Effect of dexmedetomidine on plasma brain-derived neurotrophic factor: A double-blind, randomized and placebo-controlled study

The Role of Intravenous Anesthetics for Neuro: Protection or Toxicity?

The primary intravenous anesthetics employed in clinical practice encompass dexmedetomidine (Dex), propofol, ketamine, etomidate, midazolam, and remimazolam. Apart from their established sedative, analgesic, and anxiolytic properties, an increasing body of research has uncovered neuroprotective effects of intravenous anesthetics in various animal and cellular models, as well as in clinical studies. However, there also exists conflicting evidence pointing to the potential neurotoxic effects of these intravenous anesthetics. The role of intravenous anesthetics for neuro on both sides of protection or toxicity has been rarely summarized. Considering the mentioned above, this work aims to offer a comprehensive understanding of the underlying mechanisms involved both in the central nerve system (CNS) and the peripheral nerve system (PNS) and provide valuable insights into the potential safety and risk associated with the clinical use of intravenous anesthetics.

Dexmedetomidine administration as a possible cognitive enhancer through increasing the level of brain-derived neurotrophic factors in surgical patients: a systematic review and meta-analysis

OBJECTIVE

This meta-analysis aimed to investigate the effect of dexmedetomidine on brain-derived neurotrophic factor (BDNF) levels in individuals undergoing various medical procedures. We systematically searched electronic databases and manually identified relevant articles to assess the impact of dexmedetomidine on BDNF levels in surgical patients.

METHODS

A comprehensive literature search was conducted in PubMed, Scopus, Embase, and Web of Science databases with no language restrictions. Studies that examined the effects of dexmedetomidine administration on BDNF levels in surgical patients were included.

RESULTS

The overall analysis revealed a statistically significant increase in BDNF levels in individuals receiving dexmedetomidine compared to controls (Standardized Mean Difference SMD = 1.65, 95% CI: 1.02 to 2.28; I2: 89%). Subgroup analyses based on the anesthesia method (p < 0.01), and the type of surgery (p < 0.01) showed significant between-group differences (Fig. 3). The results of the sensitivity analyses indicated that individual studies did not significantly affect the overall results.

CONCLUSION

This meta-analysis indicates that dexmedetomidine administration is associated with a significant increase in BDNF levels in individuals undergoing surgical procedures. These findings highlight the potential role of dexmedetomidine in modulating BDNF levels, which may have implications for optimizing perioperative neuroprotective strategies and improving patient outcomes.

BDNF Therapeutic Mechanisms in Neuropsychiatric Disorders

Brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the adult brain and functions as both a primary neurotrophic signal and a neuromodulator. It serves essential roles in neuronal development, maintenance, transmission, and plasticity, thereby influencing aging, cognition, and behavior. Accumulating evidence associates reduced central and peripheral BDNF levels with various neuropsychiatric disorders, supporting its potential utilization as a biomarker of central pathologies. Subsequently, extensive research has been conducted to evaluate restoring, or otherwise augmenting, BDNF transmission as a potential therapeutic approach. Promising results were indeed observed for genetic BDNF upregulation or exogenous administration using a multitude of murine models of neurological and psychiatric diseases. However, varying mechanisms have been proposed to underlie the observed therapeutic effects, and many findings indicate the engagement of disease-specific and other non-specific mechanisms. This is because BDNF essentially affects all aspects of neuronal cellular function through tropomyosin receptor kinase B (TrkB) receptor signaling, the disruptions of which vary between brain regions across different pathologies leading to diversified consequences on cognition and behavior. Herein, we review the neurophysiology of BDNF transmission and signaling and classify the converging and diverging molecular mechanisms underlying its therapeutic potentials in neuropsychiatric disorders. These include neuroprotection, synaptic maintenance, immunomodulation, plasticity facilitation, secondary neuromodulation, and preservation of neurovascular unit integrity and cellular viability. Lastly, we discuss several findings suggesting BDNF as a common mediator of the therapeutic actions of centrally acting pharmacological agents used in the treatment of neurological and psychiatric illness.

The Current Role of Dexmedetomidine as Neuroprotective Agent: An Updated Review

Dexmedetomidine, selective α2-adrenergic agonist dexmedetomidine, has been widely used clinically for sedation and anesthesia. The role of dexmedetomidine has been an interesting topic of neonatological and anesthetic research since a series of advantages of dexmedetomidine, such as enhancing recovery from surgery, reducing opioid prescription, decreasing sympathetic tone, inhibiting inflammatory reactions, and protecting organs, were reported. Particularly, an increasing number of animal studies have demonstrated that dexmedetomidine ameliorates the neurological outcomes associated with various brain and spinal cord injuries. In addition, a growing number of clinical trials have reported the efficacy of dexmedetomidine for decreasing the rates of postoperative neurological dysfunction, such as delirium and stroke, which strongly highlights the possibility of dexmedetomidine functioning as a neuroprotective agent for future clinical use. Mechanism studies have linked dexmedetomidine’s neuroprotective properties with its modulation of neuroinflammation, apoptosis, oxidative stress, and synaptic plasticity via the α2-adrenergic receptor, dependently or independently. By reviewing recent advances and preclinical and clinical evidence on the neuroprotective effects of dexmedetomidine, we hope to provide a complete understanding of the above mechanism and provide insights into the potential efficacy of this agent in clinical use for patients.

Effect of dexmedetomidine on hemodynamic responses to tracheal intubation: A meta-analysis with meta-regression and trial sequential analysis

STUDY OBJECTIVE

An uncontrolled adrenergic response during tracheal intubation may lead to life-threatening complications. Dexmedetomidine binds to α2-receptors and may attenuate this response. The primary aim of our meta-analysis is to investigate dexmedetomidine efficacy in attenuating sympathetic response to tracheal intubation, compared with placebo or no dexmedetomidine, in terms of heart rate and blood pressure at intubation.

DESIGN

Meta-analysis with meta-regression and trial sequential analysis.

SETTING

Systematic search from inception until December 1, 2020 in the following databases: Pubmed, Scopus, the Cochrane Central Register of Controlled Trials, EMBASE and Google Scholar.

INTERVENTIONS

All randomized controlled trials investigating intravenous dexmedetomidine as premedication in adult patients undergoing tracheal intubation were included in our study. Studies were included without any language or publication date restriction. A trial sequential analysis and a post-hoc meta-regression were performed on the main outcomes.

MEASUREMENTS

Hemodynamic parameters and heart rate at tracheal intubation, dose of anesthetic needed for induction of anesthesia, total anesthetic requirement throughout the operative procedure, postoperative pain and percentage of patients requiring analgesics at 24 postoperative hours, postoperative nausea and vomiting, intraoperative and postoperative bradycardia, hypotension, dizziness, shivering and/or respiratory depression.

MAIN RESULTS

Ninety-nine included studies randomized 6833 patients. During laryngoscopy, all hemodynamic parameters were significantly greater in the no dexmedetomidine group. In particular, in the dexmedetomidine group, systolic blood pressure differed by -21.8 mm Hg (95% CI -26.6 to -17.1, p-value < 0.001, I² 97%), mean arterial pressure by -12.8 mm Hg (95% CI -15.6 to -10.0, p-value < 0.001, I² 98%), and heart rate by -16.9 bpm (95% CI -19.8 to -13.9, p-value < 0.001, I² 98%).

CONCLUSIONS

Patients receiving premedication with dexmedetomidine for tracheal intubation, compared with no dexmedetomidine, have a lower blood pressure and heart rate, however, the risk of bradycardia and hypotension is relevant and its use during daily practice should be cautiously evaluated for each patient.

Intraoperative Dexmedetomidine in Peripheral or Emergency Neurologic Surgeries of Patients With Mild-to-Moderate Traumatic Brain Injuries: A Retrospective Cohort Study

Background

Although animal models have demonstrated dexmedetomidine (DEX) as neuroprotective in craniocerebral and subarachnoid injuries, but its role in humans remains to be elucidated. The objectives of the study were to compare plasma brain-derived neurotrophic factor (BDNF), cytokine, and superoxide dismutase levels of patients between those who received intraoperative DEX and those who received intraoperative normal saline (NSE) during peripheral or emergency neurologic surgeries.

Methods

Intra- and postoperative data of blood biomarkers and surgical outcomes of patients who underwent peripheral or emergency neurologic surgeries with mild-to-moderate traumatic brain injuries were analyzed retrospectively. Patients received intraoperative DEX group (n = 109) or NSE group (n = 116).

Results

At 15 minutes after intubation and before the operation, in the DEX group, plasma BDNF concentration decreased but remained much higher than the NSE group (P < .0001, q = 15.82). After 24 hours of surgeries, levels of cytokine were higher in the NSE group than the DEX group (P < .05 for all). Dexmedetomidine increased malondialdehyde (P < .0001) and superoxide dismutase (P < .0001) levels in DEX group.

Conclusions

Intraoperative infusion of DEX may have a neuroprotective, anti-inflammatory, and antioxidant effects during peripheral or emergency neurologic surgeries.

Level of Evidence

III.

Dexmedetomidine improves cognition after carotid endarterectomy by inhibiting cerebral inflammation and enhancing brain-derived neurotrophic factor expression

Objectives

Carotid endarterectomy (CEA) is efficient in preventing stroke for patients with significant carotid stenosis, but results in mild cognitive dysfunction. Dexmedetomidine is neuroprotective in stroke models. We hypothesized that dexmedetomidine may improve cognition after CEA.

Methods

Forty-nine patients scheduled for elective CEA were randomly assigned to intravenous dexmedetomidine treatment group (n = 25) and control group C (normal saline, n = 24). Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MOCA), as well as lactate, TNF-α, IL-6, and BDNF levels in blood, were assessed before, during, and after surgery.

Results

MMSE and MOCA scores showed subtle decline in both groups at 24 hours postoperatively; this decline remained at 48 hours postoperatively in group C. Both scores were higher in group D than in group C at 48 and 72 hours postoperatively. TNF-α and IL-6 were lower from 5 minutes post-clamping through 24 hours postoperatively in group D; lactate was lower at 5 minutes post-clamping in group D. BDNF was higher from 5 minutes post-clamping through 1 hour postoperatively in both groups, and remained high in group D at 24 hours postoperatively.

Conclusions

Dexmedetomidine improved recovery of cognition after CEA, potentially due to reduced inflammation and enhanced BDNF expression.

Dexmedetomidine promotes the recovery of neurogenesis in aged mouse with postoperative cognitive dysfunction

Recently, growing evidence has demonstrated Dexmedetomidine (Dex) a promising intervene preventing postoperative cognitive decline (POCD) following surgery, which is associated with neuroinflammation leading to neuronal apoptosis and deregulated neurogenesis. Previous studies suggested the anti-inflammation and anti-neuroapoptosis action of Dex. Therefore we hypothesize the promoting neurogenesis of Dex linked to stimulating BDNF and subsequent p-MPAK production in a rat model of POCD. In the present study, the POCD animal model was established by performing an exploratory laparotomy under isoflurane anaesthesia in old rats, utilizing which Dex response is confirmed by behavioural tests. Inflammatory biomarkers as IL-1β and TNF-α, mature neuron percentage measured by doublecortin staining (DCX), promoting factors as brain derived growth factor (BDNF), phosphorylated cAMP response element binding protein (CREB) and proteins of kinase A (PKA), MAPK production as p-P38-MAPK protein express were measured. Herein, we showed that surgery reduced DCX-positive neurons and expression of BDNF representing neurogenesis profoundly. As expected, Dex rescued the associated cognitive impairment and inflammatory changes, as well as up-regulated expression of BDNF, PKA, p-CREB/CREB and following p-P38-MAPK regulation. Our results confirmed the protective Dex response and indicated the proneurogenesis role of it as well, suggesting the mechanism of beneficial effects of Dex to prevent POCD.

A Pilot Study of the Use of Dexmedetomidine for the Control of Delirium by Reducing the Serum Concentrations of Brain-Derived Neurotrophic Factor, Neuron-Specific Enolase, and S100B in Polytrauma Patients

BACKGROUND

Delirium is very common among patients with polytrauma, although no suitable means exist to feasibly reduce the incidence and duration of delirium in these patients. Recent reports have suggested that continuous intravenous (IV) infusions of dexmedetomidine, rather than benzodiazepine, be administered for sedation to reduce the duration of delirium in this population. However, serum neuron-specific enolase (NSE), S100 calcium binding protein B (S100B), and brain-derived neurotrophic factor (BDNF) levels have not yet been investigated in polytrauma patients who received sedation with dexmedetomidine rather than other conventional sedatives. The aim of this study was to assess the association of blood BDNF, NSE, and S100B with the occurrence of delirium among polytrauma patients who had been sedated with dexmedetomidine.

MATERIALS AND METHODS

Consecutive patients were randomly assigned to 1 of 2 treatment study groups, namely the "dexmedetomidine group" or the "common group." This case-control study included 18 patients with delirium and 34 matched controls in a 63-bed general intensive care unit (ICU). Blood samples were collected from all patients upon ICU admission, on the day when delirium was diagnosed, and on days 3 and 5 following diagnosis. The serum levels of S100B, BDNF, and NSE were determined by enzyme-linked immunosorbent assay. The sedation levels and delirium were assessed using the Richmond Agitation and Sedation Scale and the Confusion Assessment Method for the ICU.

RESULTS

The median BDNF, NSE, and S100B concentrations were significantly lower in the dexmedetomidine group than in the common group on the day when delirium was diagnosed and on the third day after delirium was diagnosed. The rate of delirium was significantly lower in the dexmedetomidine group than in the common group. There were clear differences in the BDNF, NSE, and S100B levels between the 2 groups on the fifth day after delirium was diagnosed.

CONCLUSIONS

Our randomized controlled study suggests that the sedation of polytrauma patients with dexmedetomidine could help reduce the serum BDNF, S100B, and NSE levels, which appear to be associated with the occurrence of delirium in the dexmedetomidine group.

Effects of different doses of dexmedetomidine on heart rate and blood pressure in intensive care unit patients

The aim of the present study was to observe and compare the sedative effect of different doses of DEX on heart rate (HR) and blood pressure (BP) in critically ill patients admitted to intensive care units (ICUs). The study included patients that were retained in ICUs and required sedation between January and March 2014. Patients were excluded if they had a BP of >200 mmHg, a HR of <60 bpm or were in a state of shock. The included patients were randomized into three groups: Group A, 1.0 µg/kg/10 min DEX; group B, 0.5 µg/kg/10 min DEX; and group C, 0.4 µg/kg/h DEX. After receiving these initial designated doses of DEX via an intravenous (IV) infusion pump for 10 min, the patients were maintained continuously at an identical dose of 0.4 µg/kg/h DEX. Ramsay score, HR, systolic blood pressure (SBP), diastolic blood pressure (DBP), breathing rate (BR) and peripheral capillary oxygen saturation (SpO₂) were recorded prior to the IV pump infusion and at 2, 4, 6, 8, 10, 60, 120, 180 and 240 min following infusion. Patients in groups A and B achieved sedation more rapidly compared with those in group C (P<0.05). HR decreased more significantly at 8 and 60 min after the initial IV pump infusion with DEX in groups A and B compared with group C (P<0.05). SBP decreased significantly at 10 min after IV pump infusion in group A compared with groups B and C (P<0.05). No significant difference existed in the SBP reduction trend between the three groups during the maintenance period. Therefore, the routine dose of DEX (0.4 µg/kg/h) provides an ideal sedative effect in ICU patients. The recommended loading dose for a more rapid sedation is 0.5 µg/kg/h. High loading doses of DEX via IV pump infusion should be avoided in elderly individuals, patients with acute exacerbation of chronic obstructive pulmonary disease and anemic patients, in whom combination medication, such as midazolam or propofol, may be considered when necessary.

A comparison of dexmedetomidine and placebo on the plasma concentrations of NGF, BDNF, GDNF, and epinephrine during severe alcohol withdrawal

Alcohol withdrawal and therapies may affect nerve growth factor (NGF), brain-derived neurotrophic growth factor (BDNF), glial-derived neurotrophic growth factor (GDNF), and epinephrine (EPI). This study evaluated dexmedetomidine (DEX) on NGF, BDNF, GDNF, and EPI in severe alcohol withdrawal and related their plasma concentrations to DEX concentrations. Twenty-four subjects were randomized to DEX 1.2 mcg/kg/hour (high dose [HD]), 0.4 mcg/kg/hour (low dose [LD]), or placebo. Blood was collected at 0 (T0), 48 (T48), and 96-120 (T96) hours after starting the study drug, and concentrations of these transmitters and DEX were determined. Similar NGF suppression occurred at T48 and T96 across all groups. BDNF and GDNF levels increased insignificantly at T48 in the placebo group but steadily declined in both DEX groups, with a trend toward significance in the HD group at T48. EPI concentrations declined significantly in the HD group at T48, only to increase at T96. Median DEX concentrations during the study were insignificantly higher in HD than LD. T0 values of BDNF (r = -0.47, p = 0.02) and GDNF (r = -0.37, p = 0.05) were inversely associated with the need for mechanical ventilation before study enrollment. No other clinical parameter was associated with the plasma concentrations of these transmitters. Daily lorazepam requirements were associated with the severity of withdrawal (r = 0.7, p < 0.0001) and DEX concentrations were inversely related to daily lorazepam requirements (r = -0.33, p = 0.008). DEX utilization suppressed EPI (r = -0.57, p = 0.004). EPI concentrations were associated with BDNF values at T0 (r = 0.55, p = 0.04) and throughout the study (r = 0.25, p = 0.04). In summary, the plasma concentrations of NGF, BDNF, GDNF, and EPI during alcohol withdrawal are variable and the effects of DEX were marginal. DEX administration and higher DEX concentrations attenuated lorazepam administration in the short-term and suppressed EPI.