General Anesthetics to Treat Major Depressive Disorder: Clinical Relevance and Underlying Mechanisms

Effects of volatile anaesthetics on incidence of postoperative depression and anxiety symptoms in elderly patients: A retrospective analysis of a prospective cohort study

Studies have suggested volatile anaesthetics may alleviate depression and anxiety symptoms in patients. However, there is a paucity of research in this area. We wanted to determine the association between volatile anaesthetics and depression/anxiety symptoms in elderly patients within 7 days after surgery. This study retrospectively analysed data from a prospective database of patients aged 65 and above who underwent non-cardiac, non-neurosurgical elective surgery in 19 tertiary hospitals across 10 provinces in China. The study period spanned from April 1, 2020 to April 30, 2022. Patients receiving volatile anaesthetics received at least one volatile anaesthetic (sevoflurane, isoflurane, desflurane), and those who received non-volatile anaesthetics did not receive any volatile anaesthetic. Binary logistic regression analyses were conducted, and propensity score-matching (PSM) and subgroup analyses were also applied. A total of 7165 patients were included in the analysis. Among them, 4957 (69.18%) cases received volatile anaesthetics. The administration of volatile anaesthetics was associated with a lower rate of postoperative depression [22.76% vs. 27.26%, odds ratio (OR): 0.75, P < 0.001], and reduced the incidence of postoperative anxiety (19.59% vs. 24.68%, OR: 0.78, P < 0.001). The risk of postoperative depression (24.78% vs.27.93%, OR: 0.85, P = 0.035), and anxiety (21.45% vs. 25.92%, OR: 0.81, P = 0.006) were both significantly decreased in the volatile anaesthetics group in the PSM cohort. The results suggest that using volatile anaesthetics maybe associated with a reduction in the incidence of depression and anxiety in elderly patients during the early postoperative period.

Repurposing General Anesthetic Drugs to Treat Depression: A New Frontier for Anesthesiologists in Neuropsychiatric Care

During the last 100 years, the role of anesthesiologists in psychiatry has focused primarily on facilitating electroconvulsive therapy and mitigating postoperative delirium and other perioperative neurocognitive disorders. The discovery of the rapid and sustained antidepressant properties of ketamine, and early results suggesting that other general anesthetic drugs (including nitrous oxide, propofol, and isoflurane) have antidepressant properties, has positioned anesthesiologists at a new frontier in the treatment of neuropsychiatric disorders. Moreover, shared interest in understanding the biologic underpinnings of anesthetic drugs as psychotropic agents is eroding traditional academic boundaries between anesthesiology and psychiatry. This article presents a brief overview of anesthetic drugs as novel antidepressants and identifies promising future candidates for the treatment of depression. The authors issue a call to action and outline strategies to foster collaborations between anesthesiologists and psychiatrists as they work toward the common goals of repurposing anesthetic drugs as antidepressants and addressing mood disorders in surgical patients.

Efficacy of Esketamine among patients with treatment resistant depression in a 'real world' health-care setting in Israel

One in five people will likely suffer from major depressive disorder (MDD) during their life. Thirty percent of those with MDD will experience Treatment Resistant Depression (TRD), which is characterized by a failure to respond to two adequately administered trials of antidepressants. Esketamine is a rapidly acting intranasal antidepressant. Present-day Esketamine research has limited data in real-world populations. This study aimed to assess Esketamine treatment in a real-world community-based population. This naturalistic retrospective study included 94 individuals age 18 and above diagnosed with TRD, treated with Esketamine in an outpatient setting. The treatment was given in a single clinic, from January 2021 to January 2023, following approval of the Institutional Internal Review Board. The treatment included an acute phase (biweekly treatment, continuing 4-8 weeks), followed by a maintenance phase (once a week to once a month, for 6-12 months). Dosing ranged from 28 mg to 84 mg. Demographic and clinical data were retrospectively gathered. Depressive symptoms were assessed using the Quick Inventory of Depressive Symptomatology, at baseline and during each treatment phase. All patients completed the acute phase. About 60% completed the maintenance phase. Linear improvement of depressive symptoms was revealed in both phases. A sub-analysis of patients with comorbid personality disorder revealed a similar improvement pattern in the acute phase with milder improvement during the maintenance phase, compared to the other patients. This study supports the use of Esketamine for TRD, including patients with comorbid personality disorder and previous electroconvulsive therapy.

GABAergic neurons in the nucleus accumbens core mediate the antidepressant effects of sevoflurane

General anaesthetics have been widely applied to induce reversible loss and recovery of consciousness in clinical practice and have been shown to have reliably safe profiles. Since brief exposure to general anaesthetics can result in long-lasting and global changes in neuronal structures and function, these drugs also exhibit strong therapeutic potential for mood disorders. Preliminary and clinical studies have suggested that the inhalational anaesthetic drug sevoflurane might relieve symptoms of depression. However, the antidepressant effects of sevoflurane and the underlying mechanisms remain elusive. In the present study, we confirmed that the antidepressant and anxiolytic effects of inhaling 2.5% sevoflurane for 30 min were comparable to those of ketamine and could be sustained for 48 h. Activation of GABAergic (γ-aminobutyric acidergic) neurons in the nucleus accumbens core by chemogenetics was shown to mimic the antidepressant effects of inhaled sevoflurane, whereas inhibition of these neurons significantly prevented these effects. Considered together, these results suggested that sevoflurane might exert rapid and long-lasting antidepressant effects via modulation of neuronal activities in the nucleus accumbens core nucleus.

The efficacy and safety of asleep and awake subthalamic deep brain stimulation for Parkinson's disease patients: A 1-year follow-up

Introduction

Traditional DBS is usually conducted under local anesthesia (LA) which is intolerable to some patients, DBS under general anesthesia (GA) was opted to extended surgical indication. This study aimed to compare the efficacy and safety of bilateral subthalamic deep brain stimulation (STN-DBS) for Parkinson's disease (PD) under asleep and awake anesthesia state in 1-year postoperative follow-up.

Methods

Twenty-one PD patients were assigned to asleep group and 25 patients to awake group. Patients received bilateral STN-DBS under different anesthesia state. The PD participants were interviewed and assessed preoperatively and at 1-year postoperative follow-up.

Results

At 1-year follow-up, compared surgical coordinate in two groups, the left-side Y of asleep group showed more posterior than awake group (Y was-2.39 ± 0.23 in asleep group, -1.46 ± 0.22 in awake group, p = 0.007). Compared with preoperative OFF MED state, MDS-UPDRS III scores in OFF MED/OFF STIM state remained unchanged, while in OFF MED/ON STIM state were significantly improved in awake and asleep groups, yet without significant difference. Compared with preoperative ON MED state, MDS-UPDRS III scores in ON MED/OFF STIM, and ON MED/ON STIM state remained unchanged in both groups. In non-motor outcomes, PSQI, HAMD, and HAMA score significantly improved in asleep group compared to awake group at 1-year follow-up (PSQI, HAMD, and HAMA score in 1-year follow-up were 9.81 ± 4.43; 10.00 ± 5.80; 5.71 ± 4.75 in awake group, 6.64 ± 4.14; 5.32 ± 3.78; 3.76 ± 3.87 in asleep group, p = 0.009; 0.008; 0.015, respectively), while there was no significant difference in PDQ-39, NMSS, ESS, PDSS score, and cognitive function. Anesthesia methods was significantly associated with improvement of HAMA and HAMD score (p = 0.029; 0.002, respectively). No difference in LEDD, stimulation parameters and adverse events was observed between two groups.

Discussion

Asleep STN-DBS may be considered a good alternative method for PD patients. It is largely consistent with awake STN-DBS in motor symptoms and safety. Yet, it showed higher improvement in terms of mood and sleep compared to awake group at 1-year follow-up.

Short or moderate-time exposure to the inhalational anesthetics isoflurane and sevoflurane does not alter the marble-burying behavior in mice

Several studies suggest the involvement of glutamatergic neurotransmission in obsessive-compulsive disorder (OCD). Some NMDA glutamatergic receptor antagonists, such as the general anesthetic ketamine, have shown anti-OCD effects in preclinical and clinical studies. Therefore, we investigated whether the inhalational anesthetics isoflurane and sevoflurane, which are general anesthetics acting as NMDA receptor antagonists, would induce the same effects. To test our hypothesis, adult male Swiss mice were exposed to different concentrations of isoflurane (0.5, 1.5 or 3 %) or sevoflurane (0.8, 2.5 or 4 %) for 20 min (short-time exposure) or 1 h (moderate-time exposure) and submitted to the open field test (OFT) and the marble-burying test (MBT) in the same day (acute effect) or 7 days (long-lasting effect) after anesthetics administration. We found that single short or moderate-time exposure to isoflurane or sevoflurane, at sub-anesthetic or anesthetic concentrations, did not affect marble-burying behavior acutely or even 7 days after their administration. The same treatment schedules with isoflurane or sevoflurane did not impair total distance travelled in the OFT. A single moderate-time exposure to isoflurane (3 %) reduced, acutely, the central exploration of the open field, suggesting an anxiogenic-like effect of isoflurane in mice. Our results suggest that isoflurane and sevoflurane may not be promising anti-compulsive drugs.

Isoflurane produces antidepressant effects inducing BDNF-TrkB signaling in CUMS mice

RATIONALE

The volatile anesthetic isoflurane is suggested to produce a rapid and robust antidepressive effect in preliminary clinical trials. Recently, isoflurane was found to activate the tropomyosin receptor kinase B (TrkB) signaling which is the underlying mechanism of the rapid antidepressant ketamine.

OBJECTIVE

Our study investigated the effect of isoflurane anesthesia on chronic unpredictable mild stressed (CUMS) model in mice and verified the role of brain-derived neurotrophic factor (BDNF)/TrkB/ the mammalian target of rapamycin (mTOR) signaling in the antidepressant effect of isoflurane.

METHODS

We employed the CUMS model of depression to assess the rapid antidepressant effect of isoflurane by the forced swimming test (FST), the sucrose preference test (SPT), and the novelty suppressed feeding test (NSFT). The protein expression of BDNF and TrkB/protein kinase B (PKB or Akt)/mTOR was determined through Western blot. The dendritic spine density in the hippocampus and medial prefrontal cortex (PFC) was measured by the Golgi staining.

RESULTS

A brief burst-suppressing isoflurane anesthesia rapidly reversed the behavioral deficits caused by CUMS procedure, normalized the expression of BDNF and further activated the TrkB signaling pathway in CUMS-induced stressed mice in both prefrontal cortex (PFC) and hippocampus (HC). All of those behavioral and proteomic effects were blocked by K252a, a selective receptor inhibitor of TrkB. Isoflurane significantly promoted the formation of dendritic spines in both medial prefrontal cortex (mPFC), CA1, CA3, and DG of the hippocampus.

CONCLUSION

Our study indicates that isoflurane exerts a rapid antidepressant-like effect in CUMS depression animal model, and the activation of BDNF/TrkB signaling pathway plays an indispensable role in the biological and behavioral antidepressant effects of isoflurane. A single exposure to isoflurane could repair synaptic damage caused by chronic stimulation.

General Anesthesia: A Probe to Explore Consciousness

General anesthesia reversibly alters consciousness, without shutting down the brain globally. Depending on the anesthetic agent and dose, it may produce different consciousness states including a complete absence of subjective experience (unconsciousness), a conscious experience without perception of the environment (disconnected consciousness, like during dreaming), or episodes of oriented consciousness with awareness of the environment (connected consciousness). Each consciousness state may potentially be followed by explicit or implicit memories after the procedure. In this respect, anesthesia can be considered as a proxy to explore consciousness. During the recent years, progress in the exploration of brain function has allowed a better understanding of the neural correlates of consciousness, and of their alterations during anesthesia. Several changes in functional and effective between-region brain connectivity, consciousness network topology, and spatio-temporal dynamics of between-region interactions have been evidenced during anesthesia. Despite a set of effects that are common to many anesthetic agents, it is still uneasy to draw a comprehensive picture of the precise cascades during general anesthesia. Several questions remain unsolved, including the exact identification of the neural substrate of consciousness and its components, the detection of specific consciousness states in unresponsive patients and their associated memory processes, the processing of sensory information during anesthesia, the pharmacodynamic interactions between anesthetic agents, the direction-dependent hysteresis phenomenon during the transitions between consciousness states, the mechanisms of cognitive alterations that follow an anesthetic procedure, the identification of an eventual unitary mechanism of anesthesia-induced alteration of consciousness, the relationship between network effects and the biochemical or sleep-wake cycle targets of anesthetic agents, as well as the vast between-studies variations in dose and administration mode, leading to difficulties in between-studies comparisons. In this narrative review, we draw the picture of the current state of knowledge in anesthesia-induced unconsciousness, from insights gathered on propofol, halogenated vapors, ketamine, dexmedetomidine, benzodiazepines and xenon. We also describe how anesthesia can help understanding consciousness, we develop the above-mentioned unresolved questions, and propose tracks for future research.

Nonanesthetic Effects of Ketamine: A Review Article

Ketamine is considered a dissociative anesthetic medication, and it is commonly administered by a parenteral route. It works mainly by blocking the N-methyl-D-aspartate receptor. It inhibits the voltage-gated Na and K channels and serotonin and dopamine reuptake; also, it affects specific receptors, such as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, and aminobutyric acid A receptors. Ketamine appears to have particular mechanisms that are potentially involved during analgesic induction, including enhancing of descending inhibition and antiinflammatory effects. More recently, it has been shown that ketamine has potential in clinical practice for the management of chronic pain, cognitive function, depression, acute brain injury, and disorders of the immune system.

The relationship between seizure in electroconvulsive therapy and pupillary response using an automated pupilometer

OBJECTIVES

Seizure duration and morphology, postictal suppression, and sympathetic nervous system activation are all recommended as assessments of adequate seizure in electroconvulsive therapy (ECT). However, blood pressure and heart rate are not typically assessed as part of sympathetic nervous system activation because of the administration of anesthetic or cardiovascular agents during ECT. Although the pupils are known to reflect to the activity of autonomic nervous system and the degree of brain damage, previous studies have not examined the relationship between seizure of electroconvulsive therapy and pupillary response.

METHODS

We conducted 98 sessions of ECT with 13 patients, divided into two groups according to seizure quality: (1) adequate or (2) inadequate. Pupillary light reflex [% constriction = (maximum resting pupil size {MAX} - minimum pupil size after light stimulation)/MAX × 100] was measured using a portable infrared quantitative pupilometer before anesthesia induction and immediately after electrical stimulation.

RESULTS

The number regarded as adequate was 67 times and as inadequate was 31 times. Maximum pupil size at the control and immediately after electrical stimulation was similar between the adequate and inadequate groups. Pupillary light reflex was similar at the control between both groups, but significantly smaller immediately after stimulation in the adequate group (2.5 ± 3.6%) compared with the inadequate group (10.6 ± 11.5%). Receiver operating characteristic curve analysis revealed that pupillary light reflex (> 5.5%) predicted adequate seizure.

CONCLUSIONS

The current findings suggest that pupillary constriction immediately after ECT could provide a helpful method for assessing the efficacy of ECT.

Propofol for Treatment-Resistant Depression: A Pilot Study

BACKGROUND

We hypothesized that propofol, a unique general anesthetic that engages N-methyl-D-aspartate and gamma-aminobutyric acid receptors, has antidepressant properties. This open-label trial was designed to collect preliminary data regarding the feasibility, tolerability, and efficacy of deep propofol anesthesia for treatment-resistant depression.

METHODS

Ten participants with moderate-to-severe medication-resistant depression (age 18-45 years and otherwise healthy) each received a series of 10 propofol infusions. Propofol was dosed to strongly suppress electroencephalographic activity for 15 minutes. The primary depression outcome was the 24-item Hamilton Depression Rating Scale. Self-rated depression scores were compared with a group of 20 patients who received electroconvulsive therapy.

RESULTS

Propofol treatments were well tolerated by all subjects. No serious adverse events occurred. Montreal Cognitive Assessment scores remained stable. Hamilton scores decreased by a mean of 20 points (range 0-45 points), corresponding to a mean 58% improvement from baseline (range 0-100%). Six of the 10 subjects met the criteria for response (>50% improvement). Self-rated depression improved similarly in the propofol group and electroconvulsive therapy group. Five of the 6 propofol responders remained well for at least 3 months. In posthoc analyses, electroencephalographic measures predicted clinical response to propofol.

CONCLUSIONS

These findings demonstrate that high-dose propofol treatment is feasible and well tolerated by individuals with treatment-resistant depression who are otherwise healthy. Propofol may trigger rapid, durable antidepressant effects similar to electroconvulsive therapy but with fewer side effects. Controlled studies are warranted to further evaluate propofol's antidepressant efficacy and mechanisms of action. ClinicalTrials.gov: NCT02935647.

1,2-Diarylethylamine- and Ketamine-Based New Psychoactive Substances

While phencyclidine (PCP) and ketamine remain the most well-studied and widely known dissociative drugs, a number of other agents have appeared since the late 1950s and early 1960s, when the pharmacological potential of this class was first realized. For example, hundreds of compounds have been pursued as part of legitimate research efforts to explore these agents. Some of these found their way out of the research labs and onto illicit markets of the 1960s and following decades as PCP analogs. Other "illicit analogs" apparently never appeared in the scientific literature prior to their existence on clandestine markets, thus originating as novel innovations in the minds of clandestine chemists and their colleagues. Like so much else in this world, new technologies changed this dynamic. In the 1990s individuals separated by vast geographical distances could now communicate nearly instantaneously with ease through the Internet. Some individuals used this newly found opportunity to discuss the chemistry and psychoactive effects of dissociative drugs as well as to collaborate on the design and development of novel dissociative compounds. Similar to modern pharmaceutical companies and academic researchers, these seekers tinkered with the structure of their leads pursuing goals such as improved duration of action, analgesic effects, and reduced toxicity. Whether all these goals were achieved for any individual compound remains to be seen, but their creations have been let out of the bag and are now materialized as defined compositions of matter. Moreover, these creations now exist not only in and of themselves but live on further as permutations into various novel analogs and derivatives. In some cases these compounds have made their way to academic labs where potential clinical applications have been identified. These compounds reached wider distribution when other individuals picked up on these discussions and began to market them as "research chemicals" or "legal highs". The result is a continuously evolving game that is being played between legislatures, law enforcement, and research chemical market players. Two structurally distinct classes that have appeared as dissociative-based new psychoactive substances (NPS) are the 1,2-diarylethylamines and β-keto-arylcyclohexylamines. Examples of the former include diphenidine and various analogs such as fluorolintane and N-ethyl-lanicemine, and examples of the latter are analogs of ketamine such as methoxetamine, deschloroketamine, and 2-fluoro-2-deschloroketamine. The subject of this chapter is the introduction to some of the dissociative NPS from these classes and their known pharmacology that have emerged on the market in recent years.