Neurosurgical Anesthesiology

Defining a Taxonomy of Intracranial Hypertension: Is ICP More Than Just a Number? Intracranial pressure (ICP) monitoring and control is a cornerstone of neuroanesthesia and neurocritical care. However, because elevated ICP can be due to multiple pathophysiological processes, its interpretation is not straightforward. We propose a formal taxonomy of intracranial hypertension, which defines ICP elevations into 3 major pathophysiological subsets: increased cerebral blood volume, masses and edema, and hydrocephalus. (1) Increased cerebral blood volume increases ICP and arises secondary to arterial or venous hypervolemia. Arterial hypervolemia is produced by autoregulated or dysregulated vasodilation, both of which are importantly and disparately affected by systemic blood pressure. Dysregulated vasodilation tends to be worsened by arterial hypertension. In contrast, autoregulated vasodilation contributes to intracranial hypertension during decreases in cerebral perfusion pressure that occur within the normal range of cerebral autoregulation. Venous hypervolemia is produced by Starling resistor outflow obstruction, venous occlusion, and very high extracranial venous pressure. Starling resistor outflow obstruction tends to arise when cerebrospinal fluid pressure causes venous compression to thus increase tissue pressure and worsen tissue edema (and ICP elevation), producing a positive feedback ICP cycle. (2) Masses and edema are conditions that increase brain tissue volume and ICP, causing both vascular compression and decrease in cerebral perfusion pressure leading to oligemia. Brain edema is either vasogenic or cytotoxic, each with disparate causes and often linked to cerebral blood flow or blood volume abnormalities. Masses may arise from hematoma or neoplasia. (3) Hydrocephalus can also increase ICP, and is either communicating or noncommunicating. Further research is warranted to ascertain whether ICP therapy should be tailored to these physiological subsets of intracranial hypertension. Supported by Department of Health and Human Services, National Institutes of Health, and National Institute of Neurological Disorders and Stroke, 1R01NS082309-01A1. W.A.K.: funded by 1R01NS082309-01A1. Legal consultant; multiple legal and health care entities. Royalty payments Oxford University Press and Elsevier. Honoraria NIH study sections. Editorial Board Neurocritical Care. Editorial Board J Neurosurg Anesth. Coauthor on provisional patent number 17-8261/103241.000816 Trustees of the University of Pennsylvania. R.B.: funded by 1R01NS082309-01A1. Coauthor on provisional patent number 17-8261/103241.000816 Trustees of the University of Pennsylvania. The remaining authors have no conflicts of interest to disclose. Address correspondence to: W. Andrew Kofke, MD, MBA. E-mail: kofkea@uphs.upenn.edu. Received November 26, 2018 Accepted April 14, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved

Subanesthetic Dose of Ketamine Improved CFA-induced Inflammatory Pain and Depression-like Behaviors Via Caveolin-1 in Mice Background: Ketamine, a commonly used nonbarbiturate anesthetic drug, possesses antidepressant properties at subanesthetic doses; however, the underlying mechanisms remain unclear. Materials and Methods: The analgesic and antidepressant effects of ketamine were explored using a complete Freund adjuvant (CFA)-induced peripheral inflammatory pain model in vivo. Mice were first divided into sham or CFA injection group randomly, and were observed for mechanical hyperalgesia, depression-like behavior, and mRNA expression of caveolin-1. Then ketamine was administered in CFA-treated mice at day 7. Results: The behavioral testing results revealed mechanical hyperalgesia and depression in mice from days 7 to 21 after CFA injection. Ketamine reversed depression-like behaviors induced by CFA injection. It also restored the brain-regional expression levels of caveolin-1 in CFA-treated mice. In addition, caveolin-1 mRNA and protein expression were increased in the prefrontal cortex and nucleus accumbens of CFA-treated mice. However, ketamine reversed the increase in caveolin-1 expression in the ipsilateral and contralateral prefrontal cortex and nucleus accumbens, supporting the distinct roles of specific brain regions in the regulation of pain and depression-like behaviors. Conclusions: In CFA-treated mice that exhibited pain behavior and depression-like behavior, ketamine reversed depression-like behavior. The prefrontal cortex and nucleus accumbens are the important brain regions in this regulation network. Despite these findings, other molecules and their mechanisms in the signal pathway, as well as other regions of the brain in the pain matrix, require further exploration. J.L. and R.H. contributed equally to this work. J.W. and Q.Z. are co-first authors. This work was funded by the Beijing Municipal Administration of Hospitals' Ascent Plan (code number DFL20180502) and Clinical Medicine Development of Special Funding Support (code number ZYLX201708). R.H. is a member of the Editorial Board of the Journal of Neurosurgical Anethesiology. The authors have no conflicts of interest to disclose. Address correspondence to: Ruquan Han, MD, PhD. E-mail: ruquan.han@ccmu.edu.cn. Received November 21, 2018 Accepted April 8, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved

Editorial No abstract available

Standardized Accreditation of Neuroanesthesiology Fellowship Programs Worldwide: The International Council on Perioperative Neuroscience Training (ICPNT) No abstract available

Remifentanil Patient-controlled Analgesia in Awake Craniotomy: An Introduction of an Innovative Technique No abstract available

Effect of Daytime Versus Night-Time on Outcome in Patients Undergoing Emergent Neurosurgical Procedures Background: Timing of neurosurgical procedures is controversial. Challenges identified with night-time surgeries include physician fatigue and sleep deprivation, and fewer staff and resources compared with daytime surgery. These might contribute to medical errors and complications, and, hence, worse patient outcomes. Methods: This single center retrospective study of 304 patients who underwent emergent neurosurgical procedures between January 1, 2010 and December 31, 2016 included 2 groups based on the timing of surgery: daytime (7:00 AM to 6:59 PM) and night-time (7:00 PM to 6:59 AM) surgery groups. Patient demographics, diagnosis, surgical characteristics, complications, and neurological outcome were obtained from the medical records. Results: There was no difference in patient demographics, intraoperative complications, and length of surgery between the 2 groups. Although there was no statistically significant difference in neurological outcome between the 2 groups at hospital discharge and 1 month postdischarge, there was a higher proportion of patients in the night-time surgical group with unfavorable neurological outcome (Glasgow Outcome Score 1 to 3) at both these times. There were differences in hospital length of stay, location of postoperative management (postanesthesia care unit or intensive care unit), midline shift, baseline Glasgow Coma Scale score, and acuity of surgery between the 2 groups. Logistic regression analysis showed that age, baseline Glasgow Coma Scale score, surgery acuity status, procedure type, and intraoperative complications influenced neurological outcome. Conclusions: This study found no difference in the rate of unfavorable neurological outcome in patients undergoing emergent neurosurgical procedures during the daytime and night-time. However, our findings cannot exclude the possibility of an association between timing of surgery and outcome given its limitations, including small sample size and omission of potentially confounding variables. Further well-designed prospective trials are warranted to confirm our findings. This study is a part of Bachelor of Science (Medicine) project thesis of A.H.Q., and he received a stipend from the University of Manitoba to conduct this research project. This project is funded by Anesthesia Oversight Committee, Department of Anesthesiology, Perioperative and Pain Medicine, University of Manitoba, Winnipeg, Canada. T.C. (primary supervisor) received the above-mentioned grant. Support was provided solely from institutional and/or departmental sources. Presented at: Neuroanesthesia Rounds, August 15, 2018, University of Manitoba; Bachelor of Science (Medicine) Research Symposium, August 23, 2018, University of Manitoba. The authors have no conflicts of interest to disclose. Address correspondence to: Tumul Chowdhury, MD, DM, FRCPC. E-mail: tumul.chowdhury@umanitoba.ca. Received September 9, 2018 Accepted March 12, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved

Language Monitoring in Brain Surgery Under General Anesthesia Background: Awake surgeries for cerebral lesion resection have several limitations including patient fear, discomfort, or pain. This study aimed to determine whether components of language function could be measured under general anesthesia. In this study, the occurrence of mismatch negativity (MMN) was searched in evoked potentials for phonological sounds. Materials and Methods: Five normal hearing, French native speaker, awake volunteers participated in evaluating the phonological task (4 females and 1 male). Eleven normal-hearing, French native speaker patients (6 left and 5 right hemisphere lesions) participated at the time of their tumor neurosurgery (3 females and 8 males). Repetitions of the standard syllable /pa/ with the insertion of 1 deviant /po/ were presented through earphones. The difference between averaged epochs of standards and deviants syllables determined the MMN. During surgery, total intravenous anesthesia was performed with propofol and synthetic opioid sufentanil. The bispectral index was targeted (40 to 60). Results: The MMN was found in all awake volunteers and validated by an N250 component. In the patient group, the electroencephalogram analysis was not possible in 4 of 11 patients because of anesthesia being too deep, burst suppression, or a high level of noise (>40 μV). Significant N250 response was obtained in 5 of 7 (71.4%) patients under general anesthesia. The 2 other patients also showed MMN which did not reach significance. Conclusions: To our knowledge, this is the first demonstration that phonological processing can be measured during brain surgery under general anesthesia, suggesting that some language processing persists under the condition of unconsciousness. These results encourage further study of language processing under general anesthesia with the goal of making intraoperative neuromonitoring. Supported by the University Hospital of Geneva (in particular with the fund PRD no. 10-2015-I "Advanced electrophysiological monitoring in neurosurgery"). The authors have no conflicts of interest to disclose. Address correspondence to: Colette Boëx, PhD. E-mail: colette.boex@hcuge.ch. Received December 7, 2018 Accepted March 13, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved

The Role of Near-infrared Spectroscopy in Cerebral Autoregulation Monitoring No abstract available

Comparison of 2 Automated Pupillometry Devices in Critically Ill Patients Background: Automated pupillometry may help detect early cerebral disturbances in critically ill patients. It remains unclear whether different automated pupillometry devices can detect pupillary abnormalities with similar accuracy. The aim of this study was to compare the performance of 2 commercially available automated pupillometry devices—Neurolight Algiscan (NL) and NPi-200 (NP) versus standard pupillary light reflex (PLR) examination in an unselected cohort of critically ill patients. Materials and Methods: This prospective study included all adult (>18 y) patients admitted to the intensive care unit of a university hospital over a 20-day period. Measurements were made consecutively with each method once during the intensive care unit stay in each patient. To assess sensitivity and specificity, we calculated areas under the curve of the receiver operating characteristic curve. Results: A total of 112 patients were included in the study. There was a significant correlation between the 2 automated pupillometry devices for pupil size, constriction to light stimulation, and constriction velocity but not for pupillary latency. The mean bias for pupil size measured by the NL and the NP devices was −0.12 (limit of agreement [LoA], −1.29 to 1.06) mm, for pupil constriction −1.0% (LoA, −9.3% to 7.2%), and for latency 0.02 (LoA, −0.22 to 0.25) ms. There was a significant correlation between pupil size evaluated by clinical examination and that using the NL or NP. The areas under the curves for pupil constriction measured by NL and NP were 0.93 and 0.91, respectively, to detect clinically reactive pupils. Conclusions: Although there was a significant correlation between NL and NP values as well as with clinical examination of the PLR, the 2 devices were not always interchangeable, especially for the evaluation of pupillary latency. F.S.T., B.M.S., and S.P.: conceived and designed the study. F.S.T., B.M.S., S.P., and J.C.: selected the population. B.M.S., F.S.T., S.P., J.C., and J.L.V.: screened and collected data from the population. F.S.T., M.O., and C.R.: conduced the statistical analysis. F.S.T., M.O., and C.R.: wrote the first draft of the manuscript. J.L.V., J.C., B.M.S., and S.P.: revised the text for intellectual content. All the coauthors read and approved the final text. M.O. has received lectures fees from Neuroptics. The remaining authors have no funding or conflicts of interest to disclose. Address correspondence to: Fabio S. Taccone, MD, PhD. E-mail: ftaccone@ulb.ac.be. Received November 17, 2018 Accepted March 8, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved

Bilateral Ultrasound-guided Erector Spinae Plane Block for Postoperative Analgesia in Lumbar Spine Surgery: A Randomized Control Trial Background: Major lumbar spine surgery causes severe postoperative pain. The primary objective of this randomized controlled study was to compare the effect of ultrasound (US)-guided erector spinae plane (ESP) block on 24-hour postoperative cumulative opioid requirements with standard (opioid-based) analgesia. Postoperative pain control and patient satisfaction were also assessed. Materials and Methods: Adults scheduled for elective lumbar spine surgery under general anesthesia were randomly assigned to the following (and they are): Control group-no preoperative ESP block, or ESP block group-preoperative bilateral US-guided ESP block. Both groups received standard general anesthesia during surgery. Postoperative pain score, number of patients requiring rescue analgesia, and total morphine consumption during the first 24 postoperative hours were recorded. Patient satisfaction was assessed 24 hours after surgery. Results: Postoperative morphine consumption was significantly lower in patients in the ESP group compared with those in the control group (1.4±1.5 vs. 7.2±2.0 mg, respectively; P<0.001). All patients in the control group required supplemental morphine compared with only 9 (45%) in the ESP block group (P=0.002). Pain scores immediately after surgery (P=0.002) and at 6 hours after surgery (P=0.040) were lower in the ESP block group compared with the control group. Patient satisfaction scores were more favorable in the block group (P<0.0001). Conclusions: US-guided ESP block reduces postoperative opioid requirement and improves patient satisfaction compared with standard analgesia in lumbar spine surgery patients. The authors have no funding or conflicts of interest to disclose. Address correspondence to: Swati Singh, MD. E-mail: deepakswat@yahoo.com. Received November 24, 2018 Accepted March 13, 2019 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved

Alexandros Sfakianakis
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