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Query: UMLS:C0917798 (cerebral ischemia)
 17,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A model of cerebral ischemia by microsphere embolization in the rabbit was monitored with somatosensory evoked potentials by median nerve stimulation (SEPs) and by flash visual evoked potential (VEPs). The degree of SEP alterations paralleled the type of lesions (focal or multifocal ischemia or diffuse oedema). Alterations present at the first hour after ischemia were generally unchanged during the follow-up, which ended at the 24th hour. The prevalence of VEP alterations was low (only 16% in focal ischemia). These results are compared to EEG modifications performed in the same animals.
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PMID:Evoked potentials monitoring of a cerebral focal ischemia model. 175 17

Experience to date in both humans and controlled animal research studies substantiates that several electrophysiology tests and monitoring techniques are safe and efficacious, to a variable degree, as commonly applied in the operating room for the following procedures: EEG or SEP to monitor for cerebral ischemia; ECoG and SEP sensory cortex identification to define the limits of cortical resection; SEP spinal cord monitoring; BAEP and cranial nerve EMG monitoring during posterior fossa procedures; functional localization of cortex with direct cortical stimulation in expert hands; and EMG and compound muscle and nerve action potential measurements of various peripheral nervous system structures. All these techniques need to be applied by a well-trained, knowledgeable physician-neurophysiologist or personnel directly under his or her supervision. Clinical situations need to be chosen carefully, avoiding those in which the nervous system is only at low risk.
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PMID:Assessment: intraoperative neurophysiology. Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. 223 18

To investigate possible approaches to the treatment of neural damage induced by air embolism and other forms of acute cerebral ischemia, somatosensory evoked potentials (SEP's) were measured after cerebral air embolism in the anesthetized cat. Air was introduced into the carotid artery in increments of 0.08 ml until the SEP amplitude was reduced to approximately 10% or less of baseline values. Either a saline or lidocaine infusion was begun 5 minutes after inducing cerebral ischemia. In the saline-treated group, SEP amplitude was reduced to 6.7% +/- 1.6% (mean +/- standard error of the mean) of baseline, with a return to 32.6% +/- 4.7% of baseline over a 2-hour period. In the lidocaine-treated group, SEP amplitude was reduced to 5.9% +/- 1.5%, with a return to 77.3% +/- 6.2% over a 2-hour period. The results suggest that lidocaine administration facilitates the return of neural function after acute cerebral ischemia induced by air embolism.
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PMID:Effect of lidocaine after experimental cerebral ischemia induced by air embolism. 290 92

Somatosensory potentials evoked by median nerve stimulation were recorded bilaterally from the prerolandic and parietal scalp in 36 patients with reversible ischemic attacks in one carotid artery distribution. Responses recorded from the affected and unaffected hemisphere were compared. SEP abnormalities were observed over the affected hemisphere in 22 subjects (61.1%), irrespective of number and/or duration of episodes, and appeared selectively correlated to their clinical features. SEP studies proved to be more sensitive than conventional EEG recordings and are suitable for evaluation of the functional impairment of specific cerebral areas following transient cerebral ischemia. The occurrence of SEP abnormalities in RIA may represent an unfavourable sign, being more frequent in patients with evidence of internal carotid artery disease.
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PMID:Parietal and prerolandic somatosensory evoked responses in carotid artery reversible ischemic attacks (RIA). 343 6

In an attempt to determine the usefulness of evoked potentials as a measure of focal cerebral ischemia, we examined somatosensory evoked potentials (SEP's) and morphological neuronal changes in cats following unilateral middle cerebral artery (MCA) occlusion. Fifteen adult cats underwent transorbital occlusion of the MCA under halothane anesthesia. In seven cats the ipsilateral SEP's were abolished after middle cerebral artery occlusion, and did not show any recovery after 6 hours. The same seven cats showed the greatest area of moderate and severe ischemic neuronal changes, ranging from 21 to 64% (mean 39 +/- 14%) of the total ipsilateral cortical area. The remaining eight cats showed a complete flattening or decreased amplitude of the SEP after occlusion, but demonstrated a considerable recovery in the amplitude of the primary cortical potential during the six hours of the study. All these cats had ischemic areas of less than 15% (mean 9 +/- 3%) of the total ipsilateral cortex. These results demonstrate that the disappearance of the SEP and their failure to recover correlate with the extent and degree of histological cerebral ischemia.
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PMID:Correlation between somatosensory evoked potentials and neuronal ischemic changes following middle cerebral artery occlusion. 381 Jul 20

Somatosensory evoked potentials (SEP's) reflect the integrity of the central neuronal pathway, and as such may be used to assess function that remains during a variety of cerebral insults. To evaluate the natural history and utility of SEP's during experimental cerebral ischemia and infarction, SEP's were measured in 17 adult cats at 24 hours and 1 hour prior to right middle cerebral artery (MCA) occlusion, and again immediately afterward and at either 6 hours (five cats) or 24 hours (six cats) post-occlusion. Before occlusion of the right MCA, the SEP's were identical in the right and left hemispheres. After occlusion, there was a significant slowing of the interpeak latency of the first positive peak (P1) in the right hemisphere (3.53 +/- 0.6 msec before compared to 3.99 +/- 0.6 msec after occlusion, p less than 0.001). Maximal slowing in right hemisphere P1 latency was seen in those animals in which the stroke extended into the thalamus (4.38 +/- 0.1 msec). This was significantly slower than left hemisphere values (3.92 +/- 0.32 msec, p less than 0.01). The ipsilateral cortical components of the SEP's, the second positive peak (P2), and the major negative deflection (MN) were slowed in all cats immediately after right MCA occlusion compared to preocclusion measurements (p less than 0.001). Severe infarcts in the mid-suprasylvian and posterior ectosylvian gyri (including the somatosensory cortex) resulted in a greater slowing of the latency of MN compared to less severe infarcts in that region (20.6 +/- 3.9 msec versus 16.4 +/- 1.1 msec, p less than 0.05). There was a precipitous decrease in the amplitude or voltage of the ipsilateral P2-MN complex immediately after occlusion (5.32 +/- 0.4 microV before compared to 0.98 +/- 0.3 microV after occlusion, p less than 0.001). Therefore, the central latencies and cortical amplitudes of the SEP's are sensitive experimental tools as indicators of the onset and extent of a cerebral ischemic insult.
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PMID:Somatosensory evoked potentials as a measure of experimental cerebral ischemia. 396 67

The effect of intravenous administration of diltiazem on cerebral circulation and brain function were studied in animals. Diltiazem, at a dose of 150 micrograms/kg BW, was administered intravenously over a period of 5 minutes beginning 30 minutes after ligation of the right brachiocephalic artery in 9 cats in order to investigate its effects in the acute stage of cerebral ischemia. In 5 animals, mean arterial blood pressure was recorded and blood flow in the basilar artery was measured transdurally by use of an ultrasonic Doppler flow-meter. Mean arterial blood pressure began to elevate immediately after ligation of the right brachiocephalic artery, but the degree of elevation was minimal. It began to fall during diltiazem injection and returned to the preadministration value 30 minutes after injection. Basilar artery flow decreased slightly during injection of diltiazem, but began to increase after completion of injection. The increase relative to the preadministration value was 62 +/- 31% 10 minutes after injection, 88 +/- 38% 20 minutes after, and 24 +/- 53% 30 minutes after. The short latency somatosensory evoked potentials (short latency SEP) recorded in the other 2 animals showed no noticeable change either in amplitude or latency during the same procedures. In 1 of 2 animals in which brainstem auditory evoked potentials (BAEP) were monitored, the latency of peak IV increased after ligation of the right brachiocephalic artery, and decreased 20 minutes after injection of diltiazem.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Effect of intravenous administration of diltiazem on cerebral blood flow and brain function]. 404 Dec 87

In order to evaluate the suitability of transcranial Doppler sonography as an intraoperative monitor in carotid surgery, we compared measurements of mean blood flow velocity in the ipsilateral middle cerebral artery with the cortical response of somatosensory evoked potentials in a prospective study of 176 carotid operations. SEP recording was readily feasible during all procedures and by means of SEP loss all patients at risk for critical cross-clamp related cerebral ischemia were reliably identified. In contrast, TCD could not be used for assessment of cerebral hemodynamics in more than 40% of patients. What is more, in high risk patients with intraoperative loss of SEP, TCD could not be performed in 74% of cases. This high rate of failure limits the usefulness of TCD as an intraoperative monitor and detracts from the additional benefit of identifying cerebral embolism and hyperperfusion as potential causes of neurological deficits. In contrast to SEP recording, TCD cannot be recommended as a routine monitor in carotid surgery.
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PMID:[Neuromonitoring in carotid surgery: possibilities and limits of transcranial Doppler ultrasound]. 781 15

As with other methods long used in intensive care units (ICU) and operating rooms (OR), the goal of neuroscience ICU continuous EEG (NICU-CEEG) and evoked potential (NICU-EP) monitoring is to extend our powers of observation to detect abnormalities at a reversible stage. EEG is an appropriate monitoring tool because it is linked to cerebral metabolism, is sensitive to ischemia and hypoxemia, correlates with cerebral topography, detects neuronal dysfunction at a reversible stage, and is the best method for detecting seizure activity. When applied systematically, it can impact medical decision-making in 81% of monitored patients. It is useful in monitoring precarious cerebral perfusion at the bedside, and it has revealed that nonconvulsive seizures, undetectable otherwise, occur in 34% of NICU patients. In convulsive status epilepticus, NICU-CEEG can help avoid undertreatment and overtreatment. In comatose patients, it can provide useful prognostic information as well as detect potentially treatable causes. Traditional impediments to its application are yielding to technological advances and educational efforts. Real-time digitized EEG in particular has been a major advance. Within limits, somatosensory evoked potential monitoring (ICU-SEP) is useful in the prognosis of coma, but it is less helpful in monitoring focal cerebral ischemia. Brainstem auditory evoked potential monitoring has a relatively restricted role in the NICU but is helpful in distinguishing structural from nonstructural causes of coma and can supplement ICU-SEP in predicting outcome.
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PMID:Continuous EEG and evoked potential monitoring in the neuroscience intensive care unit. 830 43

Clamping ischaemia is responsible for the 20-30% of the neurological complications during carotid surgery. It is impossible at present to determine preoperatively for certainty the patients who are at risk and the ones who are not at risk for clamping ischemia. Intraoperative monitoring is mandatory in all the cases to point out cerebral ischemia and to prevent neurological deficit with an adequate brain protection. Methods used to predict brain ischaemia include local anesthesia, EEG, SEP, stump pressure measurement, transcranial doppler, regional cerebral blood flow measurement and evaluation of venous blood gases from the internal jugular vein. Local anesthesia is a safe and simple method of assessing cerebral ischemia during carotid clamping but has some limits particularly in case of brain ischaemia for the technical difficulties to install an indwelling shunt in an awake and often troubled patient. Moreover the only possibility of cerebral protection under local anesthesia is an increase in systemic blood pressure with a resulting growth in cardiac morbidity and mortality. For these reasons operation should be performed under general anesthesia to assure a better farmacogical brain protection when preoperative evaluation demonstrates a reduction of cerebral vasoreactivity, with a consequent high risk of clamping ischemia. At present EEG is one of the most used technique of cerebral monitoring under general anesthesia with a sensibility and specificity in the diagnosis of brain ischaemia that is about 90%. The best cerebral protection is obtained with a selective shunting. Burst suppression, with high dose thiopentone, has recently demonstrated its reliability alone or in association with an indwelling shunt in patients at high risk for clamping ischaemia. Of course a systematic cerebral protection together with an accurate control of the blood pressure is necessary in all the patients. This behaviour allowed us to obtain good results in the last 500 patients with a morbidity and mortality respectively of 1% and 1.6% with no significant differences between patients who tolerated carotid clamping and those with clamping ischaemia.
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PMID:[Update on cerebral monitoring and protective methods]. 949 73


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