Effects of low and high plasma concentrations of dexmedetomidine on myocardial perfusion and cardiac function in healthy male subjects

A comprehensive overview of clinical research on dexmedetomidine in the past 2 decades: A bibliometric analysis

Introduction: Dexmedetomidine is a potent, highly selective α-2 adrenoceptor agonist with sedative, analgesic, anxiolytic, and opioid-sparing properties. A large number of dexmedetomidine-related publications have sprung out in the last 2 decades. However, no bibliometric analysis for clinical research on dexmedetomidine has been published to analyze hot spots, trends, and frontiers in this field. Methods: The clinical articles and reviews related to dexmedetomidine, published from 2002 to 2021 in the Web of Science Core Collection, were retrieved on 19 May 2022, using relevant search terms. VOSviewer and CiteSpace were used to conduct this bibliometric study. Results: The results showed that a total of 2,299 publications were retrieved from 656 academic journals with 48,549 co-cited references by 2,335 institutions from 65 countries/regions. The United States had the most publications among all the countries (n = 870, 37.8%) and the Harvard University contributed the most among all institutions (n = 57, 2.48%). The most productive academic journal on dexmedetomidine was Pediatric Anesthesia and the first co-cited journal was Anesthesiology. Mika Scheinin is the most productive author and Pratik P Pandharipande is the most co-cited author. Co-cited reference analysis and keyword analysis illustrated hot spots in the dexmedetomidine field including pharmacokinetics and pharmacodynamics, intensive care unit sedation and outcome, pain management and nerve block, and premedication and use in children. The effect of dexmedetomidine sedation on the outcomes of critically ill patients, the analgesic effect of dexmedetomidine, and its organ protective property are the frontiers in future research. Conclusion: This bibliometric analysis provided us with concise information about the development trend and provided an important reference for researchers to guide future research.

Changes in gap junction proteins Connexin30.2 and Connexin40 expression in the sinoatrial node of rats with dexmedetomidine-induced sinus bradycardia

BACKGROUND

Dexmedetomidine (Dex) is widely used, and its most common side effect is bradycardia. The complete mechanism through which Dex induces bradycardia has not been elucidated. This research investigates the expression of gap junction proteins Connexin30.2 (Cx30.2) and Connexin40 (Cx40) within the sinoatrial node of rats with Dex-induced sinus bradycardia.

METHODS

Eighty rats were randomly assigned to five groups. Saline was administered to rats in Group C. In the other four groups, the rats were administered Dex to induce bradycardia. In groups D₁ and D₂, the rats were administered Dex at a loading dose of 30 μg.kg^-1 and 100 μg.kg^-1 for 10 min, then at 15 μg.kg^-1.h^-1 and 50 μg.kg^-1.h^-1 for 120 min separately. The rats in group D₁A and D₂A were administered Dex in the same way as in group D₁ and D₂; however, immediately after the administration of the loading dose, 0.5 mg atropine was administered intravenously, and then at 0.5 mg.kg^-1.h^-1 for 120 min. The sinoatrial node was acquired after intravenous infusion was completed. Quantitative real-time polymerase chain reaction and western blot analyses were performed to measure mRNA and protein expression of Cx30.2 and Cx40, respectively.

RESULTS

The expression of Cx30.2 increased, whereas the expression of Cx40 decreased within the sinoatrial node of rats with Dex-induced sinus bradycardia. Atropine reversed the effects of Dex on the expression of gap junction proteins.

CONCLUSION

Dex possibly altered the expression of gap junction proteins to slow down cardiac conduction velocity in the sinoatrial node.

Dexmedetomidine Reduces Incidences of Ventricular Arrhythmias in Adult Patients: A Meta-Analysis

Purpose

To assess the antiarrhythmic properties of dexmedetomidine in patients in the intensive care unit.

Methods

A literature review was conducted with Ovid MEDLINE (R), Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Embase, and Scopus. Study Selection. Randomized controlled trials were included, examining the incidence of ventricular arrhythmias, ventricular tachycardia, or ventricular fibrillation with dexmedetomidine compared to placebo or an alternative sedative agent. For each publication that met the selection criteria, the patient demographics, incidence of arrhythmias, mortality, and adverse events were collected. Data extraction was carried out by two authors independently.

Results

We identified 6 out of 126 studies that met the selection criteria for our meta-analysis, all of which focused on the perioperative cardiac surgery period. Patients receiving dexmedetomidine demonstrated a significant reduction of the overall incidence of ventricular arrhythmias (RR 0.35, 95% CI 0.16, 0.76). In particular, dexmedetomidine significantly decreased the risk of ventricular tachycardia compared with control (RR 0.25, 95% CI 0.08, 0.80, I² 0%). Regarding adverse events, dexmedetomidine significantly increased the frequency of bradycardia (RR 2.78 95% CI 2.00, 3.87). However, there was no significant difference in mortality (RR 0.59 95% CI 0.12, 3.02).

Conclusion

From this meta-analysis, we report a decreased incidence of ventricular tachycardia with dexmedetomidine in critically ill patients. This result favors the use of dexmedetomidine for its antiarrhythmic properties.

Effect of Dexmedetomidine on Cardiac Output among Parturient with Severe Preeclampsia after Cesarean Section

This study was to investigate the hemodynamic effect of dexmedetomidine among parturient with severe preeclampsia after cesarean section. Parturient with severe preeclampsia were randomly allocated to receive dexmedetomidine (0.2-0.7 μg/kg/h) or equivalent volumes of 0.9% saline as control after cesarean section, respectively. A total of 36 parturient with severe preeclampsia were enrolled, including 18 in the dexmedetomidine (DEX) group and 18 in the saline group. Compared with the saline group, among those in the DEX group, CO was reduced by 1.30 L/min (95% CI: -2.36 to 0.25; $P=0.019$ ). Additionally, HR (-13.79 bpm, 95% CI: -22.02 to -5.58; $P=0.002$ ), SBP (-16.11 mmHg, 95% CI: -30.56 to -1.66; $P=0.030$ ), DBP (-10.48 mmHg, 95% CI: -18.27 to -2.69; $P=0.002$ ), and MAP (-12.36 mmHg, 95% CI: -22.05 to -2.66; $P=0.014$ ) were reduced in the DEX group compared with the saline group. In contrast, there were no changes observed in SV and ICON between groups. In conclusion, dexmedetomidine reduces cardiac output by inhibiting the acceleration of heart rate without sacrificing myocardial contractility and stroke volume.

Intranasal Dexmedetomidine for the Treatment of Pre-operative Anxiety and Insomnia: A Prospective, Randomized, Controlled, and Clinical Trial

BACKGROUND AND OBJECTIVE

Several patients with pre-operative anxiety and insomnia refuse to take sleeping pills because of the side effects of sleeping pills. This study aimed to evaluate the applicability of intranasal dexmedetomidine (DEX) in the treatment of pre-operative anxiety and insomnia.

METHODS

A total of 72 patients with insomnia and anxiety were randomly divided into two groups of intranasal DEX (n = 36) and intranasal normal saline (NS, n = 36). The primary outcomes included patients' time to fall asleep, total sleep time, insomnia severity index (ISI) after treatment, and satisfaction with the treatment effect. The secondary outcomes were mean arterial pressure (MAP), oxygen saturation (SPO₂), heart rate (HR), Narcotrend index (NI) in the first 2 h of treatment, and the incidence of adverse events within 12 h after treatment.

RESULTS

The time to fall asleep (22.08 ± 3.95 min) and total sleep time (400.06 ± 28.84 min) in the DEX group were significantly different from those in the NS group [time to fall asleep, 89.31 ± 54.56 min; total sleep time (295.19 ± 73.51 min; P < 0.001)]. ISI after treatment in the DEX group was lower than that in the NS group (P < 0.001). Satisfaction with the treatment effect was better in the DEX group than that in the NS group (P < 0.001). The general vital signs in the two groups were stable during the treatment. The drowsiness rate in the NS group was higher than that in the DEX group (P < 0.001).

CONCLUSION

Intranasal DEX can significantly improve pre-operative anxiety and insomnia.

CLINICAL TRIAL REGISTRATION

This study was registered on Chinese Clinical Trial Registry (http://www.chictr.org.cn/searchproj.aspx, ChiCTR2100044747).

Dexmedetomidine Clearance Decreases with Increasing Drug Exposure: Implications for Current Dosing Regimens and Target-controlled Infusion Models Assuming Linear Pharmacokinetics

BACKGROUND

Numerous pharmacokinetic models have been published aiming at more accurate and safer dosing of dexmedetomidine. The vast majority of the developed models underpredict the measured plasma concentrations with respect to the target concentration, especially at plasma concentrations higher than those used in the original studies. The aim of this article was to develop a dexmedetomidine pharmacokinetic model in healthy adults emphasizing linear versus nonlinear kinetics.

METHODS

The data of two previously published clinical trials with stepwise increasing dexmedetomidine target-controlled infusion were pooled to build a pharmacokinetic model using the NONMEM software package (ICON Development Solutions, USA). Data from 48 healthy subjects, included in a stratified manner, were utilized to build the model.

RESULTS

A three-compartment mamillary model with nonlinear elimination from the central compartment was superior to a model assuming linear pharmacokinetics. Covariates included in the final model were age, sex, and total body weight. Cardiac output did not explain between-subject or within-subject variability in dexmedetomidine clearance. The results of a simulation study based on the final model showed that at concentrations up to 2 ng · ml-1, the predicted dexmedetomidine plasma concentrations were similar between the currently available Hannivoort model assuming linear pharmacokinetics and the nonlinear model developed in this study. At higher simulated plasma concentrations, exposure increased nonlinearly with target concentration due to the decreasing dexmedetomidine clearance with increasing plasma concentrations. Simulations also show that currently approved dosing regimens in the intensive care unit may potentially lead to higher-than-expected dexmedetomidine plasma concentrations.

CONCLUSIONS

This study developed a nonlinear three-compartment pharmacokinetic model that accurately described dexmedetomidine plasma concentrations. Dexmedetomidine may be safely administered up to target-controlled infusion targets under 2 ng · ml-1 using the Hannivoort model, which assumed linear pharmacokinetics. Consideration should be taken during long-term administration and during an initial loading dose when following the dosing strategies of the current guidelines.

EDITOR’S PERSPECTIVE

Combined effects of dexmedetomidine and vatinoxan infusions on minimum alveolar concentration and cardiopulmonary function in sevoflurane-anesthetized dogs

OBJECTIVE

To evaluate the effects of combined infusions of vatinoxan and dexmedetomidine on inhalant anesthetic requirement and cardiopulmonary function in dogs.

STUDY DESIGN

Prospective experimental study.

METHODS

A total of six Beagle dogs were anesthetized to determine sevoflurane minimum alveolar concentration (MAC) prior to and after an intravenous (IV) dose (loading, then continuous infusion) of dexmedetomidine (4.5 μg kg^-1 hour^-1) and after two IV doses of vatinoxan in sequence (90 and 180 μg kg^-1 hour^-1). Blood was collected for plasma dexmedetomidine and vatinoxan concentrations. During a separate anesthesia, cardiac output (CO) was measured under equivalent MAC conditions of sevoflurane and dexmedetomidine, and then with each added dose of vatinoxan. For each treatment, cardiovascular variables were measured with spontaneous and controlled ventilation. Repeated measures analyses were performed for each response variable; for all analyses, p < 0.05 was considered significant.

RESULTS

Dexmedetomidine reduced sevoflurane MAC by 67% (0.64 ± 0.1%), mean ± standard deviation in dogs. The addition of vatinoxan attenuated this to 57% (0.81 ± 0.1%) and 43% (1.1 ± 0.1%) with low and high doses, respectively, and caused a reduction in plasma dexmedetomidine concentrations. Heart rate and CO decreased while systemic vascular resistance increased with dexmedetomidine regardless of ventilation mode. The co-administration of vatinoxan dose-dependently modified these effects such that cardiovascular variables approached baseline.

CONCLUSIONS AND CLINICAL RELEVANCE

IV infusions of 90 and 180 μg kg^-1 hour^-1 of vatinoxan combined with 4.5 μg kg^-1 hour^-1 dexmedetomidine provide a meaningful reduction in sevoflurane requirement in dogs. Although sevoflurane MAC-sparing properties of dexmedetomidine in dogs are attenuated by vatinoxan, the cardiovascular function is improved. Doses of vatinoxan >180 μg kg^-1 hour^-1 might improve cardiovascular function further in combination with this dose of dexmedetomidine, but beneficial effects on anesthesia plane and recovery quality may be lost.

Clinical Practice: Should we Radically Alter our Sedation of Critical Care Patients, Especially Given the COVID-19 Pandemics?

The high number of patients infected with the SARS-CoV-2 virus requiring care for ARDS puts sedation in the critical care unit (CCU) to the edge. Depth of sedation has evolved over the last 40 years (no-sedation, deep sedation, daily emergence, minimal sedation, etc.). Most guidelines now recommend determining the depth of sedation and minimizing the use of benzodiazepines and opioids. The broader use of alpha-2 adrenergic agonists ('alpha-2 agonists') led to sedation regimens beginning at admission to the CCU that contrast with hypnotics+opioids ("conventional" sedation), with major consequences for cognition, ventilation and circulatory performance. The same doses of alpha-2 agonists used for 'cooperative' sedation (ataraxia, analgognosia) elicit no respiratory depression but modify the autonomic nervous system (cardiac parasympathetic activation, attenuation of excessive cardiac and vasomotor sympathetic activity). Alpha-2 agonists should be selected only in patients who benefit from their effects ('personalized' indications, as opposed to a 'one size fits all' approach). Then, titration to effect is required, especially in the setting of systemic hypotension and/or hypovolemia. Since no general guidelines exist for the use of alpha-2 agonists for CCU sedation, our clinical experience is summarized for the benefit of physicians in clinical situations in which a recommendation might never exist (refractory delirium tremens; unstable, hypovolemic, hypotensive patients, etc.). Because the physiology of alpha-2 receptors and the pharmacology of alpha-2 agonists lead to personalized indications, some details are offered. Since interactions between conventional sedatives and alpha-2 agonists have received little attention, these interactions are addressed. Within the existing guidelines for CCU sedation, this article could facilitate the use of alpha-2 agonists as effective and safe sedation while awaiting large, multicentre trials and more evidence-based medicine.

Effects of Propofol, Dexmedetomidine, or Ketofol on Respiratory and Hemodynamic Profiles in Cardiac Patients Undergoing Transesophageal Echocardiography: A Prospective Randomized Study

OBJECTIVES

The authors aimed to evaluate sedation characteristics, as well as cardiorespiratory effects, of propofol, dexmedetomidine, and ketofol used for conscious sedation during transesophageal echocardiography (TEE).

DESIGN

Prospective double-blind randomized study.

SETTINGS

Tanta University hospitals.

PARTICIPANTS

Seventy-five participants with left-to-right shunt requiring diagnostic TEE interventions. Patients were randomized into three groups-P, Dex, and K-to receive propofol, dexmedetomidine, or ketofol, respectively.

MEASUREMENTS AND MAIN RESULTS

Time to reach targeted sedation level, duration of the procedure, recovery time, hemodynamic parameters, incidence of oxygen desaturation <90%, as well as the cardiologist's satisfaction were recorded. The time onset and offset of sedation, duration of TEE procedure, and the need for rescue propofol were significantly less in the P and K groups compared with group Dex (p value 0.000*, 0.003*, 0.000*, and 0.000* and effect size 0.39, 0.15, 0.21, and 0.34, respectively). Mean arterial pressure, heart rate, and cardiac output significantly decreased in groups P and Dex compared with either baseline or group K. Hypoxic events were more manifest in group P; whereas group K had better cardiologist's satisfaction than the other two groups.

CONCLUSIONS

In the TEE settings, the three agents were capable of attaining the targeted sedation levels , with propofol and ketofol having a faster onset and recovery times compared with dexmedetomidine. Even though dexmedetomidine and ketofol provided a more stable respiratory profile than propofol, ketofol was favorable in providing fewer hemodynamic alterations with better satisfaction scores than both propofol and dexmedetomidine.

Safety of dexmedetomidine in the cardiac intensive care unit

AIMS

Dexmedetomidine is one of the sedative agents recommended by the Society of Critical Care Medicine as a preferred option over benzodiazepines in critically ill, mechanically ventilated patients. Little data exists describing sedation in the cardiac intensive care unit (CICU). The purpose of this study was to determine the prevalence of adverse events in CICU patients treated with dexmedetomidine.

METHODS AND RESULTS

This was a retrospective cohort analysis of patients >18 years old admitted to the University of Michigan CICU from June 2014 to October 2019 who received dexmedetomidine therapy. The primary outcome was the composite of adverse events including bradycardia, hypotension, increasing vasopressor/inotrope requirements, and asystole. Secondary outcomes included individual components of the primary outcome. Patients that experienced adverse events were compared to those that did not experience adverse events to identify risk factors for adverse events. A total of 197 patients were included. There were 116 adverse events in 106 patients. Hypotension was the most common adverse event, making up 60.3% of adverse events reported. Increased vasopressor requirement and bradycardia both occurred in 22 patients (18.9%). Asystole occurred in two patients. B-type natriuretic peptide (BNP) levels were significantly higher in those experiencing an adverse event (848 pg/mL vs. 431 pg/mL; P = 0.03).

CONCLUSIONS

Patients admitted to the CICU experienced a high rate of adverse events with dexmedetomidine use. Those experiencing adverse events were more likely to have a higher BNP. Future studies should explore the safety of alternative sedative agents to ascertain safe pharmacological options for patients admitted to the CICU.

Dexmedetomidine Improves Cardiovascular and Ventilatory Outcomes in Critically Ill Patients: Basic and Clinical Approaches

Dexmedetomidine (DEX) is a highly selective α2-adrenergic agonist with sedative and analgesic properties, with minimal respiratory effects. It is used as a sedative in the intensive care unit and the operating room. The opioid-sparing effect and the absence of respiratory effects make dexmedetomidine an attractive adjuvant drug for anesthesia in obese patients who are at an increased risk for postoperative respiratory complications. The pharmacodynamic effects on the cardiovascular system are known; however the mechanisms that induce cardioprotection are still under study. Regarding the pharmacokinetics properties, this drug is extensively metabolized in the liver by the uridine diphosphate glucuronosyltransferases. It has a relatively high hepatic extraction ratio, and therefore, its metabolism is dependent on liver blood flow. This review shows, from a basic clinical approach, the evidence supporting the use of dexmedetomidine in different settings, from its use in animal models of ischemia-reperfusion, and cardioprotective signaling pathways. In addition, pharmacokinetics and pharmacodynamics studies in obese subjects and the management of patients subjected to mechanical ventilation are described. Moreover, the clinical efficacy of delirium incidence in patients with indication of non-invasive ventilation is shown. Finally, the available evidence from DEX is described by a group of Chilean pharmacologists and clinicians who have worked for more than 10 years on DEX.

Use of dexmedetomidine in pediatric cardiac anesthesia

PURPOSE OF REVIEW

In recent years, ultrafast-track anesthesia with on-table extubation and concepts of accelerated postoperative care have gained increasing support in pediatric congenital cardiac surgery. It is believed that such approaches might ideally combine economic benefits with a striving for continuous improvement of patient outcomes. The present review summarizes the role of dexmedetomidine (DEX) in this setting.

RECENT FINDINGS

DEX is a clinical multipurpose drug that mediates its diverse responses through the activation of α2-adrenoreceptors. In pediatric cardiac surgery it has various applications. Used as a premedication, DEX provides arousable sedation and anxiolysis. As an intraoperative adjunctive agent of balanced general anesthesia the primary objectives for its administration are attenuation of the neuro-humoral stress response and facilitation of early extubation. During ICU treatment DEX spares opioids, prevents the risk of postoperative delirium or emergence agitation and impacts on important patient-centered outcomes, such as duration of mechanical ventilation, restart of enteral nutrition or length of ICU stay.

SUMMARY

Due to a favorable mix of beneficial physiologic actions and a limited adverse effect profile, DEX is established in the perioperative pediatric cardiac surgery setting. However, evidence from high-quality randomized controlled trials on the effects of supplemental DEX on meaningful patient outcomes is scarce, and research on the role of DEX in providing cardioprotection, neuroprotection, or renoprotection is still at its beginning. DEX has developed to one of the main agents in the armamentarium of cardiac anesthesiologists and pediatric intensivists, but it should not be regarded as the new 'magic bullet'.

The pearls of pediatric sedation: polish the old and embrace the new

Over the past decade, as the complexity and breadth of pediatric procedures increases, the actual choices of approved sedatives have remained relatively stagnant. Since the introduction of midazolam, there has not been a sedative approved for pediatric labelling until December 2018. This December, the European approval of ADV6209 (Ozalin) for pediatric usage marked the newest addition to the pediatric sedative armamentarium in over a decade. This review is timely and significant because it will provide a balanced evaluation of the most common sedatives in use today, the most recent sedative to be approved and, most importantly, a critical look at the literature supporting the latest approaches to the most commonly performed procedures.

Dexmedetomidine enhances glymphatic brain delivery of intrathecally administered drugs

Drug delivery to the central nervous system remains a major problem due to biological barriers. The blood-brain-barrier can be bypassed by administering drugs intrathecally directly to the cerebrospinal fluid (CSF). The glymphatic system, a network of perivascular spaces promoting fluid exchange between CSF and interstitial space, could be utilized to enhance convective drug delivery from the CSF to the parenchyma. Glymphatic flow is highest during sleep and anesthesia regimens that induce a slow-wave sleep-like state. Here, using mass spectrometry and fluorescent imaging techniques, we show that the clinically used α₂-adrenergic agonist dexmedetomidine that enhances EEG slow-wave activity, increases brain and spinal cord drug exposure of intrathecally administered drugs in mice and rats. Using oxycodone, naloxone, and an IgG-sized antibody as relevant model drugs we demonstrate that modulation of glymphatic flow has a distinct impact on the distribution of intrathecally administered therapeutics. These findings can be exploited in the clinic to improve the efficacy and safety of intrathecally administered therapeutics.

Dexmedetomidine pharmacodynamics in healthy volunteers: 2. Haemodynamic profile

Background

Dexmedetomidine, a selective α 2 -adrenoreceptor agonist, has unique characteristics, with little respiratory depression and rousability during sedations. We characterized the haemodynamic properties of dexmedetomidine by developing a pharmacokinetic-pharmacodynamic (PKPD) model with a focus on changes in mean arterial blood pressure (MAP) and heart rate.

Methods

Dexmedetomidine was delivered i.v. to 18 healthy volunteers in a step-up fashion by target-controlled infusion using the Dyck model. Exploratory PKPD modelling and covariate analysis were conducted in NONMEM.

Results

Our model adequately describes dexmedetomidine-induced hypotension, hypertension, and bradycardia, with a greater effective concentration for the hypertensive effect. Changes in MAP were best described by a double-sigmoidal E max model with hysteresis. Covariate analysis revealed no significant covariates apart from age on the baseline MAP in the population pharmacokinetic model used to develop this PKPD model. Simulations revealed good general agreement with published descriptive studies of haemodynamics after dexmedetomedine infusion.

Conclusions

The present integrated PKPD model should allow tighter control over the desired level of sedation, while limiting potential haemodynamic side-effects.

Clinical trial registration

NCT01879865.

Impact of dexmedetomidine on hemodynamics in rabbits

PURPOSE

To evaluate the effects of single intravenous administration of Dexmedetomidine (DEX) on hemodynamics in rabbits.

METHODS

A total of 32 New Zealand white rabbits were randomly divided into the control group (Group C), Group D1 (2.75 μg/kg), Group D2 (5.5 μg/kg), and Group D3 (8.25 μg/kg) to compare systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), central venous pressure (CVP), left ventricular systolic pressure (LVSP), left ventricular end-stage diastolic pressure (LVEDP), left ventricular developmental pressure (LVDP), +dp/dtmax, -dp/dtmax, and t-dp/dtmax at different time points.

RESULTS

The levels of SBP, DBP, HR, LVSP, and LVEDP in Group D1, D2, and D3 were lower than that of Group C from T1 to T5 (P<0.05), but there was no significant difference at T6 and T7 (P>0.05). Compared with T0, the levels of SBP, DBP, HR, LVSP, LVEDP, and left arterial pressure (LAP) from T1 to T7 were decreased (P<0.05), but there was no significant difference in the other indexes (P>0.05).

CONCLUSION

Dexmedetomidine can decrease blood pressure and heart rate in rabbits in a dose-dependent manner, but there is no effect on the myocardial systolic and diastolic function.

Subcutaneously administered dexmedetomidine is efficiently absorbed and is associated with attenuated cardiovascular effects in healthy volunteers

PURPOSE

Palliative care patients often need sedation to alleviate intractable anxiety, stress, and pain. Dexmedetomidine is used for sedation of intensive care patients, but there is no prior information on its subcutaneous (SC) administration, a route that would be favored in palliative care. We compared the pharmacokinetics and cardiovascular, sympatholytic, and sedative effects of SC and intravenously (IV) administered dexmedetomidine in healthy volunteers.

METHODS

An open two-period, cross-over design with balanced randomization was used. Ten male subjects were randomized to receive 1 μg/kg dexmedetomidine both IV and SC. Concentrations of dexmedetomidine and catecholamines in plasma were measured. Pharmacokinetic variables were calculated with non-compartmental methods. In addition, cardiovascular and sedative drug effects were monitored.

RESULTS

Eight subjects completed both treatment periods. Peak concentrations of dexmedetomidine were observed 15 min after SC administration (median; range 15-240). The mean bioavailability of SC dexmedetomidine was 81% (AUC_0-∞ ratio × 100%, range 49-97%). The mean (SD) peak concentration of dexmedetomidine in plasma was 0.3 (0.1) ng/ml, and plasma concentrations associated with sedative effects (i.e., > 0.2 ng/ml) were maintained for 4 h after SC dosing. Plasma noradrenaline concentrations were significantly lower (P < 0.001) within 3 h after IV than after SC administration. Subjective scores for vigilance and performance were significantly lower 0-60 min after IV than SC dosing (P < 0.001 for both). The onset of the cardiovascular, sympatholytic, and sedative effects of dexmedetomidine was clearly less abrupt after SC than IV administration.

CONCLUSIONS

Dexmedetomidine is relatively rapidly and efficiently absorbed after SC administration. Subcutaneous dexmedetomidine may be a feasible alternative in palliative sedation, and causes attenuated cardiovascular effects compared to IV administration. CLINICALTRIALS.

GOV IDENTIFIER

NCT02724098 . EUDRA CT number 2015-004698-34 .

Editor’s Choice- Sedation in the coronary intensive care unit: An adapted algorithm for critically ill cardiovascular patient

In the current era, cardiovascular intensive care units care for more complex patients who are far sicker than historical post-myocardial infarction patients, and sedation has become a common intervention in these units. Current sedation best practices derive mainly from non-cardiac units which limits their generalization to the critically ill cardiac patient. Thus, a great variability in sedation protocols, especially the selection of sedative agents, is commonly seen in daily practice across cardiac units. We present an updated review on sedation in cardiovascular critical care medicine with emphasis on the hemodynamic impact. The goal of this review is to generate a general sedation algorithm specific for the cardiac patient.

Assessment the effect of dexmedetomidine on incidence of paradoxical hypertension after surgical repair of aortic coarctation in pediatric patients

OBJECTIVE

The aim of the study was to assess the effect of dexmedetomidine on the incidence of paradoxical hypertension in patients undergoing aortic coarctation repair.

DESIGN

Randomized observational study.

SETTING

University hospital and cardiac center.

PATIENTS

The study included 108 pediatric patients with isolated aortic coarctation.

METHODS

The patients were classified into two groups (each = 54): Group D: the patients received dexmedetomidine as a loading dose of 0.5 μg/kg over 10 min followed by infusion 0.3 μg/kg/h during surgery and continued for the first 48 postoperative hours. Group C: The patients received an equal amount of normal saline. The medication was prepared by the nursing staff and given to anesthetist blindly. The collected data included the heart rate, systolic and diastolic arterial blood pressure, incidence, onset, severity and treatment of paradoxical hypertension, fentanyl dose and end-tidal sevoflurane concentration, amount of blood loss and urine output.

MAIN RESULTS

The heart rate, systolic and diastolic blood pressure decreased significantly with dexmedetomidine than Group C (P < 0.05). The incidence and severity of the paradoxical hypertension was lower with dexmedetomidine than Group C (P = 0.011, P = 0.017, respectively). The onset the paradoxical hypertension was earlier in Group C than dexmedetomidine (P = 0.026). The dose of fentanyl and sevoflurane concentration decreased significantly with dexmedetomidine (P = 0.034, P = 0.026, respectively). The blood loss decreased with dexmedetomidine (P = 0.020) and the urine output increased with dexmedetomidine (P = 0.024). The incidence of hypotension and bradycardia was more with dexmedetomidine (P < 0.05).

CONCLUSION

Dexmedetomidine is safe in pediatric patients undergoing aortic coarctation repair. It minimized the incidence and severity of paradoxical hypertension. It decreased the required antihypertensive medications.

Lack of Association Between Adrenoreceptor Genotype and the Vasoconstriction Response to Dexmedetomidine

An exaggerated vasoconstriction response to dexmedetomidine, an α-2 adrenergic agonist, has been associated with 2 genotypes: a deletion in the α-2B adrenoreceptor gene ( ADRA2B deletion) and SNP rs9922316 in the gene for protein kinase C type β ( PRKCB). We hypothesized that children with a marked systemic vascular resistance index (SVRI) increase following intravenous dexmedetomidine bolus would carry these genotypes. Following institutional review board approval, DNA samples from 16 children with transplanted hearts who participated in a study in the cardiac catheterization laboratory of hemodynamic responses to dexmedetomidine boluses underwent genotyping by polymerase chain reaction (PCR) amplification and PCR Sanger sequencing for the ADRA2B deletion and for PRKCB rs9922316. A wide range of SVRI (-12% to +76%, median 33%) and mean arterial blood pressure (MAP; -7% to +50%, median 26%) responses to dexmedetomidine was observed. The responses were not significantly different among genotype groups. An association between exaggerated SVRI or MAP responses and either ADRA2B deletion or PRKCB rs9922316 was not observed.

Bidirectional Regulatory Effects of Dexmedetomidine on Porcine Coronary Tone In Vitro

Background

Studies in vivo have shown that dexmedetomidine (DEX) could protect the myocardium and modulate the coronary blood flow. This study aimed to investigate the direct and concentration-dependent effects of DEX on the tone of porcine coronary artery in vitro and the underlying mechanisms.

Material/Methods

Distal branches of the porcine anterior descending coronary arteries were dissected and cut into 3–5 mm rings. The tones of coronary rings in response to cumulative DEX were measured using the PowerLab system. Coronary rings were divided into three groups: 1) endothelium-intact coronary rings without drug pretreatment (control); 2) endothelium-intact coronary rings pretreated with either yohimbine, tetraethylamine (TEA) or NG-nitro-L-arginine methyl ester (L-NAME); and 3) endothelium-denuded coronary rings pretreated with either yohimbine or TEA.

Results

DEX induced coronary ring relaxation at lower concentrations (10⁻⁹ to 10⁻⁷ M) followed by constriction at higher concentrations (10⁻⁶ to 10⁻⁵ M). The coronary constrictive effect of higher DEX (10⁻⁵ M) was greater in the endothelium-denuded rings than in the endothelium-intact rings. Yohimbine reduced the coronary constrictive effect of DEX at higher concentrations (10⁻⁶ to 10⁻⁵ M). TEA and L-NAME significantly reduced the coronary relaxing effect of DEX at lower concentrations (10⁻⁹ to 10⁻⁷ M) in endothelium-intact rings. TEA attenuated the coronary relaxation induced by DEX in endothelium-denuded rings.

Conclusions

DEX exerts bidirectional effects on porcine coronary tone. The coronary relaxing effect of DEX at lower concentrations is likely associated with endothelium integrity, NO synthesis and BKCa channel activation, while the coronary constrictive effect of DEX at higher concentrations is mediated by α2 adrenoceptors in the coronary smooth muscle cells.

Effect of dexmedetomidine on diseased coronary vessel diameter and myocardial protection in percutaneous coronary interventional patients

Introduction:

Dexmedetomidine is an alpha-2 agonist used for conscious sedation. It has also been shown to have a myocardial protective effect in off-pump coronary artery bypass patients. The aim of the study was to assess the effect of dexmedetomidine for myocardial protection in percutaneous coronary interventional patients.

Methodology:

A total of 60 patients (group dexmedetomidine, n = 30 and group normal saline, n = 30) were enrolled in the study. Dexmedetomidine infusion (1 mcg/kg) over 15 min was given as a loading dose after coronary angiography in group dexmedetomidine (D) while normal saline was given in the control group (C) and later maintenance infusion was started at 0.5 mcg/kg/h in both the groups. Coronary vessel diameter was noted before (T0) and after (T1) loading dose of dexmedetomidine/saline in each group. Troponin T (Trop T) values were noted at baseline (T0), 6 h (T2), 12 h (T3) and 24 h (T4) after starting the loading dose. Hemodynamic variables (heart rate [HR] and blood pressure) were monitored at T0, T1, and at regular intervals till 2 h postprocedure.

Results:

Coronary vessel diameter and HR significantly decreased in group D as compared to control group (P < 0.05) whereas the decrease in Trop T at 6 h, 12 h, and 24 h were not statistically significant between the two groups.

Conclusion:

Dexmedetomidine decreases the coronary vessel diameter, but maintains the myocardial oxygen demand-supply ratio by decreasing the HR. The decrease in Trop T is statistically insignificant at the doses used.

Comparison of Intravenous Dexmedetomidine and Midazolam for Bispectral Index-Guided Sedation During Spinal Anesthesia

Background

Despite the high frequency of hypotension during spinal anesthesia with proper sedation, no previous report has compared the hemodynamic effects of dexmedetomidine and midazolam sedation during spinal anesthesia. We compared the effects of bispectral index (BIS)-guided intravenous sedation using midazolam or dexmedetomidine on hemodynamics and recovery profiles in patients who underwent spinal anesthesia.

Material/Methods

One hundred and sixteen adult patients were randomly assigned to receive either midazolam (midazolam group; n=58) or dexmedetomidine (dexmedetomidine group; n=58) during spinal anesthesia. Systolic, diastolic, and mean arterial pressures; heart rates; peripheral oxygen saturations; and bispectral index scores were recorded during surgery, and Ramsay sedation scores and postanesthesia care unit (PACU) stay were monitored.

Results

Hypotension occurred more frequently in the midazolam group (P<0.001) and bradycardia occurred more frequently in the dexmedetomidine group (P<0.001). Mean Ramsay sedation score was significantly lower in the dexmedetomidine group after arrival in the PACU (P=0.025) and PACU stay was significantly longer in the dexmedetomidine group (P=0.003).

Conclusions

BIS-guided dexmedetomidine sedation can attenuate intraoperative hypotension, but induces more bradycardia, prolongs PACU stay, and delays recovery from sedation in patients during and after spinal anesthesia as compared with midazolam sedation.

The protective and hemodynamic effects of dexmedetomidine on hypertensive cerebral hemorrhage patients in the perioperative period

The aim of the present study was to analyze the protective and hemodynamic effects of dexmedetomidine in hypertensive cerebral hemorrhage (HCH) patients during perioperative period. In total, 50 HCH patients were selected and randomly divided into two groups, one group was administered with dexmedetomidine and the other groups with midazolam. The mean arterial pressure (MAP), heart rate (HR) and blood oxygen saturation (SpO₂) were monitored in the two groups of patients before and during the operation. The MAP, HR, SpO₂ and P_ETCO₂ recorded 5 min after admission into the operation room was considered T₁, the same parameters recorded 10 min after drug administration were considered T₂, just after starting the operation were considered T₃ and 30 min after start of operation were considered T₄. The preoperative sedation and analgesia were evaluated by the Ramsay scoring method and the neuron-specific enolase (NSE) and S100 protein (S100β) were estimated using ELISA. The patients of the midazolam group experienced mild respiratory depression during the period of sedation. Levels of, MAP, HR and P_ETCO₂ were significantly increased whereas SPO₂ was decreased (P<0.05). The MAP, HR, SPO₂ and P_ETCO₂ were stable during the period of sedation (P>0.05). The plasma concentrations of epinephrine and norepinephrine at T₁ were similar in the two groups (P>0.05), but decreased after drug administration. This decrease was more prominent in the dexmedetomidine group patients (P<0.05) than midazolam group patients. The epinephrine and norepinephrine concentrations just after starting operation (T₃) were higher than the basal level (T₁) in the midazolam group, but close to the basal level in the dexmedetomidine group (P<0.05). The serum concentration of NSE and S100β in the two groups showed no difference (P>0.05) at the end of operation (T₅), but after 24 h of operation (T₇) NSE and S100β in the dexmedetomidine group were significantly lower compared to the midazolam group (P<0.05). In conclusion, the administration of dexmedetomidine for patients with HCH during perioperative period is safe and serves as an effective sedative, without causing respiratory depression and does not influence stable haemodynamics with certain brain protective effect.

Age-related effects of dexmedetomidine on myocardial contraction and coronary circulation in isolated guinea pig hearts

Dexmedetomidine is a selective α2 adrenergic agonist. Although dexmedetomidine is widely used for sedation and analgesia, it frequently produces hypotension and bradycardia. The present study aimed to evaluate the effects of dexmedetomidine on cardiac function and coronary circulation using Langendorff-perfused guinea pig hearts. Coronary perfusion pressure (CPP) and left ventricular pressure (LVP) were continuously monitored, and electric field stimulation (EFS) was applied to stimulate sympathetic nerve terminals. Dexmedetomidine almost completely inhibited the EFS-induced increase in LVP at all ages. The effect of dexmedetomidine on coronary artery resistance varied according to postnatal age, i.e., dexmedetomidine had little effect on CPP in young hearts (<4 weeks) but increased CPP by 10 mmHg at 4-8 weeks and by 15 mmHg at >8 weeks. The increase in CPP in adult hearts was inhibited by imiloxan, an α2B antagonist, and prazosin, an α1 antagonist. The results suggest that dexmedetomidine acts on α2 adrenergic receptors at sympathetic nerve terminals to suppress the release of norepinephrine. In addition, the findings suggest that dexmedetomidine directly affects α1 adrenoceptors and/or α2B adrenoceptors on coronary smooth muscles to increase CPP. The age-related changes in α adrenoceptor subtypes may be linked to the cardiodepressant effects of dexmedetomidine.

Dexmedetomidine versus midazolam for sedation during endoscopy: A meta-analysis

Patients undergoing endoscopy frequently require sedation, which commonly includes the administration of midazolam or dexmedetomidine. Previous meta-analyses have mainly focused on comparing the effects of these two drugs in intensive care unit patients. In the present study, randomized controlled trials (RCTs) that compared the sedative and clinical effectiveness of these two drugs in patients undergoing endoscopy were searched in a number of databases. The meta-analysis showed that dexmedetomidine demonstrated a significantly lower rate of respiratory depression and adverse events compared with those presented upon midazolam administration. A significant difference was also observed in the sedation potency of the sedatives. The current controlled data suggest that dexmedetomidine may be an alternative to midazolam in the sedation for endoscopy. However, more high-quality and well-designed studies are required to further evaluate this conclusion.

Effects of perineural administration of dexmedetomidine in combination with bupivacaine in a femoral-sciatic nerve block

Background and Aim:

Perineural administration of dexmedetomidine, a α2-adrenoceptor agonist, prolongs the duration of analgesia. We hypothesized that adding dexmedetomidine to bupivacaine would prolong postoperative analgesia after below knee surgery.

Materials and Methods:

After ethical approval, 60 patients scheduled for below knee surgery under combined femoral-sciatic nerve block were randomly allocated into two groups to have their block performed using bupivacaine 0.5% alone (group B) or bupivacaine 0.5% combined with 100 μg bupivacaine-dexmedetomidine (group BD). Motor and sensory block onset times; durations of blockades and analgesia were recorded.

Results:

Sensory and motor block onset times were shorter by 20% in group BD than in group B (P < 0.01). Sensory and motor blockade durations were longer in group BD (+45% and +40%, respectively) than in group B (P < 0.01). Duration of analgesia was longer in group BD by 75% than in group B (P < 0.01). Systolic, diastolic arterial blood pressure levels, and heart rate were significantly less in group BD, six patients in group BD, and no patients in group B developed bradycardia (P < 0.05).

Conclusion:

The addition of dexmedetomidine 100 μg to bupivacaine 0.5% during ultrasound-guided combined femoral and sciatic block for below knee surgery was associated with a prolonged duration of analgesia. However, this may be associated with significant bradycardia requiring treatment.

Dexmedetomidine protects the heart against ischemia-reperfusion injury by an endothelial eNOS/NO dependent mechanism

The alpha2-adrenergic receptor agonist Dexmedetomidine (Dex) is a sedative medication used by anesthesiologists. Dex protects the heart against ischemia-reperfusion (IR) and can also act as a preconditioning mimetic. The mechanisms involved in Dex-dependent cardiac preconditioning, and whether this action occurs directly or indirectly on cardiomyocytes, still remain unclear. The endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) signaling pathway and endothelial cells are known to play key roles in cardioprotection against IR injury. Therefore, the aims of this work were to evaluate whether the eNOS/NO pathway mediates the pharmacological cardiac effect of Dex, and whether endothelial cells are required in this cardioprotective action. Isolated adult rat hearts were treated with Dex (10nM) for 25min and the dimerization of eNOS and production of NO were measured. Hearts were then subjected to global IR (30/120min) and the role of the eNOS/NO pathway was evaluated. Dex promoted the activation of eNOS and production of NO. Dex reduced the infarct size and improved the left ventricle function recovery, but this effect was reversed when Dex was co-administered with inhibitors of the eNOS/NO/PKG pathway. In addition, Dex was unable to reduce cell death in isolated adult rat cardiomyocytes subjected to simulated IR. Cardiomyocyte death was attenuated by co-culturing them with endothelial cells pre-treated with Dex. In summary, our results show that Dex triggers cardiac protection by activating the eNOS/NO signaling pathway. This pharmacological effect of Dex requires its interaction with the endothelium.

Development of an Optimized Pharmacokinetic Model of Dexmedetomidine Using Target-controlled Infusion in Healthy Volunteers

BACKGROUND

Several pharmacokinetic models are available for dexmedetomidine, but these have been shown to underestimate plasma concentrations. Most were developed with data from patients during the postoperative phase and/or in intensive care, making them susceptible to errors due to drug interactions. The aim of this study is to improve on existing models using data from healthy volunteers.

METHODS

After local ethics committee approval, the authors recruited 18 volunteers, who received a dexmedetomidine target-controlled infusion with increasing target concentrations: 1, 2, 3, 4, 6, and 8 ng/ml, repeated in two sessions, at least 1 week apart. Each level was maintained for 30 min. If one of the predefined safety criteria was breached, the infusion was terminated and the recovery period began. Arterial blood samples were collected at preset times, and NONMEM (Icon plc, Ireland) was used for model development.

RESULTS

The age, weight, and body mass index ranges of the 18 volunteers (9 male and 9 female) were 20 to 70 yr, 51 to 110 kg, and 20.6 to 29.3 kg/m, respectively. A three-compartment allometric model was developed, with the following estimated parameters for an individual of 70 kg: V1 = 1.78 l, V2 = 30.3 l, V3 = 52.0 l, CL = 0.686 l/min, Q2 = 2.98 l/min, and Q3 = 0.602 l/min. The predictive performance as calculated by the median absolute performance error and median performance error was better than that of existing models.

CONCLUSIONS

Using target-controlled infusion in healthy volunteers, the pharmacokinetics of dexmedetomidine were best described by a three-compartment allometric model. Apart from weight, no other covariates were identified.

Different effects of propofol and dexmedetomidine on preload dependency in endotoxemic shock with norepinephrine infusion

BACKGROUND

To clarify whether propofol (PROP) and dexmedetomidine (DEX) differentially affect preload dependency in an endotoxemic model based on evaluations of the systemic vascular system and cardiac function.

METHODS

Animals were prepared under PiCCO monitoring (BL), and endotoxemic shock was induced using an intravenous bolus of lipopolysaccharide (055:B5) in 16 New Zealand ketamine-anesthetized rabbits. After fluid resuscitation and norepinephrine infusion (SD0), the animals were randomized to PROP (n = 8) or DEX (n = 8) sedation at two incremental doses (SD1 and SD2). The mean arterial pressure and the central venous pressure were monitored. Pulse pressure variation (PPV) was assessed to evaluate preload dependency. Global end-diastolic volume, vascular resistance, mean systemic filling pressure, and cardiac function index were assessed at each time point.

RESULTS

PPV progressively and significantly increased with increasing infusion rates of PROP (SD1 versus SD0, P < 0.01; SD2 versus SD0, P < 0.001; and SD2 versus SD1, P = 0.024) but not DEX. PPV was higher at SD1 and SD2 in the PROP group than in the DEX group (P < 0.001). PROP increased the heart rate without affecting cardiac contractility or vascular resistance. In contrast, DEX decreased heart contractility and increased vascular resistance at the highest dose. However, neither drug affected mean arterial pressure, central venous pressure, mean systemic filling pressure, global end-diastolic volume, or venous return.

CONCLUSIONS

PROP more effectively increased PPV than DEX in an endotoxemic shock model after fluid resuscitation during norepinephrine infusion. DEX, but not PROP, at the highest dose influenced vascular resistance and heart contractility.

Hemodynamic effects of dexmedetomidine during intra-operative electrocorticography for epilepsy surgery

Background:

Dexmedetomidine, a predominant alpha-2-adrenergic agonist has been used in anesthetic practice to provide good sedation. The drug is being recently used in neuroanesthesia during awake surgery for brain tumors and in functional neurosurgery.

Materials and Methods:

This prospective study analyzed the hemodynamic effects of dexmedetomidine infusion during electrocorticography in patients undergoing surgery for mesial temporal sclerosis. Dexmedetomidine infusion was administered during intra-operative electrocorticography recording, 15 minutes after the end tidal MAC of N₂O and isoflurane were decreased to zero. Anesthesia was maintained with O₂ : air mixture = 50:50, vecuronium and fentanyl. Heart rate (HR), mean arterial pressure (MAP) and end tidal carbon dioxide (ETCO₂) were recorded across at induction, 2 min prior to dexmedetomidine (PreDEX), 5 min during dexmedetomidine infusion (DEX; 1 μg/kg), 5 min after stopping dexmedetomidine and 10 minutes after stopping dexmedetomidine.

Results:

Forty patients with mesial temporal sclerosis (M: F = 27:13, mean age = 28.15 ± 10.9 years; duration of epilepsy = 12.0 ± 7.9 years) underwent anterior temporal lobe resection with amygdalohippocampectomy for drug-resistant epilepsy. Infusion of dexmedetomidine caused a transient fall in HR in 87.5% of patients and an increase in MAP in 62.5% of patients, which showed a tendency to revert back towards PreDEX values within 10 min after stopping the infusion. Sixty-five percent of the patients showed ≤25% reduction and 10% of them showed >25% reduction in HR. 47.5% of the patients showed ≤25% increase and 15% of them showed >25% increase in MAP. These changes were over a narrow range and within physiological limits.

Conclusion:

The infusion of dexmedetomidine for a short period causes reduction of HR and increase in MAP in patients, however the variations are within acceptable range.

Detomidine and the combination of detomidine and MK-467, a peripheral alpha-2 adrenoceptor antagonist, as premedication in horses anaesthetized with isoflurane

OBJECTIVE

To investigate MK-467 as part of premedication in horses anaesthetized with isoflurane.

STUDY DESIGN

Experimental, crossover study with a 14 day wash-out period.

ANIMALS

Seven healthy horses.

METHODS

The horses received either detomidine (20 μg kg(-1) IV) and butorphanol (20 μg kg(-1) IV) alone (DET) or with MK-467 (200 μg kg(-1) IV; DET + MK) as premedication. Anaesthesia was induced with ketamine (2.2 mg kg(-1) ) and midazolam (0.06 mg kg(-1) ) IV and maintained with isoflurane. Heart rate (HR), mean arterial pressure (MAP), end-tidal isoflurane concentration, end-tidal carbon dioxide tension, central venous pressure, fraction of inspired oxygen (FiO2 ) and cardiac output were recorded. Blood samples were taken for blood gas analysis and to determine plasma drug concentrations. The cardiac index (CI), systemic vascular resistance (SVR), ratio of arterial oxygen tension to inspired oxygen (Pa O2 /FiO2 ) and tissue oxygen delivery (DO2 ) were calculated. Repeated measures anova was applied for HR, CI, MAP, SVR, lactate and blood gas variables. The Student's t-test was used for pairwise comparisons of drug concentrations, induction times and the amount of dobutamine administered. Significance was set at p < 0.05.

RESULTS

The induction time was shorter, reduction in MAP was detected, more dobutamine was given and HR and CI were higher after DET+MK, while SVR was higher with DET. Arterial oxygen tension and Pa O2 /FiO2 (40 minutes after induction), DO2 and venous partial pressure of oxygen (40 and 60 minutes after induction) were higher with DET+MK. Plasma detomidine concentrations were reduced in the group receiving MK-467. After DET+MK, the area under the plasma concentration time curve of butorphanol was smaller.

CONCLUSIONS AND CLINICAL RELEVANCE

MK-467 enhances cardiac function and tissue oxygen delivery in horses sedated with detomidine before isoflurane anaesthesia. This finding could improve patient safety in the perioperative period. The dosage of MK-467 needs to be investigated to minimise the effect of MK-467 on MAP.

A randomized controlled trial of the effect of preoperative dexmedetomidine on the half maximal effective concentration of propofol for successful i-gel insertion without muscle relaxants

BACKGROUND

Dexmedetomidine is a useful anesthetic adjuvant for general anesthesia. We determined whether preoperative dexmedetomidine administration could reduce the half maximal effective concentration (EC50) of propofol for successful i-gel insertion without muscle relaxants.

METHODS

Thirty-seven patients were randomly allocated to one of two groups. In the dexmedetomidine group (n = 19), dexmedetomidine (1 µg/kg) was loaded for 10 min preoperatively. In the control group (n = 20), the same volume of 0.9% normal saline was administered in the same manner. The EC50 of propofol for successful i-gel insertion was determined using Dixon's up-and-down method. The EC50 of propofol was calculated as the midpoint concentration after at least six crossover points had been obtained. For successful i-gel insertion, all of the following four factors were required—(1) no major movement of the body within 1 min of insertion, (2) no significant resistance to mouth opening, (3) cough ≤2, and (4) visible square wave capnogram without air leakage at a peak airway pressure of <10 cmH2O. Mean blood pressure (MBP) and heart rate (HR) were monitored during the peri-insertion period of i-gel.

RESULTS

The EC50 of propofol for successful i-gel insertion was 3.18 μg/mL in the dexmedetomidine group and 6.75 μg/mL in the control group (p < 0.001). The incidence of hypotension (MBP <80% of the baseline) during the peri-insertion period of i-gel was higher in the control group (p = 0.001), whereas the incidence of bradycardia (HR <80% of the baseline) was higher in the dexmedetomidine group (p = 0.001).

CONCLUSIONS

Preoperative dexmedetomidine reduced the EC50 of propofol for successful i-gel insertion without muscle relaxants.

Comparison of the Effects of Dexmedetomidine and Propofol on Hemodynamics and Oxygen Balance in Children with Complex Congenital Heart Disease Undergoing Cardiac Surgery

OBJECTIVE

The aim of this study was to compare the effects of anesthesia by dexmedetomidine and propofol on the hemodynamics and oxygen balance in children with complex congenital heart disease who were undergoing cardiac surgery.

METHODS

Fifty-seven children were randomized to receive either a continuous infusion of propofol (6-8 mg/kg/h) or dexmedetomidine (0.5-0.7 μg/kg/h) after anesthesia induction. Hemodynamic data were recorded. Oxygen balance parameters were assessed at baseline after midazolam sedation, before and immediately after skin incisions were made, after sternotomy, 5 minutes after protamine administration, and at the end of surgery.

RESULTS

Compared with the dexmedetomidine group, the propofol group exhibited decreases in blood pressure, cardiac output, and cardiac index before skin incision (P < .05) and increases in blood pressure, heart rate, cardiac output, and cardiac index after sternotomy (P < .01). However, very similar trends in oxygen dynamics were obtained in both groups (P > .05), and the cardiac index was not correlated with total oxygen consumption (r = -0.109, P = .066) or the oxygen extraction ratio (r = -0.107, P = .072).

CONCLUSIONS

Dexmedetomidine infusion may be superior to propofol anesthesia in children with complex congenital heart disease who are undergoing cardiopulmonary bypass because dexmedetomidine was associated with less variability in heart rate or blood pressure during surgery. However, the oxygen balance was similar when either agent was used.