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.Awake craniotomy: anesthetic considerations based on outcome evidence
Purpose of review This review highlights anaesthesia management options for awake craniotomy and discusses the advantages and disadvantages of different approaches, intraoperative complications and future directions. Recent findings For lesions located within or adjacent to eloquent regions of the brain, awake craniotomy allows maximal tumour resection with minimal consequences on neurological function. Various techniques have been described to provide anaesthesia or sedation and analgesia during the initial craniotomy, and rapid return to consciousness for intraoperative testing and tumour resection; there is no evidence that one approach is superior to another. Although very safe, awake craniotomy is associated with some well recognized complications; most are minor and self-limiting or easily reversed. In experienced hands, failure of awake craniotomy occurs in fewer than 2% of cases, irrespective of anaesthesia technique. Although brain tumour surgery remains the most common indication for awake craniotomy, the technique is finding utility in other neurosurgical procedures. Summary Several anaesthetic approaches are available for the management of patients during awake craniotomy. The choice of technique should be based on individual patient factors, location and duration of surgery, and anaesthesiologist expertise and experience. Appropriate patient selection and excellent multidisciplinary team working is associated with high levels of procedural success and patient satisfaction.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.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.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.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.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.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.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.
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