Biomedical subjects
Publications and source records attributed to G Litscher.
A computerized, PC-based system is introduced for sleep monitoring in infants. The system is capable of digitizing and storing 22 physiological variables over a whole-night sleep period. The preprocessed data can be displayed on a single page; further processing can be done on the digitally stored data.
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Multimodal evoked potentials and heart-rate variability (HRV) measurements were performed in a total of 15 comatose patients with inflammatory diseases of the brain. The following potentials were recorded: Brainstem auditory evoked potentials (BAEP), early (SSEP) and long latency (SEP) somatosensory evoked potentials and visual evoked potentials (VEP). The results of the initial BAEP recordings indicate that in 83% of the patients the IV-V interpeak latency was prolonged and out of the range of normal values. Additionally an atypical form of the IV-V wave complex was detected. The SSEP after electrical stimulation demonstrated pathological findings in 90% of the patients; long latency components after mechanical vibration could be identified only by 30%. The results of the VEP show an attenuation of vertex VEP (mean value: 43%). Heart-rate variability of the patients was calculated (mean +/- SD) to be 2.5 +/- 1.4% (norm: 7.8 +/- 2.5%) with a mean heart-rate of 95.2 +/- 16.6/min (norm: 67.8 +/- 10.7/min).
Simultaneous continuous recording and processing of evoked potentials, various cardiovascular, and respiratory signals was realized with the aid of a PC-controlled monitoring system. The system is at present used for monitoring patients in intensive care units, during neurosurgical interventions and for sleep investigations in infants.
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Visual evoked potentials (VEPs) were examined as an integrated parameter in a multimodal EP study of brain bioelectrical activity in 33 comatose patients (Glasgow Coma Score 3-6) after craniocerebral trauma. Recordings were performed not only from the occipital (01-02) but also from the central (Cz-C3, Cz-A1, Cz-C4) and frontal (F3-F4) areas. The results show an attenuation of the vertex VEP (SNR 3.2 +/- 1.7) and an increase in the occipital VEP (SNR 4.8 +/- 2.3) as compared to the control group (SNR vertex 7.0 +/- 3.0/SNR occipital 3.9 +/- 2.0). In addition, 16 of the comatose patients showed a very considerable loss of the normally polyphasic character of the occipital VEP in favour of a potential that looked almost monophasic; this was either left or right dominant, and was recorded as a negative or positive potential, respectively, in bipolar recording (01-02). Comparison of the electrophysiological and computer tomography findings showed a laterally correlated change in the occipital VEP: contralateral to the injured hemisphere, the VEP was dominant, ipsilateral it was reduced or extinguished.
Individual monitoring of EEG and evoked potentials is gradually becoming standard in neurosurgery: compressed power spectra during carotid endarterectomy, brainstem auditory evoked potentials (BAEP) during posterior fossa surgery, and somatosensory evoked potentials (SEP) mainly during spinal cord surgery. In this paper, a new technique is described in which EEG, BAEP, and SEP are recorded and evaluated simultaneously and continuously. This allows a better survey of different neuronal structures and systems in the brain and brainstem. First results from intraoperative and intensive care patient monitoring are reported.
Multimodal EPs and heart rate variability-measurements in comatose patients have been performed for few years at the university hospitals of Graz and Erlangen. The following data and parameters are analysed and discussed: brainstem auditory evoked potentials, mechanical evoked long-latency SEP, VEP recorded over the central and occipital region and heart rate variability (HRV). The method of data acquisition and processing is described and normative data are introduced. For the long-latency EP-components a signal-to-noise-ratio (SNR) is calculated. SNR is defined as ratio of the largest EP peak-to-peak amplitude and the mean amplitude (standard deviation) of a period prior to the stimulation. An unmeasurable or questionable EP is defined when SNR less than 2.6. For the vertex-SEP the following mean +/- standard deviation was obtained: SNR = 10.6 +/- 4.6; the vertex VEP was calculated with SNR = 7.0 +/- 3.0. The SNR of the bipolar recorded occipitally VEP was 3.9 +/- 2.0. Heart rate variability measurements in normal persons revealed the following mean +/- standard deviation at a heart rate of 67.8/min +/- 10.8/min: HRV = 7.8% +/- 2.5%.
Ninety patients were subjected to brain-stem auditory evoked potential (BAEP) measurements in the intensive care unit. The data are analyzed and discussed with respect to their quality, reliability, and reproducibility. BAEPs of a quality satisfactory for diagnosis were found in 90% of the patients. About 10% of the measurements were distorted by artifacts and could not be used for diagnostic purposes. Reasons for these artifacts and problems of interpretation are discussed. Examples of single BAEPs and on-line monitoring of BAEPs in the form of "compressed BAEPs" are shown.
Twenty-four infants aged between 6 days and 7 months and 2 infants (16 m and 3 y) were subjects of combined brain-stem auditory evoked potential and heart rate variability measurements. Ten infants had a sleep apnea syndrome and one a Near miss sudden infant death syndrome; thirteen infants formed the control group. Seventeen of the twenty-six infants had normal, age-depended brain stem potentials. All infants of the apnea syndrome-group, which had no therapy, had increased I to V interpeak latencies outside of the one-sigma level, the six infants treated with aminophylline were within the normal range. Heart rate variability measurements revealed the following mean +/- standard deviation of the control group: 4.5% +/- 1.5%; of the apnea syndrome-group without therapy: 5.4% +/- 2.0%.
Forty-three all-night sleep recordings have been performed on 19 control infants of the ages 6 weeks, 6 months and 1 year. During eight hour periods 22 physiological parameters were sampled by a personal computer based monitoring system and stored on an optical disk. This paper reports on spectral analysis of breathing and heart rate patterns during the first and last episode of quiet sleep at three different age groups. The results demonstrate that the respiratory rate during quiet sleep decreases (6 weeks: 37.2 +/- 5.4; 6 months: 30.1 +/- 4.9; 1 year: 24.1 +/- 1.8; adults (mean age 25.1 +/- 2.8 years; n = 10): 14.8 +/- 1.8; values are means +/- one standard deviation in breaths/min) and the respiratory coefficient Pm/Ps (higher values of Pm/Ps indicate lower respiratory variability) increases with age (6 weeks: 2.3 +/- 0.7; 6 months: 3.2 +/- 1.1; 1 year: 3.4 +/- 1.0; adults: 4.5 +/- 1.0). The calculation of the heart rate in beats per minute (bpm) and heart rate variability (%) revealed the following results: 6 weeks: 127.4 +/- 11.5 bpm, 3.8 +/- 1.5%; 6 months: 119.4 +/- 17.3 bpm, 4.2 +/- 1.7%; 1 year: 110.3 +/- 21.5 bpm, 5.8 +/- 2.3%; adults: 59.2 +/- 8.5 bpm, 4.3 +/- 2.2%. A comparison of the cardiorespiratory data from the first and last quiet sleep period showed no significant differences within either age group.
We investigated brainstem auditory evoked potentials (BAEP) in 20 infants at risk of SIDS (age 5 days to 4 months) and in 7 control infants (age 5 days to 4 months). 19 infants were diagnosed as having sleep apnea syndrome (SAS), which we consider to be a possible risk factor for SIDS. The diagnosis of SAS was made in general in the presence of clinical symptoms such as apneas, cyanosis during sleep, poorly coordinated sucking, swallowing and respiration and gastro-oesophageal reflux in combination with an abnormal pneumogramm in a one hour oxycardiorespirography. One infant had the history of a near miss event but a normal pneumogramm, 2 infants, both with SAS, were siblings of SIDS infants. We applied BAEP on 12 infants at risk of SIDS with and on 12 infants at risk of SIDS without aminophyllin treatment. 3 infants at risk of SIDS had two BAEP studies, one before and one during aminophyllin treatment. The time interval between these two studies was 1 week to 16 days. Aminophyllin, given only to infants with SAS was administered orally (therapeutic range 4-10 micrograms/ml). All infants at risk of SIDS and all control infants had normal I-V-IPL (below 2 x SD). There was a tendency to longer I-V IPL in infants at risk of SIDS. When infants at risk of SIDS with and without aminophyllin treatment were compared as a group the I-V-IPL was shorter in the infants with aminophyllin. BAEP can be useful in studying disturbances of the autonomic function of brainstem centers but do not allow the prediction of an individual SIDS risk.
In an experimental animal study (Sus scrofa domesticus) we investigated the effects of the new technique of laser needle stimulation (wavelength: 685 nm; energy density: 4.6 kJ/cm2 per point; application duration: 20 min). The results revealed changes in microcirculatory parameters of the skin resulting in an increase in blood flow. However, the quality and intensity of the laser light did not induce micromorphological alterations in the skin.
Laser Doppler flowmetry (LDF) is a noninvasive method to study the microcirculation. We studied the feasibility of the clinical use of LDF in the intensive care unit by continuously recording different LDF parameters during the cessation of cerebral and cardiocirculatory function. The LDF-Conc (concentration of red blood cells) reflected biological phenomena correlated with the heart rate and microvibration that could not be detected with conventional means (systemic blood pressure, peripheral oxygen saturation).
In the present paper, experience with the detection of burst suppression in the pEEG is described. The possibilities and limitations of the method during monitoring of anaesthesia under real conditions are discussed.
For the first time, we have studied the effects of manual acupuncture and of laser puncture on cerebral oxygenation in three healthy male volunteers using transcranial near-infrared spectroscopy (NIRO 300, Hamamatsu Photonics, Japan). The results indicate that acupuncture of specific acupuncture points leads to an increase in oxygenated haemoglobin and in the tissue oxygenation index. However, needling and laser puncture at placebo points does not produce the same effect on cerebral oxygenation. This fact provides further proof of specific quantifiable effects of acupuncture on the brain.
The heart rate variability is defined as variation in distance between sequential ventricular complexes in the electrocardiogram and can be given in percent by referring the standard deviation to the average values of heart rate. The bivariate distribution of heart rate variability and of heart rate shows a discrimination of the group of comatose patients from brain dead subjects and normals.
Since its introduction into the clinical setting at the beginning of the 'eighties, transcranial Doppler sonography (TCD) has gained increasing acceptance as a non-invasive neuromonitoring technique. The ability of TCD to detect embolic particles within the cerebral blood vessels has been the subject of intensive investigation in recent years. In the present paper, a new method for the detection of emboli (multirange principle), intra-operatively during a neurosurgical intervention in a 35-year-old patient with a tumour in the posterior fossa and an open foramen ovale, is described for the first time. The method opens up new possibilities for the intra-operative management and the rapid assessment and diagnosis of paradoxical cerebral embolism.