Surgical Complexity and Complications: The Need for a Common Language.

BACKGROUND: Quality measurement and outcome assessment have recently caught an attention of the neurosurgical community, but lack of standardized definitions and methodology significantly complicates these tasks. OBJECTIVE: To identify a uniform definition of neurosurgical complications, to classify them according to etiology, and to evaluate them comprehensively in cases of intracranial tumor removal in order to establish a new, easy, and practical grading system capable of predicting the risk of postoperative clinical worsening of the patient condition. METHODS: A retrospective analysis was conducted on all elective surgeries directed at removal of intracranial tumor in the authors' institution during 2-year study period. All sociodemographic, clinical, and surgical factors were extracted from prospectively compiled comprehensive patient registry. Data on all complications, defined as any deviation from the ideal postoperative course occurring within 30 days of the procedure, were collected with consideration of the required treatment and etiology. A logistic regression model was created for identification of independent factors associated with worsening of the Karnofsky Performance Scale (KPS) score at discharge after surgery in comparison with preoperative period. For each identified statistically significant independent predictor of the postoperative worsening, corresponding score was defined, and grading system, subsequently named Milan Complexity Scale (MCS), was formed. RESULTS: Overall, 746 cases of surgeries for removal of intracranial tumor were analyzed. Postoperative complications of any kind were observed in 311 patients (41.7%). In 223 cases (29.9%), worsening of the KPS score at the time of discharge in comparison with preoperative period was noted. It was independently associated with 5 predictive factors-major brain vessel manipulation, surgery in the posterior fossa, cranial nerve manipulation, surgery in the eloquent area, tumor size >4 cm-which comprised MCS with a range of the total score from 0 to 8 (higher score indicates more complex clinical situations). Patients who demonstrated KPS worsening after surgery had significantly higher total MCS scores in comparison with individuals whose clinical status at discharge was improved or unchanged (3.24 ± 1.55 versus 1.47 ± 1.58; P < 0.001). CONCLUSION: It is reasonable to define neurosurgical complication as any deviation from the ideal postoperative course occurring within 30 days of the procedure. Suggested MCS allows for standardized assessment of surgical complexity before intervention and for estimating the risk of clinical worsening after removal of intracranial tumor. Collection of data on surgical complexity, occurrence of complications, and postoperative outcomes, using standardized prospectively maintained comprehensive patient registries seems very important for quality measurement and should be attained in all neurosurgical centers.

Early de-tethering: analysis of urological and clinical consequences in a series of 40 children.

PURPOSE: Early de-tethering procedures are performed on spinal dysraphisms to prevent neuro-urological deterioration caused by growth. Partial lipoma removal may cause delayed deterioration by re-tethering, while complete removal may increase the risk of postoperative worsening. The present study evaluates the risk of postoperative deterioration and the protective potential of intraoperative neurophysiological monitoring (IOM), with a special reference to the conus lipomas treated with the radical approach. METHODS: Forty toddlers (< 24 months) underwent complete perioperative neurological and urological assessment, including urodynamic study (UDS). The dysraphisms were subgrouped according to Pang's classification. IOM was applied in all patients: transcranial motor evoked potentials (tMep) combined with mapping were recorded in all cases while bulbocavernosus reflex (BCR) was evaluable just in 7 cases. RESULTS: At preoperative evaluation, 11 children already had UDS impairment and 2 had motor disturbances before neurosurgery. At 1-month follow-up, preoperative motor disturbances were stable, 7/11 UDS alterations normalized, and the remaining 4 were stable. At 6-month follow-up, all motor deficits and 8/11 preoperative UDS alterations had improved. Unfortunately, 7 children with previously normal UDS experienced a new impairment after surgery: 2/7 normalized while 5/7 did not recover. This postoperative permanent urodynamic impairment occurred in 4 chaotic lipoma (CLchaos) and in one terminal myelocystocele (TMC) that means a surgical deterioration rate of 22% for the high risk cases. CONCLUSIONS: This small highly selected series confirms that early de-tethering may stop or revert the spontaneous neuro-urological deterioration: in fact, preoperative UDS impairment was frequent (27.5%) and improved in all the low surgical risk cases (limited dorsal myeloschisis, filar, transitional and dorsal lipomas). On the contrary, in CLchaos and TMC, early de-tethering was unable to revert preoperative UDS impairment, and radical surgery carried a high risk of new neuro-urological deterioration directly caused by the operation. In our experience, IOM had a protective role for motor functions, while it was less effective for the neuro-urological ones, probably due to the anesthesiology regimens applied. In conclusion, among the dysraphisms, CLchoas proved to be the worst enemy that often camouflages at MRI. Affording it without all possible IOM weapons carries a high risk to harm the patient.

Propofol and sevoflurane affect intra-operative memory formation of words differently: A prospective cohort study.

BACKGROUND: Memory priming seems possible even during apparently adequate anaesthesia. However, the effects of different anaesthetics and type of stimuli, by virtue of their specific neural underpinnings, have not been considered. OBJECTIVE: To determine if intra-operative implicit memory is affected by the type of anaesthesia (propofol or sevoflurane) or by the type of stimuli (abstract or concrete words). DESIGN: Two consecutive, randomised controlled experiments. SETTING: Neurological institute in Milan, Italy. PATIENTS: Forty-three patients undergoing anaesthesia with propofol (experiment 1) and 32 patients undergoing anaesthesia with sevoflurane (experiment 2). Patients were ASA I or II, age 18 to 65 years, native Italian speakers, right-handed and without any condition affecting memory or hearing. INTERVENTION: During anaesthesia, the patients heard a list of either concrete or abstract words or no words at all (controls). Explicit memory was tested with an explicit recall task and the Brice Interview; implicit memory was assessed through a word stem completion test. OUTCOME MEASURES: The number of explicitly recalled words, positivity to the Brice Interview, the proportion of target and nontarget hits, and a derived implicit memory score. RESULTS: With propofol, the proportion of target hits was significantly greater than the proportion of nontarget hits for the concrete word experimental group (P = 0.018). The implicit memory score of the concrete word experimental group was significantly higher than the score of both the abstract word experimental group (P  = 0.000) and the concrete word control group (P = 0.023). With sevoflurane, the proportion of target hits was significantly higher than the proportion of nontarget hits for the abstract word experimental group only (P = 0.027). No patients had a BIS above 60 and no one could recall intra-operative events or words. CONCLUSION: Intra-operative memory for words can form during apparently adequate BIS-guided anaesthesia but is modified by propofol or sevoflurane acting on different brain targets. Further studies on larger samples and using neuroimaging techniques are needed. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT03727464.

A simplified math approach to predict ICU beds and mortality rate for hospital emergency planning under Covid-19 pandemic.

The different stages of Covid-19 pandemic can be described by two key-variables: ICU patients and deaths in hospitals. We propose simple models that can be used by medical doctors and decision makers to predict the trends on both short-term and long-term horizons. Daily updates of the models with real data allow forecasting some key indicators for decision-making (an Excel file in the Supplemental material allows computing them). These are beds allocation, residence time, doubling time, rate of renewal, maximum daily rate of change (positive/negative), halfway points, maximum plateaus, asymptotic conditions, and dates and time intervals when some key thresholds are overtaken. Doubling time of ICU beds for Covid-19 emergency can be as low as 2-3 days at the outbreak of the pandemic. The models allow identifying the possible departure of the phenomenon from the predicted trend and thus can play the role of early warning systems and describe further outbreaks.

Predicting functional impairment in brain tumor surgery: the Big Five and the Milan Complexity Scale.

OBJECT The Milan Complexity Scale-a new practical grading scale designed to estimate the risk of neurological clinical worsening after performing surgery for tumor removal-is presented. METHODS A retrospective study was conducted on all elective consecutive surgical procedures for tumor resection between January 2012 and December 2014 at the Second Division of Neurosurgery at Fondazione IRCCS Istituto Neurologico Carlo Besta of Milan. A prospective database dedicated to reporting complications and all clinical and radiological data was retrospectively reviewed. The Karnofsky Performance Scale (KPS) was used to classify each patient's health status. Complications were divided into major and minor and recorded based on etiology and required treatment. A logistic regression model was used to identify possible predictors of clinical worsening after surgery in terms of changes between the preoperative and discharge KPS scores. Statistically significant predictors were rated based on their odds ratios in order to build an ad hoc complexity scale. For each patient, a corresponding total score was calculated, and ANOVA was performed to compare the mean total scores between the improved/unchanged and worsened patients. Relative risk (RR) and chi-square statistics were employed to provide the risk of worsening after surgery for each total score. RESULTS The case series was composed of 746 patients (53.2% female; mean age 51.3 ± 17.1). The most common tumors were meningiomas (28.6%) and glioblastomas (24.1%). The mortality rate was 0.94%, the major complication rate was 9.1%, and the minor complication rate was 32.6%. Of 746 patients, 523 (70.1%) patients improved or remained unchanged, and 223 (29.9%) patients worsened. The following factors were found to be statistically significant predictors of the change in KPS scores: tumor size larger than 4 cm, cranial nerve manipulation, major brain vessel manipulation, posterior fossa location, and eloquent area involvement (Nagelkerke R(2) = 0.286). A grading scale was obtained with scores ranging between 0 and 8. Worsened patients showed mean total scores that were significantly higher than the improved/unchanged scores (3.24 ± 1.55 vs 1.47 ± 1.58; p < 0.001). Finally, a grid was developed to show the risk of worsening after surgery for each total score: scores higher than 3 are suggestive of worse clinical outcome. CONCLUSIONS Through the evaluation of the 5 aforementioned parameters-the Big Five-the Milan Complexity Scale enables neurosurgeons to estimate the risk of a negative clinical course after brain tumor surgery and share these data with the patient. Furthermore, the Milan Complexity Scale could be used for research and educational purposes and better health system management.

Deep brain stimulation in critical care conditions.

Some neurological conditions require admission to an intensive care unit (ICU) where deep sedation and mechanical ventilation are administered to improve the patient's condition. Nevertheless, these treatments are not always helpful in disease control. At this stage, deep brain stimulation (DBS) could become a viable alternative in the treatment of critical neurological conditions with long-lasting clinical benefit. The value of deep brain stimulation has been investigated in the treatment of patients who had undergone surgical electrode implants as an emergency procedure to treat acute life-threatening conditions requiring admission to neurological ICU (NICU). A before-and-after perspective study was examined of seven patients who were treated with DBS for status dystonicus (SD) and post-stroke severe hemiballismus. Bilateral globus pallidus internus (GPi) DBS was performed in five SD patients and unilateral ventralis oralis anterior and posterior (Voa/Vop) nucleus of the thalamus DBS in two post-stroke hemiballismus patients. Bilateral GPi-DBS allowed SD resolution in a time lapse varying from 1 week to 3 months. No clear improvements compared to the baseline clinical condition were observed. Unilateral Voa/Vop-DBS intervention controlled hemiballismus after 10 h, and the patient was discharged in 2 days. The other patient was transferred from the NICU to the neurosurgery ward after 13 days. No surgical complications were observed in any of the above procedures. Neurostimulation procedures could represent a valuable choice in critical care conditions, when involuntary movements are continuous, life-threatening and refractory to intensive care procedures. DBS is feasible, safe and effective in selected cases.

Is a neutral head position safer than 45-degree neck rotation during ultrasound-guided internal jugular vein cannulation? Results of a randomized controlled clinical trial.

BACKGROUND: The optimal degree of neck rotation during internal jugular vein (IJV) cannulation remains undetermined because previous studies suggested using sonography, but without puncturing the vein. We assessed whether a neutral position (NP) of the head (0 degrees) during ultrasound-guided cannulation of the IJV was safer than rotating the neck to 45 degrees head turned. The effect of these 2 positions during ultrasound-guided cannulation on major complications was the primary outcome. Overall complications, venous access time, and perception of difficulty during the procedure were also evaluated. METHODS: A prospective, randomized, controlled, nonblinded study was conducted in a tertiary neurosurgical hospital. Patients undergoing major elective neurosurgical procedures requiring a central venous line were randomly allocated to 2 groups; ultrasound-guided cannulation of the IJV was then performed using an out-of-plane orientation. RESULTS: One thousand four hundred twenty-four patients were evaluated, but 92 were excluded; 670 were allocated to the head turned group and 662 to the NP group. Cannulation was 100% successful. Demographic data were similar in the 2 groups except for IJV positions. There were only 10 major complications: 6 in the 0-degree NP group and 4 in the 45-degree head turned group. The frequency of these complications was not different between the 2 groups. The overall complication rate was 13%, and was higher in women, in patients with ASA physical status ≥II, and in patients with a smaller diameter vein, or when the vein was located deeper and lateral or in the anterolateral position. An increased venous access time was associated with an increased rate of overall complications. The perception of difficulty performing the procedure with the head placed in the 2 positions was not statistically different in either group. CONCLUSION: A head NP was as safe as a 45-degree neck rotation during ultrasound-guided IJV cannulation with regard to both major and minor complications, and venous access time was similar. Ultrasound guidance helps determine optimal head rotation for IJV cannulation.

Application of an aviation model of incident reporting and investigation to the neurosurgical scenario: method and preliminary data.

OBJECT: Incident reporting systems are universally recognized as important tools for quality improvement in all complex adaptive systems, including the operating room. Nevertheless, introducing a safety culture among neurosurgeons is a slow process, and few studies are available in the literature regarding the implementation of an incident reporting system within a neurosurgical department. The authors describe the institution of an aviation model of incident reporting and investigation in neurosurgery, focusing on the method they have used and presenting some preliminary results. METHODS: In 2010, the Inpatient Safety On-Board project was developed through cooperation between a team of human factor and safety specialists with aviation backgrounds (DgSky team) and the general manager of the Fondazione Istituto Neurologico Carlo Besta. In 2011, after specific training in safety culture, the authors implemented an aviation-derived prototype of incident reporting within the Department of Neurosurgery. They then developed an experimental protocol to track, analyze, and categorize any near misses that happened in the operating room. This project officially started in January 2012, when a dedicated team of assessors was established. All members of the neurosurgical department were asked to report near misses on a voluntary, confidential, and protected form (Patient Incident Reporting System form, Besta Safety Management Programme). Reports were entered into an online database and analyzed by a dedicated team of assessors with the help of a facilitator, and an aviation-derived root cause analysis was performed. RESULTS: Since January 2012, 14 near misses were analyzed and classified. The near-miss contributing factors were mainly related to human factors (9 of 14 cases), technology (1 of 14 cases), organizational factors (3 of 14 cases), or procedural factors (1 of 14 cases). CONCLUSIONS: Implementing an incident reporting system is quite demanding; the process should involve all of the people who work within the environment under study. Persistence and strong commitment are required to enact the culture change essential in shifting from a paradigm of infallible operators to the philosophy of errare humanum est. For this paradigm shift to be successful, contributions from aviation and human factor experts are critical.

Effects of direct laryngoscopy versus Glidescope videolaryngoscopy on subjective and objective measures of cognitive workload: an in-vivo randomized trial.

BACKGROUND: Laryngoscopy and tracheal intubation are associated with high operators' workload, which potentially causes lower performance and risk of errors. Measuring anesthesiologists' mental workload during instrumental procedures allows to test the usability of the devices and, by managing operators' workload, improve clinical decision making. The aim of this study was to investigate the differences in subjective and objective cognitive workload between videolaryngoscopy with hyperangulated blade (Glidescope) vs. direct laryngoscopy in a real clinical setting. METHODS: Fourteen anesthesiologists were enrolled and performed three intubations for each device, a Glidescope videolaryngoscope (Verathon Inc., Schiltigheim, France) and a Macintosh (Apple Inc., Cupertino, CA, USA) direct laryngoscope, in a random order. The subjective workload was assessed with the NASA Task Load Index questionnaire right after intubation and reaction times to a secondary task were recorded during laryngoscopy and intubation as an objective measure of workload. RESULTS: The overall perceived workload (P<0.001) and the subscales of physical demand (P<0.001) and effort (P<0.001) were lower during Glidescope than during Macintosh laryngoscopy. Reaction times were faster during Glidescope than during Macintosh laryngoscopy (P<0.014). A significant positive correlation was found between reaction times and the overall perceived workload (P<0.001). CONCLUSIONS: A videolaryngoscope with hyperangluated blade used in a real clinical scenario of elective surgery significantly reduced both subjective and objective workload compared to a direct laryngoscope. Physical demand and effort were the key components in reducing operators' mental workload. Therefore, the expert use of a videolaryngoscope with hyperangulated blade constitutes an ergonomic option that could limit operators' workload and improve patients' safety and operators' well-being.

Reactivation of COVID-19 in a neurosurgical patient with early neuropsychiatric presentation. Does seroconversion mean immunity?

BACKGROUND: In the aftermath of COVID-19 outbreak, there is a strong need to find strategies to monitor SARSCoV-2 transmission. While the application of screening techniques plays a major role to this end, there is evidence challenging the real significance of seroconversion. We reported a case of COVID-19 reactivation associated with a neurosurgical operation with early neuropsychiatric involvement presumably promoted by olfactory and gustatory impairment in the first infection. CASE DESCRIPTIO: A 57-year-old man was referred for a 2-month history of progressive development of imbalance, dizziness, and vomiting. Magnetic resonance imaging showed two bilateral hemispheric cerebellar lesions. In line with our triage protocol, the patient underwent a nasopharyngeal swab for RNA of SARS-CoV-2 detection, which resulted positive. Of note, the patient had reported in the previous month hyposmia and hypogeusia. After a period of 14 days, three new swabs were performed with negative results, leading the way to surgery. In the early post-operative period, the patient manifested acute onset of psychotic symptoms with hyperactive delirium, followed by fever and acute respiratory failure. A chest computed tomography revealed a specific pattern of ground-glass opacities in the lower lobes bilaterally, suggesting a viral pneumonia. Serological tests demonstrated the seroconversion and a new nasopharyngeal swab confirmed SARS-CoV-2 infection. CONCLUSION: Our report highlights the importance of comprehensive screening assessments in sensitive cases highly susceptible to COVID-19 recurrence.

Analyzing the Loss and the Recovery of Consciousness: Functional Connectivity Patterns and Changes in Heart Rate Variability During Propofol-Induced Anesthesia.

The analysis of the central and the autonomic nervous systems (CNS, ANS) activities during general anesthesia (GA) provides fundamental information for the study of neural processes that support alterations of the consciousness level. In the present pilot study, we analyzed EEG signals and the heart rate (HR) variability (HRV) in a sample of 11 patients undergoing spinal surgery to investigate their CNS and ANS activities during GA obtained with propofol administration. Data were analyzed during different stages of GA: baseline, the first period of anesthetic induction, the period before the loss of consciousness, the first period after propofol discontinuation, and the period before the recovery of consciousness (ROC). In EEG spectral analysis, we found a decrease in posterior alpha and beta power in all cortical areas observed, except the occipital ones, and an increase in delta power, mainly during the induction phase. In EEG connectivity analysis, we found a significant increase of local efficiency index in alpha and delta bands between baseline and loss of consciousness as well as between baseline and ROC in delta band only and a significant reduction of the characteristic path length in alpha band between the baseline and ROC. Moreover, connectivity results showed that in the alpha band there was mainly a progressive increase in the number and in the strength of incoming connections in the frontal region, while in the beta band the parietal region showed mainly a significant increase in the number and in the strength of outcoming connections values. The HRV analysis showed that the induction of anesthesia with propofol was associated with a progressive decrease in complexity and a consequent increase in the regularity indexes and that the anesthetic procedure determined bradycardia which was accompanied by an increase in cardiac sympathetic modulation and a decrease in cardiac parasympathetic modulation during the induction. Overall, the results of this pilot study showed as propofol-induced anesthesia caused modifications on EEG signal, leading to a "rebalance" between long and short-range cortical connections, and had a direct effect on the cardiac system. Our data suggest interesting perspectives for the interactions between the central and autonomic nervous systems for the modulation of the consciousness level.

Erythropoietin in amyotrophic lateral sclerosis: a pilot, randomized, double-blind, placebo-controlled study of safety and tolerability.

Preclinical studies demonstrated that erythropoietin is neuroprotective in different models of peripheral and central nervous system diseases. We investigated safety and tolerability of recombinant human erythropoietin (rhEPO) in amyotrophic lateral sclerosis (ALS). We performed a phase II double-blind, randomized, placebo-controlled study. After screening, 23 patients were randomly assigned to rhEPO or placebo arm. Patients were examined during a six-month lead-in period, and then they received fortnightly either 40,000 units of rhEPO or placebo for 24 months. Primary outcomes were adverse events, safety, and death or tracheotomy. Treatment was safe and well tolerated. One patient in the rhEPO arm dropped out for a superficial phlebitis. Median values of haematocrit, haemoglobin, red cells, and reticulocytes were non-significantly higher in rhEPO than placebo arm. Haemoglobin did not increase >1 g/dl between subsequent doses. Anti-rhEPO antibodies were not detected. Survival and slope of ALSFRS-R curves did not significantly differ between treatment groups. RhEPO treatment was safe and well tolerated in ALS patients. Our results suggest that larger studies are warranted to confirm safety of treatment and to investigate different dose schedule and efficacy.

Prognostic factors for survival in 676 consecutive patients with newly diagnosed primary glioblastoma.

Reliable data on large cohorts of patients with glioblastoma are needed because such studies differ importantly from trials that have a strong bias toward the recruitment of younger patients with a higher performance status. We analyzed the outcome of 676 patients with histologically confirmed newly diagnosed glioblastoma who were treated consecutively at a single institution over a 7-year period (1997-2003) with follow-up to April 30, 2006. Survival probabilities were 57% at 1 year, 16% at 2 years, and 7% at 3 years. Progression-free survival was 15% at 1 year. Prolongation of survival was significantly associated with surgery in patients with a good performance status, whatever the patient's age, with an adjusted hazard ratio of 0.55 (p < 0.001) or a 45% relative decrease in the risk of death. Radiotherapy and chemotherapy improved survival, with adjusted hazard ratios of 0.61 (p = 0.001) and 0.89 (p = 0.04), respectively, regardless of age, performance status, or residual tumor volume. Recurrence occurred in 99% of patients throughout the follow-up. Reoperation was performed in one-fourth of these patients but was not effective, whether performed within 9 months (hazard ratio, 0.86; p = 0.256) or after 9 months (hazard ratio, 0.98; p = 0.860) of initial surgery, whereas second-line chemotherapy with procarbazine, lomustine, and vincristine (PCV) or with temozolomide improved survival (hazard ratio, 0.77; p = 0.008). Surgery followed by radiotherapy and chemotherapy should be considered in all patients with glioblastoma, and these treatments should not be withheld because of increasing age alone. The benefit of second surgery at recurrence is uncertain, and new trials are needed to assess its effectiveness. Chemotherapy with PCV or temozolomide seems to be a reasonable option at tumor recurrence.

Presurgical functional MR imaging of language and motor functions: validation with intraoperative electrocortical mapping.

PURPOSE: To prospectively determine the sensitivity and specificity of functional magnetic resonance (MR) imaging for mapping language and motor functions in patients with a focal mass adjacent to eloquent cortex, by using intraoperative electrocortical mapping (ECM) as the reference standard. MATERIALS AND METHODS: The ethics committee approved the study, and patients gave written informed consent. Thirty-four consecutive patients (16 women, 18 men; mean age, 43.2 years) were included who met the following three criteria: They had a focal mass in or adjacent to eloquent cortex of the language or motor system, they had the ability to perform the functional MR imaging task, and they had to undergo surgery with intraoperative ECM. Functional MR imaging with verb generation (n = 17) or finger tapping of the contralateral hand (n = 17) was performed at 1.5 T with a block design and an echo-planar gradient-echo T2*-weighted sequence. Cortex essential for language or hand motor functions was mapped with ECM. A site-by-site comparison between functional MR imaging and ECM was performed with the aid of a neuronavigational device. Sensitivity and specificity were calculated according to task performed, histopathologic findings, and tumor grade. Exact 95% confidence intervals were calculated for each sensitivity and specificity value. RESULTS: For 34 consecutive patients, there were 28 with gliomas, two with metastases, one with meningioma, and three with cavernous angiomas. A total of 251 cortical sites were tested with ECM; overall functional MR imaging sensitivity and specificity were 83% and 82%, respectively. Sensitivity (65%) was lower and specificity (93%) was higher in World Health Organization grade IV gliomas compared with grade II (sensitivity, 93%; specificity, 79%) and III (sensitivity, 93%; specificity, 76%) gliomas. At 3 months after surgery, language proficiency was unchanged in 15 patients; functionality of the contralateral arm was unchanged in 14 patients and improved in one patient. CONCLUSION: Functional MR imaging is a sensitive and specific method for mapping language and motor functions.

Motor Evoked Potentials and Bispectral Index-Guided Anaesthesia in Image-Guided Mini-Invasive Neurosurgery of Supratentorial Tumors Nearby the Cortico-Spinal Tract.

AIM: To describe and evaluate the anaesthesiological regimen used in neurophysiologically monitored image-guided mini-invasive neurosurgery. MATERIAL AND METHODS: Twenty-four patients underwent elective surgery under general anaesthesia that was administered through Target Controlled Infusion (TCI) for effect-site concentration (Ce) of Propofol and Remifentanil, targeting the Bispectral Index (BIS) in the 40-60 intervals. The stimulating intensity of transcranial motor evoked potentials (tMEP), BIS, Propofol and Remifentanil Ce were collected at MEPs threshold (T) definition (respectively BIS@T, CeProp@T and CeRemi@T). Intraoperative seizure, explicit recall for intraoperative awareness and clinical motor status were assessed. RESULTS: CeProp@T and CeRemi@T ranged respectively between 1.5-2.2 µg/ml (Median 1.6 µg/ml) and 3.5-18 ng/ml (Median 8 ng/ml) that were effective in keeping the BIS@T between 40 and 60 in all surgeries. tMEP thresholds ranged between 45 and 120 mA. There was no correlation between CeProp@T, CeRemi@T and tMEP, as well as between BIS@T and respectively tMEP, CeProp@T, CeRemi@T. None of patients had induced electrical seizure or explicit recalls. Motor scores were equal to preoperative values in 22/24 patients. CONCLUSION: BIS-guided general anaesthesia within a 40-60 interval, with low Ce of Propofol (≤2 µ/ml) and high analgesic regime allow reliable tMEP measurements, avoiding postoperative neurological impairment and major adverse outcomes, such as seizure and awareness.