Multimodal analgesia for craniotomy,                Purpose of review To explore the data for and against the use of the various components of multimodal analgesia in cranial neurosurgery. Recent findings Postcraniotomy pain is a challenging clinical problem in that analgesia must be accomplished without affecting neurologic function (i.e. ‘losing the neurologic exam’). The traditional approach with low-dose opioids is often insufficient and can cause well recognized side effects. Newer multimodal analgesic approaches have proven beneficial in a variety of other surgical patient populations. The combined use of multiple nonopioid analgesics offers the promise of improved pain control and reduced opioid administration, while preserving the clinical neurologic exam. Specifically, acetaminophen and gabapentinoids should be considered for craniotomy patients, both preoperatively and postoperatively. The gabapentinoids have the added benefit of reduced nausea. Scalp blocks have moderate quality evidence supporting their use over incisional infiltration alone, with analgesia that extends into the postoperative period. Intraoperative dexmedetomidine reduces postoperative opioid requirements with the added benefit of reduced postcraniotomy hypertension. Methocarbamol, NSAIDs [both nonspecific cyclooxygenase (COX) 1 and 2 inhibitors and specific COX-2 inhibitors], ketamine, and intravenous lidocaine require further data regarding safety and efficacy in craniotomy patients. Summary Opioids are the mainstay for treating acute postcraniotomy pain but should be minimized. The evidence to support a multimodal approach is growing; neuroanesthesiologists and neurosurgeons should seek to incorporate multimodal analgesia into the perioperative care of craniotomy patients. Preoperative and postoperative gabapentin and acetaminophen, intraoperative dexmedetomidine, and scalp blocks over incisional infiltration have the most data for benefit, with good safety profiles. Further research is needed to define the safety, efficacy, and dosing parameters for NSAIDs including COX-2 inhibitors, methocarbamol, ketamine, and intravenous lidocaine in cranial neurosurgery. Correspondence to David L. McDonagh, MD, Professor & Vice Chair; Department of Anesthesiology and Pain Management, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA. Tel: +1 214 648 6400; e-mail: David.mcdonagh@utsouthwestern.edu Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.

Anesthetic management of complex spine surgery in adult patients: a review based on outcome evidence Purpose of review The aim of this article is to review the evidence regarding the anesthetic management of blood loss, pain control, and position-related complications of adult patients undergoing complex spine procedures. Recent findings The most recent evidence of the anesthetic management of complex spine surgery was identified with a systematic search and graded. In our review, prophylactic tranexamic acid and optimal prone positioning were shown to be effective blood conservation strategies with minimal risks to the patients. Cell saver was cost-effective in complex surgeries with expected blood loss of greater than 500 ml. As for pain control, most interventions only produced mild analgesic effects, suggesting a multimodal approach is necessary to achieve optimal pain control after spine surgery. Regional techniques and NSAIDs were effective but because of their risks, their usage should be discussed with the surgical team. Further studies are required to assess the effectiveness, cost-effectiveness, and risks associated with combined uses of different analgesic interventions. On the basis of the available evidence, we recommend a combined use of gabapentinoids, ketamine, and opioids to achieve optimal analgesia. Lastly, literature for position-related injuries is heavily relied on case reports and the Anesthesia Closed Claim Study because of their rarity. Therefore, we advocate for a structured team-based approach with checklists to minimize position-related complications. Summary As the number and complexity of spine procedures are being performed worldwide is increasing, we suggested to bundle the aforementioned effective interventions as part of an ERAS spine protocol to improve the patient outcome of spine surgery. Correspondence to Jason Chui, MBChB, MSc, FANZCA, FHKCA, FHKAM, C3-106, University Hospital, 339 Windermere Road, London, ON, Canada N6A 5A5. Tel: +1 519 663 3270x34435; fax: +1 519 663 3161; e-mail: Jason.chui@lhsc.on.ca Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Website (www.co-anesthesiology.com). Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.

Hyperventilation in neurological patients: from physiology to outcome evidence Purpose of review Hyperventilation is commonly used in neurological patients to decrease elevated intracranial pressure (ICP) or relax a tense brain. However, the potentially deleterious effects of hyperventilation may limit its clinical application. The aim of this review is to summarize the physiological and outcome evidence related to hyperventilation in neurological patients. Recent findings Physiologically, hyperventilation may adversely decrease cerebral blood flow (CBF) and the match between the cerebral metabolic rate and CBF. In patients with severe traumatic brain injury (TBI), prolonged prophylactic hyperventilation with arterial carbon dioxide tension (PaCO2) less than 25 mmHg or during the first 24 h after injury is not recommended. Most patients (>90%) with an aneurysmal subarachnoid hemorrhage undergo hyperventilation (PaCO2 <35 mmHg); however, whether hyperventilation is associated with poor outcomes in this patient population is controversial. Hyperventilation is effective for brain relaxation during craniotomy; however, this practice is not based on robust outcome evidence. Summary Although hyperventilation is commonly applied in patients with TBI or intracranial hemorrhage or in those undergoing craniotomy, its effects on patient outcomes have not been proven by quality research. Hyperventilation should be used as a temporary measure when treating elevated ICP or to relax a tense brain. Outcome research is needed to better guide the clinical use of hyperventilation in neurological patients. This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. http://creativecommons.org/licenses/by-nc-nd/4.0 Correspondence to E. Wang, Department of Anesthesiology, Xiangya Hospital Central South University, Xiangya Road 87#, Changsha 410008, PR China. Tel: +86-0731-84327413; fax: +86-0731-84327413; e-mail: ewang324@csu.edu.cn Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.

The impact of frailty and sarcopenia on patient outcomes after complex spine surgery Purpose of review Frailty and sarcopenia represent a state of increased fragility and decreased reserve, and both have been associated with worse outcomes after surgery. The present review focuses on the definitions and measurement tools used to assess frailty and sarcopenia in patients with spinal disorder, and the relationships between frailty, sarcopenia, and postoperative outcomes in patients undergoing complex spine surgery. Recent findings Complex spine surgery is associated with a high rate of adverse events when using a validated, prospective data collection system. Recent studies have demonstrated that patients with spine surgery with frailty and sarcopenia have a higher risk of adverse events, although this relationship varies depending on the measurement tool and specific population studied. Both general and specific frailty assessment tools have been used in the spine surgery population, however the optimal tool is not known. Spinal disorders such as lumbar stenosis contribute to the frailty phenotype, and may be reversible with surgery. Summary Frailty and sarcopenia are increasingly recognized as important predictors of adverse outcomes after complex spine surgery. The optimal tool to measure frailty and sarcopenia in patients with spinal disorders remains unclear, and the role of surgery as an intervention to reverse frailty requires further investigation. Correspondence to Dr Alana M. Flexman, Department of Anesthesiology and Perioperative Care, Vancouver General Hospital, Room 2449 JPP 899 West 12th Avenue, Vancouver, BC, Canada, V5Z 1M9. Tel: +1 604 875 4304; fax: +1 604 875 5209; e-mail: alana.flexman@vch.ca Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.

Transfusion in adults and children undergoing neurosurgery: the outcome evidence Purpose of review Transfusion is a common practice during neurosurgery. However, there is no evidence-based consensus on transfusion practice in neurosurgery. This review summarizes the evidence pertinent to the commonly used transfusion triggers in neurosurgical patients. Recent findings In the field of neurosurgery, there is only one randomized controlled trial, performed in patients with traumatic brain injury, to investigate the transfusion trigger of red blood cells. There is a lack-of-quality evidence pertinent to the transfusion triggers of other blood products. Most of the transfusion triggers used for neurosurgical patients are extrapolated from the evidence based on studies performed in nonneurosurgical patients. Clinical experience and expert opinions have played a major role in transfusion practice in neurosurgery. Summary There is a scarcity of high-quality outcome-based evidence for transfusion practice in neurosurgery. In the absence of quality evidence, the transfusion practice in neurosurgical patients should be based on the understanding of the complex pathophysiology related to anemia and coagulopathy and the balance between the risks and benefits associated with blood product transfusion. The practice guided by tissue oximeter and viscoelastic tests appears promising, but needs to be validated by future studies. Correspondence to Tianlong Wang, MD, PhD, Department of Anesthesiology, Xuanwu Hospital of Capital Medical University, 45 Changchun Street, Beijing 100053, China. Tel: +86 139 1052 5304; e-mail: w_tl5595@hotmail.com Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.

Neurological complications after cardiac surgery: anesthetic considerations based on outcome evidence Purpose of review Neurological complications after cardiac surgery remain prevalent. This review aims to discuss the modifiable and outcome-relevant risk factors based on an up-to-date literature review, with a focus on interventions that may improve outcomes. Recent findings There is a close relationship between intraoperative blood pressure and postoperative neurological outcomes in cardiac surgical patients based on cohort studies and randomized controlled trials. Adopting an optimal and personalized blood pressure target is essential; however, the outstanding issue is the determination of this target. Maintaining cerebral tissue oxygen saturation at least 90% patient's baseline during cardiac surgery may be beneficial; however, the outstanding issues are effective intervention protocols and quality outcome evidence. Maintaining hemoglobin at least 7.5 g/dl may be adequate for cardiac surgical patients; however, this evidence is based on the pooled results of thousands of patients. We still need to know the optimal hemoglobin level for an individual patient, which is of particular relevance during the decision-making of transfusion or not. Summary The available evidence highlights the importance of maintaining optimal and individualized blood pressure, cerebral tissue oxygen saturation and hemoglobin level in improving neurological outcomes after cardiac surgery. However, outstanding issues remain and need to be addressed via outcome-oriented further research. This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. http://creativecommons.org/licenses/by-nc-nd/4.0 Correspondence to Wei Mei, MD, Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Road, Wuhan 430030, China. Tel: +86 27 83662673; e-mail: wmei@hust.edu.cn Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.

Anesthesia and brain tumor surgery: technical considerations based on current research evidence Purpose of review Anesthetics may influence cancer recurrence and metastasis following surgery by modulating the neuroendocrine stress response or by directly affecting cancer cell biology. This review summarizes the current evidence on whether commonly used anesthetics potentially affect postoperative outcomes following solid organ cancer surgery with particular focus on neurological malignancies. Recent findings Despite significant improvement in diagnostic and therapeutic technology over the past decades, mortality rates after cancer surgery (including brain tumor resection) remains high. With regards to brain tumors, interaction between microglia/macrophages and tumor cells by multiple biological factors play an important role in tumor progression and metastasis. Preclinical studies have demonstrated an association between anesthetics and brain tumor cell biology, and a potential effect on tumor progression and metastasis has been revealed. However, in the clinical setting, the current evidence is inadequate to draw firm conclusions on the optimal anesthetic technique for brain tumor surgery. Summary Further work at both the basic science and clinical level is urgently needed to evaluate the association between perioperative factors, including anesthetics/technique, and postoperative brain tumor outcomes. Correspondence to Daqing Ma, Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea & Westminster Hospital 369 Fulham Road, London SW10 9NH, UK. Tel: +44 203315 8495; fax: +44 203315 5109; e-mail: d.ma@imperial.ac.uk Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.

Neuroanesthesia and outcomes: evidence, opinions, and speculations on clinically relevant topics Purpose of review The objective of this review is to identify outstanding topics most relevant to neuroanesthesia practice and patient outcomes. We discuss the role of awake craniotomy, choice of general anesthetic agents, monitoring of anesthetic ‘depth’, mannitol-induced diuresis, neurophysiological monitoring, hyperventilation, and cerebral hypoperfusion. Recent findings Awake craniotomy, although a technique likely underused, is associated with enhanced recovery after surgery and prolonged survival after brain tumor resection compared with surgery under general anesthesia. The choice of general anesthetic must balance patient and surgical factors. Although propofol may be associated with favorable oncologic outcomes, currently available retrospective evidence does not specifically address neurosurgical patients. Both the definition and monitoring of anesthetic ‘depth’ remains elusive. Neuroanesthesiologists need to recognize and manage intraoperative light anesthesia in a timely fashion. Further evidence related to the optimal management of mannitol-induced diuresis and hyperventilation in neurosurgical patients is needed. Contemporary neurophysiological monitoring can reasonably detect intraoperative neurologic injury; however, its effect on patient outcome is unclear. Finally, cerebral hypoperfusion without stroke may be common; however, the clinical significance requires further investigation. Summary We provide an overview of several topics that are relevant to neuroanesthesia practice and patient outcomes based on evidence, opinions, and speculations. Our review highlights the need for further outcome-oriented studies to specifically address these clinically relevant issues. Correspondence to Lingzhong Meng, MD, Professor and Division Chief, Department of Anesthesiology, Yale University School of Medicine, 333 Cedar Street, TMP 3, PO Box 208051, New Haven, CT 06520, USA. Tel: +1 203 785 2802; e-mail: lingzhong.meng@yale.edu Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.

Anaesthesia for stroke thrombectomy: technical considerations based on outcome evidence Purpose of review Stroke is the second leading cause of death and the third leading cause of disability worldwide. Treatment is time limited and delays cost lives. This review discusses modern stroke management, during a time when treatments and guidelines are rapidly evolving. Recent findings Stroke thrombectomy has become the therapy of choice for large vessel occlusion (LVO) strokes. Perfusion imaging techniques, both computed tomography (CT) and MRI, now allow treatment beyond a set time window in specific patients. Both general anaesthesia and conscious sedation are options for patients undergoing stroke thrombectomy. Summary An individualized approach to the patient's anaesthetic management is optimal, and depends on close communication with the neurointerventionalist regarding patient and procedure-specific variables. No specific anaesthetic agent is preferred. Guiding principles are minimization of time delay, and maintenance of cerebral perfusion pressure. Correspondence to David L. McDonagh, MD, 5323 Harry Hines Blvd., Dallas, TX, USA. Tel: +1 214 648 6400; e-mail: David.mcdonagh@utsouthwestern.edu Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.

Neurophysiological monitoring during neurosurgery: anesthetic considerations based on outcome evidence Purpose of review This article reviews the recent outcome studies that investigated intraoperative neurophysiological monitoring (IONM) during spine, neurovascular and brain tumor surgery. Recent findings Several recent studies have focused on identifying which types of neurosurgical procedures might benefit most from IONM use. Despite conflicting literature regarding its efficacy in improving neurological outcomes, many experts have advocated for the use of IONM in neurosurgery. Several themes have emerged from the recent literature: the entire perioperative team must always work together to ensure adequate communication and intervention; systems and checklists, in which each member of the perioperative team has a clearly defined role, can be useful in the event of a sudden intraoperative changes in electrophysiological signals; regardless of the IONM modality used, any sudden change in electrophysiological signal should prompt an immediate and appropriate intervention; a multimodal IONM approach is often, but not always, advantageous over a single IONM approach. Summary For neurosurgical procedures that can be complicated by neural injury, the use of IONM should be considered according to specific patient and surgical factors. Future studies should focus on improving IONM technology and optimizing sensitivity and specificity for detecting any impending neural damage. Correspondence to Shaun E. Gruenbaum, MD, PhD, Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Jacksonville, FL 32224, USA. Tel: +1 904 956 3398; e-mail: gruenbaum.shaun@mayo.edu Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.