OBJECTIVE

To investigate whether the periodic EEG patterns seen in healthy and sick full term neonates (trace alternant and burst suppression, respectively) have different frequency characteristics.

METHODS

Burst episodes were selected from the EEGs of 9 healthy and 9 post-asphyctic full-term neonates and subjected to power spectrum analysis. Powers in two bands were estimated; 0-4 and 4-30 Hz, designated low- and high-frequency activity, respectively (LFA, HFA). The spectral edge frequency (SEF) was also assessed.

RESULTS

In bursts, the LFA power was lower in periods of burst suppression as compared to those of trace alternant. The parameter that best discriminated between the groups was the relative amount of low- and high-frequency activity. The SEF parameter had a low sensitivity to the group differences. In healthy neonates, the LFA power was higher over the posterior right as compared to the posterior left region.

CONCLUSIONS

Spectral power of low frequencies differs significantly between the burst episodes of healthy and sick neonates.

CONCLUSIONS

These results can be used when monitoring cerebral function in neonates.

The visual system constantly utilizes regularities that are embedded in the environment and by doing so reduces the computational burden of processing visual information. Recent findings have demonstrated that probabilistic information can override attentional effects, such as the cost of making an eye movement away from a visual target (antisaccade cost). The neural substrates of such probability effects have been associated with activity in the superior colliculus (SC). Given the immense reciprocal connections to SC, it is plausible that this modulation originates from higher oculomotor regions, such as the frontal eye field (FEF) and the supplementary eye field (SEF). To test this possibility, the present study employed theta burst transcranial magnetic stimulation (TMS) to selectively interfere with FEF and SEF activity. We found that TMS disrupted the effect of location probability when TMS was applied over FEF. This was not observed in the SEF TMS condition. Together, these 2 experiments suggest that the FEF plays a critical role not only in initiating saccades but also in modulating the effects of location probability on saccade production.

As accurate finger movements depend on guidance by afferent sensory feedback information, it is of interest to examine how the cortical processing of afferent signals is altered during movement states compared with rest. In the present study we evaluated afferent input to the primary somatosensory cortex (SI) in human subjects performing a finger opposition task. We recorded somatosensory evoked magnetic fields (SEFs) in 6 healthy subjects to stimulation of left and right median nerves in a resting condition and during active right-sided finger movements. At the left SI, the SEFs to right (moving hand) median nerve stimulation showed a selective and robust reduction of the P35m deflection during movement compared with rest, while there were only minor non-significant changes in the other SEF deflections, including N20m, which represents the 1st excitatory cortical event after stimulation. In contrast, at the right SI the SEFs to left (non-moving hand) median nerve stimulation were modified in the opposite direction: the P35m deflection was slightly enhanced during right-sided movement, there being no significant changes in the other deflections. The results thus show that the P35m SEF deflection can be selectively reduced during finger movements of the stimulated hand, and selectively enhanced if the movement is being performed with the fingers of the opposite hand. Because N20m was not changed, the modulation took place at the cortical level rather than in the afferent pathways. As the P35m SEF deflection likely represents postsynaptic IPSPs at SI, the results suggest that postsynaptic inhibition to somatosensory impulses from the moving part of the body is suppressed. Comparison of the present results with recent intracellular studies in behaving mice suggests that the P35m reduction specifically corresponds to a reduction in the activity of parvalbumin-containing fast-spiking inhibitory interneurons during movement. The results provide evidence that precision movements can be executed without this type of cortical postsynaptic inhibition.

We recorded somatosensory evoked magnetic fields (SEFs) to median nerve stimulation from 15 patients in the acute stage (1-15 days from the onset of the symptoms) of their first-ever unilateral stroke involving sensorimotor cortical and/or subcortical structures in the territory of the middle cerebral artery (MCA). Neuronal activity corresponding to the peaks of the N20m, P35m and P60m SEF deflections from the contralateral primary somatosensory cortex (SI) was modelled with equivalent current dipoles (ECDs), the locations and strengths of which were compared with those of an age-matched normal population. Four patients with pure motor stroke had symmetric SEFs. In one of the 4 patients with pure sensory stroke, and in 5 of the 7 patients with sensorimotor paresis, the SEFs were markedly attenuated or missing. All except one patient with abnormal SEFs had deficient two-point discrimination ability; especially the attenuation of N20m was more clearly correlated with two-point discrimination than with joint-position or vibration senses. Of the different SEF deflections, P35m and P60m were slightly more sensitive indicators of abnormality than N20m, the former being affected in two patients with symmetric N20m. Three patients with pure sensory stroke and lesions in the opercular cortex had normal SEFs from SI. We conclude that the SEF deflections N20m, P35m and P60m from SI are related to cutaneous sensation, in particular discriminative to touch. The results also demonstrate that basic somatosensory perception can be affected by lesions in the opercular cortex in patients with functionally intact SI.

Motor recovery after stroke requires continuous interaction of motor and somatosensory systems. Integration of somatosensory feedback with motor programs is needed for the automatic adjustment of the speed, range, and strength of the movement. We recorded somatosensory evoked fields (SEFs) to tactile finger stimulation with whole-scalp magnetoencephalography in 23 acute stroke patients at 1 week, 1 month, and 3 months after stroke to investigate how deficits in the somatosensory cortical network affect motor recovery. SEFs were generated in the contralateral primary somatosensory cortex (SI) and in the bilateral parietal opercula (PO) in controls and patients. In the patients, SI amplitude or latency did not correlate with any of the functional outcome measures used. In contrast, the contralateral PO (cPO) amplitude to the affected hand stimuli correlated significantly with hand function in the acute phase and during recovery; the weaker the PO activation, the clumsier the hand was. At 1 and 3 months, enhancement of the cPO activation paralleled the improvement of the hand function. Whole-scalp magnetoencephalography measurements revealed that dysfunction of somatosensory cortical areas distant from the ischemic lesion may affect the motor recovery. Activation strength of the PO paralleled motor recovery after stroke, suggesting that the PO area is an important hub in mediating modulatory afferent input to motor cortex.

The presentation of saccadic and smooth pursuit eye movements as two separate systems has recently been reconsidered: The two subsystems share a number of anatomical structures, and recent data suggest that this sharing also extends to physiological processes. The aim of our study was first to test whether these two subsystems share a common predictive process. We designed a new predictive smooth pursuit paradigm that requires the triggering of unpredictable saccades, performed either during low (ongoing pursuit) or high (pursuit direction reversal) predictive behavior. Saccade latency was used as a probe to reveal a possible sharing of prediction between the two subsystems. The main finding was that saccade latencies were markedly decreased when triggered around pursuit direction reversal and performed in the direction of the predicted pursuit. The aim of the second part of this study was to determine the neural substrate of this common predictive process. According to previous studies, the supplementary eye field (SEF) would be involved in the control of predictive pursuit. The same subjects therefore performed the same tasks, and transcranial magnetic stimulation (TMS) was applied over this area: Decreased saccade latencies were no longer observed, whereas it continued to be observed when applied over the occipital cortex. These results are consistent with (1) The existence of a common predictive process shared by both oculomotor subsystems; (2) The view of the SEF not as a primary oculomotor area but as a higher order structure able to elaborate complex processes, such as prediction, independently of the oculomotor output.

Neurons in the macaque supplementary eye field (SEF) fire at different rates in conjunction with planning saccades in different directions. They also exhibit object-centered spatial selectivity, firing at different rates when the target of the saccade is at the left or right end of a horizontal bar. To compare the rate of incidence of the two kinds of signal, and to determine how they combine, we recorded from SEF neurons while monkeys performed a task in which the target (a dot or the left or right end of a horizontal bar) could appear in any visual field quadrant. During the period when the target was visible on the screen and the monkey was preparing to make a saccade, many neurons exhibited selectivity for saccade direction, firing at a rate determined by the direction of the impending saccade irrespective of whether the target was a dot or the end of a bar. On bar trials, many of the same neurons exhibited object-centered selectivity, firing more strongly when the target was at the preferred end of the bar regardless of saccade direction. The rate of incidence of object-centered selectivity (33%) was lower overall than that of saccade-direction selectivity (56%). Signals related to saccade direction and the object-centered location of the target tended to combine additively. The results suggest that the SEF is at a transitional stage between representing the object-centered command and specifying the parameters of the saccade.

OBJECTIVE

We examined whether the inverse relation between somatic evoked N20m primary response and high-frequency oscillations during a wake-sleep cycle (Hashimoto, I., Mashiko, T., Imada, T., Somatic evoked high-frequency magnetic oscillations reflect activity of inhibitory interneurons in the human somatosensory cortex, Electroenceph clin Neurophysiol 1996;100:189-203) holds for interference stimulation.

METHODS

Somatosensory evoked fields (SEFs) from 14 subjects were measured following electric median nerve stimulation at the wrist with, and without, concurrent brushing of the palm and fingers. SEFs were recorded with a wide bandpass (0.1-1200 Hz) and then N20m and high-frequency oscillations were separated by subsequent low-pass (< 300 Hz) and high-pass >> 300 Hz) filtering.

RESULTS

The N20m decreased dramatically in amplitude during interference stimulation. In contrast, the high-frequency oscillations moderately increased in number of peaks.

CONCLUSIONS

These results demonstrate the presence of an inverse relation between N20m and high-frequency oscillations for interference stimulation. We speculate that the high-frequency oscillations represent a localized activity of GABAergic inhibitory interneurons of layer 4, characterized by a high-frequency spike burst (200-1000 Hz) without adaptation, and that the continuous interference stimulation induces tonic excitation of the interneurons, leading to a facilitation of responses to the coherent afferent volley elicited by the median nerve stimulation (bottom-up mechanism). On the other hand, refractoriness of the pyramidal neurons caused directly by interference stimulation along with an enhanced feed-forward inhibition from the interneurons will lead to a decrease of N20m amplitude.

Lesions in the primary visual cortex induce severe loss of visual perception. Depending on the size of the lesion, the visual field might be affected by small scotomas, hemianopia, or complete loss of vision (cortical blindness). In many cases, the whole visual field of the patient is affected by the lesion, but diffuse light-dark discrimination remains (residual rudimentary vision, RRV). In other cases, a sparing of a few degrees can be found (severely reduced vision, SRV). In a follow-up study, we mapped visually induced cerebral activation of three subjects with SRV using functional magnetic resonance imaging. We were especially interested in the visual areas that would be activated if subjects could perceive the stimulus consciously although information flow from V1 to higher visual areas was strongly reduced or virtually absent. Because subjects were only able to discriminate strong light from darkness, we used goggles flashing intense red light at a frequency of 3 Hz for full visual field stimulation. Besides reduced activation in V1, we found activation in the parietal cortex, the frontal eye fields (FEF), and the supplementary eye fields (SEF). In all patients, FEF activation was pronounced in the right hemisphere. These patterns were never seen in healthy volunteers. In a patient who recovered completely, we observed that extrastriate activation disappeared in parallel with the visual field restitution. This result suggests that damage to the primary visual cortex changes the responsiveness of parietal and extravisual frontal areas in patients with SRV. This unexpected result might be explained by increased stimulus-related activation of attention-related networks.

We studied 13 healthy subjects with a multichannel magnetoencephalography (MEG) system to investigate the somatotopic representation of the ear in the primary somatosensory cortex (SI). We stimulated three parts of the left ear: the helix, the lobulus, and the tragus. The somatosensory-evoked magnetic fields (SEFs) were successfully measured in 7 of 13 subjects. Short-latency responses were analyzed using both single dipole and multidipole models (brain electric source analysis, BESA). From the single dipole model, the equivalent current dipole (ECD) following the helix stimulation was estimated to be near the neck area of SI in all the subjects. In the lobulus stimulation, the ECDs were estimated around the neck area of SI in four subjects, in the face area in one subject, and in the deep white matter in two subjects. In the tragus stimulation, the ECDs were estimated around the neck area of SI in three subjects, in the hand area of SI in two subjects, and in the deep white matter in two subjects. When the ECDs were estimated to be located in unlikely sites (hand area and deep white matter), a two-dipole model, (1) the neck area of SI and (2) face area of SI, was found to be the most appropriate. Although this might be a preliminary study due to a relatively small number of subjects, it revealed that receptive fields of some part of the ear, such as the lobulus and tragus, might be present in both the neck and face areas of SI. These findings suggested that the "ear area" of SI has variability between subjects, unlike the other areas of SI, possibly because the ear is located on the border between the neck and face.

A plethora of phenomenological and structure-motivated constitutive models have thus far been used as pseudoelastic descriptors in arterial biomechanics, but their parameters have not been explicitly correlated with histology. This study associated biaxial histological data with strain-energy function (SEF) parameters derived from uniaxial tension data of arteries from different topographical sites (carotid artery vs. thoracic aorta vs. femoral artery). A two-term SEF fitted the passive stress-strain data of healthy porcine tissue, justified by the biphasic response characterizing elastin-rich tissues. Selection of a quadratic (orthotropic) over the neo-Hookean (isotropic) term was dictated by the directional dissimilarities in low-stress mechanical response, consistent with our histological data indicating orthotropic symmetry for unstressed elastin. Use of the exponential term was dictated by mechanical dissimilarities at high stresses and variations in unstressed collagen composition and orientation. Accurate fits were attained; topographical variations and anisotropy in material parameters were accounted by respective variations in histomorphometrical data.

The auditory steady-state response (ASSR) is a nearly sinusoidal electrical response of the brain to auditory stimuli delivered at fast rates. The amplitude of the response is largest for stimulus rates near 40/s, hence the label 40-Hz ASSR. We have studied the effects of propofol (1.5 mg/kg) on the 40-Hz ASSR in 14 patients. The spectral edge frequency (SEF) and median frequency (MDF) of the electroencephalogram were recorded for comparison. The study was limited to 6 min after the injection of propofol. Recordings were obtained every minute. Consciousness, defined as responsiveness to verbal command, was assessed in all patients within 1 min. Nine patients, regained consciousness before the end of the study. Propofol caused disappearance of the 40-Hz ASSR for 2 min. Th 40-Hz ASSR reappeared afterward, reaching, at the end of the study period, an amplitude of about 65% of baseline. Recovery of the 40-Hz ASSR occurred whether or not consciousness was regained during the study, but the amplitude tended to be larger in patients who had regained consciousness compared with patients still unconscious during the same recording. The SEF was reduced by 24% within 2 min and recovered more quickly than the 40-Hz ASSR, reaching 91% of baseline within 4 min. The SEF tended to be higher in patients who had regained consciousness. The MDF was reduced by 27% within 2 min, and exceeded baseline values by 25% during recovery. The MDF was not higher in patients who had regained consciousness. We conclude that propofol transiently abolishes the 40-Hz ASSR. Recovery of the 40-Hz ASSR occurs whether or not consciousness is regained, but the 40-Hz ASSR tends to be larger after the return of consciousness. An association between higher amplitude 40-Hz ASSR and the return of consciousness could not be conclusively established, perhaps because of low signal-to-noise ratio in three patients. The 40-Hz ASSR did not offer any clear advantage over the SEF in predicting the return of consciousness.

We examined the "gating" effects caused by active and passive movements of toes and by "movement imagery" (mental moving of the toe without actual movements) on somatosensory evoked magnetic fields (SEFs) following stimulation of the posterior tibial nerve in normal subjects. Active and passive movements significantly attenuated the short- and middle-latency cortical components (P < 0.001) with no latency change, and the effects of the active movements were larger than those of the passive movements. In contrast, the subsequent long-latency component with a latency of about 100 ms was enhanced only by the active movements. Therefore, both centrifugal and centripetal mechanisms should be considered. The gating effects by movements on all components may occur in the primary sensory cortex (SI) in the hemisphere contralateral to the stimulated nerve, because all of the equivalent current dipoles (ECDs) of the components in the "control" and each "interference" waveform were located there. Active movements of the toes contralateral to the stimulated nerve caused no significant gating effect. The short-latency components were not consistently changed by "movement imagery", but the middle- and long-latency components were enhanced. Their ECDs were located in the SI contralateral to the stimulated nerve and in the SII in bilateral hemispheres. Therefore, we speculated that brain responses to somatosensory stimulation, particularly components generated in SII, were affected by volitional changes.

BACKGROUND

Socioeconomic factors (SEF) influence bariatric surgery access and outcomes perhaps because of variations in patient knowledge and behaviors. This study examines the associations between income, formal education, race, health insurance, employment status, and patient self-educational and behavioral activities prior to bariatric surgery.

METHODS

From March 2005 through January 2006, we surveyed 127 individuals who contacted our office seeking bariatric surgery. Study participants were asked to report their income, formal education, health insurance, employment status, height, weight, and standard demographic data. The type and number of self-educational resources utilized were elicited; a description of current eating and exercise behaviors was obtained; and an objective assessment (OA) of knowledge of the risks of both obesity and bariatric procedures was completed.

RESULTS

The most valuable self-educational resource cited by respondents was the internet (41.2%) and was unaffected by SEF. Individuals who were employed, privately insured, white, and earning>or=$20,000/year reported using a greater number of self-educational resources than their peers, while subjects who were privately insured, had higher formal educational levels, and earned>or=$20,000/year demonstrated greater proficiency on the OA instrument. Engagement in healthy eating and exercise behaviors was unaffected by any SEF. On multivariate analysis, higher income was the sole significant factor directly related to the number of educational resources utilized and proficiency on OA.

CONCLUSIONS

Obese patients from lower-income households may benefit from additional preoperative education. All individuals, regardless of socioeconomic factors, must be encouraged to implement healthy eating and exercise behaviors preoperatively.

BACKGROUND

Saccadic eye movements are used to rapidly align the fovea with the image of objects of interest in peripheral vision. We have recently shown that in children there is a high preponderance of quick latency but poorly planned saccades that consistently fall short of the target goal. The characteristics of these multiple saccades are consistent with a lack of proper inhibitory control of cortical oculomotor areas on the brainstem saccade generation circuitry.

RESULTS

In the present paper, we directly tested this assumption by using single pulse transcranial magnetic stimulation (TMS) to transiently disrupt neuronal activity in the frontal eye fields (FEF) and supplementary eye fields (SEF) in adults performing a gap saccade task. The results showed that the incidence of multiple saccades was increased for ispiversive but not contraversive directions for the right and left FEF, the left SEF, but not for the right SEF. Moreover, this disruption was most substantial during the approximately 50 ms period around the appearance of the peripheral target. A control condition in which the dorsal motor cortex was stimulated demonstrated that this was not due to any non-specific effects of the TMS influencing the spatial distribution of attention.

CONCLUSIONS

Taken together, the results are consistent with a direction-dependent role of the FEF and left SEF in delaying the release of saccadic eye movements until they have been fully planned.

The spectral edge frequency (SEF) 95 is one of the electroencephalographic (EEG) parameters, which is a relatively simple and effective method to evaluate a sedative status. The aim of this study was to evaluate the effect of acupuncture on electroencephalographic SEF 95 in dogs (4.2 - 6.1 kg, 1-2 years old) sedated by a sedative. The acupoints used were the GV20 point and Yintang point. The sedatives used were acepromazine, butorphanol, diazepam, medetomidine, and phenobarbital, each using a different mechanism. The sedation level was assessed by a SEF 95 value under normal conditions, sedation being induced by a sedative, a combination of a sedative and acupuncture, and acupuncture release. During the sedative and acupuncture combination, the SEF 95 values significantly decreased in the butorphanol group. Although this result was just based on the changes of the brain it is suggested that acupuncture, combined with opioids, would be a useful method to produce a safe and deep sedation in clinics.

We studied the effects of sleep on somatosensory evoked magnetic fields (SEFs) following median nerve stimulation in normal subjects, to investigate the changes of functional processing of sensory perception in the primary and second sensory cortices (SI and SII). The early components, 1M, 2M and 3M, which were generated in SI contralateral to the stimulated nerve, showed no significant change of latency or amplitude in stage 1 or 2 as compared with those in the awake state. The long-latency response, 4M whose latency was about 100 ms, was significantly enhanced in stage 2. The 4M was considered to be generated in SI and SII in the awake state, but the enhanced 4M in stage 2 was restricted in SI. The 4M(I) generated in SII of the hemisphere ipsilateral to the stimulated nerve, corresponding to 4M in the contralateral hemisphere, was absent during sleep. These findings were probably due to the difference of activities between SI and SII during sleep, that is, an increase of sensitivity to somatosensory stimulation in SI but a decrease or disappearance in SII.

OBJECTIVE

To determine interhemispheric differences and effect of postmenstrual age (PMA), height, and gender on somatosensory evoked magnetic fields (SEFs) from the primary (SI) and secondary (SII) somatosensory cortices in healthy newborns.

METHODS

We recorded SEFs to stimulation of the contralateral index finger (right in 46 and left in 12) healthy fullterm newborns and analyzed the magnetic responses with equivalent current dipoles.

RESULTS

Activity from both the SI and SII was consistently detectable in the contralateral hemisphere of the newborns during quiet sleep. No significant interhemispheric differences existed in SI or SII response peak latencies, source strengths, or location (n=8, quiet sleep). SI or SII response peak latency or source strength were not significantly affected by PMA, height, or gender.

CONCLUSIONS

During the neonatal period (PMA 37-44 weeks), activity from the contralateral SI and SII can be reliably evaluated with MEG. The somatosensory responses are similar in the left and right hemispheres and no corrections for exact PMA, height, or gender are necessary for interpreting the results. However, the evaluation should be conducted in quiet sleep.

CONCLUSIONS

The reproducibility of the magnetic SI and SII responses suggests clinical applicability of the presented MEG method.

Useful landmarks on magnetic resonance (MR) images were identified for preoperative prediction of the relationship of a tumor to the primary sensory cortex of the thumb. Functional MR (fMR) imaging and magnetoencephalography were used to retrospectively localize the hand-digit sensorimotor area in four patients who underwent tumor resection around the central sulcus with intraoperative neurophysiological mapping. fMR imaging revealed the hand-digit motor cortex in the so-called "precentral knob" inside the characteristic inverted-omega on axial MR images. Equivalent current dipoles of the N20 m response in somatosensory evoked fields (SEFs) of the thumb, median nerve, and ulnar nerve stimuli were localized at the lateral portion of the inverted omega-shape from the lateral to medial directions. The SEF-based thumb sensory cortex was verified by intraoperative functional mapping with a neuronavigation system. The hand-digit somatosensory cortices were localized at the lateral shoulder of the inverted-omega, in the lateral anterior inferior position to the hand-digit motor cortices in the precentral knob. Axial MR imaging can provide useful preoperative planning information for the surgical treatment of tumors within or adjacent to the motor-somatosensory cortex.

Distributional and morphological features, especially characteristics of the ramification of serotonin-containing supraependymal fibers (SEF), were studied in the ventricular systems of mammals (mouse, rat, guinea pig, rabbit, cat, dog, monkey) by means of a modified peroxidase antiperoxidase technique, using antiserotonin antiserum prepared in our laboratory. SEF were present in all ventricular systems, except on the third ventricle floor and in the choroid plexus. The density of SEF was higher in the smaller species. In the rat, light- and scanning electron microscopical SEF were almost completely abolished 1 week after intraventricular administration of 5,6-dihydroxytryptamine. Ramification of SEF was complicated; the SEF formed a true network with frequent anastomosing. In the ventricular system of rats rendered hydrocephalic by kaolin administration, the mode of axonal branching in the supraependymal plexus could best be analyzed by the scanning electron microscope because the meshes of the plexus were spread out.

OBJECTIVE

Congenital insensitivity to pain and Anhidrosis (CIPA) or hereditary sensory and autonomic neuropathy type IV (HSAN IV) is a rare autosomal recessive neuropathy of the group of hereditary sensory and autonomic neuropathies (HSAN) characterized by insensitivity to pain, anhidrosis, and mental retardation. Since it is a rare condition, reports on the anesthetic conduct in patients with CIPA are not easily found in the literature. The objective of this report was to present the anesthetic conduct in a patient with CIPA undergoing left ankle arthrodesis with placement of an implant, and to discuss the characteristics of this disorder that concern anesthesiologists the most.

METHODS

A female patient with a history of CIPA was admitted for left ankle arthrodesis due to Charcot arthropathy. In the operating room, the patient was monitored with an electrocardiograph, bispectral index, 95% SEF, non-invasive blood pressure, and peripheral hemoglobin saturation; she was pre-medicated with midazolam and underwent intravenous anesthesia with propofol and cisatracurium. The administration of analgesics was not necessary. After tracheal intubation, monitoring of end-expiratory pressure of carbon dioxide and esophageal temperature were added. The patient did not develop postoperative complications. She was discharged from the hospital on the second postoperative day.

CONCLUSIONS

Although there is insensitivity to pain, some patients present tactile hyperesthesia that can cause unpleasant feelings during surgical manipulation. Despite reports in the literature of patients undergoing neuroaxis blocks, and even procedures without anesthesia, intravenous anesthesia, which provided adequate conditions for the anesthetic-surgical procedure was used in this case.

A patient with acute necrotizing encephalophathy (ANE) following varicella infection with a good prognosis is reported. A somatosensory evoked magnetic field (SEF) study using a 37-channel-magnetoencephalography system demonstrated normal latency and strength of the first component (N20m) elicited by median nerve stimulation, despite bilateral symmetrical thalamic lesions on MRI. The normal SEF findings and the good prognosis suggested a reversible breakdown of the blood-brain barrier, and an edematous process as the brain pathology. Furthermore, our results support the idea of distinct generators for the three earliest cortical SEF components (N20m, P30m, N45m).

OBJECTIVE

To evaluate bispectral index (BIS), spectral edge frequency 95% (SEF), and median frequency (MED) in relation to a visual analogue scale (VAS) as indicators of anesthetic depth for various concentrations of sevoflurane and isoflurane in pigs.

METHODS

32 pigs.

METHODS

Pigs were randomly allocated to 8 groups (4 pigs/group). An electroencephalogram (EEG) was recorded in each conscious pig. Pigs were then anesthetized by use of sevoflurane (n = 16) or isoflurane (16). Agents were administered in oxygen at minimum alveolar concentrations (MACs) of 1, 1.25, 1.5, and 1.75 MAC in a randomized order. End-tidal sevoflurane and isoflurane concentrations were maintained for 30 minutes, after which an EEG was recorded for 5 minutes; BIS, SEF, and MED were then calculated. Anesthetic depth was evaluated by use of the VAS. Cardiovascular and EEG responses to nociceptive stimuli were evaluated for each anesthetic agent.

RESULTS

BIS decreased significantly for the various concentrations of each anesthetic. At equivalent MACs, BIS values were significantly higher during sevoflurane-induced anesthesia than during isoflurane-induced anesthesia. Values of MED and SEF decreased significantly from basal values to 1 MAC of sevoflurane and isoflurane. For both agents, there was good correlation between VAS scores and BIS values and between VAS scores and SEF values.

CONCLUSIONS

BIS was useful for predicting changes in anesthetic depth at clinical dosages of inhalant anesthetics. Values of BIS, SEF, and MED were significantly higher during anesthesia induced by administration of sevoflurane than during anesthesia induced by administration of isoflurance at equivalent MACs.

OBJECTIVE

Dexmedetomidine, an alpha2-adrenergic agonist, has been described as being able to decrease the demand for both venous and inhalational agents. This study aimed at evaluating the influence of Dexmedetomidine upon sevoflurane end-expiratory concentration (EC) with monitoring the depth of anesthesia.

METHODS

Participated in this study 40 female adult patients, physical status ASA I, submitted to gynecological laparoscopy under general anesthesia maintained with sevoflurane, who were randomly divided in two groups: Group I (n=20), without dexmedetomidine; and Group II (n=20), with dexmedetomidine, in continuous infusion, as follows: Rapid phase (1 microg kg(-1) in 10 min(-1)) 10 minutes before anesthesia induction, followed by a maintenance phase (0.4 microg kg(-1) h(-1)) throughout the surgery. The following parameters were analyzed: BP, HR, BIS, SEF 95%, delta%, suppression rate (SR), rSO2, CE, SpO2 and P(ET)CO2, in the following moments: M1 - before dexmedetomidine or 0.9% saline infusion; M2 - prior to intubation; M3 - following intubation; M4 - before incision; M5 - following incision; M6 - before CO2 inflation; M7 - following CO2 inflation; M8 - 10 min after CO2 inflation; M9 - 10 min after M8; M10 - 20 min after M8; M11 - 30 min after M8; M12 - 40 min after M8; and M13 - at emergence. Time for emergence and hospital discharge were also recorded.

RESULTS

Dexmedetomidine has decreased sevoflurane end-expiratory concentration from M4 to M13 (p<0.05) when comparing Group I and Group II. No clinically significant changes were observed in hemodynamic parameters. Time for emergence in Groups I and II was 11 +/- 0.91 min. and 6.35 +/- 0.93 min., respectively (p < 0.05). Time for hospital discharge was 7.45 +/- 0.69 h in Group I and 8.37 +/- 0.88 h in Group II (p < 0.05).

CONCLUSIONS

Dexmedetomidine was effective in decreasing sevoflurane end-expiratory concentration while maintaining hemodynamic stability without impairing time for hospital discharge, in addition to promoting an earlier emergence.