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Biomedical subjects

G Litscher

Publications and source records attributed to G Litscher.

At least 55 records · Page 3Linked to original sources
PubMed1996

Brainstem auditory evoked potentials in respiratory insufficiency following encephalitis.

Brainstem auditory evoked potentials (BAEPs) were recorded in 14 artificially ventilated patients (12 males, 2 females; mean age 33.3 +/- 16.3 years, range 18-67) with respiratory insufficiency resulting from severe inflammatory encephalopathies. The results were compared with those of 17 healthy volunteers (13 males, 4 females; mean age 27.4 +/- 5.3 years, range 21-45). BAEPs in the study patients showed prolonged interpeak latencies (I-III, I-V, III-V, IV-V) and delayed absolute latencies of waves I, II, III, and V at least on one side. Because the auditory pathways are in the near vicinity of the respiratory control centers in the brainstem, the electrophysiologic abnormalities of wave III and the IV/V complex may be a reflection of the disturbed central control of ventilation.

Acoustic Stimulation↗
PubMed1996

Abnormal brain stem auditory evoked potentials in a girl with the central alveolar hypoventilation syndrome.

Brainstem auditory evoked potentials were recorded in a 3-year-old girl with the central alveolar hypoventilation syndrome (Ondine's syndrome). Abnormal findings were seen at the level of the mid to upper brain stem (wave III), which was not reproducibly recordable on the left side. This electrophysiologic abnormality is consistent with a previous finding in a patient with sleep apnea.

Child, Preschool↗
PubMed1995

Brain-stem auditory evoked potential monitoring. Variations of stimulus artifact in brain death.

Brain-stem auditory evoked potentials (BAEPs) were recorded in 20 subjects with brain death (mean age, 33.2 +/- 15.1 years) and 20 healthy volunteers (mean age, 29.8 +/- 6.8 years). Brain death was due to head injury (n = 14), encephalitis (n = 3), brain-stem hemorrhage (n = 1), cerebellar hemorrhage (n = 1) or cerebral infarction (n = 1). The presence, latency and amplitude of the individual BAEP components and variations of the stimulus artifact were evaluated. The mean (+/- S.D.) amplitude of the stimulus artifact was 0.26 +/- 0.12 microV in the brain-dead subjects and 0.09 +/- 0.05 microV in the control group (P < 0.001, t test). The causes of the phenomenon of increasing stimulus artifacts in the evolution of brain death remain unclear.

Acoustic Stimulation↗
PubMed1995

[Noninvasive monitoring of regional cerebral oxygen saturation--experiences in critical care medicine].

Regional cerebral oxygen saturation (rSO2) was studied in 15 healthy volunteers aged between 23 and 53 years (mean age: 34.2 +/- 8.7 years) and in 17 intensive care patients (mean age: 37.2 +/- 18.6 years; range 17-70). An infrared spectroscopy technique (INVOS 3100, Somanetics Co.) was used. The results were analysed in terms of age, heart rate, temperature at the recording site, blood pressure and peripheral oxygen saturation. The mean +/- SD of rSO2 was 69.4% +/- 7.0% in the healthy volunteers and 66.4% +/- 7.4% in intensive care patients (65.3% +/- 6.2% in 7 patients with a cerebral lesion, 67.1% +/- 8.4% in 10 patients with no cerebral lesion). Individual examples are presented to show that infrared spectroscopy is a useful non-invasive method of investigating cerebral oxygenation. However, regional pathological-anatomical limitations of the technique, and possible extracerebral artefacts make necessary a critical interpretation of the rSO2 values.

Adolescent↗
PubMed1995

[Near infrared spectroscopy. Limits and problems in the intensive care unit].

Near infrared spectroscopy is a non-invasive method of calculating changes in cerebral oxygenation. We have now evaluated a new near infrared spectroscope, the NIRO-500 (Hamamatsu Photonics, Japan), in an intensive care unit setting. The influence of extracerebral and intracerebral physical-technical, physiological and pathophysiological parameters was investigated. The results showed that the method is very sensitive to changes in oxygenation and perfusion in the cerebral vasculature. However, the influence of other factors can be considerable and not always easy to detect and interpret.

Adult↗
PubMed1995

[Cerebral monitoring in anesthesia and intensive care].

To ensure efficient computer-based cerebral monitoring in the ICU and during anaesthesia, sophisticated and sometimes expensive equipment is needed. It is thus all the more important that the clinician should have a good understanding and knowledge of the various methods involved, the origins of the different signals and their relationships, and of the possibilities of artefacts occurring, if the information that this equipment is capable of providing is to be fully and properly utilized. The present paper describes a number of new techniques of cerebral monitoring, and their successful application in the intensive care unit and the operating theatre.

Adult↗
PubMed1995

Middle latency auditory evoked potentials in intensive care patients and normal controls.

Evoked potentials have been introduced into intensive care unit to objectively measure parameters of coma. In particular, auditory brainstem evoked potentials have been useful for localizing brainstem dysfunction in comatose patients. The middle latency auditory evoked potentials (MLAEPs) believed to be a response of subcortical auditory radiations and the primary auditory cortex. MLAEPs were measured in 40 adults (mean age 24.9 +/- 2.9 years; range: 19-34 years) with normal hearing and in 102 intensive care patients (mean age: 48.4 +/- 18.9 years; range: 14-86 years) under the influence of biological variables. Latencies (control group, mean +/- SD: V = 5.74 +/- .29 ms, N0 = 9.11 +/- 1.74 ms, P0 = 12.94 +/- 1.87 ms, Na = 17.23 +/- 1.77 ms, and Pa = 29.22 +/- 3.43 ms), amplitudes (control group, mean +/- SE: N0-P0 = 2.00 +/- .34 microV, P0-Na = 3.88 +/- .67 microV, Na-Pa = 2.83 +/- .29 microV) and the amplitude ratio (control group, mean +/- SE: P0-Na/Na-Pa = 1.53 +/- .39) were calculated. In the control group in both females and males, right-sided stimulation produced shorter average MLAEP latencies and higher amplitudes than left-sided stimulation (Pa-right 28.26 +/- 3.53 ms; Pa-left 30.17 +/- 3.33 ms). MLAEPs showed significant differences according to sex but did not depend significantly on age. A temperature dependence was found for the latency of wave V (short latency AEP), which was prolonged at lower temperatures and for the amplitude Na-Pa, which was increased at decreased temperatures between 38.9 and 35.4 degrees C. There was a significant association between the amplitude Na-Pa and PO2 (P = .017). Alterations of PCO2 in the range of 26 to 54 mmHg did not influence the MLAEPs. Also, renal dysfunction or hepatic dysfunction and alterations of mean arterial pressure (range: 50-102 mmHg) did not affect MLAEP latencies and amplitudes significantly. Increases in latencies and decreases in amplitude were seen in sedated patients. These results in intensive care patients suggest that the combination of early AEP (acute phase) and MLAEP (post acute phase) may be useful to monitor comatose patients.

Adolescent↗
PubMed1995

Continuous brainstem auditory evoked potential monitoring during nocturnal sleep.

Continuous monitoring of brainstem auditory evoked potentials (BAEPs) was performed simultaneously with polysomnographic recordings during nocturnal sleep in 9 normal males (mean age 25.3 +/- 2.7 years). Four-channel electroencephalography, respiration (abdominal and thoracic), rectal temperature, electrocardiography, electrooculography, chin electromyography, non-invasive blood pressure (Finapres), oxygen saturation and two channels of BAEPs were recorded by a multivariable computer system. All data except BAEPs were preprocessed, integrated over 30 s and printed on a single sheet. Sleep stages were classified visually. Latencies, interpeak latencies, amplitudes and the I/V amplitude ratio of the BAEPs were analysed in the awake state and different sleep stages. The results confirm that, as previously reported, the slight BAEP latency modifications observed during sleep are correlated to body temperature variations. The analysis of the absolute amplitudes of BAEPs showed insignificant (ANOVA) variations with sleep (e.g., mean amplitude of peak V +/- SD: wakefulness = .36 microV +/- .11, REM = .22 microV +/- .05, stage 2 = .27 microV +/- .14, stage 3 = .25 microV +/- .14, stage 4 = .26 microV +/- .11). A significant change between wakefulness and deep sleep could be found in the latencies of wave IV and V and in the amplitude ratio I/V (P < .05, ANOVA, Student-Newman-Keuls method).

Adult↗
PubMed1994

Analysis of cardiorespiratory signals--methodology and applications in infants.

Heart rate variability and thoracal respiratory movements were examined in two babies aged six months during eight hour polysomnographic recordings. Computer-assisted analysis in the time and frequency domain were performed to investigate the mechanisms underlying cardiorespiratory control. Coherence and phase relation between cardiac cycles and respiration were investigated in detail. Both methods demonstrated that during quiet sleep (stage 3/4), the cardiorespiratory coupling was significantly increased as compared to active sleep (REM sleep).

Brain Stem↗
PubMed1994

Computer-assisted neurovegetative monitoring in patients after heart transplantation.

The effects of orthotopic heart transplantation on spontaneous fluctuations of the respiration rate and heart rate were studied with a computer-assisted system for neurovegetative monitoring in 22 patients (mean age +/- SD: 48.7 +/- 9.4 years) 19.5 +/- 14.4 months after transplantation. The control group consisted of 12 healthy volunteers (mean age +/- SD: 38.7 +/- 6.6 years). The mean (+/- SE) respiratory rate was higher in the transplantation group than in the control group (17.7 +/- 0.8/min vs. 14.6 +/- 1.1 breaths/min, P < 0.2). The mean variability of the respiratory rate was smaller in the transplant patients than in the controls (3.7 +/- 0.3 vs. 2.8 +/- 0.4, P < 0.2). The heart rate variability coefficient in the patients after transplantation was lower than that in the controls (1.3 +/- 0.1% vs. 6.9 +/- 0.5%, P < 0.001). Spectral analysis of heart rate variability showed a smaller decrease of variability of respiration (P < 0.05) than of blood pressure regulation (P < 0.001) or of the angiotensin-renin system (P < 0.001). A separate group of 7 transplant patients (mean age 51.0 +/- 7.7 years) had activated cardiac pacemakers and thus no spontaneous physiologic heart rate oscillations. The variability of the respiratory rate in these patients was lower than in the other 22 transplant patients (1.8 +/- 0.2 vs. 3.7 +/- 0.3, P < 0.001). The data provided by multiparametric neurovegetative monitoring support the evaluation of complex regulatory mechanisms of respiratory and cardiovascular function and their adaptability after orthotopic heart transplantation.

Adult↗
PubMed1993

Computer-based analysis of continuous non-invasive blood pressure and heart rate variability-methodology and normal values during wakefulness and sleep.

Polysomnographic recordings were made in 10 healthy male adult subjects (mean age 25.1 +/- 2.8 years). Parameters were obtained from continuous non-invasive measurement of blood pressure and from heart rate spectra analysed both in the waking state and during sleep (stage 4). The total heart rate variability (mean +/- SE) was not significantly diminished (p < 0.2; paired t-test) during stage 4 sleep (6.2 +/- 0.5%) as compared with the waking state (7.1 +/- 0.5%). The relative heart rate variability coefficient within the frequency band HRV-II ((3-9)/min) was, however, significantly higher (p < 0.001) during slow-wave sleep (0.55 +/- 0.04) than during wakefulness (0.34 +/- 0.04). This fact is in accordance with results concerning an estimated value of the baroreflex sensitivity, which was also significantly higher (p < 0.001) during sleep stage 4 (7.0 +/- 0.8 ms/mmHg vs. 10.4 +/- 1.4 mmHg).

Adult↗
PubMed1993

[Computer controlled brain death documentation in the intensive care unit].

An interactive, knowledge-based computer system for brain death documentation is presented. The specific exponents BRAINDEX R and G were realised by the software tool Personal Consultant Plus and the programming language Clipper, respectively. The strategies of conclusion were forward chaining for approximate evaluation of coma stages and backward chaining for analysing the brain death syndrome. BRAINDEX was developed for use with an IBM personal computer or compatible equipment. Systemic analyses were compared retrospectively with the data from clinical brain death protocols (n = 132) of 128 comatose patients (mean age 35.1 +/- 15.8 years) with a Glasgow Coma Score of 3. Identical classifications (system vs physician) were found in all patients without diagnosis of brain death (n = 35). Differences related to the findings of the physician were evaluated in lower numbers of the systemic positive diagnosis of brain death (82 vs 89) and higher numbers of impossibility of systemic evaluation (11 vs 2). These results were obtained by conclusions of the computer system drawn by restrictive systemic mechanisms to avoid false-negative diagnoses. The system therefore seems to be useful for documentation, consultation, and as a teaching instrument and data bank in brain death.

Adult↗
PubMed1992

Brain death: timing of apnea testing in primary brain stem lesion.

In a 73-year-old patient complete areflexia of the cerebral and peripheral nerves following the rupture of an aneurysm of the basilar artery was diagnosed. During apnea testing the spectral analysis of electroencephalography (EEG) revealed an irreversible shift of peak from 6 to 3 Hz within the low-frequency bands. These findings suggest that apnea testing in patients with primary lesion of the brain stem should be carried out only after an isoelectric EEG.

Aged↗
PubMed1992

[Acoustic evoked brainstem potentials--patterns of stimulus artefacts in irreversible coma].

Brainstem auditory evoked potentials (BAEP) were performed in a total of 20 subjects (mean age 33.2 +/- 15.1 years; severe head injury in most cases) with the diagnosis of coma dépassé. The control group consisted of 33 healthy volunteers (mean age 26.9 +/- 5.3 years). The presence, latency and amplitude of the single BAEP-components and the variations of the stimulus artifact were evaluated. The mean amplitudes of the stimulus artifact of the brain dead subjects were calculated (means +/- SD) to be 0.26 +/- 0.12 microV (control group: 0.11 +/- 0.03 microV). Pathological alterations of the mechanics of the inner ear as well as extracerebral changes in conductivity or stimulus related depolarization processes in extracerebral parts of the auditory system were taken into consideration to be possible reasons for this significant (p less than 0.001; t-test) difference.

Adolescent↗
PubMed1991

Continuous multivariable monitoring in neurological intensive care patients--preliminary reports on four cases.

Evoked potential monitoring is a standard examination method in neurological intensive therapy units. Previously, multimodality observation was only possible in follow-up examinations. First experience with a new bed-side system continuously monitoring 12 neurophysiological and clinical parameters is reported. It consists of a personal computer and various stimulation units. EEG activity, median nerve somatosensory evoked potentials (SEPs) and brainstem auditory evoked potential (BAEPs) are recorded. Additionally, EEG spectral band power, heart rate, heart rate variability, intracranial pressure, body temperature, expiratory PCO2, blood pressure and transcutaneously measured oxygenation can be monitored. This paper reports on 4 exemplary cases of the 33 patients we have monitored to date, illustrating the principles and main advantages of the system. The system was developed to support the observation of ICU patients as well as to aid therapeutic decisions. It supports the clinical determination of brain death by specifying the deterioration of various neurological systems.

Aged↗
PubMed1990

Electroencephalographic and evoked potential monitoring in the hyperbaric environment.

The purpose of this study was to investigate brain bioelectrical activity during hyperbaric oxygenation by continuous and simultaneous monitoring of electroencephalographic and bimodal (auditory, somatosensory) evoked potentials. Multivariable recordings (electroencephalogram, brainstem auditory evoked potentials, early somatosensory evoked potentials, heart rate, heart rate variability, and transcutaneous partial pressure of oxygen) were measured with a new technique in 12 healthy male volunteers 26 to 52 years old (mean +/- SD, 35.9 +/- 9.5 years). Recordings were obtained while the subjects breathed (1) air at normal atmospheric pressure, (2) 100% oxygen at normal atmospheric pressure, (3) air at 2 atm (10 meters sea water [msw]), and (4) 100% oxygen at 2 atm (10 msw). Spontaneous brain electrical activity, somatosensory evoked potentials, and heart rate variability were not significantly affected during hyperbaric oxygenation, whereas the heart rate showed a significant decrease (paired t test, P less than 0.05). Alterations in brainstem auditory evoked potentials were seen under hyperbaric conditions and did not reach statistical significance (increase of the I-V interpeak latency by paired t test; P less than 0.2). All subjects showed insignificant increases in dominant alpha frequency and decreases in delta frequency under hyperbaric situations.

Adult↗