Alpha-2 adrenergic receptor agonists: a review of current clinical applications

Multimodal Analgesia for Perioperative Management of Patients presenting for Spinal Surgery

Multimodal, non-opioid based analgesia has become the cornerstone of ERAS protocols for effective analgesia after spinal surgery. Opioid side effects, dependence and legislation restricting long term opioid use has led to a resurgence in interest in opioid sparing techniques. The increasing array of multimodal opioid sparing analgesics available for spinal surgery targeting novel receptors, transmitters, and altering epigenetics can help provide an optimal perioperative experience with less opioid side effects and long-term dependence. Epigenetic mechanisms of pain may enhance or suppress gene expression, without altering the genome itself. Such mechanisms are complex, dynamic and responsive to environment. Alterations that occur can affect the pathophysiology of pain management at a DNA level, modifying perceived pain relief. In this review, we provide a brief overview of epigenetics of pain, systemic local anesthetics and neuraxial techniques that continue to remain useful for spinal surgery, neuropathic agents, as well as other common and less common target receptors for a truly multimodal approach to perioperative pain management.

Systemic adjunct analgesics for cesarean delivery: a narrative review

It is critical to adequately treat postoperative cesarean delivery pain. The use of parenteral or neuraxial opioids has been a mainstay, but opioids have side effects that can be troubling and the opioid crisis in the United States has highlighted the necessity to utilize analgesics other than opioids. Other analgesic options include neuraxial analgesics, nerve blocks such as the transversus abdominis plane block, and non-opioid parenteral and oral medications. The goal of this article is to review non-opioid systemic analgesic adjuncts following cesarean delivery, focusing on their efficacy and side effects as well as their impact on reduction of opioid requirements after surgery.

Update on the pharmacogenomics of pain management

Pharmacogenomics is the study of genetic variants that impact drug effects through changes in a drug’s pharmacokinetics and pharmacodynamics. Pharmacogenomics is being integrated into clinical pain management practice because variants in individual genes can be predictive of how a patient may respond to a drug treatment. Pain is subjective and is considered challenging to treat. Furthermore, pain patients do not respond to treatments in the same way, which makes it hard to issue a consistent treatment regimen for all pain conditions. Pharmacogenomics would bring consistency to the subjective nature of pain and could revolutionize the field of pain management by providing personalized medical care tailored to each patient based on their gene variants. Additionally, pharmacogenomics offers a solution to the opioid crisis by identifying potentially opioid-vulnerable patients who could be recommended a nonopioid treatment for their pain condition. The integration of pharmacogenomics into clinical practice creates better and safer healthcare practices for patients. In this article, we provide a comprehensive history of pharmacogenomics and pain management, and focus on up to date information on the pharmacogenomics of pain management, describing genes involved in pain, genes that may reduce or guard against pain and discuss specific pain management drugs and their genetic correlations.

Dexmedetomidine protects PC12 cells from lidocaine-induced cytotoxicity via downregulation of Stathmin 1

Background: Understanding of lidocaine-induced neurotoxicity is not complete, resulting in the unsuccessful treatment in some clinical settings. Dexmedetomidine (DEX) has been shown to alleviate lidocaine-induced neurotoxicity in our previous cell model. However, the rationale for DEX combined with lidocaine to reduce lidocaine-induced neurotoxicity in the clinical setting remains to be further clarified in the detailed molecular mechanism. Methods: In this study, we established a cellular injury model by lidocaine preconditioning. Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) proliferation assay kit were used to analyze cell proliferation. Cell apoptosis was measured by flow cytometry and Hoechst 33342 staining. Cell cycle progression was detected by flow cytometry. The protein expression levels were detected by Western blotting and immunofluorescence staining. Results: Our results showed that DEX dose-dependently restored impaired proliferation of PC12 cells induced by lidocaine，as reflected by the increased cell viability and EdU positive cells, which were consistent with the decreased expression of tumor suppressor protein p21 and increased expression of cell cycle-related cyclin D1 and CDK1. In addition, DEX dose-dependently reduced apoptotic PC12 cells induced by lidocaine，as reflected by the decreased expression of apoptosis-related Bax, caspase-3 and caspase-9 and increased expression of anti-apoptotic Bcl-2 compared to the cells only treated with lidocaine. Mechanistically, with gain-or-loss-of-function of STMN1, we showed that DEX-mediated neuroprotection by lidocaine-induced damage is associated with downregulation of STMN1 which might be an upstream molecule involved in regulation of mitochondria death pathway. Conclusion: Our results reveal that DEX is likely to be an effective adjunct to alleviate chronic neurotoxicity induced by lidocaine.

Adjunctive dexmedetomidine for treatment of delirium tremens: Case report and brief review

Alcohol withdrawal delirium (delirium tremens [DT]) is a medical emergency. Gamma-aminobutyric acid type A agonists (benzodiazepines [BZDs]) are the mainstay of treatment. Resistant alcohol withdrawal requires adjunctive medications along with BZDs and supportive care. DT is associated with significant autonomic dysfunction (sympathetic hyperactivity). Dexmedetomidine is a selective a2-adrenergic receptor agonist which reduces sympathetic over-activity and agitation in delirious patients. We present a case of alcohol withdrawal delirium (DT) who responded well to adjunctive dexmedetomidine infusion resulting in reduced sympathetic activity and reduced dose requirement of BZDs.

Amygdala and Hypothalamus: Historical Overview With Focus on Aggression

Aggressiveness has a high prevalence in psychiatric patients and is a major health problem. Two brain areas involved in the neural network of aggressive behavior are the amygdala and the hypothalamus. While pharmacological treatments are effective in most patients, some do not properly respond to conventional therapies and are considered medically refractory. In this population, surgical procedures (ie, stereotactic lesions and deep brain stimulation) have been performed in an attempt to improve symptomatology and quality of life. Clinical results obtained after surgery are difficult to interpret, and the mechanisms responsible for postoperative reductions in aggressive behavior are unknown. We review the rationale and neurobiological characteristics that may help to explain why functional neurosurgery has been proposed to control aggressive behavior.

Geriatric Pharmacology: An Update

An aging worldwide population demands that anesthesiologists consider geriatrics a unique subset of patients requiring customization of practice. This article reviews the current literature investigating physiologic changes of the elderly that affect pharmacokinetics and pharmacodynamics. Changes in drug absorption, distribution, metabolism, and excretion are discussed as well as the ultimate effects of medications. Implications for practice regarding specific anesthetic and analgesic drugs are addressed. Despite the immense body of research that contributes to understanding of geriatric pharmacology, elderly patients often are excluded from rigorous research trials, and further scientific investigation to inform best practices for this group of patients is needed.

Sedation Strategies for Procedures Outside the Operating Room

With the rapid development of diagnostic and therapeutic procedures performed outside the operating room (OR), the need for appropriate sedation care has emerged in importance to ensure the safety and comfort of patients and clinicians. The preparation and administration of sedatives and sedation care outside the OR require careful attention, proper monitoring systems, and clinically useful sedation guidelines. This literature review addresses proper monitoring and selection of sedatives for diagnostic and interventional procedures outside the OR. As the depth of sedation increases, respiratory depression and cardiovascular suppression become serious, necessitating careful surveillance using appropriate monitoring equipment.

Pharmacological screening of a new alpha-2 adrenergic receptor agonist, mafedine, in zebrafish

Pharmacological agents acting at alpha-2 adrenergic receptors are widely used in physiology and neuroscience research. Mounting evidence of their potential utility in clinical and experimental psychopharmacology, necessitates new models and novel model organisms for their screening. Here, we characterize behavioral effects of mafedine (6-oxo-1-phenyl-2- (phenylamino)-1,6-dihydropyrimidine-4-sodium olate), a novel drug with alpha-2 adrenergic receptor agonistic effects, in adult zebrafish (Danio rerio) in the novel tank test of anxiety and activity. Following an acute 20-min exposure, mafedine at 60 mg/L produced a mild psychostimulant action with some anxiogenic-like effects. Repeated acute 20-min/day administration of mafedine for 7 consecutive days at 1, 5 and 10 mg/L had a similar action on fish behavior as an acute exposure to 60 mg/L. Since mafedine demonstrated robust behavioral effects in zebrafish - a sensitive vertebrate aquatic model, it is likely that it may modulate rodent and human behavior as well. Thus, further studies are needed to explore this possibility in detail, and whether it may foster clinical application of mafedine and related alpha-2 adrenergic agents.

Dose-dependent neurotoxicity caused by the addition of perineural dexmedetomidine to ropivacaine for continuous femoral nerve block in rabbits

OBJECTIVE

This study was designed to evaluate the neurotoxicity of dexmedetomidine combined with ropivacaine for continuous femoral nerve block in rabbits.

METHODS

Thirty New Zealand rabbits were randomly divided into 5 groups of 6 rabbits each and received a continuous femoral nerve block with saline; 0.25% ropivacaine; or 1, 2, or 3 µg/mL of dexmedetomidine added to 0.25% ropivacaine (Groups A-E, respectively). Sensory and motor function was assessed after the nerve block. The rabbits were anesthetized and killed after 48 hours of a continuous femoral nerve block, and the femoral nerves were removed for light and electron microscopy analyses.

RESULTS

The behavior scores were highest in Group A at 2 and 6 hours after injection. The scores were higher in Groups B and C than in Groups D and E at these same time points. All groups showed normal pathological tissues in the femoral nerves under optical microscopy. Under electron microscopy, histological abnormalities were observed only in Group E; none of the other groups exhibited pathological abnormalities. Quantitative analysis of the myelin sheath area revealed no significant difference in the axonal area, total area of the myelin sheath, or ratio of the total axonal area to the total area of the myelin sheath in all groups.

CONCLUSION

The lowest doses of dexmedetomidine (1 and 2 µg/mL) combined with 0.25% ropivacaine for continuous femoral nerve block resulted in no neurotoxic lesions, but the higher dose (3 µg/mL) resulted in neurotoxic lesions in this rabbit experimental model.

Use Profile of Magnesium Sulfate in Anesthesia in Brazil

Objectives: The use of magnesium sulfate in the perioperative period has several benefits, including analgesia, inhibition of the release of catecholamines and prevention of vasospasm. The aim of this survey was to provide an overview of the use of magnesium sulfate in anesthesia. Method: This was a prospective descriptive cross-sectional study. An online questionnaire was sent to 9,869 Brazilian anesthesiologists and trainees. The questionnaire comprised closed questions mainly regarding the frequency, clinical effects, adverse events, and doses of magnesium sulfate used in anesthesia. Results: Of the 954 doctors who responded to the survey, 337 (35.32%) reported using magnesium sulfate in anesthesia. The most commonly cited clinical effects for the use of magnesium sulfate in anesthesia were (n/%): postoperative analgesia (245/72.70%), reduction of anesthetic consumption (240/71.21%) and prevention and treatment of preeclampsia and seizures in eclampsia (220/65.28%). The most frequently reported adverse events were hypotension (187/55.48%), residual neuromuscular blockade (133/39.46%), hypermagnesemia (30/8.90%), and intravenous injection pain (26/7.71%). The intravenous doses of magnesium sulfate used in most general anesthesia inductions were between 30 and 40 mg.kg-1. Conclusions: Magnesium sulfate is an important adjuvant drug in the practice of anesthesia, with several clinical effects and a low incidence of adverse events when used at recommended doses.

Combination of Dexmedetomidine and Ketamine for Magnetic Resonance Imaging Sedation

Objectives: The use of dexmedetomidine and ketamine (DEX-KET) combination for magnetic resonance imaging (MRI) sedation has not been evaluated. We investigated the efficacy and safety of DEX-KET for sedation of patients undergoing MRI of the brain. Methods: This quasi-experimental study was conducted to compare the DEX-KET combination and midazolam for MRI sedation. We included 72 patients undergoing brain MRI following bolus injection of midazolam or DEX-KET. In August 1, 2016 a new MRI sedation protocol was implemented. After protocol implementation, bolus doses of DEX-KET were administered (DEX-KET group). Thirty-six patients from the MIDA group and 36 patients from the DEX-KET group underwent MRI sequences and were compared regarding the MRI scan time and sedation-related complications (desaturation, hypotension, cardiorespiratory arrest, and aspiration pneumonia). Results: All MRI sequences were completed for 30 patients (83.3%) from the MIDA group and for 33 patients (91.7%) from the DEX-KET group (P = 0.476). The median MRI scan time was 100.0 min (interquartile range, 87.0-111.5 min) in the MIDA group and 53.5 min (interquartile range, 45.0-60.5 min) in the DEX-KET group (P < 0.001). Complications occurred in 24 (66.7%) and 8 (22.2%) patients of the MIDA and DEX-KET group, respectively (P < 0.001). Conclusions: The efficacy of DEX-KET sedation was comparable to that of midazolam for MRI examination. DEX-KET was related to shorter scan time and lower occurrence of complications compared to midazolam.

Acute Management of Hypertension Following Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is responsible for approximately 15% of strokes annually in the United States, with nearly 1 in 3 of these patients dying without ever leaving the hospital. Because this disproportionate mortality risk has been stagnant for nearly 3 decades, a main area of research has been focused on the optimal strategies to reduce mortality and improve functional outcomes. The acute hypertensive response following ICH has been shown to facilitate ICH expansion and is a strong predictor of mortality. Rapidly reducing blood pressure was once thought to induce cerebral ischemia, though has been found to be safe in certain patient populations. Clinicians must work quickly to determine whether specific patient populations may benefit from acute lowering of systolic blood pressure (SBP) following ICH. This review provides nurses with a summary of the available literature on blood pressure control following ICH. It focuses on intravenous and oral antihypertensive medications available in the United States that may be utilized to acutely lower SBP, as well as medications outside of the antihypertensive class used during the acute setting that may reduce SBP.

Spinal α2 -adrenoceptors and neuropathic pain modulation; therapeutic target

Neuropathic pain can arise from disease or damage to the nervous system. The most common symptoms of neuropathic pain include spontaneous pain, allodynia, and hyperalgesia. There is still limited knowledge about the factors that initiate and maintain neuropathic pain. However, ample evidence has proved the antinociceptive role of spinal α-adrenoceptors following nerve injury. It is well-documented that noradrenergic descending pathways from supraspinal loci exert an inhibitory influence on the spinal cord nociceptive neurons, mostly through the activation of spinal α₂ -adrenoceptors. This, in turn, suppresses transmission of pain input and the hyperexcitability of spinal dorsal horn neurons. There is considerable evidence demonstrating that spinal application of α₂ -adrenoceptor agonists leads to analgesic effects in animal models of neuropathic pain. Today, despite the recent rapid development of neuroscience and drug discovery, effective drugs with clear basic mechanisms have remained a mystery. Here, we give an overview of the cellular mechanisms through which brainstem adrenergic descending inhibitory processing can alter spinal pain transmission to the higher centres, and how these pathways change in neuropathic pain conditions focusing on the role of spinal α₂ -adrenoceptors in the spinal dorsal horn. We then suggest that α₂ -adrenoceptor agonist may be useful to treat neuropathic pain. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.

Sex differential effect of dexmedetomidine on fear memory extinction and anxiety behavior in adolescent rats

Exposure to stressful stimuli, including fear and anxiety, modulates the central noradrenergic system. Dexmedetomidine is a commonly used α2-adrenoreceptor agonist. Because the effect of fear acquisition varies between sexes, the present study was designed to investigate sex-related differences in the effects of dexmedetomidine on fear memory and anxiety-like behavior. We conducted a fear test and an elevated plus maze test in 6-8-week-old male and female rats. Two doses of dexmedetomidine (20 and 40 μg/kg) were injected intraperitoneally three times at 24 h intervals after the tests: after fear expression, extinction 1, and extinction 2. The repeated administration of dexmedetomidine showed significant acceleration of fear memory extinction in female rats but not in male rats; the effect increased proportionally to concentrations of dexmedetomidine. Compared to male rats, female rats treated with both concentrations of dexmedetomidine showed significant anxiolytic behavior after 1 week. Dexmedetomidine accelerated the fear memory extinction and reduced anxiety; it was more effective in female rats than in male rats. Our results suggest that dexmedetomidine may exert protective effects against fear-related and anxiety-like behaviors in rats with fear memory after repeated administration, and the sex-specific effects of dexmedetomidine should be considered.

Sarcolemmal α2-adrenoceptors in feedback control of myocardial response to sympathetic challenge

α2-adrenoceptor (α2-AR) isoforms, abundant in sympathetic synapses and noradrenergic neurons of the central nervous system, are integral in the presynaptic feed-back loop mechanism that moderates norepinephrine surges. We recently identified that postsynaptic α2-ARs, found in the myocellular sarcolemma, also contribute to a muscle-delimited feedback control capable of attenuating mobilization of intracellular Ca²⁺ and myocardial contractility. This previously unrecognized α2-AR-dependent rheostat is able to counteract competing adrenergic receptor actions in cardiac muscle. Specifically, in ventricular myocytes, nitric oxide (NO) and cGMP are the intracellular messengers of α2-AR signal transduction pathways that gauge the kinase-phosphatase balance and manage cellular Ca²⁺ handling preventing catecholamine-induced Ca²⁺ overload. Moreover, α2-AR signaling counterbalances phospholipase C - PKC-dependent mechanisms underscoring a broader cardioprotective potential under sympathoadrenergic and angiotensinergic challenge. Recruitment of such tissue-specific features of α2-AR under sustained sympathoadrenergic drive may, in principle, be harnessed to mitigate or prevent cardiac malfunction. However, cardiovascular disease may compromise peripheral α2-AR signaling limiting pharmacological targeting of these receptors. Prospective cardiac-specific gene or cell-based therapeutic approaches aimed at repairing or improving stress-protective α2-AR signaling may offer an alternative towards enhanced preservation of cardiac muscle structure and function.

[Background and current use of adjuvants for regional anesthesia : From research to evidence-based patient treatment]

The discovery of the local anaesthetic effect by blocking sodium ion channels was a milestone in anaesthesia but was soon limited by sometimes life-threatening toxic effects of the local anaesthetics. By developing novel local anaesthetics and also by adding so-called adjuvants, attempts have been made to limit these life-threatening events. This article focuses on the historic background and the current state of the use of these adjuvants for regional anaesthesia. Adding epinephrine, clonidine or dexmedetomidine, but only as a single dose, results in a faster onset, longer duration of action and increased intensity of neuronal blockade of regional anaesthesia. The benefits of adding sodium bicarbonate, on the other hand, are relatively minor and, therefore, clinically negligible. Although increasing evidence in the literature suggests an improvement and prolongation of the analgesic effect after axonal administration of opioids, which can also be given continuously, systemic effects are not fully ruled out due to the increased incidence of central side effects. The partial local anaesthetic effects of opioids cannot always be distinguished from opioid receptor-specific effects. Mechanistic studies postulate a functional coupling of opioid receptors in injured rather than in intact peripheral nerves. Recent studies have identified glucocorticoid and mineralocorticoid receptors predominantly on peripheral nociceptive nerve fibers. This is consistent with numerous clinical reports of a marked prolongation of the local anaesthetic effect. In addition to the known genomic effects of steroids that occur via a change in gene expression of pain-sustaining protein structures, faster non-genomic effects are also discussed, which occur via a change in intracellular signaling pathways. In summary, new insights into mechanisms and novel results from clinical trials will help the anaesthesiologist in the decision to use adjuvants for regional anaesthesia which, however, requires to weigh the individual patient's benefits against the risks.

A Review of 3,4-methylenedioxymethamphetamine (MDMA)-Assisted Psychotherapy

This paper provides a brief review of the history, proposed pharmacological mechanisms, safety issues, and clinical applications of the medicine 3,4-methylenedioxymethamphetamine (MDMA). Most clinical MDMA research in patients to date has focused on MDMA-assisted psychotherapy to treat posttraumatic stress disorder (PTSD). In this review paper other potential therapeutic applications for MDMA therapy are described, including contemporary studies treating anxiety associated with autism and the authors' ongoing study exploring the potential role for MDMA-assisted psychotherapy to treat alcohol use disorder. MDMA therapy for PTSD is now entering the final Phase 3 stage of drug development, with a target set for licensing by the FDA and EMA in 2021. This means that if clinical efficacy criteria are achieved, MDMA would become a medicine.

Low-dose brimonidine for relief of ocular redness: integrated analysis of four clinical trials

BACKGROUND

The aim of this study was to provide an integrated analysis of safety and efficacy data for brimonidine tartrate ophthalmic solution 0.025 per cent (low-dose; Bausch & Lomb Incorporated), a topical vasoconstrictor for relief of ocular redness.

METHODS

Integrated efficacy data from two randomised, double-masked, vehicle-controlled studies in subjects with ocular redness as well as safety data from the two efficacy studies, a vehicle-controlled safety study, and a pharmacokinetic study were analysed. Efficacy outcomes analysed included investigator-assessed ocular redness (scale, 0-4) before treatment instillation and at five to 240 minutes post-instillation on Day 1, at five minutes post-instillation on Days 15 and 29, and one week after treatment discontinuation (Day 36), and redness self-assessed by subjects recorded daily in diaries. Safety assessments included adverse events, ophthalmic examinations, and rebound redness upon treatment discontinuation. Drop comfort (scale, 0-10) was a tolerability measure.

RESULTS

The efficacy population included 117 subjects (brimonidine, n = 78; vehicle, n = 39). The safety population included 635 subjects (brimonidine, n = 426; vehicle, n = 209). Investigator-assessed ocular redness was significantly lower with brimonidine versus vehicle at all post-instillation time points on Day 1 (mean change from pre-instillation of -1.4 units for brimonidine and -0.2 units for vehicle; p < 0.0001). Subject-assessed ocular redness was also significantly lower with brimonidine versus vehicle (mean treatment difference in average daily ratings of -0.9; p < 0.0001). There was no evidence of tachyphylaxis through Day 29 and rebound redness was rare. Incidence of ocular adverse events was low, the most common being reduced visual acuity (brimonidine, 4.0 per cent; vehicle, 4.3 per cent) and conjunctival hyperaemia (2.6 and 2.9 per cent, respectively). Both brimonidine and vehicle were rated as very comfortable (mean post-instillation scores, 0.4-0.5).

CONCLUSION

In this integrated analysis, low-dose brimonidine significantly reduced ocular redness with no tachyphylaxis, and minimal rebound redness, and was generally safe and well tolerated.

Impact of stress response systems on forced choice recognition in an experimental trauma film paradigm

INTRODUCTION

Traumatic events are often followed by memory impairments of key features of the trauma. Stress hormones are involved in emotional memory formation. However, little is known about their influence during trauma on subsequent recognition memory.

MATERIAL AND METHODS

A pooled analysis of two double-blind, placebo-controlled studies (N = 175) was performed to assess the influence of the noradrenergic system and the hypothalamus-pituitaryadrenal (HPA) axis on intrusion formation. Participants received either 10 mg yohimbine (stimulating noradrenergic activity), 0.15 mg clonidine (inhibiting noradrenergic activity), or placebo (noradrenergic manipulation study) or 20 mg hydrocortisone or placebo (hydrocortisone manipulation study), each 60 min before watching a distressing film depicting severe sexual and physical violence. After seven days, the participants performed a 24-item forced choice recognition test. Memory was assessed for pre-, peri-, and post-trauma film scenes.

RESULTS

A significant film scene by intervention interaction indicated a differential influence of drug intervention on the number of correct pre-, peri-, and post-trauma film scene memories one week after the distressing film. Post hoc tests revealed that clonidine led to significantly fewer correct peri-trauma film scene memories compared to placebo and, on a trend level, to yohimbine.

DISCUSSION

Pharmacological inhibition of noradrenaline during a distressing film leads to impaired emotional recognition memory for the peri-trauma film scene.

Anesthetic Management of the Hypertensive Patient: Part II

Hypertension is an important health challenge that affects millions of people across the world today and is a major risk factor for cardiovascular disease. It is critical that anesthesia providers have a working knowledge of the systemic implications of hypertension. This review article will discuss the medical definitions of hypertension, the physiology of maintaining blood pressure, outpatient treatment of hypertension, anesthetic implications, and the common medications used by anesthesia providers in the treatment of hypertension. Part I provided an overview of hypertension and blood pressure regulation. In addition, drugs predominantly affecting control of hypertension via renal mechanisms such as diuretics, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and renin-inhibiting agents were discussed. In part II, the remaining major antihypertensive medications will be reviewed as well as anesthetic implications of managing patients with hypertension.

Effectivness of Clonidine in Treating Dexmedetomidine Withdrawal in a Patient with Co-Existing Psychiatric Illness: A Case Report

Patient: Female, 40

Final Diagnosis: Dexmedetomidine withdrawal

Symptoms: Severe agitation • sweating • tachycardia

Medication: —

Clinical Procedure: None

Specialty: Critical Care Medicine

Acute presentation of a partially obstructing laryngeal tumour: adjuvant agents to gaseous induction of anaesthesia

We present the case of a 53-year-old man who attended our emergency department with stridor. He had recently undergone investigation for possible glottic cancer. We discuss the airway management of such a case. We believe this to be the first description of propofol target controlled infusion and clonidine to supplement a sevoflurane gas induction, in order to obtund response to intubation while maintaining spontaneous ventilation. We also consider how airway interventions may impact prognosis and need to be considered.

Management of hypertensive crises in the elderly

Hypertensive crises are elevations of blood pressure higher than 180/120 mmHg. These can be urgent or emergent, depending on the presence of end organ damage. The clinical presentation of hypertensive crises is quite variable in elderly patients, and clinicians must be suspicious of non-specific symptoms. Managing hypertensive crises in elderly patients needs meticulous knowledge of the pathophysiological changes in them, pharmacological options, pharmacokinetics of the medications used, their side effects, and their interactions with other medications. Clevidipine, nicardipine, labetalol, esmolol, and fenoldopam are among the preferred choices in the elderly due to their efficacy and tolerability. Nitroprusside, hydralazine, and nifedipine should be avoided, unless there are no other options available, due to the high risk of complications and unpredictable responses.

Differentially expressed genes in response to amitraz treatment suggests a proposed model of resistance to amitraz in R. decoloratus ticks

The widespread geographical distribution of Rhipicephalus decoloratus in southern Africa and its ability to transmit the pathogens causing redwater, gallsickness and spirochaetosis in cattle makes this hematophagous ectoparasite of economic importance. In South Africa, the most commonly used chemical acaricides to control tick populations are pyrethroids and amitraz. The current amitraz resistance mechanism described in R. microplus, from South Africa and Australia, involves mutations in the octopamine receptor, but it is unlikely that this will be the only contributing factor to mediate resistance. Therefore, in this study we aimed to gain insight into the more complex mechanism(s) underlying amitraz resistance in R. decoloratus using RNA-sequencing. Differentially expressed genes (DEGs) were identified when comparing amitraz susceptible and resistant ticks in the presence of amitraz while fed on bovine hosts. The most significant DEGs were further analysed using several annotation tools. The predicted annotations from these genes, as well as KEGG pathways potentially point towards a relationship between the α-adrenergic-like octopamine receptor and ionotropic glutamate receptors in establishing amitraz resistance. All genes with KEGG pathway annotations were further validated using RT-qPCR across all life stages of the tick. In susceptible ticks, the proposed model is that in the presence of amitraz, there is inhibition of Ca²⁺ entry into cells and subsequent membrane hyperpolarization which prevents the release of neurotransmitters. In resistant ticks, we hypothesize that this is overcome by ionotropic glutamate receptors (NMDA and AMPA) to enhance synaptic transmission and plasticity in the presence of neurosteroids. Activation of NMDA receptors initiates long term potentiation (LTP) which may allow the ticks to respond more rapidly and with less stimulus when exposed to amitraz in future. Overactivation of the NMDA receptor and excitotoxicity is attenuated by the estrone, NAD⁺ and ATP hydrolysing enzymes. This proposed pathway paves the way to future studies on understanding amitraz resistance and should be validated using in vivo activity assays (through the use of inhibitors or antagonists) in combination with metabolome analyses.

Noradrenergic targets for the treatment of alcohol use disorder

The role of norepinephrine (NE) in the development of alcohol use disorder (AUD) has been studied over the past several decades. However, the NE system has been largely ignored for many years as a potential target for medication development for AUD. More recently, preclinical and clinical studies have demonstrated the potential value of targeting NE signaling for developing new pharmacological treatments for AUD. This review contributes to a special issue of Psychopharmacology focused on promising targets for alcohol addiction. Specifically, this review coalesces preclinical and clinical neuroscience that re-evaluate the noradrenergic system, and in particular the alpha-1 receptor, as a potential target for AUD.

Enteral Guanfacine to Treat Severe Anxiety and Agitation Complicating Critical Care After Cardiac Surgery

This article is the first reported case describing the off-label use of enteral immediate-release guanfacine, a long-acting α-2 adrenergic agonist most commonly used in the treatment of attention-deficit hyperactivity disorder, for sedation in a patient with severe anxiety and agitation limiting mechanical ventilation weaning several days after cardiac surgery. In this case, after several days of unsuccessful attempts to control his agitation and anxiety with conventional therapies, guanfacine therapy was initiated, and the patient was rapidly weaned from all other sedatives and mechanical ventilation shortly thereafter. The patient was weaned from guanfacine therapy without evidence of bradycardia, hypotension, or rebound syndrome. Enteral guanfacine therapy should be further studied as a potentially useful and cost-effective sedative therapy for patients with severe anxiety and/or agitation in the intensive care unit following cardiac and thoracic surgical procedures.

Role of the equine CYP3A94, CYP3A95 and CYP3A97 in ketamine metabolism in presence of medetomidine, diazepam and methadone studied by enantioselective capillary electrophoresis

The anesthetic ketamine is often combined with analgesics and benzodiazepines in equine medicine. Therefore, drug-drug interactions are possible. Enzyme kinetics for ketamine N-demethylation were determined using equine CYP3A94, CYP3A95 and CYP3A97, and the effect of medetomidine, diazepam and methadone on the ketamine metabolism was studied in vitro. Ketamine was incubated with the CYPs or equine liver microsomes (ELM) alone or in presence of medetomidine, diazepam and/or methadone for different times. Norketamine levels were determined using enantioselective capillary electrophoresis (CE) with highly sulfated γ-cyclodextrin as chiral selector. The three equine CYPs were demonstrated to be involved in ketamine N-demethylation and the kinetics can be described with the Michaelis-Menten model. V_max values calculated for CYP3A94 and CYP3A97 were higher than for CYP3A95. The lowest K_m value was found for CYP3A94. In contrast to diazepam and methadone, the α₂-recepor agonist medetomidine diminished the norketamine formation significantly in CYP3A94 and CYP3A97. In ELM, increasing concentrations of diazepam inhibited the norketamine formation. Despite the differences in ketamine N-demethylation in combination with diazepam and methadone, the effect is unlikely to be of clinical relevance because ketamine and the other drugs do not have a small therapeutic margin.

Anesthesia for off-floor dental and oral surgery

PURPOSE OF REVIEW

Anesthesia for dentistry is commonly performed outside the operating room. The combination of a shared airway between surgeon and anesthetist, the variety of open airway techniques, and the out-of-operating room setting often results in anxiety and avoidance of dental cases among anesthesia personnel. This review attempts to demystify dental treatment and facilitate the anesthesia provider in providing effective sedation of dental procedures performed in the nonoperating room setting.

RECENT FINDINGS

Specific indications for dental anesthesia improve the patient selection process. Airway assessment and strategies to secure the difficult airway are paramount because of the nature of the procedures and the patients on whom they are performed. Pediatric patients and those with special needs present specific preanesthetic assessment, induction, and management challenges. Emergence delirium is disruptive, possibly dangerous, prolongs recovery time, and may necessitate hospitalization. Simplified techniques and objective recovery criteria are necessary to ensure a safe and smooth discharge to home. Airway fire precautions should not be overlooked given the rare but potential risk of airway fire during dental treatment.

SUMMARY

This article reviews the indications, facility and equipment needs, monitoring requirements, treatment methods, and recovery protocols necessary for the safe administration of off-floor anesthesia for dentistry.

Molecular biology and functional genomics of immune-endocrine interactions in the Japanese eel, Anguilla japonica

Immune-endocrine interactions are an important pathogen resistance mechanism in fish. We review the immune-endocrine interactions in the Japanese eel, Anguilla japonica, with special reference to high throughput gene sequencing. These data may be relevant to the significant decrease in the eel harvest in recent years and will aid in the selection of appropriate disease-resistant strains for aquaculture. More than 1000 sequences that whose expression in elvers responded to air exposure were identified through comprehensive gene expression analysis using next-generation sequencing. These included transcription factors within the MAPK pathway. Significant changes in expression after air exposure were detected by quantitative polymerase chain reaction analysis in many genes related to disease resistance. These factors include innate immune system factors and cytokines that interact with the endocrine system during the stress response. Other applications of immune-endocrine interactions in eel culture are discussed.

Comparison of two sedation protocols for short electroretinography in cats

Objectives The objectives were to compare two different sedative combinations, xylazine-ketamine and dexmedetomidine-ketamine, for the short electroretinography (ERG) protocol and their impact on sedative effect, reversal times and physiological variables in cats. Methods Six healthy spayed female domestic cats were sedated using one of two ketamine-containing protocols: intramuscular xylazine hydrochloride (1 mg/kg) plus ketamine hydrochloride (3 mg/kg) (XK), and dexmedetomidine hydrochloride (5 µg/kg) plus ketamine hydrochloride (3 mg/kg) (DK). A short ERG protocol was recorded from the left eye of each cat under XK and DK sedation. Thirty minutes later, the effects were reversed with yohimbine or atipamezole for the XK and DK treatment, respectively. The cats were evaluated for time to recumbency, time to head elevation, and time to standing position after reversal treatments. Other variables recorded were: systolic blood pressure, cardiac rhythm, heart rate, pulse oximetry and respiratory rate. Recorded ERG variables included a- and b-wave amplitudes and implicit times under photopic, scotopic and scotopic mixed ERG conditions. Results Time to lateral recumbency with XK was shorter than for DK ( P <0.05). After reversal, head elevation and standing position times were significantly longer for the XK than the DK group ( P <0.05). Heart rate increased and systolic blood pressure decreased from baseline in both groups ( P <0.05), but there were no significant differences between treatment groups. The b-wave amplitude recorded in the photopic study of cats treated with XK was lower than in animals treated with DK ( P <0.05). No other significant differences in ERG variables were observed between treatment groups ( P >0.05). Conclusions and relevance The present study shows that XK and DK treatments are chemical restraint alternatives for ERG recording in cats, with significant differences only in the photopic b-wave amplitude.

Dexmedetomidine prevents acute kidney injury after adult cardiac surgery: a meta-analysis of randomized controlled trials

BACKGROUND

Dexmedetomidine has been shown to confer direct renoprotection by stabilizing the sympathetic system, exerting anti-inflammatory effects and attenuating ischemia/reperfusion (I/R) injury in preclinical studies. Results from clinical trials of dexmedetomidine on acute kidney injury (AKI) following adult cardiac surgery are controversial.

METHODS

We searched EMBASE, PubMed, and Cochrane CENTRAL databases for randomized controlled trials (RCTs) comparing the renal effect of dexmedetomidine versus placebo or other anesthetic drugs in adult patients undergoing cardiac surgery. The primary outcome was the incidence of AKI. The secondary outcomes were mechanical ventilation (MV) duration, intensive care unit (ICU) stay and hospital length of stay(LOS), and postoperative mortality (in-hospital or within 30 days).

RESULTS

Ten trials with a total of 1575 study patients were selected. Compared with controls, dexmedetomidine significantly reduced the incidence of postoperative AKI [68/788 vs 97/787; odds ratio(OR), 0.65; 95% confidence interval (CI), 0.45-0.92; P = 0.02; I² = 0.0%], and there was no difference between groups in postoperative mortality (4/487 vs 11/483; OR, 0.43; 95% CI, 0.14-1.28; P = 0.13; I² = 0.0%), MV duration [in days; n = 1229; weighted mean difference(WMD), -0.22; 95% CI, -2.04 to 1.70; P = 0.81], ICU stay (in days; n = 1363; WMD, -0.85; 95% CI, -2.14 to 0.45; P = 0.20), and hospital LOS (in days; n = 878; WMD, -0.24; 95% CI, -0.71 to 0.23; P = 0.32).

CONCLUSIONS

Perioperative administration of dexmedetomidine in adult patients undergoing cardiac surgery may reduce the incidence of postoperative AKI. Future trials are needed to determine the dose and timing of dexmedetomidine in improving outcomes, especially in patients with decreased baseline kidney function.

Effects of intrathecal dexmedetomidine as an additive to low-dose bupivacaine in patients undergoing transurethral resection of prostate

Background and Aims:

In patients undergoing transurethral resection of prostate (TURP), it is vital to restrict the level of block to T₁₀dermatome during spinal anaesthesia. Low-dose bupivacaine causes minimum haemodynamic alterations, but may provide insufficient surgical anaesthesia. Dexmedetomidine, a selective α₂-adrenoreceptor agonist, is a potent anti-nociceptive agent when given intrathecally. The aim of this study was to compare the adjuvant effects of intrathecal dexmedetomidine with low-dose bupivacaine spinal anaesthesia versus a higher dose of bupivacaine in patients undergoing TURP.

Methods:

The study was designed as a prospective, double-blind, randomised trial that included sixty patients of American Society of Anesthesiologists Grade I–III scheduled for TURP. They were allocated into two groups: Group I receiving only hyperbaric bupivacaine intrathecally and Group II receiving dexmedetomidine with low dose bupivacaine. The time to regression of two dermatomes from the peak sensory block level was the primary outcome of the study.

Results:

With comparable baseline and demographic attributes, both groups had similar peak sensory block levels (T₉). Patients in Group II had quicker onset with the time to reach T₁₀being faster (10.72 ± 3.50 vs. 12.72 ± 3.90 min, P = 0.041), longer duration of motor block (200 ± 18.23 vs. 190 ± 10.15 min, P = 0.011) and increased time to first analgesic requirement (300 ± 25.30 vs. 220 ± 15.12 min, P = 0.0001).

Conclusion:

Intrathecal dexmedetomidine with low-dose bupivacaine provides faster onset, prolonged sensory and motor block and reduced rescue analgesic requirement in patients undergoing TURP.

Pharmacokinetics of dexmedetomidine during analgosedation in ICU patients

Dexmedetomidine (DEX) is a fairly new alfa₂-agonist which has been increasingly used in recent years for analgosedation, mostly because it offers a unique ability of providing both moderate level of sedation and analgesia without respiratory depression. Despite of many papers published, there are still only a few concerning the PK of the drug given as long-term infusion in ICU patients. The aim of this work was to characterize the population pharmacokinetics of dexmedetomidine and to investigate the potential benefits of individualization of drug dosing based on patient characteristics in the heterogeneous group of medical and surgical patients staying in intensive care unit. This study was performed in the group of 17 males and 10 females patients with a median age of 59.5 years and median body weight of 75 kg. Blood samples for dexmedetomidine assay were collected from arterial catheter, during and after discontinuation of a standard infusion, that ranged from 24 to 102 h. The following covariates were examined to influence dexmedetomidine PK: age, sex, body weight, patients’ health status described by Sequential Organ Failure Assessment Score (SOFA), inotropes usage, and infusion duration. The dexmedetomidine PK was best described by a two-compartment model. The typical values of PK parameters were estimated as 27 L for the volume of the central compartment, 87.6 L for the volume of the peripheral compartment, 38.5 L/h (9.2 mL/min/kg for a 70 kg patient) for systemic clearance and 46.4 L/h for the distribution clearance. Those values are consistent with literature findings. We were unable to show any significant relationship between collected covariates and dexmedetomidine PK. This study does not provide sufficient evidence to support the individualization of dexmedetomidine dosing based on age, sex, body weight, SOFA, and infusion duration.

Pharmacologic and clinical assessment of kratom

PURPOSE

This article reviews the pharmacology, clinical utility, adverse effects, and abuse potential of kratom.

SUMMARY

The leaves of Mitragyna speciosa contain the biologically active alkaloids of kratom. Kratom exerts opioid and α-2 receptor agonistic effects as well as antiinflammatory and parasympathetic-impeding effects. There are no published human pharmacologic, pharmacokinetic, or drug interaction studies on kratom or mitragynine, making it virtually impossible to fully understand kratom's therapeutic potential and risks and the populations most likely to benefit or experience harm from its use. Kratom has been used to ameliorate opioid withdrawal symptoms but also induces withdrawal. Human pharmacologic, pharmacokinetic, and clinical data are of low quality, precluding any firm conclusions regarding safety and efficacy. Respiratory depression has not been commonly reported, but kratom does cause a host of adverse effects without clear guidance for how they should be treated. There are numerous assessments where people have been unable to stop using kratom therapy, and withdrawal signs and symptoms are problematic. Kratom does not appear in normal drug screens and, when taken with other substances of abuse, may not be recognized. Thirty-six deaths have been attributed to kratom, and the Food and Drug Administration issued a public health warning about the substance in November 2017.

CONCLUSION

Kratom exerts opioid and α-2 receptor agonistic effects as well as antiinflammatory and parasympathetic-impeding effects. Human pharmacologic, pharmacokinetic, and clinical data are of low quality, precluding any firm conclusions regarding safety and efficacy.

Post-Operative Cognitive Dysfunction: An exploration of the inflammatory hypothesis and novel therapies

Post-Operative Cognitive Dysfunction (POCD) is a highly prevalent condition with significant clinical, social and financial impacts for patients and their communities. The underlying pathophysiology is becoming increasingly understood, with the role of neuroinflammation and oxidative stress secondary to surgery and anaesthesia strongly implicated. This review aims to describe the putative mechanisms by which surgery-induced inflammation produces cognitive sequelae, with a focus on identifying potential novel therapies based upon their ability to modify these pathways.

MiR-29b expression is associated with a dexmedetomidine-mediated protective effect against oxygen-glucose deprivation-induced injury to SK-N-SH cells in vitro

Ischemic cerebral stroke is a leading cause of death and long-term disability world-wide. Neuronal injury following cerebral ischemia initiates a complex series of signaling cascades that lead to neuronal cell death. MicroRNA 29b (miR-29b) has reported involvement in the pathogenic process of ischemic brain injury. Dexmedetomidine (Dex) is a highly selective α₂ adrenergic receptor stimulant that exerts a protective effect on brain tissue. To determine whether Dex might directly influence miR-29b expression after an ischemic injury, human neuroblastoma SK-N-SH cells were subjected to oxygen-glucose deprivation (OGD) for the purpose of creating a neuronal injury model that mimics the effects of brain ischemia in vitro. Next, the association of miR-29b with the protective effect of Dex against ischemic brain injury was studied through the enhancement or inhibition of miR-29b expression by transfection with an miR-29b mimic or inhibitor. We demonstrated that Dex treatment could reduce miR-29b expression, increase cell viability, and inhibit cell apoptosis in the OGD-induced neuronal injury model in vitro. Furthermore, down-regulation of miR-29b expression produced effects on OGD-induced neuronal injuries that were similar to those produced by Dex treatment. Moreover, up-regulation of miR-29b reversed the protective effect of Dex treatment against OGD-induced neuronal injury. Therefore, down-regulation of miR-29b expression might play a role in anti-apoptotic signaling similar to that played by Dex. Elucidation of the role played by miR-29b in ischemia, and identification of a definite association between Dex and miR-29b may lead to the development of new strategies for treating ischemic brain injuries.

Why MDMA therapy for alcohol use disorder? And why now?

Alcohol use disorder represents a serious clinical, social and personal burden on its sufferers and a significant financial strain on society. Current treatments, both psychological and pharmacological are poor, with high rates of relapse after medical detoxification and dedicated treatment programs. The earliest historical roots of psychedelic drug-assisted psychotherapy in the 1950s were associated with Lysergic acid diethylamide (LSD)-assisted psychotherapy to treat what was then called, alcoholism. But results were varied and psychedelic therapy with LSD and other 'classical' psychedelics fell out of favour in the wake of socio-political pressures and cultural changes. A current revisiting of psychedelic clinical research is now targeting substance use disorders - and particularly alcohol use disorder - again. 3,4-Methylenedioxymethamphetamine (MDMA)-assisted psychotherapy has never been formally explored as a treatment for any form of substance use disorder. But in recent years MDMA has risen in prominence as an agent to treat posttraumatic stress disorder (PTSD). With its unique receptor profile and a relatively well-tolerated subjective experience of drug effects when used clinically, MDMA Therapy is ideally suited to allow a patient to explore and address painful memories without being overwhelmed by negative affect. Given that alcohol use disorder is so often associated with early traumatic experiences, the author is proposing in a current on-going UK-based study that patients with alcohol use disorder who have undergone a medical detoxification from alcohol might benefit from a course of MDMA-assisted psychotherapy. This article is part of the Special Issue entitled 'Psychedelics: New Doors, Altered Perceptions'.

Noradrenaline Modulates the Membrane Potential and Holding Current of Medial Prefrontal Cortex Pyramidal Neurons via β1-Adrenergic Receptors and HCN Channels

The medial prefrontal cortex (mPFC) receives dense noradrenergic projections from the locus coeruleus. Adrenergic innervation of mPFC pyramidal neurons plays an essential role in both physiology (control of memory formation, attention, working memory, and cognitive behavior) and pathophysiology (attention deficit hyperactivity disorder, posttraumatic stress disorder, cognitive deterioration after traumatic brain injury, behavioral changes related to addiction, Alzheimer's disease and depression). The aim of this study was to elucidate the mechanism responsible for adrenergic receptor-mediated control of the resting membrane potential in layer V mPFC pyramidal neurons. The membrane potential or holding current of synaptically isolated layer V mPFC pyramidal neurons was recorded in perforated-patch and classical whole-cell configurations in slices from young rats. Application of noradrenaline (NA), a neurotransmitter with affinity for all types of adrenergic receptors, evoked depolarization or inward current in the tested neurons irrespective of whether the recordings were performed in the perforated-patch or classical whole-cell configuration. The effect of noradrenaline depended on β1- and not α1- or α2-adrenergic receptor stimulation. Activation of β1-adrenergic receptors led to an increase in inward Na+ current through hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which carry a mixed Na+/K+ current. The protein kinase A- and C-, glycogen synthase kinase-3β- and tyrosine kinase-linked signaling pathways were not involved in the signal transduction between β1-adrenergic receptors and HCN channels. The transduction system operated in a membrane-delimited fashion and involved the βγ subunit of G-protein. Thus, noradrenaline controls the resting membrane potential and holding current in mPFC pyramidal neurons through β1-adrenergic receptors, which in turn activate HCN channels via a signaling pathway involving the βγ subunit.