Ville Jäntti

Sevoflurane mask induction of anaesthesia is associated with epileptiform EEG in children.

Background: Sevoflurane inhalation induction of anaesthesia is widely used in paediatric anaesthesia. We have found that this method is frequently associated with epileptiform electroencephalogram (EEG) in adults, especially if controlled hyperventilation is used.

Deficient auditory processing in children with Asperger Syndrome, as indexed by event-related potentials.

Asperger Syndrome (AS) is characterized by normal language development but deficient understanding and use of the intonation and prosody of speech. While individuals with AS report difficulties in auditory perception, there are no studies addressing auditory processing at the sensory level. In this study, event-related potentials (ERP) were recorded for syllables and tones in children with AS and in their control counterparts. Children with AS displayed abnormalities in transient sound-feature encoding, as indexed by the obligatory ERPs, and in sound discrimination, as indexed by the mismatch negativity. These deficits were more severe for the tone stimuli than for the syllables. These results indicate that auditory sensory processing is deficient in children with AS, and that these deficits might be implicated in the perceptual problems encountered by children with AS.

Automatic analysis and monitoring of burst suppression in anesthesia

Objective.We studied the spectral characteristics of the EEGburst suppression patterns (BSP) of two intravenous anesthetics,propofol and thiopental. Based on the obtained results, we developed amethod for automatic segmentation, classification and compactpresentation of burst suppression patterns. Methods.The spectralanalysis was performed with the short time Fourier transform and withautoregressive modeling to provide information of frequency contents ofbursts. This information was used when designing appropriate filters forsegmentation algorithms. The adaptive segmentation was carried out usingtwo different nonparametric methods. The first one was based on theabsolute values of amplitudes and is referred to as the ADIF method. Thesecond method used the absolute values of the Nonlinear Energy Operator(NLEO) and is referred to as the NLEO method. Both methods have beendescribed earlier but they were modified for the purposes of BSPdetection. The signal was classified to bursts, suppressions andartifacts. Automatic classification was compared with manualclassification. Results.The NLEO method was more accurate,especially in the detection of artifacts. NLEO method classifiedcorrectly 94.0% of the propofol data and 92.8% of thethiopental data. With the ADIF method, the results were 90.5% and88.1% respectively. Conclusions.Our results show thatburst suppression caused by the different anesthetics can be reliablydetected with our segmentation and classification methods. The analysisof normal and pathological EEG, however, should include information ofthe anesthetic used. Knowledge of the normal variation of the EEG isnecessary in order to detect the abnormal BSP of, for instance, seizurepatients.

Propofol anesthesia induces phase synchronization changes in EEG

OBJECTIVEnPhase coupling between EEG channel pairs in various frequency bands was evaluated during propofol anesthetic induction and recovery periods.nnnMETHODSnTwenty-three patients participated in the study. Phase synchronization indices based on the Hilbert transform were investigated on frequency bands 0.05-1 Hz, 1-4 Hz, 4-8 Hz, 8-12 Hz and 12-16 Hz for all pairs of the 9 EEG channels covering midline and frontal areas. A straight line was used to approximate the index values as a function of time and the Sign Test statistics were applied to the slope parameters.nnnRESULTSnSystematic phase synchronization changes were detected. Generally, phase synchronization in the sub-delta band decreased during the induction and increased during the recovery, while the directions were reversed in the alpha band. The changes were dependent on the channel pair. In the delta, theta and beta bands, the changes were aligned more irregularly than in the sub-delta or in the alpha bands. Highly asymmetric behavior between the induction and the recovery periods was also observed in these bands.nnnCONCLUSIONSnInduction and recovery from propofol anesthesia changes the phase synchronization between the EEG channels. The passband and location-specific behavior of these changes reveals the effects of the anesthetic to the different neural mechanisms.

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.

Effects of hypothermia and sternal retractors on median nerve somatosensory evoked potentials.

Background: Somatosensory evoked potentials (SEPs) are altered by hypothermia, which is often used during cardiopulmonary bypass (CPB). However, the effect of hypothermia on SEP amplitudes is unclear. Also, the sternal retractors used during open heart surgery are reported to cause brachial plexus distension and SEP changes.

Topographic electroencephalogram in children during mask induction of anaesthesia with sevoflurane

Background: Epileptiform patterns, spikes, polyspikes and periodic epileptiform discharges (PED) have been reported in electroencephalograms (EEGs) during anaesthesia induction with sevoflurane in healthy adults and children. Published recordings have been performed with a limited number of channels, and therefore the topographic distributions of these patterns are not known.

Cold retrograde cerebral perfusion improves cerebral protection during moderate hypothermic circulatory arrest: A long-term study in a porcine model

BACKGROUNDnDeep hypothermic circulatory arrest is an effective method of cerebral protection, but it is associated with long cardiopulmonary bypass times and coagulation disturbances. Previous studies have shown that retrograde cerebral perfusion can improve neurologic outcomes after prolonged hypothermic circulatory arrest. We tested the hypothesis that deep hypothermic retrograde cerebral perfusion could improve cerebral outcome during moderate hypothermic circulatory arrest.nnnMETHODSnTwelve pigs (23-29 kg) were randomly assigned to undergo either retrograde cerebral perfusion (15 degrees C) at 25 degrees C or hypothermic circulatory arrest with the head packed in ice at 25 degrees C for 45 minutes. Flow was adjusted to maintain superior vena cava pressure at 20 mm Hg throughout retrograde cerebral perfusion. Hemodynamic, electrophysiologic, metabolic, and temperature monitoring were carried out until 4 hours after the start of rewarming. Daily behavioral assessment was performed until elective death on day 7. A postmortem histologic analysis of the brain was carried out on all animals.nnnRESULTSnIn the retrograde cerebral perfusion group, 5 (83%) of 6 animals survived 7 days compared with 2 (33%) of 6 in the hypothermic circulatory arrest group. Complete behavioral recovery was seen in 4 (67%) animals after retrograde cerebral perfusion but only in 1 (17%) animal after hypothermic circulatory arrest. Postoperative levels of serum lactate were higher, and blood pH was lower in the hypothermic circulatory arrest group. There were no significant hemodynamic differences between the study groups.nnnCONCLUSIONSnCold hypothermic retrograde cerebral perfusion during moderate hypothermic circulatory arrest seems to improve neurologic outcome compared with moderate hypothermic circulatory arrest with the head packed in ice.

Adaptive segmentation of burst-suppression pattern in isoflurane and enflurane anesthesia

In this paper a developed novel algorithm for adaptive segmentation of Burst-suppression EEG is presented. The algorithm can detect bursts, suppression and artifacts dividing the signal into corresponding segments. A compact representation of burst-suppression EEG, useful in monitoring long-term recordings, is presented. In the second part of the paper the burst-suppression patterns of isoflurane and enflurane anesthesia are compared. It is found that bursts as well as suppression segments are shorter in enflurane anesthsia while the coefficient of variability of the segment lengths is similar for the two anesthetics.

Lamotrigine plus leukocyte filtration as a neuroprotective strategy in experimental hypothermic circulatory arrest

BACKGROUNDnLamotrigine and leukocyte filtration seem to improve cerebral protection during experimental hypothermic circulatory arrest (HCA). This study was performed to evaluate whether their combined use may further improve cerebral protection.nnnMETHODSnTwenty-four pigs undergoing 75-minute period of HCA at 20 degrees C were randomly assigned to receive saline; lamotrigine (20 mg/kg) before HCA (L); or lamotrigine (20 mg/kg) before HCA plus leukocyte filtration before and after HCA (L + LF).nnnRESULTSnSeven animals (87%) in the L + LF group, 4 (50%) in the L group, and 3 (37%) in the control group were alive on the seventh postoperative day. The median electroencephalogram burst recovery was 94% in the L + LF group (p = 0.024 versus control group), 81% in the L group, and 64% in the control group. Among the surviving animals, the median behavioral scores were 9, 9, and 6 at the seventh day, respectively (p = 0.005 between the L + LF group and the control group). The median histopathologic score was 14 in the L + LF group (p = 0.046 versus control group), 14.5 in the L group (p = 0.062 versus control group), and 21 in the control group.nnnCONCLUSIONSnLamotrigine has neuroprotective effect during HCA. The combined use of lamotrigine and LF may further improve the survival outcome.