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The study reports the results of monitoring the depth of anesthesia with BIS technology in 456 neurosurgical patients with different neurosurgical pathology: sub- and supratentorial tumors, aneurisms, arteriovenous malformations, spinal pathology, etc. BIS reflects hypnotic state of the brain during anesthesia in almost all the cases, except for bifon-tal surgical approach when sensor placement is impossible. BIS monitoring of the depth of anesthesia is most advantageous in the following cases: epilepsy surgery, spine surgery with neurophysiological monitoring, awake craniotomy, severe cardiovascular pathology, massive blood loss, neurosurgery in pregnant patients.

The analysis of the results of bilateral monitoring of the depth of anesthesia in 22 patients with neurosurgical pathology of the posterior cranial fossa using the technique bispectral index (BIS). The results showed that more than half of the observations (at 19 and 22 patients) during the main phase of the operation (removal of the tumor) were observed differences in the BIS index values between the right and left side. In 1/3 of patients, these differences were driven by higher values of BIS on the side of surgery. By the end of removal of the tumor and, particularly, by the end of surgery there was a complete alignment of values of the BIS on the right and left.

The paper describes an unusual clinical case. During a neurosurgical operation (removal of parastem tumor (neuroma) on the right side), bilateral registration of the bispectal index (BSI) in order to monitor a hypnotic component of anesthesia showed that the tumor removal stage was marked by a paradoxical reaction of the BSI as an increase in its values up to 70-80% (corresponds to the patient's emergence) on the right, ipsilaterally, with the preserved low BSI values on the left--30-40%. Possible explanations of the observed are considered.

The paper discusses pre- and intraoperative application of different guiding techniques (frameless neuronavigation, fMRI, electrophysiological monitoring). We performed comparative analysis of different combinations of these methods. 74 patients with intracerebral tumors involving eloquent areas (sensorimotor cortex in 56 and speech zones in 18) were operated. In 9 cases 'awake surgery' was applied. We found that frameless navigation combined with brain mapping allows to optimize planning of surgical approach and to decrease postoperative neurological deficit. Also in certain cases 'awake craniotomy' can be replaced by fMRI and neuronavigation.

The paper analyzes the efficiency of multimodal neuromonitoring (transcranial ultrasound Doppler study, cerebral oximetry, and electroencephalography) for the early intraoperative diagnosis of cerebral ischemia in patients during carotid reparative interventions. On the basis of the findings, the authors have developed a diagnostic algorithm of cerebral ischemia in this group of patients at surgery. Its basis is Doppler monitoring; the data of cerebral oximetry and EEG are taken into account with the borderline values of linear blood flow velocity. The diagnosis of cerebral ischemia during operation on the carotids is a direct indication for the usage of a temporary intraluminal shunt. During carotid reconstructive interventions made under general anesthesia, the application of multimodal neuromonitoring is a valid approach and it should make the most use.

A total of 144 neurosurgical interventions were performed in 138 patients with cerebrovascular diseases (arterial aneurysms in the acute and cold periods after a subarachnoidal hemorrhage, arteriovenous malformations, and carotid-cavernous anastomoses). Intraoperative monitoring of regional saturation of hemoglobin with oxygen in the blood flowing in brain vessels was carried out by a cerebral oximeter INVOS 3100 for early intraoperative diagnosis of cerebral ischemia. This paper analyzes factors affecting changes in rSO2 parameter during surgery and discusses the prognostic significance of the detected shifts. Various factors affected the time course of rSO2: decrease in AP within the framework of controlled arterial hypotone and other causes, insertion of autosupported retractor spatulae, temporary clipping and embolism of cerebral arteries, vasospasm, aneurysm rupture, dissection of arteriovenous malformation, etc. Any intraoperative shift of rSO2 surpassing 5%, no matter of what direction (decrease or increase), deserves special attention of anesthesiologist, as it indicates development of cerebral ischemia with a high degree of probability.

Simultaneous monitoring by cerebral oximetry and electrophysiological methods (electroencephalography and electrocorticography) was performed in 21 patients with arterial cerebral aneurysms during direct intracranial interventions, endovascular interventions, and Matas' test. Electrophysiological methods are sufficiently accurate indicators of cerebral ischemia even at a functionally reversible level. The results of simultaneous monitoring were similar in 80% cases, indicating cerebral ischemia even at functionally reversible level, which was detected by both electrophysiological methods and cerebral oximetry. Variously directed shifts were detected in 4 cases; the causes are discussed. Cerebral oximetry detects cerebral ischemia with a sensitivity similar to that of electrophysiological methods. The method does not depend on temperature or anesthetics. Limitations of the method are due to its local application.

The studies were carried out in 33 patients with intrastem volumetric tumors. In 6 patients the monitoring was impossible because of technological problems. Somatosensory evoked potentials (SSEP) were recorded in 10 and acoustic stem evoked potentials (ASEP) in 18 out of 27 patients and the findings correlated to changes in the neurological status on day 1 postoperation. In 3 out of 9 patients operated on in a sitting posture SSEP monitoring during the main stage of the operation became impossible because the response disappeared due to an air layer above the parietal cortex. Transitory or constant changes in SSEP at the stage of tumor removal were detected in 5 patients. In 9 patients intraoperative changes in ASEP were recorded. False-positive results of ASEP monitoring were obtained in 4 cases. In 2 cases a discrepancy between intraoperative changes of SSEP and the postoperative neurologic deficit were detected. The authors discuss the technological and methodological problems of intraoperative monitoring of evoked potentials and approaches to solution of these problems.

Visual EEG monitoring and EEG monitoring using a special "Neuro-2" monitor controlling the changes in quantitative EEG parameters (power range and coherence) have been used during surgery in 42 patients with arterial aneurysms of brain vessels performed in conditions of profound controlled arterial hypotension. Computer processing facilitates EEG analysis and reveals the most early signs of the developing cerebral ischemia on the basis of specific changes in power ranges and coherence.

In 43 patients serial SSER recordings were made during operations for the clipping of arterial aneurysms of cerebral vessels performed under controlled arterial hypotension. SSER recordings during the preliminary phase of the operation showed an average decrease in the response amplitude of 20% during trepanation and a reduction (by 23% of the initial value) during the phase of arterial hypotension. The response recovered to 84% of its initial level by the moment of the beginning of the operation. There was no statistically significant relationship between serial SSER parameter values during arterial pressure reduction and the duration or degree of hypotension. The results testify to the higher information content of such SSER parameters as the amplitude of the first positive complex, as compared with latency criteria and in particular the CCT. It has also been found that a significant increase in the information value of the SSER for the evaluation of ischemia effect on the brain function may be obtained by synchronous stimulation of both arms and registration of cortical responses from both hemispheres.