb1, Oz-Cb1, Fz'-F3', F3'-C3, C3-P3, and P3-Oz. The electrodes Fz' and F3' were positioned on the forehead near to Fz and F3, respectively. These sites were chosen because they allow easy application of electrodes. The relationship between channels was calculated with Bravais-Person's coefficient of correlation for the power and the absolute power in the frequency bands delta (0.5-3.5 Hz), theta (3.5-7.5 Hz), alpha (7.5-12.5 Hz), and beta (> 12.5 Hz). RESULTS. In visual and statistical analyses of the two- and ten-channel recordings under the influence of anaesthetics/narcotics, similar changes of EEG activity could be observed in all channels. Although differences in the absolute power of the frequency bands were present, there was high conformity in the composition of the spectral content of the different channels. Classification of the EEG into stages of anaesthesia by means of a single channel led to consistent results for all channels. Alpha activity as leading feature of the awake state predominated occipitally. In channels including the region around the ears, contamination with EKG artifacts was observed. CONCLUSIONS. EEG patterns under the influence of different anaesthetics/narcotics are adequately represented by a reduced number of channels. For the choice of an appropriate set of channels the following aspects should be considered. Contamination with artifacts should be as low as possible, electrode sites should easily be accessible, and special features of the awake state should be identifiable. Experience with routinely conducted EEG recordings in the operating theatre and the intensive care unit showed that the channels C3-P3 or C4-P4 provide a sufficient basis for automatic staging of the depth of anaesthesia, which is implemented in the EEG monitor Narkograph.

Adolescent↗
PubMed1992

[Reduction of the number of recorded EEG channels for routine monitoring in the intensive care unit].

Monitoring patients in the intensive care unit with the aid of the conventional electroencephalogram employing a large number of recording channels is rather difficult, and can be laborious. This imposes limits on the routine application of this method. To investigate the possibility of developing a new monitoring device for easier application in the ICU, we aimed to establish whether the relevant information provided by a multi-channel EEG could be found in a subgroup of channels, thus reducing the number of channels required. Preferably those channels should be identified for use which are least contaminated by artefacts under routine conditions in the ICU. A total of 150 EEG recordings from the intensive care unit were inspected visually for the presence of artefacts. The derivations C3-P3 and C4-P4 proved to be least contaminated, at 35% and 39%, respectively. In these derivations visual assessment of the EEG was found to be impossible due to artefacts in only 4 and 5%, of all cases, respectively. A data set comprising 52 EEG segments with the fewest possible artefacts, was analysed using time series methods. On the basis of multivariate autoregressive processes, a measure was derived which describes the loss of information associated with a reduction in the number of EEG channels. The computation of the information loss for several channel combinations revealed that the derivations F3-C3, C3-P3 and A1-Cz represent a good compromise between information content, number of channels and frequency of artefacts. Practical experience shows that, at least for the control of sedation, a further reduction to a single channel should be possible.(ABSTRACT TRUNCATED AT 250 WORDS)

Artifacts↗
PubMed1992

Testing the Gaussianity of the human EEG during anesthesia.

The Gaussian properties of human EEGs, which were measured over various stages of general anesthesia, were tested. The basis of the method was to describe the EEG signals by autoregressive models and to test the normality of the regression residuals with the Shapiro-Wilk statistic. The results show that in general the human EEG during anesthesia can be considered as a realization of a Gaussian stochastic process.

Anesthesia, General↗
PubMed1991

[Fatty emulsions in parenteral feeding following liver transplantation. A study of the neurotropic effect of MCT/LCT emulsions using EEG].

In the early postoperative period after liver transplantation a possible neurotropic side effect of middle-chain triglycerides used for total parenteral nutrition (TPN) was evaluated by EEG and Glasgow Coma Scale. Group I: no fat for TPN; Group II: 0.7 g/kg body weight (BW) and day, of MCT/LCT emulsion; Group III: 1.5 g/kg BW and day, of MCT/LCT emulsion. Only on postoperative day 5/6 significant differences in distribution of background activity in the EEG were seen between Group I and II. Patients in Group I showed more pathological EEG patterns (Mann-Whitney-U-test p less than 0.05). Per discriminant analysis an influence of applicated fatty acids on the registered background activity could be excluded. Instead an underlying rejection of the graft in 7 of 10 patients could be made responsible for deterioration of the EEG pattern. Following the presented data a negative neurotropic effect of MCT/LCT emulsions in the described dosages can be negated.

Adult↗
PubMed1991

Identification of EEG patterns occurring in anesthesia by means of autoregressive parameters.

In EEG analysis an automatic pattern recognition is of interest. In this paper the usefulness of autoregressive parameters to classify EEG segments recorded during anesthesia is examined. Assuming that the AR parameters are multivariate normally distributed, parametric methods of discriminant analysis can be applied. The results show that AR parameters have high discriminating power and that the lowest error classification rate (smaller than 3%) is obtained by using quadratic discriminant functions. Consequently autoregressive parameters are efficient for classifying EEG segments into general stages of anesthesia.

Adult↗
PubMed1991

[Slowing down of the EEG during hypoventilation in emergence from anesthesia].

Electroencephalographic (EEG) recordings were made using a "Narkograph", which performs an automatic on-line interpretation of electroencephalographic data obtained during anesthesia. The EEG was classified into one of 13 stages from A (awake) to F (very deep narcosis). In 20 of roughly 600 patients EEG changes were observed that could not be explained by the effects of anesthetics. Slowing of the EEG occurred during the transition from controlled to spontaneous ventilation and disappeared after minute ventilation increased. The alterations seen during hypoventilation were similar to the effects of hypoxia described in the literature. During the slowing in the rough EEG, waves appeared that were very regularly formed and corresponded to sharp peaks in the power spectrum. These features are rather atypical of the effects of anesthetics such as thiopental, propofol, halothane, isoflurane, and enflurane and were not observed when patients went back to sleep after extubation. If depth of anesthesia is monitored by EEG recording, clinical circumstances should be taken into account because conditions such as hypoxia may cause alterations of the EEG that bear a resemblance to the effects of anesthetics.

Anesthesia Recovery Period↗
PubMed1991

[Can ventilation based on the principle of the iron lung act today as a substitute for or an alternative method to conventional forms of ventilation?].

A plastic lung working on the same principles as an iron lung has been developed at the Medical School in Hannover. Functional and practical tests were performed in a representative group of patients. Respirators support following the principles of an iron lung may be provided as a supplement or an alternative to existing artificial respirator therapy. The modern artificial respirators are superior to the plastic lung, which however, has advantages for particular indications: Respiratory therapy performed in a plastic lung is well tolerated by the patients. It requires specific skills which can easily be learned by the medical staff. Routine use certainly cannot be instituted before further technical improvement has been achieved; in particular the noise level should be reduced. The plastic lung is suitable for short-term ventilation (2-10 h); in view of the restricted nursing procedures possible, prolonged artificial respiration cannot be recommended. In conclusion, immediate postoperative ventilation is the area of application for the plastic lung. Several advantages are known: the endotracheal tube can be removed, there is no indication for sedative drugs, cardiac function and organ blood flow are positively influenced, mucolysis and lung expansion are adequate. A patient whose spontaneous respiratory activity is borderline benefits from short-term therapy, which can be repeated as necessary. Protracted artificial ventilation can be avoided. The gradual process of weaning from the ventilator following prolonged artificial respiration is facilitated by the use of a plastic lung. Plastic lung therapy is superior to other common methods of treating persistent atelectasis, because its mucolytic effects lead to expansion of the atelectatic lobe or segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗
PubMed1990

[Long-term therapy of tumor pain using morphine-retard tablets].

We analysed the effect of sustained-release morphine tablets in 174 patients with severe cancer pain. A good relief of pain could be obtained in 65% of the patients within the first week and in 80% of the patients at the end of therapy. The mean daily dose was at 178 mg morphine, six patients needed more than 1000 mg per day. The sustained-release morphine was given at fixed intervals, in 80% of the cases every eight hours. No severe side-effects were associated with long-term morphine therapy. We often saw nausea and vomiting, constipation and drowsiness, but these side-effects decreased after the first weeks of treatment. Only in ten patients we had to stop therapy because of side-effects. Morphine can be used successfully in the treatment of cancer pain for long periods without concern about tolerance.

Administration, Oral↗
PubMed1990

[Complications of intravenous therapy with peripheral indwelling catheter].

Intravenous fluid replacement via a peripheral catheter harbours several risks. The study presented emphasizes that about 50% of the patients show complications during the first days after positioning of an intravenous line. Women patients have been affected more often than male patients. Small catheters positioned in a major vessel away from a joint in the forearm, yield the best results. Peripheral lines should be removed within 8 to 12 hours after surgical procedures, when early symptoms are observed. Complications can be avoided by following these recommendations.

Catheterization, Peripheral↗
PubMed1990

[Pain therapy in gynecologic neoplasms].

A great number of patients with gynaecological malignant diseases suffer from severe pain, caused, for example, by bone metastases of breast cancer or tumour infiltration of the pelvis and the lumbar plexus in uterine cancer. Several methods of treatment are available depending upon the origin of pain. It is possible to achieve pain relief by radiotherapy or by cytostatic therapy. Sometimes, anaesthesiological and neurosurgical measures are successful, but the most important method is treatment with analgesics. Strong opioids are given, if pain relief is insufficient under treatment with non-narcotic drugs or weak opioids, like codeine. Morphine and other strong opioids are not reserved for pain control only in terminally sick women, as they can be administered successfully for long periods without severe side effects. If possible, the oral route should be selected. If vomiting occurs, or if patients are unable to take oral medication, morphine can be given peridurally, intrathecally or by infusion. Often, an additional treatment is necessary with different medicaments like tricyclic antidepressants and corticosteroids.

Analgesics↗
PubMed1990

[Postoperative ventilation in non-intubated patients with iron lung versus conventional ventilation].

Postoperative ventilation using a steel lung is an alternative to conventional ventilation through an endotracheal cannula. Both methods were compared in two groups of patients undergoing major abdominal surgery. Group A was ventilated using a Servo Ventilator 900C, whereas group B was ventilated using a newly designed steel lung. The duration of ventilation using the steel lung and that of postoperative intubation were significantly shorter than those used in group A, in spite of a higher anesthesiological and surgical risk in patients in group B. pO2 was significantly increased during ventilation with the steel lung in comparison to conventional ventilation. An automatic classification of EEG activity was used to estimate depth of anesthesia. This showed a close correlation between clinical signs and anesthesiological levels. The spectroanalytical evaluation of ventilation curves allowed the early recognition of spontaneous breathing and determined tidal volumes using steel lung ventilation.

Aged↗
PubMed1990

[Postoperative ventilation in the "iron lung"].

Postoperative artificial ventilation by using an endotracheal tube may cause a pulmonary infection. A possibly necessary permanent sedation and relaxation may result in an additional danger for the patient. The principle of the "iron lung" represents an alternative to endotracheal artificial respiration, which applies especially to endangered patients who are under postoperative artificial respiration. After an abdominal operation five patients have been extubated and artificially respirated by using the "iron lung" principle while not being able to breath by themselves. The degree of the sedation was monitored both intraoperatively and postoperatively using an automatic EEG classification. The performance spectrum of the respiratory curve enabled very early detection of the onset of spontaneous respiration.

Abdomen↗
PubMed1990

[Fat emulsions in parenteral feeding following liver transplantation. I. Effect on the recovery of RES function in the transplant].

Following liver transplantation, the effect of postoperative parenteral nutrition with MCT/LCT fatty emulsions on the recovery of RES function in the allograft was investigated in a randomised prospective study of three groups of patients (group I: 50 g MCT/LCT fats twice weekly, group II: 0.7 g/kg body weight per day MCT/LCT fats, group III: 1.5 g/kg body weight per day MCT/LCT fats). RES function was assessed using 99mTc-HSA-MM clearance. There were no statistically significant differences in the recovery of RES function after transplantation between the three groups. A negative effect on RES function as a result of the administration of MCT/LCT fats up to 1.5 g/kg body weight per day can therefore be excluded.

Fat Emulsions, Intravenous↗
PubMed1990

[The effects of ketamine on the electroencephalogram--typical patterns and spectral representations].

In 40 female patients aged between 17 and 79 years, the pre- and intraoperative EEG was recorded and processed by personal computer. For induction of general anesthesia patients received between 2 and 3 mg/kg ketamine i.v. within 30 s. In the phase of diminished ketamine effects enflurane was given in addition. Activity in the theta band was observed in all patients during general anesthesia, and in 30% there were complexes. These complexes differ in their spectral content of burst suppression patterns. Under effect of ketamine nearly all patients showed fast beta waves in the EEG. It is proposed that the spectral domain of EEG evaluations be enhanced to an upper limit of 45 Hz.

Adolescent↗
PubMed1990

[The ovarian hyperstimulation syndrome. Anesthesiologic aspects based on a severe case].

Ovarian hyperstimulation syndrome (OHS) is an iatrogenic syndrome in which induction of ovulation results in a wide spectrum of clinical symptoms and signs and laboratory manifestations. Based on the severity of the symptoms and signs, three degrees of hyperstimulation have been described: mild, moderate and severe. The most severe manifestation, presented in this paper with reference to the case of a 27-year-old woman, takes the form of massive ovarian enlargement with multiple cysts, hemoconcentration and third-space accumulation of fluid in the form of ascites, pleural and pericardial effusion. The full-blown clinical syndrome may be complicated by renal failure and oliguria, hypovolemic shock, thromboembolic episodes, adult respiratory distress syndrome (ARDS) and even death. The pathophysiologic mechanisms responsible for the development of OHS are still not known. The incidence of this iatrogenic syndrome can be reduced by monitoring plasma estradiol and by ultrasonographic evaluation of growing follicles. The anesthesiological aspects of OHS are discussed. A strategy for treatment, based on repeated ultrasonographic examination, clinical and biochemical evaluation, plasma volume replacement, abdominal paracentesis and aspiration puncture of the pleural effusion, is suggested.

Adult↗
PubMed1989

[Atelectasis treatment by ventilatory support using an iron lung].

Total atelectasis of the left lung occurred in a 61-year-old woman after several weeks ventilator-assisted breathing following an operation for ileus, when the tracheal cannula was removed. It was quickly replaced and artificial ventilation resumed. But despite daily bronchoscopic suction for three weeks the patient's state failed to improve (vital capacity 39%, arterial pO2 47 mm Hg, pCO2 37 mm Hg). Mechanical ventilation with an "iron lung" was therefore instituted over a six month period, at first for two hours daily (as an in-patient) and then weekly (as out-patient). During this time her condition and general state clearly improved. On re-hospitalization to remove the tracheal cannula her vital capacity was 75%, pO2 78 mm Hg and pCO2 38 mm Hg.

Carbon Dioxide↗