Anesthetics fragment hippocampal network activity, alter spine dynamics, and affect memory consolidation.

General anesthesia is characterized by reversible loss of consciousness accompanied by transient amnesia. Yet, long-term memory impairment is an undesirable side effect. How different types of general anesthetics (GAs) affect the hippocampus, a brain region central to memory formation and consolidation, is poorly understood. Using extracellular recordings, chronic 2-photon imaging, and behavioral analysis, we monitor the effects of isoflurane (Iso), medetomidine/midazolam/fentanyl (MMF), and ketamine/xylazine (Keta/Xyl) on network activity and structural spine dynamics in the hippocampal CA1 area of adult mice. GAs robustly reduced spiking activity, decorrelated cellular ensembles, albeit with distinct activity signatures, and altered spine dynamics. CA1 network activity under all 3 anesthetics was different to natural sleep. Iso anesthesia most closely resembled unperturbed activity during wakefulness and sleep, and network alterations recovered more readily than with Keta/Xyl and MMF. Correspondingly, memory consolidation was impaired after exposure to Keta/Xyl and MMF, but not Iso. Thus, different anesthetics distinctly alter hippocampal network dynamics, synaptic connectivity, and memory consolidation, with implications for GA strategy appraisal in animal research and clinical settings.

Reported Xylazine Use Among Adults Aged ≥18 Years Evaluated for Substance Use Treatment - United States, July 2022-September 2023.

Xylazine has been increasingly detected in illegally manufactured fentanyl (IMF) products and overdose deaths in the United States; most xylazine-involved overdose deaths involve IMF. A convenience sample of U.S. adults aged ≥18 years was identified from those evaluated for substance use treatment during July 2022-September 2023. Data were collected using the Addiction Severity Index-Multimedia Version clinical assessment tool. Among 43,947 adults, 6,415 (14.6%) reported IMF or heroin as their primary lifetime substance-use problem; 5,344 (12.2%) reported recent (i.e., past-30-day) IMF or heroin use. Among adults reporting IMF or heroin as their primary lifetime substance-use problem, 817 (12.7%) reported ever using xylazine. Among adults reporting recent IMF or heroin use, 443 (8.3%) reported recent xylazine use. Among adults reporting IMF or heroin use recently or as their primary lifetime substance-use problem, those reporting xylazine use reported a median of two past nonfatal overdoses from any drug compared with a median of one overdose among those who did not report xylazine use; as well, higher percentages of persons who reported xylazine use reported other recent substance use and polysubstance use. Provision of nonjudgmental care and services, including naloxone, wound care, and linkage to and retention of persons in effective substance use treatment, might reduce harms including overdose among persons reporting xylazine use.

The Acute Impact of Propofol on Blood-Brain Barrier Integrity in Mice.

PURPOSE: We investigated whether short term infusion of propofol, a highly lipophilic agonist at GABAA receptors, which is in widespread clinical use as anesthetic and sedative, affects passive blood-brain barrier (BBB) permeability in vivo. METHODS: Mice were anesthetized with an intraperitoneal injection of ketamine/xylazine followed by a continuous IV infusion of propofol in lipid emulsion through a tail vein catheter. Control groups received ketamine/xylazine anesthesia and an infusion of Intralipid, or ketamine/xylazine anesthesia only. [13C12]sucrose as a permeability marker was injected as IV bolus 15 min after start of the infusions. Brain uptake clearance, Kin, of sucrose was calculated from the brain concentrations at 30 min and the area under the plasma-concentration time curve. We also measured the plasma and brain concentration of propofol at the terminal time point. RESULTS: The Kin value for propofol-infused mice was significantly higher, by a factor of 1.55 and 1.87, compared to the Intralipid infusion and the ketamine/xylazine groups, respectively, while the control groups were not significantly different. No difference was seen in the expression levels of tight junction proteins in brain across all groups. The propofol plasma concentration at the end of infusion (10.7 µM) matched the clinically relevant range of blood concentrations reported in humans, while concentration in brain was 2.5-fold higher than plasma. CONCLUSIONS: Propofol at clinical plasma concentrations acutely increases BBB permeability, extending our previous results with volatile anesthetics to a lipophilic injectable agent. This prompts further exploration, potentially refining clinical practices and ensuring safety, especially during extended propofol infusion schemes.

National Institute on Drug Abuse Clinical Trials Network Meeting Report: Managing Patients Exposed to Xylazine-Adulterated Opioids in Emergency, Hospital and Addiction Care Settings.

Used as a veterinary sedative and not approved for human use, xylazine has been increasingly linked with opioid overdose deaths in the United States. A growing number of people have been exposed to xylazine in the illicit opioid supply (especially fentanyl) or in other drugs, particularly in some areas of the Northeast. Xylazine is an α-2 adrenergic agonist that decreases sympathetic nervous system activity. When combined with fentanyl or heroin, it is purported to extend the duration of the opioid's sedative effect and to cause dependence and an associated withdrawal syndrome; however, data to support these concerns are limited. Despite the escalating frequency of detection of xylazine in people with nonfatal and fatal opioid overdose, direct links to these outcomes have not been identified. Because the strongest causal link is to fentanyl coexposure, ventilatory support and naloxone remain the cornerstones of overdose management. Xylazine is also associated with severe tissue injury, including skin ulcers and tissue loss, but little is known about the underlying mechanisms. Nonetheless, strategies for prevention and treatment are emerging. The significance and clinical effects of xylazine as an adulterant is focused on 4 domains that merit further evaluation: fentanyl-xylazine overdose, xylazine dependence and withdrawal, xylazine-associated dermal manifestations, and xylazine surveillance and detection in clinical and nonclinical settings. This report reflects the Proceedings of the National Institute on Drug Abuse Center for the Clinical Trials Network convening of clinical and scientific experts, federal staff, and other stakeholders to describe emerging best practices for treating people exposed to xylazine-adulterated opioids. Participants identified scientific gaps and opportunities for research to inform clinical practice in emergency departments, hospitals, and addiction medicine settings.

Xylazine: A Drug Adulterant of Clinical Concern.

PURPOSE OF REVIEW: The opioid epidemic has been responsible for significant morbidity and mortality in the USA and worldwide. As a result, it is essential to recognize the threat these potent drugs can cause when illicitly used. Specifically, introducing fentanyl as a drug adulterant has been shown to impact overdose rates drastically. In this regard, the Drug Enforcement Agency recently released a public safety alert announcing the new threat of a new adulterant called xylazine. Xylazine is a powerful animal sedative with a different mechanism of action when compared to illicit opioids such as heroin and fentanyl. Xylazine is typically injected intravenously via a syringe, often in combination with multiple other drugs. One of the most common drugs, xylazine, is taken in combination with fentanyl, with users of this drug combination describing xylazine as prolonging the euphoric sensation produced by fentanyl. RECENT FINDINGS: Xylazine may cause adverse effects such as bradycardia, brief hypertension followed by hypotension, premature ventricular contractions, ataxia, slurred speech, sedation, and respiratory depression. Much of the recent literature on xylazine use in humans comes from case reports and review articles. Related to widespread use in veterinary medicine and increasing circulation in illicit drug markets, there is a critical need for public awareness and additional clinical-based studies to further increase understanding of mediated or modulated pharmacological effects of xylazine in humans. Further research is urgently needed to more clearly understand the implications of unregulated xylazine in the illicit drug market, to formulate public health interventions, and to implement harm reduction strategies.

Xylazine Adulteration of the Heroin-Fentanyl Drug Supply : A Narrative Review.

Xylazine is an animal sedative, approved by the U.S. Food and Drug Administration, that is commonly used in veterinary medicine and is not approved for human use. Since 2016, xylazine has consistently appeared in the illicitly manufactured fentanyl supply and has significantly increased in prevalence, likely due to its low cost, easy availability, and presumed synergistic psychoactive effect. Clinical experience along with the available pertinent research were used to review xylazine adulteration of the drug supply and provide guidance on the care of patients exposed to xylazine. This review discusses xylazine pharmacology, animal and human clinical effects, and what is known to date about care of patients experiencing acute overdose, xylazine-fentanyl withdrawal, and xylazine-associated wounds.

A confirmed case of xylazine-induced skin ulcers in a person who injects drugs in Miami, Florida, USA.

BACKGROUND: Xylazine is an alpha-2 adrenergic receptor agonist that has emerged as a contaminant in the illicit drug supply of fentanyl. Xylazine use may be suspected in naloxone-resistant overdoses and atypical, chronic wounds in people who use drugs (PWUD). This case is unique because it is the first case to our knowledge describing wound care for a xylazine-induced wound with a confirmatory xylazine test strip (XTS) in the setting of a syringe services program (SSP) and in the state of Florida. CASE PRESENTATION: A 43-year-old woman with a past medical history of severe opioid use disorder and stimulant use disorder presented to a student-run clinic at a Miami SSP for wound care. She had multiple ulcerations diffusely over her bilateral forearms with surrounding erythema and warmth. Seven weeks later, she presented to clinic again for wound care because her wounds had progressed. At this visit, a XTS was used to confirm the presence of xylazine in her urine. Wound care management and harm reduction strategies employed at both visits were informed by best clinical judgement due to lack of formal guidelines at the time. Wound outcomes are unknown as the patient has not returned to clinic. CONCLUSIONS: Many PWUD at highest risk for acute and chronic health consequences of xylazine-adulterated fentanyl do not have access to healthcare outside of low barrier clinics and SSPs due to lack of insurance or mistrust of the traditional healthcare system due to stigma. There is an urgent need for access to XTS for PWUD and clinical practice guidelines for the treatment of xylazine-related wounds in outpatient clinics.

Reported xylazine exposure highly associated with overdose outcomes in a rapid community assessment among people who inject drugs in Baltimore.

BACKGROUND: Addressing xylazine harms are now a critical harm reduction priority, but relatively little epidemiological information exists to determine prevalence, magnitude, and correlates of xylazine use or related outcomes. METHODS: We conducted a rapid behavioral survey among people who inject drugs (n = 96) in Baltimore November-December 2022. Using a novel indicator of self-reported presumed xylazine effects, we examined prevalence and sociodemographic correlates of past year presumed xylazine effects and association with overdose and wound-related outcomes. Chi-square and descriptive statistics were used to examine bivariate associations overall and separately for those who reported xylazine by name and by reported fentanyl use frequency. RESULTS: Almost two-thirds (61.5%) reported experiencing xylazine effects. There were no differences by socio-demographics, but xylazine effects were more commonly reported among those who reported injecting alone (66% vs 38%%, p < 0.007) and daily fentanyl use (47% vs 24% p < 0.003). Those reporting xylazine exposure was three times as likely to report overdose (32% vs 11%, p < 0.03) and twice as likely to have used naloxone (78% vs 46%, p < 0.003). They also more commonly reported knowing someone who died of an overdose (92% vs 76%, p < 0.09) and to report an abscess requiring medical attention (36% vs 19%, p < 0.80). These associations were higher among respondents who specifically named xylazine and those who used fentanyl more frequently, but fentanyl frequency did not fully explain the heightened associations with xylazine effects. CONCLUSIONS: This study provides insight into the scope of xylazine exposure and associated health concerns among community-based PWID and suggests measures that may be instrumental for urgently needed research.

Xylazine co-occurrence with illicit fentanyl is a growing threat in the Deep South: a retrospective study of decedent data.

BACKGROUND: Xylazine is a dangerous veterinary sedative found mainly in illicit fentanyl in the Northeast and Midwest. Its role in the Deep South overdose crisis is not well-characterized. METHODS: We conducted a retrospective review of autopsy data in Jefferson County, Alabama to identify trends in xylazine prevalence among people who fatally overdosed from June 2019 through June 2023. RESULTS: 165 decedents met inclusion criteria. While the first identified xylazine-associated overdose was in June 2019, xylazine has become consistently prevalent since January 2021. All cases of xylazine-associated fatal overdoses were accompanied by fentanyl, and most (75.4%) involved poly-drug stimulant use. The average age was 42.2, and most decedents were white (58.8%) and male (68.5%). Overall, 18.2% of people were unhoused at the time of death. DISCUSSION: Xylazine is prevalent in the Deep South. Efforts to promote harm reduction, publicly viewable drug supply trends, and legalization of drug checking and syringe service programs should be prioritized.

Syringe services program staff and participant perspectives on changing drug consumption behaviors in response to xylazine adulteration.

BACKGROUND: Xylazine is an increasingly common adulterant in the North American unregulated drug supply that is associated with adverse health outcomes (e.g., skin infections, overdose). However, there are significant knowledge gaps regarding how xylazine was initially identified and how syringe services program (SSP) staff and clients (people who use drugs) responded to its emergence. METHODS: From June-July 2023, we conducted qualitative interviews with medical (e.g., clinicians) and frontline SSP staff (e.g., outreach workers) and adult clients with a history of injection drug use at a Miami-based SSP. Inductive memos identified emergent codes; thematic analysis involving team consensus established final themes. RESULTS: From interviews with SSP staff (n = 8) and clients (n = 17), xylazine emergence was identified at different times, in various ways. Initially, during summer 2022, clients identified a "tranquilizer-like substance" that worsened sedation and withdrawal and caused wounds. SSP medical staff later identified this adulterant as xylazine by treating new medical cases and through diverse information-sharing networks that included professional societies and news sources; however, frontline SSP staff and clients needed additional educational resources about xylazine and its side effects. With limited guidance on how to reduce harm from xylazine, SSP clients altered their drug consumption routes, reduced drug use, and relied on peers' experiences with the drug supply to protect themselves. Some individuals also reported preferring xylazine-adulterated opioids and increasing their drug use, including the use of stimulants to avoid over sedation. CONCLUSIONS: Xylazine's emergence characterizes the current era of unprecedented shifts in the unregulated drug supply. We found that xylazine spurred important behavioral changes among people who use drugs (e.g., transitioning from injecting to smoking). Incorporating these experiences into early drug warning surveillance systems and scaling up drug-checking services and safer smoking supply distribution could help mitigate significant health harms caused by xylazine and other emergent adulterants.

Providers' knowledge and perception of xylazine in the unregulated drug supply: a sequential explanatory mixed-methods study.

BACKGROUND: Xylazine is increasingly prevalent in the unregulated opioid supply in the United States. Exposure to this adulterant can lead to significant harm, including prolonged sedation and necrotic wounds. In the absence of literature describing healthcare providers' experiences with treating patients who have been exposed to xylazine, we aimed to explore what gaps must be addressed to improve healthcare education and best practices. METHODS: From October 2023 to February 2024, we conducted a sequential explanatory mixed-methods study, with (1) a quantitative survey phase utilizing convenience sampling of healthcare providers treating patients in Connecticut and (2) a qualitative semi-structured interview phase utilizing purposive sampling of providers with experience treating patients with xylazine exposure. Summary statistics from the survey were tabulated; interview transcripts were analyzed using thematic analysis. RESULTS: Seventy-eight eligible healthcare providers participated in our survey. Most participants had heard of xylazine (n = 69, 95.8%) and had some knowledge about this adulterant; however, fewer reported seeing one or more patients exposed to xylazine (n = 46, 59.8%). After sampling from this subgroup, we conducted fifteen in-depth interviews. This qualitative phase revealed five themes: (1) while xylazine is novel and of concern, this is not necessarily exceptional (i.e., there are other emerging issues for patients who use drugs); (2) participants perceived that xylazine was increasingly prevalent in the drug supply, even if they were not necessarily seeing more patients with xylazine-related outcomes (XROs); (3) patients primarily presented with non-XROs, making it difficult to know when conversations about xylazine were appropriate; (4) patients with XROs may experience issues accessing healthcare; (5) providers and their patients are learning together about how to minimize XROs and reduce the sense of helplessness in the face of a novel adulterant. CONCLUSIONS: Xylazine-specific education for healthcare providers is currently insufficient. Improving this education, as well as resources (e.g., drug checking technologies) and data (e.g., research on prevention and treatment of XROs), is crucial to improve care for patients who use drugs.

Substance use patterns, sociodemographics, and health profiles of harm reduction service recipients in Burlington, Vermont.

BACKGROUND: Understanding current substance use practices is critical to reduce and prevent overdose deaths among individuals at increased risk including persons who use and inject drugs. Because individuals participating in harm reduction and syringe service programs are actively using drugs and vary in treatment participation, information on their current drug use and preferred drugs provides a unique window into the drug use ecology of communities that can inform future intervention services and treatment provision. METHODS: Between March and June 2023, 150 participants in a harm reduction program in Burlington, Vermont completed a survey examining sociodemographics; treatment and medication for opioid use disorder (MOUD) status; substance use; injection information; overdose information; and mental health, medical, and health information. Descriptive analyses assessed overall findings. Comparisons between primary drug subgroups (stimulants, opioids, stimulants-opioids) of past-three-month drug use and treatment participation were analyzed using chi-square and Fisher's exact test. RESULTS: Most participants reported being unhoused or unstable housing (80.7%) and unemployed (64.0%) or on disability (21.3%). The drug with the greatest proportion of participants reporting past three-month use was crack cocaine (83.3%). Fentanyl use was reported by 69.3% of participants and xylazine by 38.0% of participants. High rates of stimulant use were reported across all participants independent of whether stimulants were a participant's primary drug. Fentanyl, heroin, and xylazine use was less common in the stimulants subgroup compared to opioid-containing subgroups (p < .001). Current- and past-year MOUD treatment was reported by 58.0% and 77.3% of participants. Emergency rooms were the most common past-year medical treatment location (48.7%; M = 2.72 visits). CONCLUSIONS: Findings indicate high rates of polysubstance use and the underrecognized effects of stimulant use among people who use drugs-including its notable and increasing role in drug-overdose deaths. Crack cocaine was the most used stimulant, a geographical difference from much of the US where methamphetamine is most common. With the increasing prevalence of fentanyl-adulterated stimulants and differences in opioid use observed between subgroups, these findings highlight the importance and necessity of harm reduction interventions (e.g., drug checking services, fentanyl test strips) and effective treatment for individuals using stimulants alongside MOUD treatment.

Xylazine awareness and attitudes among people who use drugs in Ohio, 2023-2024.

BACKGROUND: The prevalence of xylazine, a non-opioid tranquilizer not for human consumption, in illicitly manufactured fentanyl is increasing in the United States. However, little is known about xylazine awareness and attitudes among people who use drugs. METHODS: A cross-sectional survey of people who use drugs in Ohio was conducted from November 2023 - May 2024 to identify xylazine awareness and attitudes in rural and urban counties across the state. Study participants were recruited from naloxone distribution sites, including health departments, syringe service programs, and community-based organizations. RESULTS: Among 630 people who use drugs in Ohio, more than one-half (53.5%) were unaware of xylazine being in "street drugs," regardless of urbanicity. Among individuals who were aware of xylazine, most (73.0%) indicated they did not want to use the drug and try to avoid it. In addition, 75.8% of this group felt it was "very" or "extremely" important to know if xylazine was in their drugs. DISCUSSION: This research found that many people who use drugs in Ohio are unaware of xylazine and its risks. An important finding of this study is that most individuals who had heard of xylazine did not want to use it and were concerned about knowing whether xylazine was in their drugs.

Harm reduction nursing and the path toward developing best practice: Lessons from caring for people with xylazine-associated wounds in Philadelphia, PA.

Xylazine-associated wounds are a distinct, novel clinical entity characterized by co-occurrence with substance use, progressive necrosis of skin, muscle, tendon, and bone, and slow healing. In Philadelphia, the specter of limb loss, stigma, and shame has hung over hospital-based care for xylazine-associated wounds among people who use drugs (PWUD) and kept many people away from engaging in care. Continued engagement in harm reduction wound care nursing, however, offers an opportunity for PWUD to address their wounds and their fears with members of the medical world. In the absence of established best practices, harm reduction's model of risk-reductive care offers a way forward for patients and practitioners alike. Here, "harm reduction" describes an ethic of practical, trauma-informed, patient-centered care. It is this integration of harm reduction into medicine and public health that effectively promotes the safety, survival, and recovery of PWUD across all spectrums of drug use habits and housing stability.

Optimal clinical dose of medetomidine for sedation of young cows during dehorning surgery.

The present paper reports on the clinical efficacy and optimal clinical dose of medetomidine for sedation of young cows during dehorning surgery. Medical records of 24 female Holstein cows that underwent dehorning surgery were used in this study. In four groups, the sedation of animals was carried out by one of the four intravenous treatments: 0.1 mg kg-1 xylazine (Xyl group, n = 6), 5.0 µg kg-1 medetomidine (5.0 Med group, n = 6), 10.0 µg kg-1 medetomidine (10.0 Med group, n = 6) or 20.0 µg kg-1 medetomidine (20.0 Med group, n = 6). The clinical sedation score (CSS) and heart rate (HR) were recorded. The CSSs after intravenous administration of each α2-adrenergic receptor agonist increased rapidly and peaked at 12.5 (10.0-16.0) at t = 20 min in the Xyl group, 11.5 (10.0-15.0) at t = 10 min in the 5.0 Med group, 16.0 (14.0-16.0) at t = 20 min in the 10.0 Med group and 16.0 (14.0 - 16.0) at t = 20 min in the 20.0 Med group. A similar degree of bradycardia was observed after every sedative treatment. We conclude that the intravenous administration of 10.0-20.0 µg kg-1 medetomidine is appropriate for sedation of young cows without severe side effects.

TILETAMINE-ZOLAZEPAM-XYLAZINE ANESTHESIA IN EX SITU BLACK-HANDED SPIDER MONKEYS (ATELES GEOFFROYI SSP.).

Black-handed spider monkeys (Ateles geoffroyi ssp.) are endangered in Mexico. Safe anesthetic protocols are important for in situ and ex situ conservation problems. Such protocols are scarce in the literature; nor have safety and physiologic responses been reported. High doses and volume are a counter side for field immobilizations. We tested an anesthetic protocol with a combination of tiletamine-zolazepam (5 mg/kg) plus xylazine (1 mg/kg) in 14 black-handed spider monkeys under human care from two facilities in Mexico. Physiological parameters such as HR, RR, T, SPO2, systolic arterial pressure (), diastolic arterial pressure (DAP), and median arterial pressure (MAP) were obtained. HR and RR decreased over time, but T increased significantly during the anesthetic time for the whole group; RR and T decreased for juveniles only. Variation between individuals was observed for HR, RR, and DAP. Volume reduction of drugs was achieved compared to previously reported anesthesia protocols. Induction time was fast (6.2 ± 10.4 min) and no tail prehension was seen. Recovery was prolonged (mean and SD). Physiologic parameters remained stable throughout. The protocol proved to be safe for the chemical immobilization of black-handed spider monkeys.

Xylazine in the Unregulated Drug Market: An Integrative Review of Its Prevalence, Health Impacts, and Detection and Intervention Challenges in the United States.

Xylazine, a veterinary sedative, has emerged as a concerning element in the landscape of substance use in the United States. This integrative review synthesizes evidence from a systematic examination of 14 selected studies conducted between 2008 and 2023. The primary objective is to comprehensively understand the epidemiology and prevalence of xylazine use, particularly its involvement in drug-related deaths, regional variations, national impact, co-occurrence with opioids, and challenges associated with detection and intervention. The results underscore stark regional disparities in xylazine prevalence. West Virginia and Miami-Dade County have experienced alarming surges in xylazine-involved drug-related deaths. Nationally, its influence extends beyond regional boundaries, predominantly affecting white males in the Northeast. The co-occurrence of xylazine with opioids, especially fentanyl and heroin, significantly amplifies the risks of fatal overdoses. Detecting xylazine presents formidable challenges due to its frequent presence alongside other substances, necessitating enhanced surveillance and more effective detection methods. User perspectives emerge as pivotal, emphasizing the importance of user-informed harm reduction strategies. In conclusion, this review has significant policy implications. Tailored, region-specific strategies are imperative to address the diverse prevalence of xylazine use. A nationwide response is indispensable, prioritizing harm reduction initiatives, enhanced detection methods, and active user engagement. The multifaceted nature of the xylazine issue requires comprehensive approaches to mitigate its profound risks effectively. Policymakers are urged to consider regional disparities and the co-occurrence of xylazine with opioids when crafting targeted interventions. Immediate, user-informed harm reduction is vital to address the evolving landscape of xylazine use in the United States.

Optimizing anesthesia and delivery approaches for dosing into lungs of mice.

Microbes, toxins, therapeutics, and cells are often instilled into lungs of mice to model diseases and test experimental interventions. Consistent pulmonary delivery is critical for experimental power and reproducibility, but we observed variation in outcomes between handlers using different anesthetic approaches for intranasal dosing in mice. We therefore used a radiotracer to quantify lung delivery after intranasal dosing under inhalational (isoflurane) versus injectable (ketamine/xylazine) anesthesia in C57BL/6 mice. We found that ketamine/xylazine anesthesia resulted in delivery of a greater proportion (52 ± 9%) of an intranasal dose to lungs relative to isoflurane anesthesia (30 ± 15%). This difference in pulmonary dose delivery altered key outcomes in models of viral and bacterial pneumonia, with mice anesthetized with ketamine/xylazine for intranasal infection with influenza A virus or Pseudomonas aeruginosa developing more robust lung inflammation responses relative to control animals randomized to isoflurane anesthesia. Pulmonary dosing efficiency through oropharyngeal aspiration was not affected by anesthetic method and resulted in delivery of 63 ± 8% of dose to lungs, and a nonsurgical intratracheal dosing approach further increased lung delivery to 92 ± 6% of dose. The use of either of these more precise dosing methods yielded greater experimental power in the bacterial pneumonia model relative to intranasal infection. Both anesthetic approach and dosing route can impact pulmonary dosing efficiency. These factors affect experimental power and so should be considered when planning and reporting studies involving delivery of fluids to lungs of mice.NEW & NOTEWORTHY Many lung research studies involve dosing fluids into lungs of mice. In this study, the authors measure lung deposition using intranasal (i.n.), oropharyngeal aspiration (o.a.), and intratracheal (i.t.) dosing methods in mice. Anesthetic approach and administration route were found to affect pulmonary dosing efficiency. The authors demonstrate that refinements to dosing techniques can enable reductions in the number of animals needed for bacterial and viral pneumonia studies.

Effects of Volatile Anesthetics versus Ketamine on Blood-Brain Barrier Permeability via Lipid-Mediated Alterations of Endothelial Cell Membranes.

The purpose of this study was to investigate the effects of the volatile anesthetic agents isoflurane and sevoflurane, at clinically relevant concentrations, on the fluidity of lipid membranes and permeability of the blood-brain barrier (BBB). We analyzed the in vitro effects of isoflurane or ketamine using erythrocyte ghosts (sodium fluorescein permeability), monolayers of brain microvascular endothelial cells ([13C]sucrose and fluorescein permeability), or liposomes (fluorescence anisotropy). Additionally, we determined the effects of 30-minute exposure of mice to isoflurane on the brain tight junction proteins. Finally, we investigated in vivo brain uptake of [13C]mannitol and [13C]sucrose after intravenous administration in mice under anesthesia with isoflurane, sevoflurane, or ketamine/xylazine in addition to the awake condition. Isoflurane at 1-mM and 5-mM concentrations increased fluorescein efflux from the erythrocyte ghosts in a concentration-dependent manner. Similarly, in endothelial cell monolayers exposed to 3% (v/v) isoflurane, permeability coefficients rose by about 25% for fluorescein and 40% for [13C]sucrose, whereas transendothelial resistance and cell viability remained unaffected. Although isoflurane caused a significant decrease in liposomes anisotropy values, ketamine/xylazine did not show any effects. Brain uptake clearance (apparent Kin) of the passive permeability markers in vivo in mice approximately doubled under isoflurane or sevoflurane anesthesia compared with either ketamine/xylazine anesthesia or the awake condition. In vivo exposure of mice to isoflurane did not change any of the brain tight junction proteins. Our data support membrane permeabilization rather than loosening of intercellular tight junctions as an underlying mechanism for increased permeability of the endothelial cell monolayers and the BBB in vivo. SIGNIFICANCE STATEMENT: The blood-brain barrier controls the entry of endogenous substances and xenobiotics from the circulation into the central nervous system. Volatile anesthetic agents like isoflurane alter the lipid structure of cell membranes, transiently facilitating the brain uptake of otherwise poorly permeable, hydrophilic small molecules. Clinical implications may arise when potentially neurotoxic drugs gain enhanced access to the central nervous system under inhalational anesthetics.

Illicitly Manufactured Fentanyl-Involved Overdose Deaths with Detected Xylazine - United States, January 2019-June 2022.

In 2022, provisional data indicated that more than two thirds (68%) of the reported 107,081 drug overdose deaths in the United States involved synthetic opioids other than methadone, principally illicitly manufactured fentanyls (IMFs) (1). Xylazine, a nonopioid sedative not approved for human use and with no known antidote, has been increasingly detected in IMF products in the U.S. drug supply* and in IMF-involved overdose deaths (2). Limited studies suggest xylazine can cause central nervous system depression, respiratory depression, bradycardia, and hypotension in humans (3,4); chronic use might lead to severe withdrawal symptoms† as well as skin ulcerations (4). This report uses data from CDC's State Unintentional Drug Overdose Reporting System (SUDORS) to describe IMF-involved§ overdose deaths with and without xylazine detected that occurred during January 2019-June 2022. Among 21 jurisdictions, which included 20 states and the District of Columbia, the monthly percentage of IMF-involved deaths with xylazine detected increased 276%, from 2.9% to 10.9%. Among IMF-involved deaths during January 2021-June 2022 in 32 jurisdictions, xylazine was detected in a higher percentage of jurisdictions in the Northeast U.S. Census Bureau region; listing detected xylazine as a cause of death varied across jurisdictions. Expanded postmortem and illicit drug product testing for xylazine is needed to clarify prevalence in drug supplies; further investigation of xylazine's effects on humans is necessary to characterize morbidity and overdose risk. It is important for overdose prevention and response messages to highlight the potential presence of xylazine in IMF products and emphasize the need for respiratory and cardiovascular support to address the sedative effects of xylazine.