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V Jäntti

Publications and source records attributed to V Jäntti.

At least 19 recordsLinked to original sources
PubMed1995

Visually evoked bursts during isoflurane anaesthesia.

We studied EEG reactivity to visual stimuli during deep isoflurane (1.5-2.05 vol% end-tidal concentration) anaesthesia. Twelve patients were anaesthetized with isoflurane until burst suppression occurred in the EEG. Red LED goggles were used to give visual stimulation of 60 flashes, 4-ms duration each, at a frequency of 20 Hz. The stimuli, 3-strains of flashes, were given at random intervals. Both onset and offset of stimulation evoked bursts. The latency of visually evoked bursts was comparable with long latency evoked potentials, which are known to be related to cognitive processing. Our data showed that the central nervous system reacts strongly to photic stimulation during deep anaesthesia.

Anesthesia, General↗
PubMed1995

Cortical reactivity during isoflurane burst-suppression anesthesia.

We studied cortical reactivity to auditory, visual, and somatosensory stimuli during moderate and deep levels of isoflurane anesthesia at which the electroencephalogram (EEG) showed burst suppression patterns, defined as alternating high amplitude bursts and periods of suppressed background activity. Fifteen patients scheduled for gynecologic surgery were anesthetized with isoflurane until burst suppression appeared in the EEG. During steady state burst suppression at 1.5 end-tidal isoflurane concentration (ETisof), each patient was given a 5-min interval each of episodes of visual, auditory, and somatosensory stimulation. During the 5-min interval of visual stimulation the patient was given 3-s episodes of 60 flashes, 4 ms duration each, at a 20-Hz frequency via redlight-emitting diode goggles. Corresponding auditory and somatosensory stimulation consisted of 60 clicks (80 dB, 0.1 ms, 20 Hz) via earphones and 60 pulses to the median nerve at the wrist (20 mA, 0.2 ms, 20 Hz). The 3-s episodes of stimulation were given at irregular intervals ranging from 5 to 20 s. End-tidal isoflurane was then increased by 0.3 vol% and 15 min later the stimulation sequence was repeated. During anesthesia at 1.5 +/- 0.1 ETisof all stimulus modalities readily evoked bursts. One hundred percent of visual stimuli, 98% +/- 4% of somatosensory stimuli, and 94% +/- 9% of auditory stimuli, given during EEG suppression, evoked bursts. Somatosensory and visual stimulation evoked bursts at both onset and offset of the 3-s episodes of stimuli. The responses to auditory stimuli were related mainly to the ending of the 3-s episode of clicks.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1995

Propofol and isoflurane induced EEG burst suppression patterns in rabbits.

The aim of this study was to compare propofol produced EEG burst suppression with isoflurane produced burst suppression in rabbits and to see whether rabbits can serve as models in studying the effects of different anaesthetics on human EEG. We recorded EEG of eight rabbits anaesthetised with isoflurane and propofol. The isoflurane bursts had higher amplitude than propofol bursts (P < 0.005). Isoflurane bursts appeared on distinct DC-shifts while propofol bursts were on slow waves. The EEG patterns were, however, different from those seen in humans. Rabbits did not have the rhythms seen in humans. We conclude that rabbits can be used to study the EEG effects of anaesthetics, such as the timing properties and reactivity of burst suppression pattern. However, this model seems less promising in the study of rhythmic activity seen in human EEG during burst suppression.

Anesthesia↗
PubMed1995

MEG burst suppression in an anaesthetized dog.

Recording of the magnetic fields of the brain, magnetoencephalography (MEG), has proved to be a valuable method in neurophysiological research. In order to study the feasibility of MEG recording during anaesthesia we recorded magnetoecephalographic burst suppression in a dog during enflurane and propofol anaesthesia. The observed signal distribution implies a complex current distribution underlying the burst activity. This experiment also proves that an essentially artefact-free MEG recording can be obtained during respirator-assisted anaesthesia.

Anesthesia, Inhalation↗
PubMed1994

Epileptic EEG discharges during burst suppression.

Barbiturate anaesthesia is used in the treatment of status epilepticus and severe epilepsy of children. EEG is then used as a measure of the depth of anaesthesia, burst suppression being an easily identified EEG pattern. In this case report we describe epileptiform discharges during EEG suppression in two children undergoing barbiturate anaesthesia for treatment of intractable seizures. One of them had focal, rhythmic discharges of negative spikes on the positive suppression level. Bursts were readily produced by visual stimuli with flashes of red light but this did not increase the frequency of focal spike discharges after bursts. The other patient had generalised, high amplitude spike-wave complexes, which were easy to distinguish from the bursts. We emphasise that it is important to make a distinction between electrocerebral silence, or isoelectric EEG as it was previously called, from EEG suppression. It is also important to distinguish epileptiform discharges from bursts, if the intention is to keep the anaesthesia at EEG burst suppression level.

Anesthesia↗
PubMed1994

Somatosensory evoked potentials during isoflurane anaesthesia.

Short latency somatosensory evoked potentials (SEPs) to median nerve stimulation during isoflurane anaesthesia were recorded in 12 elective-surgery patients. The effect of isoflurane on the shape, amplitude and latency of SEPs was evaluated. SEPs were recorded at awake, 1 MAC, 1.5 MAC, at electroencephalogram (EEG) burst suppression and at continuous suppression levels. Finally, SEPs were recorded when anaesthesia was lightened back to 1 MAC. The peak latency and amplitude of the first cortical N20 wave were measured. The latencies increased with increasing isoflurane concentrations. At high concentrations only an almost monophasic N20 wave was recorded, reduced in shape and amplitude. No specific changes could be correlated with the burst suppression or suppression patterns. This suggests that EEG and SEP generators are differently affected with increasing isoflurane concentration. The results indicate that SEPs can also be recorded in drug-induced EEG suppression.

Adult↗
PubMed1994

DC-level detection of burst-suppression EEG.

The EEG signal is usually recorded with low time constant analog prefilters to avoid low frequency artefacts. During this kind of recording the frequency components below the cutoff frequency of the analog prefilter (usually below about 1 to 3 Hz) are lost. By visual examination of some experimental recordings taken with a higher time constant, it was noticed that during burst-suppression EEG the DC-level of the signal rises sharply when the burst begins and falls when the burst ends. Thus, a burst actually consists of a mixed frequency discharge on a pulse-like DC-shift. We developed a filter algorithm to estimate the change in the DC-level during bursts as accurately as possible.

Algorithms↗
PubMed1994

Nonlinear interpretation of respiratory sinus arrhythmia in anesthesia.

A non-parametric method is presented for modelling nonlinear dynamic mechanisms of respiratory sinus arrhythmia (RSA) in anesthesia caused by positive pressure ventilation. RR interval sequences are shown with Tsay's linearity test to contain both short-term and long-term nonlinear components, which cannot completely be modelled with optimal linear methods. The nonlinear approach is based on Wiener's theory for broad-band random input signal. The input-output model is formed for tracheal pressure and RR interval sequence. Second-order and third-order nonlinearities in RSA fluctuation are found and demonstrated.

Adult↗
PubMed1993

Vibration stimulus induced EEG bursts in isoflurane anaesthesia.

The EEG and heart rate reactions to vibration stimulus were studied in 14 patients during moderately deep surgical isoflurane anaesthesia, at a level when EEG showed a burst suppression pattern. Vibration applied to the palm of the hand induced bursts in EEG in 12 patients, usually with a latency of about 0.5 sec from the onset, or from the end of the 3 sec stimulus. Increases in heart rate were seen at bursts related to both vibration onset and offset, as well as at spontaneous bursts. With spontaneous bursts, an initial positive wave was frequently seen. In 6 patients the vibration induced bursts were different in shape from the spontaneous bursts; no initial positive wave was seen before the negative DC shift in Cz-Fz recording. We conclude that EEG bursts can be evoked by a non-noxious stimulus such as vibration in patients during isoflurane anaesthesia.

Adult↗
PubMed1993

Changes in the T-wave amplitude of ECG during isoflurane anaesthesia.

R/T-wave amplitude ratio of electrocardiogram (ECG), heart rate (HR) and systolic arterial pressure (SAP) were recorded in 15 patients awake, at 1 minimal alveolar concentration of isoflurane before and during surgery, and in deep anaesthesia (electroencephalogram burst suppression) during surgery. R/T-wave amplitude ratio and HR were sensitive to both surgery and changes in the level of isoflurane anaesthesia; induction of anaesthesia, skin incision and the rapid increase in the concentration of isoflurane all significantly decreased the T-wave amplitude, without influence on the R-wave. Changes in the T-wave amplitude correlated directly to HR. SAP increased at skin incision and decreased when the anaesthesia was deepened. The authors conclude that the R/T-wave amplitude ratio of ECG provides a reliable method for monitoring the sympathetic tone during isoflurane anaesthesia.

Adult↗
PubMed1993

Atropine abolishes electroencephalogram-associated heart rate changes without an effect on respiratory sinus arrhythmia during anaesthesia in humans.

Heart rate fluctuates with the electroencephalogram burst suppression pattern during anaesthesia: increasing at burst onset and decreasing at suppression. Heart rate also oscillates with positive pressure ventilation. The effects of atropine on these heart rate changes were studied in 12 patients during isoflurane anaesthesia and positive pressure ventilation at a frequency of 6 cycles min-1. Four additional patients served as controls. A bolus dose of atropine (20 micrograms kg-1 intravenously) abolished the electroencephalogram-correlated heart rate changes; however, the amplitude of respiratory sinus arrhythmia was not changed after atropine. The control mechanism of the burst suppression pattern in electroencephalogram also affects parasympathetic heart rate control. The control mechanisms of respiratory sinus arrhythmia during anaesthesia with positive pressure ventilation differ from those during spontaneous breathing awake.

Adult↗
PubMed1991

Respiratory sinus arrhythmia is reversed during positive pressure ventilation.

In order to study the relationship between heart rate and depth of anaesthesia, respiratory sinus arrhythmia (RSA) was investigated during enflurane and isoflurane anaesthesia in 28 patients (15-39 years). Positive pressure ventilation (six breaths min-1) was used. Respiratory sinus arrhythmia was evaluated during light anaesthesia, deep anaesthesia (burst suppression in EEG) and light anaesthesia again by using signal averaging technique. In most patients, decrease of the heart rate was seen during inspiration (positive tracheal pressure), and increase during expiration. Respiratory sinus arrhythmia did not disappear in deep anaesthesia. Inter-individual variation in the magnitude and phase relationship of respiratory sinus arrhythmia was considerable, and was not associated to the level of anaesthesia.

Adolescent↗
PubMed1990

Correlation of instantaneous heart rate and EEG suppression during enflurane anaesthesia: synchronous inhibition of heart rate and cortical electrical activity?

EEG burst suppression and instantaneous heart rate were studied during enflurane anaesthesia in 15 patients. Heart rate increased at EEG burst onset and decreased at suppression onset. Short epileptic discharges accompanied by an increase in heart rate were seen in 2 patients. We suggest that suppressions in EEG may be caused by active inhibition, with synchronous decrease of heart rate.

Adolescent↗
PubMed1990

Correlation between EEG and heart rate variation in deep enflurane anaesthesia.

Variations in heart rate during deep enflurane anaesthesia were studied in 11 women admitted for elective surgery. Correlation was found between heart rate variations and bursts and suppressions in the EEG patterns. The onset of bursts coincided with accelerating heart rate, and the onset of suppressions was combined with a fall in heart rate in all patients. The correlation is not explained by ventilation arrhythmia. Both the cortical electrical activity and heart rate fluctuation are probably controlled by the same subcortical factor.

Adult↗
PubMed1990

EEG burst-suppression pattern correlates with the instantaneous heart rate under isoflurane anaesthesia.

The correlation between electroencephalogram (EEG) and instantaneous heart rate was studied in deep isoflurane anaesthesia when the EEG showed a burst-suppression pattern in 15 patients aged 19-39 years. At the onset of EEG burst, the heart rate started to accelerate, and at the onset of suppression it started to decelerate. These changes in heart rate are similar to those we have previously described with enflurane, despite several differences in the effects of these two anaesthetics on EEG and on the cardiovascular system. We hypothesise that the heart-rate changes are due to central inhibition mediated by the vagus nerve during EEG suppression.

Adult↗
PubMed1990

Carpal tunnel syndrome in vibration disease.

The presence of carpal tunnel syndrome (CTS) in 125 forestry workers with exposure to vibration was examined clinically by electromyography and by determining vibration detection thresholds. Numbness of the hands was present in 43%, history of diminished hand muscle force in 15%, and Raynaud's phenomenon in 27%. The muscle weakness correlated significantly with motor nerve conduction velocity in the median nerve in both hands. In 25 forestry workers CTS was diagnosed. The condition was bilateral in 48%; otherwise it was more common on the right side. Fifteen patients were referred for surgery but because of spontaneous recovery or refusal by the patients only five underwent surgery; of these four improved. The motor conduction velocity of the ulnar nerve was decreased among patients with CTS supporting the idea that entrapment neuropathies in the hands may be due to tissue swelling caused by vibration at work. Total exposure time to vibration correlated with the decrease in motor conduction velocity in the ulnar nerve.

Adult↗