Frailty Assessment and Prehabilitation Before Complex Spine Surgery in Patients With Degenerative Spine Disease: A Narrative Review.

Degenerative spine disease increases in prevalence and may become debilitating as people age. Complex spine surgery may offer relief but becomes riskier with age. Efforts to lessen the physiological impact of surgery through minimally invasive techniques and enhanced recovery programs mitigate risk only after the decision for surgery.

Functional connectivity predicts changes in attention observed across minutes, days, and months.

The ability to sustain attention differs across people and changes within a single person over time. Although recent work has demonstrated that patterns of functional brain connectivity predict individual differences in sustained attention, whether these same patterns capture fluctuations in attention within individuals remains unclear. Here, across five independent studies, we demonstrate that the sustained attention connectome-based predictive model (CPM), a validated model of sustained attention function, generalizes to predict attentional state from data collected across minutes, days, weeks, and months.

Multi-modal analysis of functional connectivity and cerebral blood flow reveals shared and unique effects of propofol in large-scale brain networks.

Anesthesia-induced changes in functional connectivity and cerebral blow flow (CBF) in large-scale brain networks have emerged as key markers of reduced consciousness. However, studies of functional connectivity disagree on which large-scale networks are altered or preserved during anesthesia, making it difficult to find a consensus amount studies. Additionally, pharmacological alterations in CBF could amplify or occlude changes in connectivity due to the shared variance between CBF and connectivity.

Functional Connectivity and Anesthesia.

Various anesthetic agents at various concentrations have been studied as described above. The analysis techniques for the BOLD fMRI data are also institution and investigator dependent. Despite this variability there seems to be some common patterns in the connectivity effect of various anesthetics/sedatives when the endpoint is LOC.

fMRI and Anesthesia.

BOLD activation studies discussed vary in the anesthetic agent studied (propofol, sevoflurane, and isoflurane), the concentration of the anesthetic (mostly under 0.5MAC or equivalent doses), and the activation paradigm/functional activation. The data analysis technique also differs between the studies.

Geriatric Pharmacology.

Aging involves changes in several physiologic processes that lead to decreased volumes of distribution, slowed metabolism, and increased end-organ sensitivity to anesthetics. These changes generally result in increased potency. Elderly patients require less anesthetic medication, but the true extent of reduction is underappreciated and less uniformly practiced.

Connectivity.

Purpose Of Review: Connectivity is a technique that uses functional MRI (fMRI) to explore global brain function in healthy and diseased states. Connectivity is now being studied as a part of global brain function in major national and international studies. It is, therefore, timely to review its relevance to anaesthesia.

Functional MRI and pain.

Purpose Of Review: This article reviews the current state of knowledge in functional MRI (fMRI) research related to pain with primary focus on clinical studies.

Recent Findings: With fMRI, the subjective effects of pain (sensory, affect, emotion, and motor components) can be objectively imaged. Although the conventional fMRI technique has been the isolation of regions in the brain transmitting and modulating pain, functional connectivity measurement can identify functionally linked regions associated with pain processing.

The impact of NMDA receptor blockade on human working memory-related prefrontal function and connectivity.

Preclinical research suggests that N-methyl-D-aspartate glutamate receptors (NMDA-Rs) have a crucial role in working memory (WM). In this study, we investigated the role of NMDA-Rs in the brain activation and connectivity that subserve WM. Because of its importance in WM, the lateral prefrontal cortex, particularly the dorsolateral prefrontal cortex and its connections, were the focus of analyses.

NMDA receptor function in large-scale anticorrelated neural systems with implications for cognition and schizophrenia.

Glutamatergic neurotransmission mediated by N-methyl-d-aspartate (NMDA) receptors is vital for the cortical computations underlying cognition and might be disrupted in severe neuropsychiatric illnesses such as schizophrenia. Studies on this topic have been limited to processes in local circuits; however, cognition involves large-scale brain systems with multiple interacting regions. A prominent feature of the human brain's global architecture is the anticorrelation of default-mode vs.

A whole-brain voxel based measure of intrinsic connectivity contrast reveals local changes in tissue connectivity with anesthetic without a priori assumptions on thresholds or regions of interest.

The analysis of spontaneous fluctuations of functional magnetic resonance imaging (fMRI) signals has recently gained attention as a powerful tool for investigating brain circuits in a non-invasive manner. Correlation-based connectivity analysis investigates the correlations of spontaneous fluctuations of the fMRI signal either between a single seed region of interest (ROI) and the rest of the brain or between multiple ROIs. To do this, a priori knowledge is required for defining the ROI(s) and without such knowledge functional connectivity fMRI cannot be used as an exploratory tool for investigating the functional organization of the brain and its modulation under different conditions.

Functional connectivity and alterations in baseline brain state in humans.

This work examines the influence of changes in baseline activity on the intrinsic functional connectivity fMRI (fc-fMRI) in humans. Baseline brain activity was altered by inducing anesthesia (sevoflurane end-tidal concentration 1%) in human volunteers and fc-fMRI maps between the pre-anesthetized and anesthetized conditions were compared across different brain networks. We particularly focused on low-level sensory areas (primary somatosensory, visual, and auditory cortices), the thalamus, and pain (insula), memory (hippocampus) circuits, and the default mode network (DMN), the latter three to examine higher-order brain regions.

Anesthetic effects on regional CBF, BOLD, and the coupling between task-induced changes in CBF and BOLD: an fMRI study in normal human subjects.

Functional MR imaging was performed in sixteen healthy human subjects measuring both regional cerebral blood flow (CBF) and blood oxygen level dependent (BOLD) signal when visual and auditory stimuli were presented to subjects in the presence or absence of anesthesia. During anesthesia, 0.25 mean alveolar concentration (MAC) sevoflurane was administrated.

Understanding anesthesia through functional imaging.

Purpose Of Review: This review will highlight the recent functional magnetic resonance imaging, positron emission tomogram scan and connectivity studies in anesthesia and analgesia.

Recent Findings: In regional cerebral blood flow (rCBF) studies with isoflurane and sevoflurane, there is a consistent pattern of rise in rCBF in the anterior cingulate cortex and insula while the thalamus, lingual cortex and cerebellum show a decrease in rCBF, in a dose range of 0.2-1 minimum alveolar concentration.

Vagus nerve stimulation therapy for seizures.

Of the 3 million patients with seizures in North America approximately 70% have effective seizure control with medications. In the group refractory to medical treatment only a minority fit the criteria for surgical therapy. Vagus nerve stimulation therapy seems to be a suitable nonpharmacologic therapy for reducing seizure frequency in these cases.

Spatial nonuniformity of the resting CBF and BOLD responses to sevoflurane: in vivo study of normal human subjects with magnetic resonance imaging.

Pulsed arterial spin labeling magnetic resonance imaging (MRI) was performed to investigate the local coupling between resting regional cerebral blood flow (rCBF) and BOLD (blood oxygen level dependent) signal changes in 22 normal human subjects during the administration of 0.25 MAC (minimum alveolar concentration) sevoflurane. Two states were compared with subjects at rest: anesthesia and no-anesthesia.

Sevoflurane 0.25 MAC preferentially affects higher order association areas: a functional magnetic resonance imaging study in volunteers.

Background: Functional magnetic resonance imaging (fMRI) can objectively measure the subjective effects of anesthesia. Memory-related regions (association areas) are affected by subanesthetic doses of volatile anesthetics. In this study we measured the regional neuronal effects of 0.

Hypothermia for brain protection and resuscitation.

Purpose Of Review: Clinicians are actively looking for an effective brain protection technique. With pharmacologic agents, several phase III trials in stroke, severe traumatic brain injury, and post-cardiac arrest survivors have failed. Hence there is renewed interest in mild to moderate hypothermia for brain protection.

Sedation after spinal anesthesia in elderly patients: a preliminary observational study with the PSA-4000.

Purpose: Neuraxial blockade is known to have a sedative effect, decreasing the need for inhalational and iv anesthetic agents. The purpose of the present study was to quantify the sedative effect of spinal anesthesia and to determine the time of maximum sedation.

Methods: This is an observational study in which 20 unsedated patients were scheduled to undergo urologic and orthopedic surgeries under spinal anesthesia.