Anesthesia During Positive-pressure Myelogram: A New Role for Cerebral Oximetry Background: Positive-pressure myelogram (PPM) is an emerging radiologic study used to localize spinal dural defects. During PPM, cerebrospinal fluid pressure (CSFp) is increased by injecting saline with contrast into the cerebrospinal fluid. This has the potential to increase intracranial pressure and compromise cerebral perfusion. Methods: We performed a retrospective chart review and analysis of 11 patients. The aim was to describe the periprocedural anesthetic management of patients undergoing PPM. Results: All patients underwent PPM with general anesthesia and intra-arterial blood pressure and near-infrared spectroscopy monitoring of regional cerebral tissue oxygen saturation. Mean±SD maximum lumbar CSFp was 58±12 mm Hg. Upon intrathecal injection, mean systolic blood pressure increased from 115±21 to 142±32 mm Hg (P<0.001), diastolic blood pressure from 68±12 to 80±20 mm Hg (P≤0.001), and mean blood pressure from 87±10 to 98±14 mm Hg (P=0.02). Ten of 11 patients received blood pressure augmentation with phenylephrine to minimize the risk of reduced cerebral perfusion secondary to increased CSFp after intrathecal injection. The mean heart rate before and following injection was similar (68±15 vs. 70±15 bpm, respectively; P=0.16). There was a decrease in regional cerebral oxygen saturation after positioning from supine to prone position (79±10% to 74±9%, P=0.02) and a further decrease upon intrathecal injection (75±10% to 69±9%, P≤0.01). Conclusions: Systemic blood pressure increased following intrathecal injection during PPM, possibly due to a physiologic response to intracranial hypertension/reduced cerebral perfusion or administration of phenylephrine. Regional cerebral oxygen saturation decreased with the change to prone position and further decreased upon intrathecal injection. Cerebral near-infrared spectroscopy has a potential role to monitor the adequacy of cerebral perfusion and guide adjustment of systemic blood pressure during PPM. The authors have no conflicts of interest to disclose. Address correspondence to: Tasha L. Welch, MD. E-mail: welch.tasha@mayo.edu. Received May 14, 2019 Accepted August 20, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved

Power and Challenges of Big Data: Why Clinical Researchers Should Not Be Ignored No abstract available

Recent Preoperative Concussion and Postoperative Complications: A Retrospective Matched-cohort Study Background: Physiological alterations during the perianesthetic period may contribute to secondary neurocognitive injury after a concussion. Methods: Patients exposed to concussion and who received an anesthetic within 90 days were matched to unexposed patients without concussion. Intraoperative and postoperative events were compared. Subgroup analyses assessed relationships among patients with a concussion in the prior 30, 31 to 60, and 61 to 90 days and their respective unexposed matches. To facilitate identification of potential targets for further investigation, statistical comparisons are reported before, as well as after, correction for multiple comparisons. Results: Sixty concussion patients were matched to 176 unexposed patients. Before correction, 28.3% postconcussion versus 14.8% unexposed patients reported postanesthesia care unit pain score≥7 (P=0.02); 16.7% concussion versus 6.5% unexposed patients reported headache within 90 days of anesthesia (P=0.02) and 23.5% of patients who received surgery and anesthesia within 30 days of concussion experienced headache within 90 days of anesthesia compared with 7.1% in the unexposed group (P=0.01). Patients who experienced concussion and had anesthesia between 31 and 60 days after injury had a postanesthesia care unit Richmond Agitation and Sedation Scale score of −1.61±1.29 versus a score of −0.2±0.45 in unexposed patients (P=0.002). After adjusting the P-value threshold for multiple comparisons, the P-value for significance was instead 0.0016 for the overall cohort. Our study revealed no significant associations with application of adjusted significance thresholds. Conclusions: There were no differences in intraoperative and postoperative outcomes in patients with recent concussion compared with unexposed patients. Before correction for multiple comparisons, several potential targets for further investigation are identified. Well-powered studies are warranted. Presented in abstract form at the Annual Meeting of the Society for Neuroscience in Anesthesiology and Critical Care in San Francisco, CA, October 12, 2018. The authors have no funding or conflicts of interest to disclose. Address correspondence to: Arnoley S. Abcejo, MD. E-mail: abcejo.arnoley@mayo.edu. Received March 5, 2019 Accepted September 19, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved

Intraoperative Magnetic Resonance Imaging–induced Oropharyngeal Thermal Injury in a Patient With Acromegaly No abstract available

Revisiting Ischemia After Brain Injury: Oxygen May Not Be the Only Problem No abstract available

The Promise and Perils of Big Data in the Clinical Neurosciences No abstract available

A Novel Approach to Investigating Brain Waste Removal in Humans No abstract available

A Bolus Dose of Ketamine Reduces the Amplitude of the Transcranial Electrical Motor-evoked Potential: A Randomized, Double-blinded, Placebo-controlled Study Background: A low-dose bolus or infusion of ketamine does not affect transcranial electrical motor-evoked potential (MEP) amplitude, but a dose ≥1 mg/kg may reduce MEP amplitude. We conducted a randomized, double-blinded, placebo-controlled study to evaluate the effect of ketamine (1 mg/kg) on transcranial electrical MEP. Methods: Twenty female patients (aged 12 to 18 y) with adolescent idiopathic scoliosis scheduled to undergo posterior spinal fusion were randomly allocated to receive ketamine or saline. General anesthesia was induced and maintained with continuous infusions of propofol and remifentanil. MEP was elicited by supramaximal transcranial electrical stimulation. MEP recordings were obtained at baseline and then at 2, 4, 6, 8, and 10 minutes after administration of ketamine (1 mg/kg) or saline (0.1 ml/kg). The primary endpoint was the minimum relative MEP amplitude (peak-to-peak amplitude, % of baseline value) recorded from the left tibialis anterior muscle. The baseline amplitude recorded before test drug administration was defined as 100%. Results: Medians (interquartile range) minimum MEP amplitudes in the left tibialis anterior muscle in the ketamine and saline groups were 26% (9% to 34%) and 87% (55% to 103%) of the baseline value, respectively (P<0.001). MEP amplitudes in other muscles were significantly reduced by ketamine. The suppressive effect of ketamine lasted for at least 10 minutes in each muscle. Conclusion: A 1-mg/kg bolus dose of ketamine can reduce MEP amplitude. Anesthesiologists should consider the dosage and timing of intravenous ketamine administration during MEP monitoring. Previously presented at the Japanese Society of Anesthesiologist Annual Meeting, May 17, 2018, Yokohama, Japan and Anesthesiology 2018, October 15, 2018, San Francisco, CA. Supported by JSPS Grant-in-Aid for Scientific Research (C) (grant number JP18K08810). The authors have no conflicts of interest to disclose. Address correspondence to: Kenta Furutani, MD, PhD. E-mail: kenta-f@med.niigata-u.ac.jp. Received February 3, 2019 Accepted August 30, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved

The Incidence and Magnitude of Cerebral Desaturation in Traumatic Brain Injury: An Observational Cohort Study Background: Cerebral ischemia in patients with traumatic brain injury (TBI) may propagate secondary neurological injury. Episodes of cerebral ischemia can be revealed through the use of cerebral oximetry monitoring. The objective of this study was to determine the incidence and severity of regional cerebral oxygen (rSO2) desaturation (rSO2<65%) in patients with severe TBI. Secondary outcomes included changes in other monitoring parameters associated with cerebral desaturation. Materials and Methods: In this single-center prospective observational cohort study, cerebral oximetry data were collected continuously for up to 72 hours in 18 adult patients with a diagnosis of severe nonpenetrating TBI who were being mechanically ventilated and undergoing intracranial pressure (ICP) monitoring an in intensive care unit in Canada. Mean arterial pressure (MAP), ICP, and cerebral perfusion pressure were collected at 5-minute intervals during the study period. Results: Twelve of 18 (67%) patients experienced an episode of cerebral desaturation. The median (interquartile range) nadir rSO2 was 57% (51% to 62%). The duration of desaturation was 265 (57 to 1277) minutes or 8.1% (2.6% to 26.0%) of recording time. In all patients, a linear regression analysis of the area under threshold of 65% for rSO2 was moderately correlated with the area above an ICP threshold of 20 mm Hg (R2=0.52; P<0.01). Similarly, there was a modest correlation between rSO2 and MAP (R2=0.41; P<0.01). These relationships also held true for those patients who experienced cerebral desaturation. Patients having episodes of ICP >20 mm Hg were 6 times more likely to have a cerebral desaturation (relative risk: 6.0; 95% confidence interval: 1.3-34.7). Conclusions: Cerebral desaturations occur frequently in patients with severe TBI, and their duration can be protracted. Episodes of desaturation were moderately correlated with increased ICP and decreased MAP. The authors have no funding or conflicts of interest to disclose. Address correspondence to: Duane J. Funk, MD, FRCPC. E-mail: duane.funk@umanitoba.ca. Received April 12, 2019 Accepted September 11, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved

Effect of General Anesthetics on Caspase-3 Levels in Patients With Aneurysmal Subarachnoid Hemorrhage: A Preliminary Study Background: General anesthesia has been associated with neuronal apoptosis and activation of caspases. Apoptosis is a crucial factor in early brain injury following aneurysmal subarachnoid hemorrhage (aSAH). We conducted a double-blind, prospective, randomized pilot study to evaluate the effect of 4 anesthetic agents on cerebrospinal fluid (CSF) and serum caspase-3 levels in aSAH patients. Materials and Methods: A total of 44 good-grade aSAH patients with preoperative lumbar drain scheduled for surgical clipping or endovascular coiling were randomized to receive maintenance of anesthesia with propofol, isoflurane, sevoflurane, or desflurane. Caspase-3 levels were measured in CSF and serum samples collected at baseline, 1 hour after induction, and 1 hour after cessation of anesthesia. Results: Compared with baseline, there was a decrease in CSF caspase-3 levels and an increase in serum caspase-3 levels 1 hour after exposure to all 4 anesthetic agents; levels returned to baseline values after cessation of anesthesia. Median CSF caspase-3 levels at baseline, 1 hour after anesthesia exposure, and 1 hour after cessation of anesthesia were 0.0679, 0.0004, and 0.0689 ng/mL, respectively (P<0.05). Median serum caspase-3 levels at baseline, 1 hour after anesthesia exposure, and 1-hour after cessation of anesthesia were 0.0028, 0.0682, and 0.0044 ng/mL, respectively (P<0.05). Conclusions: Propofol, isoflurane, sevoflurane, or desflurane have similar effects on CSF and serum caspase-3. The reduction of intraoperative CSF caspase-3 levels suggests a possible role for general anesthesia in neuroresuscitation by slowing the neuronal apoptotic pathway. M.B., A. Kuberan, and H.B.: study concept. M.B., H.B., A.R., S.D., N.P, and A. Kumar: study design. M.B., A.K.S., S.D., A. Kumar, T.S., and M.K.: enrolment of patients, collection of baseline data. N.P., A.K.S., T.S., and M.K.: anesthesia and collection of intraoperative data. M.B., A.R., H.B., A. Kuberan, H.B., A.K.S., T.S., M.K.: analysis and interpretation of data. M.B., A. Kuberan, H.B., and P.S.G.: contribution in statistical analysis. M.B., H.B., A. Kuberan, P.S.G., A.R., A.K., S.D., and N.P.: drafting of the manuscript. H.B, A. Kuberan, M.B., and P.S.G.: critical revision of the manuscript. M.B. and H.B.: principal investigator and overall responsibility for the trial. Supported by PGIMER, Chandigarh. The authors have no conflicts of interest to disclose. Address correspondence to: Hemant Bhagat, DM. E-mail: hembhagat@rediffmail.com. Received March 16, 2019 Accepted August 16, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved