Dexmedetomidine's inhibitory effects on acetylcholine release from cholinergic nerves in guinea pig trachea: a mechanism that accounts for its clinical benefit during airway irritation

Dexmedetomidine improves pulmonary outcomes in thoracic surgery under one-lung ventilation: A meta-analysis

INTRODUCTION

Dexmedetomidine improves intrapulmonary shunt in thoracic surgery and minimizes inflammatory response during one-lung ventilation (OLV). However, it is unclear whether such benefits translate into less postoperative pulmonary complications (PPCs). Our objective was to determine the impact of dexmedetomidine on the incidence of PPCs after thoracic surgery.

METHODS

Major databases were used to identify randomized trials that compared dexmedetomidine versus placebo during thoracic surgery in terms of PPCs. Our primary outcome was atelectasis within 7 days after surgery. Other specific PPCs included hypoxemia, pneumonia, and acute respiratory distress syndrome (ARDS). Secondary outcome included intraoperative respiratory mechanics (respiratory compliance [Cdyn]) and postoperative lung function (forced expiratory volume [FEV1]). Random effects models were used to estimate odds ratios (OR).

RESULTS

Twelve randomized trials, including 365 patients in the dexmedetomidine group and 359 in the placebo group, were analyzed in this meta-analysis. Patients in the dexmedetomidine group were less likely to develop postoperative atelectasis (2.3% vs 6.8%, OR 0.42, 95%CI 0.18-0.95, P = 0.04; low certainty) and hypoxemia (3.4% vs 11.7%, OR 0.26, 95%CI 0.10-0.68, P = 0.01; moderate certainty) compared to the placebo group. The incidence of postoperative pneumonia (3.2% vs 5.8%, OR 0.57, 95%CI 0.25-1.26, P = 0.17; moderate certainty) or ARDS (0.9% vs 3.5%, OR 0.39, 95%CI 0.07-2.08, P = 0.27; moderate certainty) was comparable between groups. Both intraoperative Cdyn and postoperative FEV1 were higher among patients that received dexmedetomidine with a mean difference of 4.42 mL/cmH2O (95%CI 3.13-5.72) and 0.27 L (95%CI 0.12-0.41), respectively.

CONCLUSION

Dexmedetomidine administration during thoracic surgery may potentially reduce the risk of postoperative atelectasis and hypoxemia. However, current evidence is insufficient to demonstrate an effect on pneumonia or ARDS.

Clinical usefulness of nebulized dexmedetomidine for conscious sedation in daycare flexible bronchoscopy in Southern India

BACKGROUND

Sedative agents used in bronchoscopy require trained personnel to administer and monitor the patient. This increases the procedure cost, duration, and inpatient stay. Inhalational administration of sedative agents can be a practical solution to the issue. Dexmedetomidine in the inhalational form could give results similar to the intravenous form without significant adverse events.

MATERIALS AND METHODS

The study is prospective, randomized, and double-blinded study. Patients needing bronchoscopy were randomized to receive the nebulized form of either dexmedetomidine or saline (0.9%) before bronchoscopy. The study parameters are assessed and recorded before, during, and after bronchoscopy. Data collected are analyzed using the SPSS software.

DISCUSSION

The side effects limit using commonly administered sedation agents in bronchoscopy, such as midazolam, fentanyl, and dexmedetomidine. The nebulized dexmedetomidine is safe with proven efficacy when compared to the placebo. Proceduralist-administered conscious sedation reduces the overall cost and shortens inpatient stays. Attenuation of hemodynamic parameters by dexmedetomidine could be an advantage for the physician in reducing an untoward cardiac event.

CONCLUSION

Dexmedetomidine in the nebulized form improves the comfort of patients during the procedure. It blunts the pressure response during bronchoscopy and could be a safer and cost-effective agent in its nebulized form for conscious sedation in bronchoscopy. The study is approved by the institutional ethics committee (IEC KMC MLR 10-2021-310).

The Mechanism of α2 adrenoreceptor-dependent Modulation of Neurotransmitter Release at the Neuromuscular Junctions

α2-Adrenoreceptors (ARs) are main Gi-protein coupled autoreceptors in sympathetic nerve terminals and targets for dexmedetomidine (DEX), a widely used sedative. We hypothesize that α2-ARs are also potent regulators of neuromuscular transmission via G protein-gated inwardly rectifying potassium (GIRK) channels. Using extracellular microelectrode recording of postsynaptic potentials, we found DEX-induced inhibition of spontaneous and evoked neurotransmitter release as well as desynchronization of evoked exocytotic events in the mouse diaphragm neuromuscular junction. These effects were suppressed by SKF-86,466, a selective α2-AR antagonist. An activator of GIRK channels ML297 had the same effects on neurotransmitter release as DEX. By contrast, inhibition of GIRK channels with tertiapin-Q prevented the action of DEX on evoked neurotransmitter release, but not on spontaneous exocytosis. The synaptic vesicle exocytosis is strongly dependent on Ca2+ influx through voltage-gated Ca2+ channels (VGCCs), which can be negatively regulated via α2-AR - GIRK channel axis. Indeed, inhibition of P/Q-, L-, N- or R-type VGCCs prevented the inhibitory action of DEX on evoked neurotransmitter release; antagonists of P/Q- and N-type channels also suppressed the DEX-mediated desynchronization of evoked exocytotic events. Furthermore, inhibition of P/Q-, L- or N-type VGCCs precluded the frequency decrease of spontaneous exocytosis upon DEX application. Thus, α2-ARs acting via GIRK channels and VGCCs (mainly, P/Q- and N-types) exert inhibitory effect on the neuromuscular communication by attenuating and desynchronizing evoked exocytosis. In addition, α2-ARs can suppress spontaneous exocytosis through GIRK channel-independent, but VGCC-dependent pathway.

Perioperative Care of the Pediatric Patient and an Algorithm for the Treatment of Intraoperative Bronchospasm

Asthma remains a common comorbid condition in patients presenting for anesthetic care. As a chronic inflammatory disease of the airway, asthma is known to increase the risk of intraoperative bronchospasm. As the incidence and severity of asthma and other chronic respiratory conditions that alter airway reactivity is increasing, a greater number of patients at risk for perioperative bronchospasm are presenting for anesthetic care. As bronchospasm remains one of the more common intraoperative adverse events, recognizing and mitigating preoperative risk factors and having a pre-determined treatment algorithm for acute events are essential to ensuring effective resolution of this intraoperative emergency. The following article reviews the perioperative care of pediatric patients with asthma, discusses modifiable risk factors for intraoperative bronchospasm, and outlines the differential diagnosis of intraoperative wheezing. Additionally, a treatment algorithm for intraoperative bronchospasm is suggested.

Dexmedetomidine Protects against Airway Inflammation and Airway Remodeling in a Murine Model of Chronic Asthma through TLR4/NF-κB Signaling Pathway

Asthma is a common respiratory disease characterized by chronic airway inflammation. Dexmedetomidine (DEX), a highly selective α2 adrenergic receptor agonist, has been shown to participate in regulating inflammatory states and thus exert organ protective actions. However, the potential of DEX in asthma is still unknown. This study is aimed at investigating the role of DEX in a mouse model of house dust mite- (HDM-) induced asthma and exploring its underlying mechanism. Here, we found that DEX treatment significantly ameliorated airway hyperresponsiveness, airway inflammation, and airway remodeling in the asthmatic mice, which were similar to the efficacy of the reference anti-inflammatory drug dexamethasone. In addition, DEX reversed the increased expression of toll-like receptor 4 (TLR4) and its downstream signaling adaptor molecule nuclear factor-κB (NF-κB) in the lung tissue of asthmatic mice. Furthermore, these protective effects of DEX were abolished by yohimbine, an α2 adrenergic receptor antagonist. These results indicate that DEX is capable of ameliorating airway inflammation and remodeling in asthmatic mice, and this protective effect is associated with the inhibition of the TLR4/NF-κB signaling pathway.

Pharmacologic methods to minimise coughing during extubation in the era of COVID-19

BACKGROUND/AIM

Given the current severe acute respiratory syndrome coronavirus 2 pandemic, coughing at the time of extubation is at risk of creating aerosolisation. This may place health care workers at risk of nosocomial infection during the perioperative period. This study aims to summarise the current pharmacologic methods to minimise cough at the time of extubation, and to determine whether some strategies could be more beneficial than others.

METHODS

This is a summary of systematic reviews. A comprehensive search through MEDLINE was performed. Thirty-three publications were screened for eligibility. Only the manuscripts discussing pharmacologic methods to minimise coughing on extubation were included in this review.

FINDINGS

Many pharmacological agents have been proposed to decrease the incidence of cough at the time of extubation. Of these, intravenous administration of dexmedetomidine (relative risk 0.4; 95% CI: 0.4-0.5) or remifentanil (RR 0.4; 95% CI: 0.4-0.5) seems to have the largest effect to reduce cough on extubation.

CONCLUSION

The available data in the current literature is sparse. Yet, dexmedetomidine and remifentanil seem to be the most efficient agents to decrease the incidence of emergence coughing.

Efficacy of Levobupivacaine Versus Levobupivacaine Plus Dexmedetomidine Infiltration for Post-Tonsillectomy Analgesia: A Randomized Controlled Trial

Background. The study evaluated the analgesic effects of levobupivacaine infiltration in the tonsil bed, and a combination of levobupivacaine and dexmedetomidine in patients undergoing tonsillectomy. Methods. Ninety children (ages 3 to 7 years) who were scheduled for a tonsillectomy were allocated randomly into two groups. (L Group): peritonsillar infiltration with 0.25% levobupivacaine (2 ml + 0.5 ml saline 0.9% per tonsil). (LD Group): levobupivacaine 0.25% (2 ml) plus dexmedetomidine 1 μg/kg diluted in 1 ml saline 0.9% (0.5 ml in each tonsil), and administered by peritonsillar infiltration (2.5 ml per tonsil) following intubation 3–5 minutes before operation. To avoid bias, infiltrate a total volume of 2.5 ml in each tonsil. The first analgesic request time was the primary outcome, with postoperative pain score, total analgesic consumption, total oral intake, sedation, and side effects as secondary outcomes. Results. The first rescue analgesia time in the LD group was longer (644.31 ± 112.89 min) than in the L group (551.51 ± 146.16 min, $P$ -value <0.001). The number of patients who required >1 analgesic dose in the L group (n = 13) was higher than in the LD group (n = 5). The LD group consumes a lower total dose of IV paracetamol in the first 24 hours postoperatively (321.89 ± 93.25 mg) than the L group (394.89 ± 183.71 mg, $P<0.00$ -value < 0.050). On the first day postoperatively, patients in the LD group had a higher total oral intake ( $P<0.001$ ). Except for a slight increase in laryngospasm in the L group, there were no side effects. Conclusions. The Children’s peritonsillar infiltration of levobupivacaine and dexmedetomidine improved postoperative pain after adenotonsillectomy. The topically applied levobupivacaine and dexmedetomidine were concomitant with no systemic effects, greater total oral intake on the first day postoperative, and higher family satisfaction.

Effect of Intranasal Dexmedetomidine or Midazolam for Premedication on the Occurrence of Respiratory Adverse Events in Children Undergoing Tonsillectomy and Adenoidectomy: A Randomized Clinical Trial

IMPORTANCE

Perioperative respiratory adverse events (PRAEs) are the most common complication during pediatric anesthesia, and they may be affected by the administration of preoperative sedatives.

OBJECTIVE

To investigate the effect of intranasal dexmedetomidine or midazolam used for premedication on the occurrence of PRAEs.

DESIGN, SETTING, AND PARTICIPANTS

This single-center, double-blind, randomized clinical trial was conducted among children aged 0 to 12 years undergoing elective tonsillectomy and adenoidectomy from October 2020 to June 2021 at Children's Hospital of Xuzhou Medical University, Xuzhou, China. Data analysis was performed from June to October 2021.

INTERVENTIONS

Children were randomly assigned to 3 groups: the midazolam group received intranasal midazolam (0.1 mg/kg), and the dexmedetomidine group received intranasal dexmedetomidine (2.0 μg/kg) for premedication. The normal saline group received intranasal 0.9% saline for control.

MAIN OUTCOMES AND MEASURES

The primary outcome was the difference in the incidence of PRAEs among the 3 groups. The secondary outcomes were the frequency of the individual PRAEs, including the incidence of such events during the induction and recovery periods, postoperative emergence delirium, postoperative pain score, sedation success rate, and heart rate values.

RESULTS

A total of 384 children (median [IQR] age, 7 [5-10] years; 227 boys [59.1%]) were enrolled and randomized; 373 data sets were available for intention-to-treat analysis (124 children in the midazolam group, 124 children in the dexmedetomidine group, and 125 children in the normal saline group). After the data were adjusted for age, sex, American Society of Anesthesiologists physical status, body mass index, obstructive sleep apnea, upper respiratory tract infection, and passive smoking, children in the midazolam group were more likely to experience PRAEs than those in the normal saline group (70 of 124 children [56.5%] vs 51 of 125 children [40.8%]; adjusted odds ratio [aOR], 1.99; 95% CI, 1.18-3.35), whereas the dexmedetomidine group had a significantly lower PRAEs incidence than the normal saline group (30 of 124 children [24.2%] vs 51 of 125 children [40.8%]; aOR, 0.45; 95% CI, 0.26-0.78). Compared with the dexmedetomidine group, the midazolam group had a higher risk of PRAEs (aOR, 4.44; 95% CI, 2.54-7.76), but no other serious clinical adverse events were observed.

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial, intranasal midazolam used for premedication was associated with increased incidence of PRAEs, whereas premedication with intranasal dexmedetomidine was associated with reduced incidence of PRAEs. Where clinically appropriate, anesthesiologists should consider using intranasal dexmedetomidine for sedation in children undergoing tonsillectomy and adenoidectomy.

TRIAL REGISTRATION

Chinese Clinical Trial Register Identifier: ChiCTR2000038359.

Development and Validation of a Risk Nomogram Model for Perioperative Respiratory Adverse Events in Children Undergoing Airway Surgery: An Observational Prospective Cohort Study

Purpose

The aim of this study was to explore the associated risk factors of perioperative respiratory adverse events (PRAEs) in children undergoing airway surgery and establish and validate a nomogram prediction model for PRAEs.

Patients and Methods

This study involved 709 children undergoing airway surgery between November 2020 and July 2021, aged ≤18 years in the affiliated hospital of Xuzhou Medical University. They were divided into training (70%; n = 496) and validation (30%; n = 213) cohorts. The least absolute shrinkage and selection operator (LASSO) was used to develop a risk nomogram model. Concordance index values, calibration plot, decision curve analysis, and the area under the curve (AUC) were examined.

Results

PRAEs were found in 226 of 496 patients (45.6%) and 88 of 213 patients (41.3%) in the training and validation cohorts, respectively. The perioperative risk factors associated with PRAEs were age, obesity, degree of upper respiratory tract infection, premedication, and passive smoking. The risk nomogram model showed good discrimination power, and the AUC generated to predict survival in the training cohort was 0.760 (95% confidence interval, 0.695–0.875). In the validation cohort, the AUC of survival predictions was 0.802 (95% confidence interval, 0.797–0.895). Calibration plots and decision curve analysis showed good model performance in both datasets. The sensitivity and specificity of the risk nomogram model were calculated, and the result showed the sensitivity of 69.5% and 64.8% and specificity of 73.3% and 81.6% for the training and validation cohorts, respectively.

Conclusion

The present study showed the proposed nomogram achieved an optimal prediction of PRAEs in patients undergoing airway surgery, which can provide a certain reference value for predicting the high-risk population of perioperative respiratory adverse events and can lead to reasonable preventive and treatment measures.

Dexmedetomidine attenuates haemorrhage-induced thalamic pain by inhibiting the TLR4/NF-κB/ERK1/2 pathway in mice

BACKGROUND

Thalamic pain, a neuropathic pain syndrome, frequently occurs after stroke. This research aimed to investigate the effect of dexmedetomidine (DEX) on thalamic pain.

METHODS

The cellular localization of the TLR4 protein was determined by immunostaining. The expression of Iba1, GFAP and protein associated with the TLR4/NF-κB/ERK1/2 pathway was measured by Western blotting. Continuous pain hypersensitivity was evaluated by behavioural tests. The results were analysed by one-way ANOVA, two-way ANOVA and Tukey's post hoc test.

RESULTS

The results demonstrated that DEX obviously alleviated thalamic pain induced by haemorrhage on the ipsilateral side and delayed the development of pain hypersensitivity. Furthermore, the expression levels of Iba1, GFAP and proteins associated with the TLR4/NF-κB/ERK1/2 signalling pathway were greatly increased in mice with thalamic pain, but these effects were reversed by DEX.

CONCLUSION

Our findings suggest that DEX alleviates the inflammatory response during thalamic pain through the TLR4/NF-κB/ERK1/2 signalling pathway and might be a potential therapeutic agent for thalamic pain.

Dexmedetomidine as an Analgesic Agent with Neuroprotective Properties: Experimental and Clinical Aspects

Dexmedetomidine (Dexdor or Precedex®) is considered as a sedative agent which is widely used as an adjuvant in general anesthesia and critical care practice. There is extensive evidence indicating its neuroprotective properties especially in various ischemic and hemorrhagic brain injury models of animals. Clinical trials have shown that dexmedetomidine (DEX) can improve the outcome of intensive care unit (ICU) patients. Also, DEX is appropriate as a non-opioid analgesic therapy whenever minimizing opioid-related side effects is necessary. The present article reviews the recent advances in the use of DEX as a neuroprotective agent in both animal and human studies including newest findings about the mechanism of the drug as well as analgesic efficacy of this drug at all perioperative stages. In spite of the beneficial effects of the drug on the nervous system, there are potential adverse effects, such as hypotension and bradycardia, which can be treated pharmacologically and must be taken into consideration by clinicians.

Pulmonary effects of dexmedetomidine infusion in thoracic aortic surgery under hypothermic circulatory arrest: a randomized placebo-controlled trial

Dexmedetomidine has emerged as a promising organ protective agent. We performed prospective randomized placebo-controlled trial investigating effects of perioperative dexmedetomidine infusion on pulmonary function following thoracic aortic surgery with cardiopulmonary bypass and moderate hypothermic circulatory arrest. Fifty-two patients were randomized to two groups: the dexmedetomidine group received 1 µg/kg of dexmedetomidine over 20 min after induction of anesthesia, followed by 0.5 µg/kg/h infusion until 12 h after aortic cross clamp (ACC)-off, while the control group received the same volume of normal saline. The primary endpoints were oxygenation indices including arterial O₂ partial pressure (PaO₂) to alveolar O₂ partial pressure ratio (a/A ratio), (A-a) O₂ gradient, PaO₂/FiO₂ and lung mechanics including peak inspiratory and plateau pressures and compliances, which were assessed after anesthesia induction, 1 h, 6 h, 12 h, and 24 h after ACC-off. The secondary endpoints were serum biomarkers including interleukin-6, tumor necrosis factor-α, superoxide dismutase, and malondialdehyde (MDA). As a result, dexmedetomidine did not confer protective effects on the lungs, but inhibited elevation of serum MDA level, indicative of anti-oxidative stress property, and improved urine output and lower requirements of vasopressors.

Intranasal dexmedetomidine premedication in children with recent upper respiratory tract infection undergoing interventional cardiac catheterisation: A randomised controlled trial

BACKGROUND

Recent upper respiratory tract infection (URI) is a risk factor for the occurrence of peri-operative respiratory adverse events (PRAE). This risk may be higher in children with congenital heart disease (CHD), particularly in those undergoing interventional cardiac catheterisation. It is therefore essential to adapt the anaesthetic strategy in these children to prevent from the occurrence of PRAE.

OBJECTIVE

To determine whether intranasal dexmedetomidine (DEX) premedication can reduce the incidence of PRAE in children with recent URI undergoing interventional cardiac catheterisation.

DESIGN

Randomised controlled trial.

SETTING

Single-centre study based at a tertiary care centre in Shanghai, China.

PATIENTS

A total of 134 children with CHD aged 0 to 16 years with recent URI undergoing interventional cardiac catheterisation.

INTERVENTIONS

Children were randomised to receive either intranasal DEX 1.5 μg kg (DEX group) or intranasal saline (Placebo group) 30 to 45 min before anaesthesia induction.

MAIN OUTCOME MEASURES

The incidence of PRAE.

RESULTS

Intranasal DEX significantly reduced the incidence of PRAE (P = 0.001), particularly oxygen desaturation (P = 0.012). Most PRAE were observed during the emergence phase. The incidence of PRAE was comparable among the three types of left-right shunt CHD children in both groups. In children aged less than 3 years, the incidence of PRAE was significantly lower in the DEX group (P = 0.003). In contrast, the incidence of PRAE was comparable between the two groups in children aged at least 3 years. No differences in the incidence of emergence agitation, fever and vomiting between the two groups were noted.

CONCLUSION

Administration of intranasal DEX 1.5 μg kg 30 to 45 min before induction led to a reduction in the incidence of PRAE in children aged less than 3 years with recent URI undergoing interventional cardiac catheterisation.

TRIAL REGISTRATION

chictr.org.cn identifier: ChiCTR-RRC-17012519.

Dexmedetomidine versus midazolam for sedation during endobronchial ultrasound-guided transbronchial needle aspiration: A randomised controlled trial

BACKGROUND

Desaturation is a common complication of endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). Dexmedetomidine (DEX), a commonly used sedative in intensive care, is associated with less respiratory depression compared with other sedatives.

OBJECTIVE

We compared DEX with midazolam (MDZ) when used as a sedative during EBUS-TBNA.

DESIGN

A randomised, parallel, double-blinded trial.

SETTING

A university-affiliated teaching hospital between June 2014 and July 2015.

PATIENTS

A total of 102 patients who underwent EBUS-TBNA were randomly allocated to two groups (48 DEX group, 54 MDZ group).

INTERVENTIONS

DEX group received 0.25 to 0.75 μg kg-1 h-1 (start with 0.5 μg kg-1 h-1, modulated in three steps from 0.25 to 0.75 μg kg-1 h-1) of DEX after a loading dose of 0.25 μg kg-1 h-1 for 10 min to maintain a Ramsay Sedation Scale (RSS) of 3 to 5. If the patient was agitated, 1 mg of MDZ bolus was used as a rescue drug. Patients in the MDZ group initially received 0.05 mg kg-1 of MDZ as a bolus. For maintenance and rescue, 1 mg of MDZ bolus was used.

MAIN OUTCOME MEASURES

The primary outcome was the presence of oxygen desaturation. Secondary outcomes were level of sedation (Ramsay Sedation Scale score), cough score, sedation and procedure satisfaction score.

RESULTS

The baseline characteristics of the patients, duration of EBUS-TBNA procedures and the use of rescue MDZ were not different between the groups. There was no significant difference in desaturation events between the DEX and MDZ groups (56.3 and 68.5%, respectively; P = 0.20). The level of sedation and the sedation satisfaction scores were similar between the two groups. However, cough score was significantly lower in the DEX group (41.9 vs. 53.4; P = 0.02).

CONCLUSION

The use of DEX during EBUS-TBNA was not superior to MDZ in terms of oxygen desaturation.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT02157818.

Mechanism and Management of Fentanyl-Induced Cough

Fentanyl-induced cough (FIC) often occurs after intravenous bolus administration of fentanyl analogs during induction of general anesthesia and analgesia procedure. The cough is generally benign, but sometimes it causes undesirable side effects, including elevated intra-abdominal, intracranial or intraocular pressure. Therefore, understanding the related mechanisms and influencing factors are of great significance to prevent and treat the cough. This paper reviews the molecular mechanism, influencing factors and preventive administration of FIC, focusing on the efficacy and side effects of various drugs in inhibiting FIC to provide some medical reference for anesthesiologists.

Delayed Adjunctive Treatment of Organophosphate-Induced Status Epilepticus in Rats with Phenobarbital, Memantine, or Dexmedetomidine

Organophosphate (OP) exposure induces status epilepticus (SE), a medical emergency with high morbidity and mortality. Current standard medical countermeasures lose efficacy with time so that treatment delays, in the range of tens of minutes, result in increasingly poor outcomes. As part of the Countermeasures Against Chemical Threats Neurotherapeutics Screening Program, we previously developed a realistic model of delayed treatment of OP-induced SE using the OP diisopropyl fluorophosphate (DFP) to screen compounds for efficacy in the termination of SE and elimination of neuronal death. Male rats were implanted for electroencephalogram (EEG) recordings 7 days prior to experimentation. Rats were then exposed to DFP, and SE was induced for 60 minutes and then treated with midazolam (MDZ) plus one of three antiseizure drugs (ASDs)-phenobarbital (PHB), memantine (MEM), or dexmedetomidine (DMT)-in conjunction with antidotes. EEG was recorded for 24 hours, and brains were stained with Fluoro-Jade B for quantification of degenerating neurons. We found that PHB + MDZ induced a prolonged suppression of SE and reduced neuronal death. MEM + MDZ treatment exacerbated SE and increased mortality; however, surviving rats had fewer degenerating neurons. DMT + MDZ significantly suppressed SE with only a minimal reduction in neuronal death. These data demonstrate that delayed treatment of OP-induced SE with other ASDs, when added to MDZ, can achieve greater seizure suppression with additional reduction in degenerating neurons throughout the brain compared with MDZ alone. The effect of a drug on the severity of seizure activity did not necessarily determine the drug's effect on neuronal death under these conditions. SIGNIFICANCE STATEMENT: This study assesses the relative effectiveness of three different delayed-treatment regimens for the control of organophosphate-induced status epilepticus and reduction of subsequent neuronal death. The data demonstrate the potential for highly effective therapies despite significant treatment delay and a potential disconnect between seizure severity and neuronal death.

Dexmedetomidine for prevention of postoperative pulmonary complications in patients after oral and maxillofacial surgery with fibular free flap reconstruction:a prospective, double-blind, randomized, placebo-controlled trial

BACKGROUND

Postoperative pulmonary complications (PPCs) are common and significant problems for oral and maxillofacial surgery patients. Dexmedetomidine (DEX), an α₂-adrenoreceptor agonist, has been proven having lung protection effects. However, since now, there has not been final conclusion about whether DEX can reduce the incidence of PPCs. We hypothesize that, in oral and maxillofacial surgery with fibular free flap reconstruction patients, DEX may decrease the incidence of PPCs.

METHODS

This was a prospective, double-blind, randomized, placebo-controlled, single-centered trial with two parallel arms. A total of 160 patients at intermediate-to-high risk of PPCs undergoing oral and maxillofacial surgery with fibular free flap reconstruction and tracheotomy were enrolled and randomized to receive continuous infusion of either DEX or placebo (normal saline). 0.4 μg/kg of DEX was given over 10mins as an initial dose followed by a maintaining dose of 0.4 μg/kg/h till the second day morning after surgery. At the same time, the normal saline was administered a similar quantity. The primary outcome was the incidence of PPCs according to Clavien-Dindo score within 7 days after surgery.

RESULTS

The two groups had similar characteristics at baseline. 18(22.5%) of 80 patients administered DEX, and 32(40.0%) of 80 patient administered placebo experienced PPCs within the first 7 days after surgery (relative risk [RR] 0.563,95% confidence interval [CI] 0.346-0.916; P = 0.017). In the first 7 days after surgery, the DEX group had a lower incidence of PPCs and a better postoperative survival probability (Log-rank test, P = 0.019), and was less prone to occur PPCs (Cox regression, P = 0.025, HR = 0.516). When the total dose of DEX was more than 328 μg, the patients were unlikely to have PPCs (ROC curve, AUC = 0.614, P = 0.009).

CONCLUSIONS

For patients undergoing oral and maxillofacial surgery with fibular free flap reconstruction and tracheotomy who were at intermediate or high risk of developing PPCs, continuous infusion of DEX could decrease the occurrence of PPCs during the first 7 days after surgery and shorten the length of hospital stay after surgery, but did not increase the prevalence of bradycardia or hypotension.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, www.chictr.org.cn, number: ChiCTR1800016153; Registered on May 15, 2018.

Nebulized dexmedetomidine-lidocaine inhalation as a premedication for flexible bronchoscopy: a randomized trial

Background

Dexmedetomidine plus opioid infusion after topical anaesthesia with nebulized lidocaine for cough suppression is a commonly used method for flexible bronchoscopy. Recently, the use of dexmedetomidine as an additive to local anaesthetics has been reported to have several advantages over conventional intravenous administration. However, there are no data regarding the use of nebulized dexmedetomidine-lidocaine for topical anaesthesia as a premedication for flexible bronchoscopy. Therefore, this study compared the tolerability and safety of nebulized dexmedetomidine with that of conventional intravenous administration in patients undergoing bronchoscopy with moderate sedation.

Methods

Sixty patients requiring flexible bronchoscopy were randomly assigned to three groups: (I) nebulized dexmedetomidine + lidocaine, n=20; (II) intravenous dexmedetomidine + nebulized lidocaine, n=20; and (III) nebulized lidocaine alone (no dexmedetomidine), n=20. The patients' coughing scores were assessed and graded. Our primary hypothesis was that nebulized dexmedetomidine-lidocaine could reduce the incidence of moderate to severe coughing. The secondary endpoints were the rates of glottis closure, complete jaw relaxation and limb movement during the procedure; the elapsed time until recovery; and the dosages of vasoconstrictors and atropine.

Results

The incidence of moderate to severe coughing was 15% in the nebulized dexmedetomidine group, 50% in the intravenous dexmedetomidine group and 55% in the no dexmedetomidine group. The nebulized dexmedetomidine group had the lowest incidence of moderate to severe coughing (P=0.019). Nebulized dexmedetomidine showed a protective effect for reducing coughing compared with intravenous dexmedetomidine [P=0.008, odds ratio (OR): 0.273, 95% confidence interval (CI): 0.089-0.833]. No differences in the rates of complete jaw relaxation and limb movement during the procedure were observed among the three groups (all P>0.05). The rates of glottis closure were similar (20%, 25%, and 35%; P>0.05). The elapsed time until recovery in the nebulized dexmedetomidine group was significantly shorter than that in the intravenous dexmedetomidine group (10.60±1.39 vs. 15.10±1.45, P<0.001). The vasoconstrictor dosages were significantly lower in the nebulized dexmedetomidine group than in the intravenous dexmedetomidine group (P<0.001).

Conclusions

Nebulized dexmedetomidine-lidocaine inhalation as a premedication for flexible bronchoscopy was well tolerated during bronchoscopies performed under moderate sedation and was associated with a reduced incidence of moderate to severe coughing, a shorter recovery time and reduced vasoconstrictor consumption.

Effect of dexmedetomidine anesthesia on respiratory function in pediatric patients undergoing retinoblastoma resection

The aim of this study was to investigate the effect of dexmedetomidine (Dex) on the respiratory function during anesthesia induction in pediatric patients undergoing retinoblastoma (RB) resection. A total of 87 pediatric patients who underwent RB resection in Yidu Central Hospital of Weifang were recruited into this study. General anesthesia was first induced for all patients, of which 45 were randomly assigned to the experimental group and received Dex through an intravenous infusion pump to maintain general anesthesia. The remaining 42 patients were assigned to the control group and received saline through an intravenous infusion pump. Respiratory function and hemodynamic indexes at five time-points, i.e., before anesthesia induction (T0), 5 min after injection of anesthetic agents (T1), before intubation (T2), 15 min after intubation (T3), and 30 min after extubation (T4), were recorded and compared. Incidence of perioperative cardiac and respiratory adverse events was counted in both groups, and post-anesthesia resuscitation was evaluated and compared. Compared with T0, the respiratory rate (R) of the experimental group was lower at T1-T4, but there was no statistical difference (P<0.05). Compared with T0, the control group had a higher R at T2, lower R at T3 and T4 (P<0.05), and there was no significant difference in R between T0 and T1 (P>0.05). At the same time-point, compared with the experimental group, the R was higher at T2, and lower at T3 and T4 in the control group (P<0.05), and no significant difference was found at T1. Blood oxygen saturation (SpO₂) of the experimental group was slightly lower than that of T0 at T1-T4 (P>0.05). In the control group, the levels of SpO₂ were significantly lower at T1-T4 than those at T0 (P<0.05). Compared with the experimental group at the same time-point, SpO₂ of the control group at T1-T4 decreased significantly (P<0.05). The heart rate (HR) of the experimental and control groups was lower at T1-T4 than that at T0 (P<0.05). The HR of the experimental group was higher than that of the control group at T1-T4 (P<0.05). Mean arterial pressure (MAP) of the experimental and control groups was lower at T1-T4 than that at T0 (P<0.05). MAP of the control group was higher than that of the experimental group at T2 but lower than that at T0 of the control group. MAP of the control group was lower than that of the experimental group at T1-T4. There was no significant difference in incidence of tachycardia, bradycardia, vomiting, hypoxia and laryngism between the two groups (P>0.05). There was no difference in resuscitation and extubation time between the two groups (P>0.05). Finally, agitation of the control group was more severe than that of the experimental group (P<0.05). Therefore, Dex can improve the respiratory function and hemodynamic stability during anesthesia induction in children with RB resection.

Dexmedetomidine stops benzodiazepine-refractory nerve agent-induced status epilepticus

Nerve agents are highly toxic chemicals that pose an imminent threat to soldiers and civilians alike. Nerve agent exposure leads to an increase in acetylcholine within the central nervous system, resulting in development of protracted seizures known as status epilepticus (SE). Currently, benzodiazepines are the standard of care for nerve agent-induced SE, but their efficacy quickly wanes as the time to treatment increases. Here, we examine the role of the α2-adrenoceptor in termination of nerve agent-induced SE using the highly specific agonist dexmedetomidine (DEX). Adult male rats were exposed to soman and entered SE as confirmed by electroencephalograph (EEG). We observed that administration of DEX in combination with the benzodiazepine midazolam (MDZ) 20 or 40 min after the onset of SE stopped seizures and returned processed EEG measurements to baseline levels. The protective effect of DEX was blocked by the α2-adrenoceptor antagonist atipamezole (ATI), but ATI failed to restore seizure activity after it was already halted by DEX in most cases, suggesting that α2-adrenoceptors may be involved in initiating SE cessation rather than merely suppressing seizure activity. Histologically, treatment with DEX + MDZ significantly reduced the number of dying neurons as measured by FluoroJade B in the amygdala, thalamus, and piriform cortex, but did not protect the hippocampus or parietal cortex even when SE was successfully halted. We conclude that DEX serves not just as a valuable potential addition to the anticonvulsant regimen for nerve agent exposure, but also as a tool for dissecting the neural circuitry that drives SE.

Effects of selective α2 -adrenergic receptor agonists on electrical field-stimulated contractions of isolated bronchi in horses

We investigated the effects of different selective α₂ -adrenergic receptor (AR) agonists (detomidine, medetomidine, xylazine, and brimonidine) on the contractions of horse-isolated bronchi induced by electrical field stimulation (EFS) and by carbachol. No effects were observed on the contraction induced by carbachol, while α₂ -AR agonists reduced EFS-evoked contractions in a concentration-related fashion. The rank order of potency (pD₂ ) was brimonidine (7.40 ± 0.20) >medetomidine (7.09 ± 0.24) >detomidine (6.13 ± 0.55) >xylazine (4.59 ± 0.16). The maximal effects (E_max ) were -56.3% ± 6.3%, -40.4% ± 6.9%, -48.6% ± 9.9%, and -72.7% ± 12.7% for brimonidine, medetomidine, detomidine, and xylazine, respectively. Adrenergic block by guanethidine enhanced the potency (8.10 ± 0.05, 7.30 ± 0.15, 6.83 ± 0.41, and 5.40 ± 0.22) and the efficacy (-95.2% ± 0.7%, -45.2% ± 11.7%, -58.5% ± 9.8%, and -97.9% ± 0.6%) of brimonidine, medetomidine, detomidine, and xylazine, respectively. Selective α₂ -AR antagonist, atipamezole, competitively antagonized the inhibition of EFS-evoked contractions induced by all agonists except xylazine. These results suggest the existence of presynaptic α₂ -ARs on cholinergic neurons, negatively regulating the release of acetylcholine in horse bronchial muscle, and that α₂ -AR agonists may be beneficial against vagally mediated bronchoconstriction.