Pharmacokinetics and pharmacodynamics of dexmedetomidine

Insight into Cardioprotective Effects and Mechanisms of Dexmedetomidine

PURPOSE

Cardiovascular disease remains the leading cause of death worldwide. Dexmedetomidine is a highly selective α2 adrenergic receptor agonist with sedative, analgesic, anxiolytic, and sympatholytic properties, and several studies have shown its possible protective effects in cardiac injury. The aim of this review is to further elucidate the underlying cardioprotective mechanisms of dexmedetomidine, thus suggesting its potential in the clinical management of cardiac injury.

RESULTS AND CONCLUSION

Our review summarizes the findings related to the involvement of dexmedetomidine in cardiac injury and discusses the results in the light of different mechanisms. We found that numerous mechanisms may contribute to the cardioprotective effects of dexmedetomidine, including the regulation of programmed cell death, autophagy and fibrosis, alleviation of inflammatory response, endothelial dysfunction and microcirculatory derangements, improvement of mitochondrial dysregulation, hemodynamics, and arrhythmias. Dexmedetomidine may play a promising and beneficial role in the treatment of cardiovascular disease.

Dexmedetomidine - An Alternative to Midazolam in the Treatment of Ketamine-Induced Emergence Delirium: A Systematic Review

PURPOSE

Analyze the effectiveness of dexmedetomidine compared to midazolam for the treatment of ketamine-induced emergence delirium in noncardiac surgical patients.

DESIGN

Systematic review.

METHODS

Guidelines outlined in the Preferred Reporting Items For Systematic Reviews and Meta-analyses (PRISMA)22 were used for this review. PubMed, Cumulative Index To Nursing And Allied Health Literature (CINAHL), MEDLINE, The Cochrane Library, EBSCOhost, National Institute of Health clinical trials, Google Scholar, and gray literature were searched for relevant studies. Only peer-reviewed nonexperimental studies, quasi-experimental studies, and randomized control trials with or without meta-analysis were included. The evidence was assessed using the Johns Hopkins Nursing Evidence-Based Practice guidelines for quality ratings and evidence level.

FINDINGS

Five blinded randomized controlled trials, three quasi-experimental studies, and two retrospective nonexperimental studies comprised of 1,024 subjects were evaluated for this review. Dexmedetomidine was more effective at reducing ketamine-induced delirium in adult patients, although midazolam attenuated the psychomimetic effects of ketamine better in pediatric patients. Furthermore, postanesthesia care unit discharge times were similar between patients treated with dexmedetomidine and midazolam. The studies in this review were categorized as Level I, Level II, or Level III and rated Grade A, implying strong confidence in the actual effects of dexmedetomidine in all outcome measures of the review.

CONCLUSIONS

The current evidence suggests that dexmedetomidine is an effective alternative for alleviating ketamine-induced delirium in noncardiac adult surgical patients. Multiple studies in this review noted improved hemodynamics and reduced postoperative analgesic requirements after administration of dexmedetomidine in conjunction with ketamine.

Alpha 2 agonists for sedation to produce better outcomes from critical illness (A2B Trial): protocol for a multicentre phase 3 pragmatic clinical and cost-effectiveness randomised trial in the UK

INTRODUCTION

Almost all patients receiving mechanical ventilation (MV) in intensive care units (ICUs) require analgesia and sedation. The most widely used sedative drug is propofol, but there is uncertainty whether alpha2-agonists are superior. The alpha 2 agonists for sedation to produce better outcomes from critical illness (A2B) trial aims to determine whether clonidine or dexmedetomidine (or both) are clinically and cost-effective in MV ICU patients compared with usual care.

METHODS AND ANALYSIS

Adult ICU patients within 48 hours of starting MV, expected to require at least 24 hours further MV, are randomised in an open-label three arm trial to receive propofol (usual care) or clonidine or dexmedetomidine as primary sedative, plus analgesia according to local practice. Exclusions include patients with primary brain injury; postcardiac arrest; other neurological conditions; or bradycardia. Unless clinically contraindicated, sedation is titrated using weight-based dosing guidance to achieve a Richmond-Agitation-Sedation score of -2 or greater as early as considered safe by clinicians. The primary outcome is time to successful extubation. Secondary ICU outcomes include delirium and coma incidence/duration, sedation quality, predefined adverse events, mortality and ICU length of stay. Post-ICU outcomes include mortality, anxiety and depression, post-traumatic stress, cognitive function and health-related quality of life at 6-month follow-up. A process evaluation and health economic evaluation are embedded in the trial.The analytic framework uses a hierarchical approach to maximise efficiency and control type I error. Stage 1 tests whether each alpha2-agonist is superior to propofol. If either/both interventions are superior, stages 2 and 3 testing explores which alpha2-agonist is more effective. To detect a mean difference of 2 days in MV duration, we aim to recruit 1437 patients (479 per group) in 40-50 UK ICUs.

ETHICS AND DISSEMINATION

The Scotland A REC approved the trial (18/SS/0085). We use a surrogate decision-maker or deferred consent model consistent with UK law. Dissemination will be via publications, presentations and updated guidelines.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT03653832.

Dexmedetomidine Attenuates Apoptosis and Neurological Deficits by Modulating Neuronal NADPH Oxidase 2-Derived Oxidative Stress in Neonates Following Hypoxic Brain Injury

Hypoxic-ischemic brain injury is an important cause of neonatal neurological deficits. Our previous study demonstrated that dexmedetomidine (Dex) provided neuroprotection against neonatal hypoxic brain injury; however, the underlying mechanisms remain incompletely elucidated. Overactivation of NADPH oxidase 2 (NOX2) can cause neuronal apoptosis and neurological deficits. Hence, we aimed to investigate the role of neuronal NOX2 in Dex-mediated neuroprotection and to explore its potential mechanisms. Hypoxic injury was modeled in neonatal rodents in vivo and in cultured hippocampal neurons in vitro. Our results showed that pre- or post-treatment with Dex improved the neurological deficits and alleviated the hippocampal neuronal damage and apoptosis caused by neonatal hypoxia. In addition, Dex treatment significantly suppressed hypoxia-induced neuronal NOX2 activation; it also reduced oxidative stress, as evidenced by decreases in intracellular reactive oxygen species (ROS) production, malondialdehyde, and 8-hydroxy-2-deoxyguanosine, as well as increases in the antioxidant enzymatic activity of superoxide dismutase and glutathione peroxidase in neonatal rat hippocampi and in hippocampal neurons. Lastly, the posthypoxicneuroprotective action of Dex was almost completely abolished in NOX2-deficient neonatal mice and NOX2-knockdown neurons. In conclusion, our data demonstrated that neuronal NOX2-mediated oxidative stress is involved in the neuroprotection that Dex provides against apoptosis and neurological deficits in neonates following hypoxia.

The Role of miRNAs in Dexmedetomidine's Neuroprotective Effects against Brain Disorders

There are limited neuroprotective strategies for various central nervous system conditions in which fast and sustained management is essential. Neuroprotection-based therapeutics have become an intensively researched topic in the neuroscience field, with multiple novel promising agents, from natural products to mesenchymal stem cells, homing peptides, and nanoparticles-mediated agents, all aiming to significantly provide neuroprotection in experimental and clinical studies. Dexmedetomidine (DEX), an α2 agonist commonly used as an anesthetic adjuvant for sedation and as an opioid-sparing medication, stands out in this context due to its well-established neuroprotective effects. Emerging evidence from preclinical and clinical studies suggested that DEX could be used to protect against cerebral ischemia, traumatic brain injury (TBI), spinal cord injury, neurodegenerative diseases, and postoperative cognitive disorders. MicroRNAs (miRNAs) regulate gene expression at a post-transcriptional level, inhibiting the translation of mRNA into functional proteins. In vivo and in vitro studies deciphered brain-related miRNAs and dysregulated miRNA profiles after several brain disorders, including TBI, ischemic stroke, Alzheimer’s disease, and multiple sclerosis, providing emerging new perspectives in neuroprotective therapy by modulating these miRNAs. Experimental studies revealed that some of the neuroprotective effects of DEX are mediated by various miRNAs, counteracting multiple mechanisms in several disease models, such as lipopolysaccharides induced neuroinflammation, β-amyloid induced dysfunction, brain ischemic-reperfusion injury, and anesthesia-induced neurotoxicity models. This review aims to outline the neuroprotective mechanisms of DEX in brain disorders by modulating miRNAs. We address the neuroprotective effects of DEX by targeting miRNAs in modulating ischemic brain injury, ameliorating the neurotoxicity of anesthetics, reducing postoperative cognitive dysfunction, and improving the effects of neurodegenerative diseases.

[Dexmedetomidine preconditioning alleviates acute lung injury induced by intestinal ischemia-reperfusion in rats by inhibiting NLRP3 inflammasome activation]

OBJECTIVE

To investigate the protective effect of dexmedetomidine (Dex) against acute lung injury induced by intestinal ischemia-reperfusion (II/R) in rats and its effect on NLRP3 inflammasome activity.

METHODS

Thirty-two normal male SD rats were randomly divided into 4 groups (n=8): the sham operation group, where the superior mesenteric artery (SMA) was exposed only; II/R group, where the SMA was occluded for 1 h followed by reperfusion for 2 h; Dex+II/R group, where the rats were subjected to II/R and received intraperitoneal injection of Dex before reperfusion; and Dex group, where the rats received Dex pretreatment and sham operation. The rats in sham operation group and II/R group received intraperitoneal injection of normal saline. The wet/dry weight ratio (W/D) and myeloperoxidase (MPO) activity in the lung tissues were measured, and HE staining was used to evaluate lung pathologies and determine lung injury score of the rats. The levels of inflammatory cytokines (TNF-α, IL-18, and IL-1β) in the lung tissue were detected using ELISA, and the expressions of NLRP3, ASC, caspase-1 and p-AMPK proteins were determined with Western blotting.

RESULTS

Compared with the sham-operated rats, the rats with II/R injury showed obvious lung pathologies and significantly increased W/D value, MPO activity and expression of TNF-α, IL-18 and IL-1β in the lung tissue (P < 0.05) with also significantly increased expressions of NLRP3, ASC, and caspase-1 proteins (P < 0.05) but obviously lowered expression of p-AMPK protein (P < 0.05) in the lung tissues. Compared with those in II/R group, the rats in Dex+II/R group showed milder lung pathologies, significantly reduced W/D value, MPO activity and expressions of TNF-α, IL-18 and IL-1β in the lung tissue (P < 0.05), and significant lower expressions of NLRP3, ASC, and caspase-1 (P < 0.05) but higher expression of p-AMPK protein (P < 0.05).

CONCLUSION

Dex treatment reduces II/R-induced inflammatory response by inhibiting the activation of NLRP3 inflammasomes, thereby improving acute lung injury caused by II/R in rats.

The Protective Mechanism of Dexmedetomidine in Regulating Atg14L-Beclin1-Vps34 Complex Against Myocardial Ischemia-Reperfusion Injury

The blood flow restoration of ischemic tissues causes myocardial injury. Dexmedetomidine (Dex) protects multi-organs against ischemia/reperfusion (I/R) injury. This study investigated the protective mechanism of Dex post-treatment in myocardial I/R injury. The rat model of myocardial I/R was established. The effects of Dex post-treatment on cardiac function and autophagy flow were observed. Dex attenuated myocardial I/R injury and reduced I/R-induced autophagy in rats. Dex weakened the interactions between Beclin1 and Vps34 and Beclin1 and Atg14L, thus downregulating Vps34 kinase activity. In vitro, the cardiomyocytes subjected to oxygen glucose deprivation/reoxygenation were treated with Dex and PI3K inhibitor LY294002. LY294002 attenuated the myocardial protective effect of DEX, indicating that Dex protected against cardiac I/R by activating the PI3K/Akt pathway. In conclusion, Dex upregulated the phosphorylation of Beclin1 at S295 site by activating the PI3K/Akt pathway and reduced the interactions of Atg14L-Beclin1-Vps34 complex, thus inhibiting autophagy and protecting against myocardial I/R injury.

Effect of Different Modes of Administration of Dexmedetomidine Combined with Nerve Block on Postoperative Analgesia in Total Knee Arthroplasty

INTRODUCTION

Dexmedetomidine (DEX) as a nerve block adjuvant can significantly prolong analgesia. However, whether perineural or systemic administration of DEX is more beneficial in patients undergoing total knee arthroplasty (TKA) has not been thoroughly investigated. To this end, we evaluated the effects of perineural and systemic DEX administration on postoperative analgesia in patients undergoing TKA surgery.

METHODS

We randomly assigned patients undergoing TKA under general anesthesia combined with femoral nerve block and sciatic nerve block to one of three groups: (1) ropivacaine plus perineural dexmedetomidine (DP): 0.25% ropivacaine 40 mL plus 0.5 μg/kg dexmedetomidine; (2) ropivacaine plus systemic dexmedetomidine (DS): 0.25% ropivacaine 40 mL plus systemic 0.5 μg/kg dexmedetomidine; (3) control group (C): 0.25% ropivacaine 40 mL.

RESULTS

The average length of time until patients first experienced postoperative pain was significantly longer in the DP group (26.0 h [22.0-30.0 h]) than in the DS group (22.4 h [18-26.8 h]) and the control group (22.9 h [19.5-26.3 h], P = 0.001). For this result there was no significant difference between the DS and the control group. Compared with the DS and control groups, patients in the DP group had lower resting visual analogue scale (VAS) scores at 24, 48, and 72 h after surgery (P < 0.05). VAS activity scores at 12, 24, and 48 h after surgery in the DP group were lower than those in the DS and control groups, with a statistically significant difference (P < 0.05). Compared with the DS and control groups, the amount of postoperative opioids in the DP group was also significantly reduced, and the number of people needing postoperative rescue analgesia was significantly lower, with a statistical difference (P < 0.05). Meanwhile, the sleep satisfaction of patients in the DP group on the first night after surgery and the satisfaction with pain control at 72 h after surgery were both higher than those in the DS group and control group (P < 0.05).

CONCLUSIONS

Perineural administration of DEX can significantly prolong the interval until patients report pain for the first time after TKA, relieve postoperative pain, reduce postoperative opioid dosage, and improve postoperative sleep quality and satisfaction with pain control.

TRIAL REGISTRATION

The trial was registered at the Chinese Clinical Trial Registry, identifier ChiCTR1900025808.

Dexmedetomidine alleviates hepatic ischaemia-reperfusion injury via the PI3K/AKT/Nrf2-NLRP3 pathway

Hepatic ischaemia-reperfusion (I/R) injury constitutes a tough difficulty in liver surgery. Dexmedetomidine (Dex) plays a protective role in I/R injury. This study investigated protective mechanism of Dex in hepatic I/R injury. The human hepatocyte line L02 received hypoxia/reoxygenation (H/R) treatment to stimulate cell model of hepatic I/R. The levels of pyroptosis proteins and inflammatory factors were detected. Functional rescue experiments were performed to confirm the effects of miR-494 and JUND on hepatic I/R injury. The levels of JUND, PI3K/p-PI3K, AKT/p-AKT, Nrf2, and NLRP3 activation were detected. The rat model of hepatic I/R injury was established to confirm the effect of Dex in vivo. Dex reduced pyroptosis and inflammation in H/R cells. Dex increased miR-494 expression, and miR-494 targeted JUND. miR-494 inhibition or JUND upregulation reversed the protective effect of Dex. Dex repressed NLRP3 inflammasome by activating the PI3K/AKT/Nrf2 pathway. In vivo experiments confirmed the protective effect of Dex on hepatic I/R injury. Overall, Dex repressed NLRP3 inflammasome and alleviated hepatic I/R injury via the miR-494/JUND/PI3K/AKT/Nrf2 axis.

Effect of continuous infusion of dexmedetomidine on blood loss in orthognathic surgery: a retrospective study

BACKGROUND

Patients with maxillofacial deformities require orthognathic surgeries to correct occlusion. The surgical procedure may lead to massive bleeding, which is associated with haematoma, respiratory obstruction, and asphyxia. Dexmedetomidine has been used in controlled hypotension and may reduce blood loss in orthognathic surgery. We conducted a retrospective cohort study to evaluate the effect of dexmedetomidine on blood loss in orthognathic surgeries.

METHODS

The primary outcome examined was blood loss, and secondary outcomes were postoperative haemoglobin level; intraoperative heart rate and blood pressure (T1: at incision; T2: 30 min after incision; T3: 60 min after incision; T4: 120 min after incision); dosage of fentanyl, remifentanil, urapidil, and esmolol; operation time; and incidence of allogeneic blood transfusion.

RESULTS

A total of 1247 patients were included in this study, and 540 patient pairs were matched via propensity score matching. There were significant decreases in mean blood loss, heart rate at T1-T4, blood pressure at T1, and remifentanil and esmolol dosage in the dexmedetomidine group compared with those in the control group. There was also a significant increase in the postoperative haemoglobin level of the dexmedetomidine group.

CONCLUSIONS

Continuous infusion of dexmedetomidine can decrease blood loss in orthognathic surgery.

TRIAL REGISTRATION

ChiCTR1800018794 (retrospectively registered) Name of registry: Chinese Clinical Trial Registry Date of registration: 2018/10/09 URL: www.chictr.org.cn/showproj.aspx?proj=30612.

Cardioprotective effects of propofol-dexmedetomidine in open-heart surgery: A prospective double-blind study

Background:

Myocardial protection in cardiac surgeries is a must and requires multimodal approaches in perioperative period to decrease and prevent the increase of myocardial oxygen demand and consumption that lead to postoperative cardiac complications including myocardial ischemia, dysfunction, and heart failure.

Study Design:

Prospective, controlled, randomized, double-blinded study.

Aims:

This study aims to study the effect of propofol-dexmedetomidine continuous infusion cardioprotection during open-heart surgery in adult patients.

Materials and Methods:

Sixty adult patients of both sexes aged from 30 to 60 years old belonging to the American Society of Anesthesiologists III or IV undergoing open-heart surgery were randomly divided into two equal groups: Group P (control group) received continuous infusion of propofol at a rate of 2 mg/kg/h and 50 cc 0.9% sodium chloride solution infused at a rate of 0.4 μg/kg/h (used as a placebo) and Group PD received continuous infusion of propofol at a rate of 2 mg/kg/h and dexmedetomidine 200 μg diluted in 50 cc 0.9% sodium chloride solution infused at a rate of 0.4 μg/kg/h. Infusion for all patients started immediately preoperative till skin closure. Hemodynamic measurements of heart rate (HR), invasive mean arterial pressure, and oxygen saturation were recorded at baseline before induction of anesthesia, immediately after intubation, at skin incision, at sternotomy and every 15 min in the 1^st h then every 30 min during the prebypass period then every 15 min in the 1^st h then every 30 min after weaning from CPB till the end of the surgery. Serum biomarkers; cardiac troponin (cTnI) and creatine kinase-myocardial bound (CK-MB) samples were measured basally (T1), 15 min after unclamping of the aorta (T2), immediate postoperative (T3), and 24 h postoperative (T4). Intraoperative data were also recorded including the number of coronary grafts, aortic cross-clamping duration, duration of cardiopulmonary bypass (CPB), duration of surgery, and rhythm of reperfusion. Fentanyl requirement, extubation time, and length of intensive care unit (ICU) stay were also recorded for every case.

Results:

There was no statistically significant differences as regard to demographic data between the studied two groups. HR and blood pressure recorded was lower in the PD group than the control group, and this difference was noted to be statistically significant. Furthermore, the PD group showed lower levels of myocardial enzymes (cTnI and CK-MB), decreased total fentanyl requirement, earlier postoperative extubation, and shorter ICU stay than the P (control) group.

Conclusion:

The use of propofol-dexmedetomidine in CPB surgeries offers more cardioprotective effects than the use of propofol alone.

Dexmedetomidine Alleviates Hypoxia-Induced Synaptic Loss and Cognitive Impairment via Inhibition of Microglial NOX2 Activation in the Hippocampus of Neonatal Rats

BACKGROUND

Perinatal hypoxia is a universal cause of death and neurological deficits in neonates worldwide. Activation of microglial NADPH oxidase 2 (NOX2) leads to oxidative stress and neuroinflammation, which may contribute to hypoxic damage in the developing brain. Dexmedetomidine has been reported to exert potent neuroprotection in several neurological diseases, but the mechanism remains unclear. We investigated whether dexmedetomidine acts through microglial NOX2 to reduce neonatal hypoxic brain damage.

METHODS

The potential role of microglial NOX2 in dexmedetomidine-mediated alleviation of hypoxic damage was evaluated in cultured BV2 microglia and neonatal rats subjected to hypoxia. In vivo, neonatal rats received dexmedetomidine (25 μg/kg, i.p.) 30 min before or immediately after hypoxia (5% O2, 2 h). Apocynin-mediated NOX inhibition and lentivirus-mediated NOX2 overexpression were applied to further assess the involvement of microglial NOX2 activation.

RESULTS

Pre- or posttreatment with dexmedetomidine alleviated hypoxia-induced cognitive impairment, restored damaged synapses, and increased postsynaptic density-95 and synaptophysin protein expression following neonatal hypoxia. Importantly, dexmedetomidine treatment suppressed hypoxia-induced microglial NOX2 activation and subsequent oxidative stress and the neuroinflammatory response, as reflected by reduced 4-hydroxynonenal and ROS accumulation, and decreased nuclear NF-κB p65 and proinflammatory cytokine levels in cultured BV2 microglia and the developing hippocampus. In addition, treating primary hippocampal neurons with conditioned medium (CM) from hypoxia-activated BV2 microglia resulted in neuronal damage, which was alleviated by CM from dexmedetomidine-treated microglia. Moreover, the neuroprotective effect of dexmedetomidine was reversed in NOX2-overexpressing BV2 microglia and diminished in apocynin-pretreated neonatal rats.

CONCLUSION

Dexmedetomidine targets microglial NOX2 to reduce oxidative stress and neuroinflammation and subsequently protects against hippocampal synaptic loss following neonatal hypoxia.

Effect of dexmedetomidine on brain function and hemodynamics in patients undergoing lung cancer resection

Effect of dexmedetomidine on the brain function and hemodynamics in patients undergoing lung cancer resection were explored. Eighty-seven patients with lung cancer undergoing lung cancer resection in Weifang People's Hospital from January 2014 to June 2018 were enrolled in this study. Patients conventionally anesthetized by propofol, midazolam, sufentanil, or cisatracurium besilate (41 cases) were assigned to the control group and those anesthetized by conventional anesthetic and dexmedetomidine (46 cases) were assigned to the research group. The hemodynamic parameters, neuron-specific enolase (NSE), and astrocyte S-100p protein (S-100β) were compared between the two groups before induction (T0), 5 min after induction (T1), at the end of surgery (T2), time of extubation (T3), and 5 min after extubation (T4). The cognitive function of patients was graded by the mini-mental state examination (MMSE) after patients recovered from anesthesia. In both the control group and the research group, the levels of mean arterial pressure (MAP), heart rate (HR), and central venous pressure (CVP). were statistically higher at T2 and T3 than those at T0 (all P<0.05). The levels of MAP, HR, and CVP were statistically lower in the research group than those in the control group at T2 and T3 (P<0.05). The levels of serum NSE and S100β protein in the research group and the control group increased at T2, T3, and T4, the control group was higher than the research group at each time point, and the difference was statistically significant (P<0.05). Comparison of the MMSE score and the total case number of adverse reactions between the two groups showed no statistical difference (both P>0.05). The MMSE score was positively correlated with the serum levels of NSE and S100β in the two groups (r-values were 0.661 and 0.585, P<0.05). Dexmedetomidine can effectively protect patients' perioperative brain function with small impacts on perioperative hemodynamics, so it is worthy of clinical application.

The effect of dexmedetomidine and midazolam on combined spinal-epidural anesthesia in patients undergoing total knee arthroplasty

Background

Intravenous dexmedetomidine has been reported to potentiate the anesthetic effect of local anesthetics and improve the quality of postoperative analgesia when used as an adjuvant in neuraxial block. We compared the effects of intravenous dexmedetomidine and midazolam for sedation on combined spinal-epidural (CSE) anesthesia.

Methods

This study included 50 patients undergoing total knee arthroplasty. CSE anesthesia was given using 10 mg bupivacaine for all patients. After checking the maximum sensory and motor levels, the patients were randomly allocated into two groups of 25 each to receive intravenous continuous infusion of dexmedetomidine (Group D) or midazolam (Group M) for sedation during surgery. Regression block level, hemodynamic changes, and sedation score were compared between the groups when the patients entered the postanesthetic care unit (PACU). For patient-controlled epidural analgesia, 0.2% levobupivacaine with 650 µg of fentanyl (150 ml in total) was infused at a rate of 1 ml/h, in addition to a 3-ml bolus dose with a 30-min lockout time. The visual analogue scale scores, additional analgesic demand, patient satisfaction, and adverse events between the two groups were also compared postoperatively.

Results

A significant difference was observed in relation to the sensory block level in the PACU (Group D: 6.3 ± 2.1; Group M: 3.2 ± 1.9) (P = 0.002). The motor block level and other outcomes showed no significant intergroup differences.

Conclusions

Intravenous injection of dexmedetomidine, rather than midazolam, for procedural sedation is associated with prolonged sensory block, with comparable incidences of adverse events during CSE anesthesia.

Pretreatment with dexmedetomidine alleviates lung injury in a rat model of intestinal ischemia reperfusion

The aim of the present study was to investigate the antioxidant mechanisms of dexmedetomidine against lung injury during intestinal ischemia reperfusion (IIR) in rats. The model of IIR-induced acute lung injury was established by occluding the superior mesenteric artery (SMA) for 1 h and reperfusing for 2 h using Sprague-Dawley rats. Pathological examination was used to assess the extent of the lung injury. Oxidative stress was evaluated by measuring malondialdehyde, myeloperoxidase and superoxide dismutase in the lung and plasma. The proinflammatory cytokines tumor necrosis factor-α and interleukin-6 were determined via an enzyme-linked immunosorbent assay. The mRNA and protein expression of nuclear factor-erythroid 2 related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) were determined using a reverse transcription-quantitative polymerase chain reaction and western blotting. Pretreatment with dexmedetomidine significantly inhibited the oxidative stress response and proinflammatory factor release caused by IIR compared with the normal saline group (MDA and SOD in lung and plasma, P<0.05; MPO, IL-1β and TNF-α in lung and plasma, P<0.05). Dexmedetomidine improved pulmonary pathological changes in IIR rats compared with the normal saline group. Investigations into the molecular mechanism revealed that dexmedetomidine increased the expression levels of Nrf2 and HO-1 via activating α2 adrenergic receptors compared with the normal saline group. The antagonism of α2 adrenergic receptors may reverse the protective effect of dexmedetomidine on lung injury during IIR, including decreasing the expression levels of Nrf2 and HO-1, elevating the oxidative stress response and increasing the proinflammatory factor release. In conclusion, pretreatment with dexmedetomidine demonstrated protective effects against lung injury during IIR via α2 adrenergic receptors. The Nrf2/HO-1 signaling pathway may serve a function in the protective effect of dexmedetomidine.

A Population Pharmacokinetic Model of Intravenous Dexmedetomidine for Mechanically Ventilated Children after Neurosurgery

Dexmedetomidine is a selective alpha-2 adrenergic agonist with concurrent sedative and analgesic effects, and it is being increasingly used in pediatric anesthesia and intensive care. This study aimed to investigate the pharmacokinetics of intravenous dexmedetomidine in mechanically ventilated children in the intensive care unit (ICU) after neurosurgery. Pediatric patients aged 2–12 years, who were mechanically ventilated in ICU after neurosurgery, were allocated into a low-dose (n = 15) or high-dose (n = 14) group. The low-dose group received dexmedetomidine at a loading dose of 0.25 µg/kg for 10 min, followed by a maintenance dose of 0.25 µg/kg/h for 50 min, whereas the high-dose group received dexmedetomidine at a loading dose of 0.5 µg/kg for 10 min, followed by a maintenance dose of 0.5 µg/kg/h for 50 min. Serial blood samples were collected for a pharmacokinetic analysis up to 480 min after the end of the infusion. The sedative effect of dexmedetomidine was assessed using the Bispectral Index and University of Michigan Sedation Scale. Adverse reactions, electrocardiography findings, and vital signs were monitored for a safety assessment. A population pharmacokinetic analysis was performed using non-linear mixed effects modeling. Dexmedetomidine induced a moderate-to-deep degree of sedation during infusion in both groups. The pharmacokinetics of dexmedetomidine were best described by a two-compartment disposition model with first-order elimination kinetics. The parameters were standardized for a body weight of 70 kg using an allometric power model. The population estimates (95% confidence interval) per 70 kg body weight were as follows: clearance of 81.0 (72.9–90.9) L/h, central volume of distribution of 64.2 (50.6–81.0) L, intercompartment clearance of 116.4 (90.6–156.0) L/h, and peripheral volume of distribution of 167 (132–217) L. No serious adverse reactions or hemodynamic changes requiring the discontinuation of dexmedetomidine were observed. Dexmedetomidine had increased clearance and volume of distribution in mechanically ventilated children in ICU after neurosurgery, thereby indicating the need to adjust the dosage to obtain a target plasma concentration.

The influence of dexmedetomidine on remifentanil-induced hyperalgesia and the sex differences

In the clinical settings, patients often develop opioid-induced hyperalgesia (OIH) after utilization of high dose intra-operative remifentanil. Systemic α2 agonists, including dexmedetomidine, are believed to reduce pain and opioid requirements after surgery, thus decreasing the incidence of hyperalgesia. The present study aimed to investigate the effect of dexmedetomidine on remifentanil-induced hyperalgesia and explored the sex differences. A total of 48 patients (24 male, 24 female) with an American Society of Anesthesiologists physical status of I-II that were undergoing thyroidectomy were randomly assigned to one of the following six groups: Male controlled group (MC) and female controlled group (FC) (group MC, n=8 and group FC, n=8), which received a preoperative placebo of 0.2 µg.kg^-1 normal saline and intraoperative remifentanil 0.2 µg.kg^-1.min^-1; male and female group with low-dose dexmedetomidine (group MD1, n=8 and group FD1, n=8), which received preoperative dexmedetomidine 0.2 µg.kg^-1 and intraoperative remifentanil 0.2 µg.kg^-1.min^-1; and male and female groups with high-dose dexmedetomidine (group MD2, n=8 and group FD2, n=8), which received dexmedetomidine 0.6 µg.kg^-1 and intraoperative remifentanil 0.2 µg.kg^-1.min^-1. Result indicated that the visual analog scale (VAS) scores and morphine dosing frequency were significantly higher in MC and FC groups compared with the other same sex groups. Furthermore, the mechanical hyperalgesia threshold and patients' analgesia satisfaction score after surgery were significantly lower in MC and FC groups. Notably, the frequency of post-operative chills, nausea and vomiting were significantly lower in groups MD1, MD2, FD1 and FD2. The present findings indicated that low- and high-dose dexmedetomidine injection significantly decreased the patient's risk of enhanced pain intensity and increased postoperative morphine dosing caused by remifentanil-induced hyperalgesia. These findings suggest that the influence of dexmedetomidine displayed minimal significant differences between sex. Trial registration no., IRB2018-YX-001 (Name of registry: Institutional Medical Ethics Committee of Tianjin Medical University General Hospital; date of registration: February 1, 2016).

Dexmedetomidine Protects Mouse Brain from Ischemia-Reperfusion Injury via Inhibiting Neuronal Autophagy through Up-Regulating HIF-1α

Stroke is the leading cause of death in China and produces a heavy socio-economic burden in the past decades. Previous studies have shown that dexmedetomidine (DEX) is neuroprotective after cerebral ischemia. However, the role of autophagy during DEX-mediated neuroprotection after cerebral ischemia is still unknown. In this study, we found that post-conditioning with DEX and DEX+3-methyladenine (3-MA) (autophagy inhibitor) reduced brain infarct size and improved neurological deficits compared with DEX+RAPA (autophagy inducer) 24 h after transient middle cerebral artery artery occlusion (tMCAO) model in mice. DEX inhibited the neuronal autophagy in the peri-ischemic brain, and increased viability and decreased apoptosis of primary cultured neurons in oxygen-glucose deprivation (OGD) model. DEX induced expression of Bcl-1 and p62, while reduced the expression of microtubule-associated protein 1 light chain 3 (LC3) and Beclin 1 in primary cultured neurons through inhibition of apoptosis and autophagy. Meanwhile, DEX promoted the expression of hypoxia-inducible factor-1α (HIF-1α) both in vivo and in vitro, and 2-Methoxyestradiol (2ME2), an inhibitor of HIF-1α, could reverse DEX-induced autophagic inhibition. In conclusion, our study suggests that post-conditioning with DEX at the beginning of reperfusion protects mouse brain from ischemia-reperfusion injury via inhibition of neuronal autophagy by upregulation of HIF-1α, which provides a potential therapeutic treatment for acute ischemic injury.

Intraoperative use of dexmedetomidine promotes postoperative sleep and recovery following radical mastectomy under general anesthesia

Postoperative sleep disturbance and fatigue following radical mastectomy were high risks for prolonged convalescence in patients with breast cancer. The present study was designed to observe the effect of intraoperative use of dexmedetomidine on postoperative sleep, fatigue and recovery following radical mastectomy under general anesthesia. Forty-seven patients were randomized into two groups that were maintained with propofol/remifentanil/Ringer's solution (Control group), or propofol/remifentanil/Dexmedetomidine (DEX group) for surgery under general anesthesia. During the first night following surgery, patients receiving dexmedetomine spent more time sleeping when compared with those form the Control group. During the first week following operation, when compared with the Control group, patients from the DEX group had a higher score of global 40-item recovery questionnaire on day 3 following operation, and lower 9-question fatigue severity scores on day 3 and day 7 following operation. In conclusion, intraoperative use of dexmedetomidine is sufficient to improve postoperative sleep disorder, promote postoperative recovery. The adverse effect of dexmedetomidine on sleep disturbance might be contributed to its recovery-promoting effect.

Dexmedetomidine Improves Postoperative Patient-Controlled Analgesia following Radical Mastectomy

Acute postoperative pain following radical mastectomy is a high risk for prolonged convalescence and potential persistent pain in patients with breast cancer. The present study was designed to observe the effect of intraoperative use of dexmedetomidine on acute postoperative pain following radical mastectomy under general anesthesia. Forty-five patients were enrolled into the study and divided into two groups that were maintained with propofol/remifentanil/Ringer's solution or propofol/remifentanil/Dexmedetomidine followed by morphine-based patient-controlled analgesia. During the first 24 h following surgery, patients receiving dexmedetomine had lower NRS pain scores, decreased morphine consumption, longer time to first morphine request as well as a trending decreased incidence of adverse effects when compared to those received Ringer's solution. In conclusion, the present study finds that intraoperative use of dexmedetomidine could promote analgesic property of postoperative morphine.