[SNACC 1] Effects of Adrenergic Signalling on Anesthetic Sensitivity and Resistance to State Transition in Mice

Andrew McKinstry-Wu, Timothy Jiang, Aden Mandel, Kofi Ayensu, Steven Thomas. University of Pennsylvania, Pennsylvania, United States

Introduction: Adrenergic signaling plays a significant role in sleep-to-wake transitions, with increases in locus coeruleus (LC) activity preceding transitions to arousal and LC stimulation inducing those transitions. Animals lacking norepinephrine demonstrate increased sensitivity to anesthetics, and stimulation of LC signaling has been shown to speed emergence. Suppression of LC activity alone, however, has not been shown to have a sedative effect. Here, we investigate the effect of inhibition of adrenergic signaling on behavioral measures of sedation, and on dynamic and EEG measures of anesthetic response at isoflurane steady-state.

Methods: Pupillometry: Male and female Dbh-Cre x stop-floxed hM4di (M4) mice (n=6) under 1.0% isoflurane had a camera trained on one eye. After 10 min baseline, they received saline or 20 μg/kg deschlorclozapine (DCZ) I.P. Pupil size was measured with video processing functions in Matlab 2022b. Spontaneous and Forced Movement: Mice previously trained on rotarod (n=17) were given IP DCZ/saline and evaluated on rotarod 20 minutes after injection, then placed in beam-break cages for 1 hour. Baseline, post-rotatrod testing, and post-beam break testing temperature was recorded, Righting Reflex (RR): M4 mice were warmed and exposed to continuous population EC20 isoflurane (n=17). RR was checked every 3 minutes starting after 90 min of isoflurane. After 90 min of baseline, IP saline or DCZ was given and RR checks resumed after 5 minutes for another 90 min. This was repeated in WT controls at EC50. EEG Spectral Analysis: M4 mice (n=7) implanted with 10-lead EEG were exposed to EC20 isoflurane for 2 hours with continuous EEG recording while being warmed. Mice then received 20 μg/kg DCZ IP and recording continued for 90 minutes. Noisy channels were removed, EEG mean rereferenced and filtered between 0.8-35 Hz, and artifacts manually removed. Signal from M1/M2 was analyzed using the Chronux package in Matlab 2022b, comparing spectra of the last 30 minutes baseline to 30-60 minutes after DCZ injection. Spectral slope was calculated as described previously(1) to compare anesthetic depth. Data Analysis: Markov matrix estimation and calculation of sensitivity and resistance to state transition (RST) performed with Matlab 2022b as described previously.(2) Spectral analysis performed using Matlab 2022b and the Chronux package. Statistical calculations used PRISM 9.5 or Matlab 2022b, using paired t-test, one-way ANOVA, or mixed-effect as appropriate with significance set at P< 0.05.

Results: M4 mice showed significantly greater pupillary constriction (n=6, P< 0.05) in response to DCZ than saline control, indicating a decrease in central adrenergic tone (Fig. 1A.) This same line showed significant behavioral sedation with DCZ, with a decrease in forced and spontaneous movement (P< 0.0001, Fig. 1C, D.) M4 mice given DCZ also had decreased temperature after rotarod and beam break (P< 0.0001, 3 degree and 12 degree difference, Fig. 1B.) At steady-state isoflurane, DCZ exposure significantly increased population EC to a median 77, compared with no change to saline (P< 0.0001, Fig. 2A.) The change in anesthetic sensitivity DCZ was reflected in EEG spectra, with a greater negative slope induced by DCZ, indicating a deeper anesthetic state (Fig 2B-C.) RST significantly increased in response to DCZ (P< 0.05, Fig 2D.) In contrast, in WT controls, no changes occurred with DCZ (Fig 2E.).

FIGURE 1:

Decrease in Adrenergic Tone in Male and Female Dbh-Cre x stop-floxed hM4di mice with DCZ Results in Behavioral Sedation and Temperature Decrease. (A) M4 mice show significant pupilary constriction with DCZ.

Discussion: We show for the first time behavioral sedation in response to inhibition of adrenergic neurons. Decrease in temperature may be a central adrenergic effect, given known common neural pathways controlling temperature and sedation in response to alpha-2 adrenergic agonists, but may also be a confounding factor in measuring sedation. We show for the first time that acute adrenergic inhibition sensitizes animals to anesthetic hypnosis and show the first change in neural activity, rather than a pharmacologic intervention, that alters RST. This is evidence for control of RST by a neural population implicated in similar sleep-to-wake transitions. Changes in RST and anesthetic sensitivity do not relate to temperature changes as those mice were kept at constant temperature.

Decreasing Adrenergic Tone in M4 mice Increases Sensitivity to Isoflurane and Increases Resistance to State Transitions. Male and female M4 mice exposed to unchanging stead-state population EC20 Isoflurane show a profound increase in sensitivity in response to DCZ administration.

[SNACC 2] Simultaneous Assessment of Cerebral Oxygenation in Multiple Brain Regions during Adult Shoulder Surgery Full-Head Coverage Multi-Channel Time-Resolved Near-Infrared Spectroscopy: A Pilot Study

Farah Kamar, Jason Chui, Mamadou D, Darren D, Daniel M, John M, Leena N, Keith L. University of Western Ontario, Ontario, Canada

Introduction: Perioperative stroke is associated with an 8-fold increase in perioperative mortality, prolonged length of hospital stay, and decreased quality of life.1 For shoulder surgery performed in the beach chair position, due to systemic hypotension, cerebral desaturation events occur in up to 80% of patients.2 However, current commercial cerebral oximeters have limitations, including non-specificity due to contamination from extracerebral tissue and only having two channels to monitor frontal lobe regions. Limited spatial coverage may result in undetected stroke. The current research project employed a novel full-head coverage, multi-channel, time-resolved (tr)-NIRS, Kernel Flow, to address these limitations.3 This high-density NIRS system contains 52 light sources, 312 detectors and can record 2206 measurement channels of oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) simultaneously. As this system is a tr-NIRS device, the measurements have superior depth sensitivity compared to conventional NIRS devices. We conducted a pilot prospective cohort study with two objectives: (i) to assess the feasibility of using this device to monitor multiple brain regions during adult shoulder surgery, and (ii) to determine differences in cerebral oxygenation (StO2) between brain regions during surgery, specifically during periods of hypotension and following phenylephrine administration.

Methods: After ethics approval, we prospectively recruited adult patients undergoing shoulder surgery in beach chair position from Oct 2022 to Mar 2023 in St. Joseph Hospital, London, Ontario, Canada. The Kernel Flow device was used to continuously measure StO2 that provides increased depth sensitivity (Fig. 1). Continuous blood pressure was measured by finger photoplethysmography (Finometer, Finapres Medical Systems, Enschede, Netherlands), and oxygen saturation, end-tidal carbon dioxide, body temperature and anesthetic depth were maintained stable throughout the surgery. Channels were assessed for signal quality and scalp contact. The changes in HbO, HbR, total hemoglobin (HbT), and StO2 were calculated for good-quality channels. Channels were grouped into frontal, somatosensory, temporal, and occipital regions; and regional averages were calculated. We further evaluate any regional differences during hypotensive and phenylephrine administration events.

FIGURE 1:

Kernel Flow system. The Kernel Flow device is composed of 52 modules arranged in a headset design, which can be seen in Figures 1A, B & C. These modules are grouped into four plates that cover the frontal, parietal, temporal, and occipital cortices on each side of the head. Each module consists of a dual wavelength laser source (690 and 850 nm) at its center, surrounded by six detectors arranged hexagonally, each of which is 10 mm away from the source. The device uses spring-loaded light pipes to transmit light to or from the source and detector locations. The source-detector separation (SDS) within a module is 10 mm, and cross-module channels can also be analyzed. Each module has three sub-assemblies: the laser assembly, detector assembly, and optical assembly. These sub-assemblies are shown together in an exploded view in Figure 1C. During shoulder surgery in the beach chair position under general anesthesia, the Kernel Flow system was used to monitor a patient, as shown in Figure 1D. The patient's head was secured with headrests and straps to hold the Kernel helmet in place.

Results: A total of 27 patients have been included in this study. All patients were successfully monitored with the Kernel flow system without complications, except one patient who had minor skin abrasion caused by the helmet. There were 17 events of phenylephrine administration in 5 patients, with an average age (standard deviation (SD)) of 65 (SD: 15). After phenylephrine administration, the HbO significantly decreased by 2.1 (SD: 1.1) µM (P≤0.01) and StO2 decreased from 64.6% (SD: 1.0) to 61.8% (SD:1.5) (P≤0.03), while HbR significantly increased by 1.0 µM (SD: 0.2) (P≤0.0004). The HbT was unchanged (P=0.06). There was a trend of a more prominent desaturation in the frontal regions compared to the other brain regions after the first dose of phenylephrine administration (Fig. 2; P= 0.055). There was no cerebral desaturation in subsequent phenylephrine doses compared to the first dose. The magnitude of StO2 changes also decreased with repeated doses of phenylephrine administration (Fig. 2).

FIGURE 2:

A (left) shows measurements of somatosensory, temporal, and occipital regions after administration of phenylephrine bolus in one patient. The trends of oxyhemoglobin (HbO, red line) and deoxyhemoglobin (HbR, blue line) concentrations (in µmol) changes across time (in seconds) were showed. Fig. 2B (right upper) shows the regional differences of regional differences in HbO, HbR, HbT, and StO2. The changes in frontal regions were more prominent than other regions. Fig. 2C (right lower) shows the change in the extent of cerebral desaturation with repeated bolus of phenylephrine in patient 5. This patient has received 6 boluses of phenylephrine during the surgery and the cerebral desaturation was most prominent in the first bolus.

Discussion: This study successfully demonstrated the feasibility of simultaneously monitoring and comparing StO2 in multiple brain regions during surgery, providing a unique opportunity to explore regional differences when patients experience hypotension and various pharmacological interventions. There was a concern in previous studies that the cerebral desaturation accompanying phenylephrine administration may have been caused by extracranial vasoconstriction. But our findings using tr-NIRS suggest that the desaturation events are of cerebral origin. These events were predominantly observed in frontal regions, and their effects were reduced with repeated administration of phenylephrine. However, due to the small number of events observed, this pilot study may be underpowered. We are currently conducting an analysis of the hypotensive events. Our subsequent main study will provide a better understanding of these differences in various events.

[SNACC 3] Optimizing Patient Positioning for Craniotomy in ECMO-Supported Patients: Strategies for Improved Safety and Surgical Access

Sagar Jolly, Rafi Avitsian, Gurjit Saini, Anna Maria Nuti. Cleveland Clinic Foundation, Cleveland, Ohio, United States

Introduction: The COVID-19 pandemic has resulted in a substantial increase in the number of patients requiring extracorporeal membrane oxygenation (ECMO). This has created new challenges in managing patients with intracranial hemorrhage (ICH) who need hematoma evacuation while on ECMO support. Patient positioning during hematoma evacuation must take into account ECMO circuit access and management. This article examines two cases of posterior fossa craniotomy with different patient positioning approaches. Case 1: A 37-year-old female with refractory cardiogenic shock required VA (Veno-Arterial) ECMO (right axillary return and right internal jugular drainage) support. She experienced severe coagulopathy, underwent prone hematoma evacuation for posterior fossa hemorrhage, and was repositioned supine for chest exploration due to tamponade. Unfortunately, her hemorrhage worsened in the ICU, leading to comfort care. Case 2: A 39-year-old female with post-operative complications from a kidney transplant was placed on VV (Veno-Venous) ECMO support due to COVID-19-induced ARDS (Acute Respiratory Distress Syndrome). She developed acute altered mental status from subarachnoid, intraventricular, and posterior fossa subdural hemorrhage. Emergent suboccipital craniectomy was performed in the sitting position due to high risk of accidental ECMO decannulation in the prone position. Although her neurological exam improved postoperatively, she failed to make a durable neurologic recovery and was eventually placed in comfort care.

Discussion: ECMO is a life-saving intervention, but it carries risks, including bleeding, thrombosis, infections, and circuit complications. Intracranial hemorrhage is a life-threatening complication in ECMO patients, and regular neurological assessments and neuroimaging are vital for early detection. Proper patient positioning and vigilant monitoring are crucial for managing the challenges of using the prone or sitting position for posterior fossa hemorrhage evacuation in patients on ECMO support. Both positions have their advantages and risks, necessitating careful evaluation of each patient's specific circumstances. Prone positioning can be safe with well-organized technique and offers benefits, such as improved access to the posterior fossa and reduced risk of ventilator-induced lung injury.1 However, it also has risks, including endotracheal tube displacement, cannula compression, circuit disruption, bleeding, and fatal outcomes. Sitting position has advantages like improved surgical access and venous drainage from the posterior fossa, but can lead to hypotension and reduced blood flow to the brain in patients with compromised cardiovascular function.2 Multidisciplinary communication between neurosurgery, anesthesia, cardiovascular intensive care unit, and perfusion teams is essential for proper patient selection and management. When considering the sitting or prone position craniotomy, it is crucial to evaluate the severity of respiratory or circulatory impairment, ECMO support stability, and expected procedure duration. Ensuring proper positioning of ECMO cannula and tubing, along with continuous monitoring of hemodynamics, oxygenation, and circuit function, is vital for maintaining ECMO support and patient safety throughout the procedure. In conclusion, successful intracranial hemorrhage evacuation on ECMO support necessitates collaboration among neurosurgical, anesthesia, and cardiovascular teams. Careful patient positioning, ECMO cannula placement, addressing potential complications, and effective communication are vital for optimal outcomes in this challenging situation.

[SNACC 4] Comparing Relative Effects on Cognitive Function Following Sedation with Remimazolam vs Midazolam as Measured by the Hopkins Verbal Learning Test

Lynn Bichajian1, Randall Ostroff2, Mike Greenberg1. Eagle Pharmaceuticals, New Jersey, United States; The Surgery Center, Illinois, Unites States

Purpose: The interaction between anesthetic/sedative agents and the CNS, specifically the brain, are likely the least understood of all interactions between these agents and the various organ systems. In recent years far more attention has been paid to this interaction with particular interest and concern towards the effects on developing young brains and declining older brains. The manifestations of potential untoward effects range from emergence delirium to postoperative cognitive dysfunction and ICU delirium. Different measurements have been employed to demonstrate and quantify both short-term and long-term changes in cognitive function following anesthesia and sedation, yet the significance of these measurements has not been fully elucidated. The Hopkins Verbal Learning Test (HVLT) is one such scale. Devised to measure the development of dementia, its application to anesthesia/sedation is still somewhat speculative, however HVLT can certainly demonstrate relative changes in cognitive function from baseline, and additionally relative differences between agents of different or even the same classes of drugs. Benzodiazepines like midazolam are used ubiquitously for anxiolysis, sedation and as an adjunct to general anesthesia, yet have been implicated as potential contributing factors to delirium1 and potentially the exacerbation of dementia in the elderly. Remimazolam (Byfavo®, Acacia Pharma, Ltd) is a novel benzodiazepine, approved by the US FDA in July 2020 for sedation in patients undergoing procedures of < 30 minutes in duration. Esterase metabolism and biotransformation to an inactive metabolite provide unique pK differences vs other benzodiazepines. With greater exposure and potentially additional indications it is important to identify and compare any cognitive effects from remimazolam vs those associated with other commonly used sedatives such as midazolam.

Methods: In two pivotal US phase 3 efficacy trials2,3 remimazolam was compared to a blinded placebo arm for sedation of patients undergoing either colonoscopy or bronchoscopy. Patients were rescued with midazolam, dosed at investigator’s discretion, if sedation was inadequate. Patients were also given a prescribed pre-treatment dose of fentanyl and received additional doses subsequently for analgesia only. Since > 95% of placebo patients received midazolam rescue, they essentially represent midazolam standard of care. Patients were administered a baseline HVLT within 45 minutes prior to procedure and subsequently a comparator HVLT was administered 5 minutes after fully awake. The differences between remimazolam and midazolam treated patients at 5 minutes post fully awake were analyzed.

Results: Results from both studies are shown in Figures 1 and 2. Results were consistent and similar between studies. Patients in both treatment groups experienced a significant decrease in all 4 HVLT parameters. However, the decreases in HVLT were consistently greater in the midazolam treated patients vs. the remimazolam treated patients.

FIGURE 1:

Hopkins Verbal Learning Test (HVLT-R), Study CNS0756-006 (Colonoscopy). Please note that > 95% of Placebo group received rescue sedation with midazolam, according to standard of care.

FIGURE 2:

Hopkins Verbal Leaning Test-Revised (HVLT-R), Study CNS7056-008 (Bronchoscopy). Please note that > 95% of Placebo group received rescue sedation with midazolam, according to standard of care.

Conclusions: Although primarily utilized to measure dementia, the Hopkins Verbal Learning Test would seem a potentially useful tool to assess the effects on cognition from exposure to anesthetic/sedative agents. Relative differences between agents can perhaps provide some useful preliminary information as we seek to better understand the interactions between anesthetic/sedative agents and the brain. These preliminary data suggest changes in cognitive function, which occurred after even a brief exposure (< 30 minutes) may be less with remimazolam vs midazolam when used in conjunction with fentanyl for procedural sedation. The ultimate interpretation and significance of measurements done with HVLT still remain to be elucidated and viewed in perspective with other cognitive testing and clinical outcomes. For instance, is there a dose response relationship such that these differences would become greater with increasing doses used for longer procedures or different indications? Additionally, questions with respect to how these differences relate to real life and whether they are temporary or correlate to other longer term outcomes is yet to be determined in future investigations.

[SNACC 5] Safety in Prone Positioning for Neurosurgery: An Educational Quality Improvement Project

Christina Besi, Valpuri Luoma, Michelle Leemans, Michael Errico. National Hospital of Neurology and Neurosurgery, London, United Kingdom

Introduction: The prone position is frequently used in neurosurgery to facilitate surgical access. Despite being a core anaesthetic skill, and part of both the ICPNT and RCOA syllabus, safe practice for prone position remains relative unfamiliar to the majority of anaesthetists. Proning is highly important as it is associated with the risk of life-changing injuries including peripheral nerve injuries and post-operative visual loss (1:5000) We conducted a Quality Improvement Project (QIP) with the aim of improving anaesthetic trainees’ confidence with prone position for neurosurgery. A local education program for proning including bite-size practical teaching was introduced following a baseline audit. Bite-size teaching is an effective way to deliver concise and relevant teaching in the workplace. The first audit cycle confirmed the need for ongoing structured teaching program and improvement in the consent process specifically for proning. Trainee confidence with prone position improved from 40% to 83% while using the Mayfield clamp and from 70% to 92% using the ProneView TM.

Methods: This QIP is locally registered. An 11-question, electronic survey on prone position for surgery was distributed to all neuroanaesthetic trainees in our department using Microsoft 365 Forms. As part of the 2nd cycle trainees were also asked about changes in their consent practice post training. All trainees were invited to participate in the survey at the beginning and the end of their neuroanaesthesia rotation to assess: i) confidence with proning using the ProneViewTM and Mayfield Clamp; ii) effectiveness of the educational program on proning; iv) improvements in the consent procedure for prone position; iv) areas for improvement. All data were analysed using Microsoft 365 Form and Excel. We developed cognitive aids for prone position using the Mayfield clamp and ProneViewTM. The cognitive aids underwent multidisciplinary peer-review.

Results: The second cycle of our QIP took place from February to April 2023 The response rate for our survey was 60%. 75% of the responders were SpRs and 25% fellows. The survey (n=12) at the start of the neuroanaesthesia rotation showed that trainees were more comfortable in using Mayfield clamp (59%) compared to the ProneViewTM (50%). Nearly 1 in 4 trainees felt somewhat uncomfortable using either. 41% of the trainees did not regularly consent the patient specifically for proning and over 50% had never received training in proning or had it long time ago. All trainees believed that teaching in proning was essential. The end of rotation survey (n=12) showed that over 75% of trainees found the educational program satisfactory. Confidence with prone positioning increased from 59% to 84% and from 50% to 84% using Mayfield clamp and ProneViewTM respectively. Consent of patients specifically for proning increased from 58% to 100%. Not all trainees were able to attend the teaching program as it was not included in the formal teaching schedule.

Conclusion: Our teaching program appears to have improved trainees’ confidence and knowledge in prone position for neurosurgery. The case of Montgomery vs Lancashire Health Board has resulted in a fresh focus on procedural consent. The Montgomery decision requires the doctor to inform the patient about “material risks” and to explore what that specific patient would want to know. Trainees at our institution are now aware of the need to consent for prone position. Our next steps are to 1) incorporate it as part of our departmental induction; 2) further formalise bite-size teaching; 3) implement the use of the cognitive aid; 4) determine impact on patient safety. Safe proning is a transferable skill which could be applied outside neuroanaesthesia. We planning to involve other specialities at our institution to ensure high quality of care and a standardised approach to proning.

[SNACC 6] Why Choose Spinal Anesthesia for Spine Surgery: A Case Report

Gabriella White-Dzuro, Xiaodong Bao, Francis McGovern, Robert Peterfreund. Massachusetts General Hospital, Boston, United States

Reports of spinal anesthesia for lumbar spine surgery have been published for more than sixty years. Over the past decade, eight English language meta-analyses and review publications suggest the advantages of spinal anesthesia over general anesthesia. Four were published in the last two years. Touted benefits of spinal anesthesia include decreased operative time, estimated blood loss, postoperative nausea and vomiting, and improved pain control. However, it has yet to be widely adopted for lumbar spine surgery. A surgeon presented for lumbar decompression, requesting spinal anesthesia for surgery. Surgery was performed under uneventful spinal anesthesia without sedation. The patient recovered from surgery quickly and without incident, requiring no postoperative opioid analgesia. What data supports this choice? The medically knowledgeable patient’s strong preference for spinal anesthesia prompted an examination of English language review articles and meta-analyses comparing spinal anesthesia to general anesthesia for lumbar spine surgery. The literature search found 8 relevant reports. Six of the eight reviews found a decrease in either postoperative pain scores or analgesic requirements when spinal anesthesia was used.De Cassai et al noted that while they found a difference, the quality of evidence was very low. Furthermore, 4 of the 8 papers noted no difference in pain scores at 24 hours. There are obvious deficiencies in these review articles. Six of the eight cited review articles include both spinal and epidural anesthesia. Researchers should not equate the two and draw conclusions off the combination is inappropriate. They represent distinct forms of anesthesia and should be treated as such. The intentionality of the inclusion of epidural anesthesia is unclear, as the authors neglect to address this effect and refer to epidural anesthesia as intrathecal injections. One must consider the strength of review papers that are all based on the same six primary studies and draw different conclusions. (Table 1) The oldest study was published in 1996 by Jellish et al and was included in six out of the eight review papers. The most recent primary research was published in 2014. The evolution of general anesthesia over that period has been significant. With the advancement of Enhanced Recovery After Surgery protocols and the focus on multi-modal analgesics and postoperative nausea and vomiting prophylaxis, it is unclear if a more recent study would have similar findings. Providers seeking to identify potential advantages and disadvantages of spinal anesthesia for lumbar spine surgery should appreciate that the multiple reviews and meta-analyses cite many of the same primary research reports. These include considerably older studies that may not reflect practice changes over time, thereby limiting their utility in forming our current recommendations. Consequently, recommendations for spinal anesthesia vs general anesthesia for lumbar spine surgery are not necessarily grounded in strong evidence. As providers, we must think critically when we look at meta-analyses to ensure that the studies that they include are recent and relevant. A meta-analysis and the conclusions it draws are only as good as the research that it cites.

[SNACC 7] A comparison of Regional Cerebral Oxygen Saturation Using Near-infrared Spectroscopy (NIRS) of NIRO-200NX and O3 in Patients With Pulmonary Endarterectomy

Sho Masuda, Kenji Yoshitani, Akito Tsukinaga. National Cerebaral and Cardiovascular Center, Suita, Osaka, Japan

Background: Several devices are now available for measuring regional cerebral oxygen saturation using near-infrared spectroscopy. There were wide varieties in regional cerebral oxygen saturation among several devices (1). Among devices, NIRO-200NXⓇ (Hamamatsu Photonics, Hamamatsu, Japan) has had small contamination of the skull and cerebrospinal fluid layer compared with INVOS (2). Also, O3Ⓡ (Masimo, Neuchatel, Switzerland) had received Food Drug Administration (FDA) approval for use on infant and neonatal patients (< 10 kg) and has been used widely in addition in adult patients. However, no studies have investigated the difference between these two devices during deep hypothermic circulatory cardiac arrest to our best knowledge. Therefore, we compared the cerebral oxygen saturation of NIRO-200 NX (TOI) and O3(rSO2).

Methods: This study was approved by the Ethics Committee of our institute.We compared TOI with rSO2 in patients with chronic thromboembolic pulmonary hypertension (CTEPH) undergoing pulmonary endarterectomy (PEA), which requires deep hypothermic circulatory arrest (DHCA) to prevent the backflow of blood from the pulmonary artery several times for approximately 20 minutes. Both the NIRO-200NX sensor and O3 sensor were attached to the forehead to measure cerebral oxygen saturation simultaneously. We recorded the TOI and rSO2 during DHCA and compared whether NIRO and O3 changed similarly, because the value of TOI and rSO2 decreased dramatically in each DHCA typically.

Results: Twenty-nine patients were enrolled in this study. There were 144 times of DHCA in this study. We obtained bilateral cerebral oxygen saturation (CH1: left frontal side, CH2: right frontal side) at 288 points. The values of rSO2 were compared with TOI at pre-DHCA, DHCA, and the end of reperfusion. The values of rSO2 decreased during DHCA and improved in reperfusion phase in both devices. The time course of change of TOI and rSO2 was shown in Figure 1. Further %change of rSO2 and TOI were in Figure 2 We used mixed linear regression model to examine the difference between NIRO and O3. There were significant interactions between the rSO2 and TOI value in DHCA (P< 0.001) (Figure 1) Also, there was a significant interaction between the % change of rSO2 and TOI (P< 0.001) (Figure 2).

FIGURE 1:

Time course of change of rSO2 and TOI.

FIGURE 2:

Time course of change of %change of TOI and rSO2.

Conclusion: The values and the %changes of TOI and rSO2 were significantly different during DHCA. Both devices reflected the change in cerebral oxygen saturation in DHCA.

[SNACC 8] Neuroanesthesiologist’s Brain Protection Strategies during Brief Ischemic Episodes in Neurosurgery: An Intradepartmental Survey

Sagar Jolly, Anna Maria Nuti, Rafi Avitsian. Cleveland Clinic Foundation, Cleveland, Ohio, United States

Background: Neurosurgical procedures often involve transient ischemic episodes that may lead to postoperative cognitive deficits or long-lasting neurological complications. This survey aims to evaluate the anesthesia management and intraoperative monitoring strategies employed by neuroanesthesiologists during neurosurgical procedures with short-ischemic periods. We administered a questionnaire to 13 neuroanesthesiologists from a single institution, focusing on their clinical experience and application of brain protection strategies focusing on three critical neurosurgical procedures: intracranial aneurysm clipping, carotid endarterectomy, and extracranial-intracranial(EC-IC) bypass. The results will provide valuable insights into the current practices among neuroanesthesiologists and help identify the most effective brain protection strategies during short-ischemic periods in neurosurgery. By sharing and implementing these best practices, we can enhance patient safety and improve outcomes in this critical aspect of neurosurgical care.

Material and Methods: The survey was divided into two sections: anesthesia management strategies and monitoring techniques. In the first section, participants were asked to identify the anesthetic management strategies they commonly used for brain protection during short-ischemic periods for each procedure, including propofol bolus, propofol infusion, Raising Volatile agent, raising FiO2% above baseline, and induced hypertension. The second section addressed the intraoperative neuromonitoring techniques routinely employed, such as BIS, EEG by Neuromonitoring team if available, cerebral oximetry, or other methods.

Results: The survey comprised 13 neuroanesthesiologists from a single institution, and we present the findings in Table 1.

Discussion: The survey results provide valuable insights into the anesthetic management and monitoring techniques employed by neuroanesthesiologists during neurosurgical procedures involving clipping, endarterectomy, and EC-IC bypass surgeries. The data reveal a preference for certain strategies depending on the type of procedure, highlighting the importance of tailoring anesthetic management to the specific needs of the surgery and patient. In terms of anesthetic management, induced hypertension was consistently used across all three procedures, with the highest frequency in endarterectomy (92%), followed closely by clipping (69%) and EC-IC bypass (85%). This strategy may be preferred due to its ability to maintain cerebral perfusion during ischemic events. Propofol bolus was more commonly used in clipping (100%) and EC-IC bypass (77%) compared to endarterectomy (38%), possibly because of its rapid onset and short duration of action, which may be beneficial in these procedures. Raising FiO2 from baseline was utilized similarly in all three surgeries while raising the volatile agent concentration was less frequently employed. Regarding monitoring techniques, the use of EEG by the neuromonitoring team was most prevalent during endarterectomy (92%), showing the importance of real-time monitoring of cerebral electrical activity to detect and prevent potential ischemic events. BIS-EEG tracing was more common in clipping (54%), especially when EEG-neuromonitoring was not available. Cerebral oximetry was utilized in Endarterectomy procedures more frequently (38%) compared to EC-IC bypass (23%) and clipping (15%). This might be because cerebral oximetry is less accessible or more expensive, or because it's perceived to provide less accurate information when compared to EEG-based techniques. These results show the diverse range of anesthetic management strategies and monitoring techniques employed by neuroanesthesiologists during brief ischemic episodes in neurosurgery. Further research is needed to establish the most effective approaches for each procedure, taking into consideration factors such as patient demographics, comorbidities, and institutional protocols. By identifying and implementing evidence-based best practices, we can improve patient outcomes and enhance the quality of care in neurosurgical procedures.

Table 1: Frequencies of anesthetic management strategies and monitoring techniques used for Clipping, Endarterectomy, and EC-IC bypass surgery

[SNACC 9] The Dichotomy of Blood Pressure Management: Abdominal Aortic Aneurysm in a Carotid Endarterectomy Case

Calvin Wong, Benjarat Changyaleket. University of Chicago, Chicago, Illinois, United States

Cerebrovascular accidents are the fifth leading cause of death and the leading cause of disability in the United States. The 1991 North American Symptomatic Carotid Endarterectomy Trial (NASCET) has published a two-year decrease in stroke occurrence in patients with carotid stenosis who underwent carotid endarterectomy, which involves the removal of plaque through an open surgical incision, compared to medical management. Aortic aneurysm is a permanent dilatation of greater than 3 centimeters (cm) along the path of the aorta, including the ascending, arch, thoracic, and abdominal components. Prevalence is estimated to be 4.9-9.9% of the population, with increasing incidence related to age, especially those with many comorbidities. Beyond 5 cm, the progression and rupture risk of abdominal aortic aneurysms (AAA) is increased in a nonlinear fashion, with women having a higher risk of aneurysm rupture and mortality. Of note, smoking is one of the most important modifiable risk factors of AAA. Current guidelines for intraoperative blood pressure management of a carotid endarterectomy case recommend maintaining mean arterial pressure (MAP) close to baseline, while increasing MAP during cross-clamp placement to promote collateral cerebral blood flow through the Circle of Willis and decreasing MAP prior to cross-clamp release to avoid intimal tear and hyperperfusion. Guidelines for blood pressure management of patients with AAA recommend maintaining blood pressure less than or equal to 140/90 mmHg to reduce the risk of cardiovascular events. Currently, there exists no guidelines for the management of blood pressure in patients with concomitant AAA and carotid stenosis undergoing a carotid endarterectomy. We present a case of a 67-year-old female with AAA and right carotid stenosis complicated by right vision loss who underwent carotid endarterectomy. Our patient has a history of hypertension with baseline blood pressures of 100-120 / 60-70’s and new-onset paroxysmal atrial fibrillation on admission, started on diltiazem and followed by the cardiology service. Right common carotid artery angiogram demonstrates an ulcerated plaque with at least 50% stenosis at the bifurcation, and the patient was subsequently determined to be a good candidate for carotid endarterectomy. The procedure was performed by the neurosurgical team with intraoperative neurophysiologic monitoring and under general anesthesia. Prior to the surgery, blood pressure goals were discussed with the surgical service and systolic blood pressure before internal carotid artery cross clamping was set to be around 140’s. When there was a decrease in neurophysiologic monitoring signals, such as somatosensory (SSEP) and motor evoked potentials (MEP), after cross clamping, systolic blood pressure was allowed to increase to 160-180’s temporarily until the addition of a shunt placement, with improvement of signals back to baseline. Importantly, during cross clamping and surgical manipulation, the patient’s cardiac rhythm notably converted to supraventricular tachycardia (SVT) with heart rates over 180’s and a precipitous decrease in systolic blood pressures from 150’s to 80’s as well as loss of SSEP and MEP. Surgical team was immediately notified and surgical stimulation paused. The SVT was treated successfully with 30 mg of intravenous administration of esmolol with the return of SSEP and MEP. Patient tolerated the rest of the procedure well without adverse outcomes and recovery was uneventful. This case highlights the challenges of managing patients with concomitant aortic aneurysm and cerebrovascular stenotic disease whose hemodynamic goals between “the head and the heart” may be conflicting. Intraoperative blood pressure goals should involve remaining vigilant during critical portions of the operation, especially during internal carotid artery cross clamping and unclamping. Effective teamwork and constant communication with the surgical service is essential for optimal outcome.

[SNACC 10] Extensive Cerebral Venous Thrombosis Following CSF Drainage in a Patient Diagnosed With Idiopathic Intracranial Hypertension: A Case Report

Anna Maria Nuti, Rafi Avitsian, Sagar Jolly. Cleveland Clinic Foundation, Cleveland, Ohio, United States

Introduction: Cerebral venous thrombosis is a rare and potentially life-threatening complication that can occur as a result of CSF drainage. It has been suggested that the over-drainage of CSF, leading to decreased intracranial pressure, can cause venous stasis and thrombosis.

Methods: We report the case of a 22-year-old male who presented with headaches, progressive vision loss in the right eye, and new-onset blurred vision in the left eye. Optometry revealed bilateral papilledema and imaging studies ruled out acute findings, cerebral venous thrombosis or hydrocephalus, although a mild/moderate stenosis of the left sigmoid sinus was documented. CSF infection was ruled out and the patient was diagnosed with suspected IIH (idiopathic intracranial hypertension). Lumbar puncture was performed by the interventional radiology team and vision in the right eye improved. A lumbar drain was placed to relieve symptoms, followed by the positioning of a ventriculoperitoneal shunt (VPS). However, the patient subsequently developed worsening right-sided hemiparesis, facial paralysis and expressive aphasia. An MRI and CT scan were repeated, demonstrating extensive dural venous thrombosis, and immediate thrombectomy was performed with successful radiological results. Patient was initiated on a heparin drip, but unfortunately did not recover from his neurological deficits.

Discussion: The temporal association between CSF drainage and the onset of hemiparesis, facial paralysis and aphasia suggests a correlation between the decrease in CSF volume and the development of extensive cerebral venous thrombosis. According to the Monroe-Kellie hypothesis, the decrease in CSF volume leads to an increase in cerebral blood volume, causing venous structures to dilate and blood velocity to reduce, resulting in intracranial venous thrombosis as a consequence of venous stasis.

Conclusions: Cerebral venous thrombosis, as a complication of excessive CSF drainage, is a rare complication and seldom discussed in literature. The extensive dural venous thrombosis in this patient was likely caused by blood stasis as a result of over-drainage of CSF after positioning of a lumbar catheter and ventriculoperitoneal shunting. Predisposing factors, such as venous sinus stenosis or genetic mutations of coagulation factors, may also be involved. This report agrees with previously described ones that suggest decrease in CSF responsible for the thrombosis, possibly following an increase in venous blood volume and stasis. Unlike the other reported cases, our patient never had a diagnosis of hydrocephalus, and the VPS was performed after noticing improvement of symptoms second to lumbar drainage through a catheter. In our knowledge, cerebral venous thrombosis in patients with IIH and after CSF drainage have been discussed in four previous cases. Since the development of dural venous thrombosis could lead to permanent neurological deficits and, in some cases, to death, we suggest close monitoring of patients undergoing lumbar drainage and/or VPS, in order to early recognize its development and significantly alter their prognosis.

MRV at entrance

MRV following LP and VPS

[SNACC 11] Assessing the Perception of Nigerian Medical Students towards Neuroscience Education: A Cross-sectional Study

Nicholas Aderinto. Ladoke Akintola University of Technology, Ogbomosho, Nigeria

Background: Neuroscience education is a crucial aspect of medical training as it equips medical students with the knowledge and skills to diagnose and manage neurological conditions. The aim of this cross-sectional study was to assess the perception of Nigerian medical students towards neuroscience education.

Methods: A self-administered questionnaire was used to collect data from 300 medical students from four universities in Nigeria. The questionnaire consisted of 15 items that assessed the students' perception of neuroscience education. The data collected were analyzed using descriptive statistics and chi-square test.

Results: The results showed that the majority of medical students had a positive perception of neuroscience education. Specifically, 84.3% of the respondents believed that neuroscience education is important for medical practice, while 76.7% agreed that the current neuroscience curriculum is relevant to their training. Additionally, 70.3% of the respondents expressed interest in pursuing further studies in neuroscience. However, the study also revealed that 58.7% of the respondents found the neuroscience curriculum challenging, and 41.3% expressed the need for more practical sessions in neuroscience education.

Conclusion: The study highlights the positive perception of Nigerian medical students towards neuroscience education, with most students acknowledging its relevance to medical practice. However, the study also underscores the need for more practical sessions in neuroscience education to enhance the students' understanding of the subject. These findings provide valuable insights that can be used to improve the quality of neuroscience education in Nigerian medical schools, and also inform policy decisions aimed at enhancing medical education in Nigeria.

[SNACC 12] Large Volume Epidural Blood Patch for the Treatment of Spontaneous Intracranial Hypotension: A Retrospective Cohort Study

Jason Chui, Maria Gomez. University of Western Ontario, Ontario, Canada

Introduction: The large volume epidural blood patch (EBP) has increasingly been used to treat patients with refractory spontaneous intracranial hypotension (SIH).1–3 However, there is a paucity of studies reporting on the technique and experience of large volume EPB. The primary objective of this study is to summarize our experience of EBP in managing patients with SIH.

Methods: We retrospectively reviewed the records of all adult patients who underwent EBP for the treatment of SIH between January 2010 and June 2022 at London Health Science Centre, London, ON, Canada. We excluded pediatric patients and patients with cerebrospinal fluid leaks secondary to lumbar puncture or surgery. We summarized the demographics, clinical presentation, and treatment of patients with SIH. We performed multiple variable logistic regression analysis to identify factors predicting the success of EBP.

Results: Of 188 patients with EBP performed during the study period, 37 patients were included. A history of inciting trauma was identified in more than half of the included patients. More than half (56%) of the patients did not have an identifiable leakage site on imaging. Despite an average of 4 weeks of conservative management including bed rest, hydration, and oral analgesia, only 5% (2) of patients were responsive. A total of 81 EBPs were performed in 37 patients. The mean (SD) volume of the first EBP was 29 (12) ml. The volume of subsequent EBPs increased with the number of attempts (Fig 1). At the 7th, 8th, and 9th EBP, all patients received catheter-guided large volume blood patches with 90-120 mL of blood injected from cervical to lower lumbar spinal levels under fluoroscopic guidance. The complete resolution rate after the first EBP was 35%. The success rate of subsequent EBPs progressively decreased with the number of EBPs performed. The distribution of the number of EBPs is shown in Figure 2. 67% of patients experienced no complications after EBP. Low back pain during the procedure was the most commonly reported minor complication. Major complications are rare. In the