The pharmacokinetics of dexmedetomidine in volunteers with severe renal impairment

Perioperative acute kidney injury: The renoprotective effect and mechanism of dexmedetomidine

Dexmedetomidine (DEX) is a highly selective and potent α2-adrenoceptor (α2-AR) agonist that is widely used as a clinical anesthetic to induce anxiolytic, sedative, and analgesic effects. In recent years, a growing body of evidence has demonstrated that DEX protects against acute kidney injury (AKI) caused by sepsis, drugs, surgery, and ischemia-reperfusion (I/R) in organs or tissues, indicating its potential role in the prevention and treatment of AKI. In this review, we summarized the evidence of the renoprotective effects of DEX on different models of AKI and explored the mechanism. We found that the renoprotective effects of DEX mainly involved antisympathetic effects, reducing inflammatory reactions and oxidative stress, reducing apoptosis, increasing autophagy, reducing ferroptosis, protecting renal tubular epithelial cells (RTECs), and inhibiting renal fibrosis. Thus, the use of DEX is a promising strategy for the management and treatment of perioperative AKI. The aim of this review is to further clarify the renoprotective mechanism of DEX to provide a theoretical basis for its use in basic research in various AKI models, clinical management, and the treatment of perioperative AKI.

The efficacy of dexmedetomidine for septic shock: A meta-analysis of randomized controlled trials

INTRODUCTION

The efficacy of dexmedetomidine was elusive for septic shock. This meta-analysis aimed to explore the efficacy of dexmedetomidine for septic shock.

METHODS

PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases have been searched through October 2022 and we included randomized controlled trials reporting the effect of dexmedetomidine in patients with septic shock.

RESULTS

Five randomized controlled trials were included in the meta-analysis. Compared with control group for septic shock, dexmedetomidine treatment was able to substantially decrease Sequential Organ Failure Assessment score (mean difference [MD] = -0.99; 95% confidence interval [CI] = -1.14 to -0.84; P < .00001) and duration of mechanical ventilation (MD = -0.90; 95% CI = -1.27 to -0.54; P < .00001), but showed no obvious influence on morality at 28 days (odds ratio = 0.79; 95% CI = 0.38 to 1.66; P = 054), hospital mortality (odds ratio = 0.66; 95% CI = 0.35 to 1.24; P = .20) or intensive care unit length of stay (MD = -1.47; 95% CI = -4.60 to 1.66; P = .36).

CONCLUSIONS

Dexmedetomidine administration may help treat patients with septic shock.

Real-time evaluation of the independent analgesic efficacy of dexmedetomidine

BACKGROUND

Dexmedetomidine has analgesic properties, but the intraoperative analgesic effect of dexmedetomidine is often masked by the effects of other general anaesthetics. Therefore, the degree to which it reduces intraoperative pain intensity remains unclear. The objective of this double-blind, randomised controlled trial was to evaluate the independent intraoperative analgesic efficacy of dexmedetomidine in real-time.

METHODS

This single-centre study enrolled 181 patients who were hospitalised for below-knee orthopaedic surgeries between 19 January 2021 to 3 August 2021 were eligible for this is single-centre study. Peripheral neural block was performed on patients scheduled for below-knee orthopaedic surgeries. Patients were randomly assigned to the dexmedetomidine or midazolam group and were intravenously administered with 1.5 µg kg^-1 h^-1 dexmedetomidine or 50 µg kg^-1 h^-1 midazolam, respectively. The analgesic efficacy was evaluated using the real-time non-invasive nociception monitoring. The primary endpoint was the attainment rate of the nociception index target. The secondary endpoints included the occurrence of intraoperative hypoxemia, haemodynamic parameters, the consciousness index, electromyography and patient outcomes.

RESULTS

On Kaplan-Meier survival analysis, the defined nociception index target was attained in 95.45% and 40.91% of patients receiving dexmedetomidine and midazolam, respectively. Log-rank analysis revealed that the dexmedetomidine group attained the nociception index target significantly faster and the median attainment time of the nociception index target in the dexmedetomidine group was 15 min. Dexmedetomidine group was associated with a significantly lower incidence of hypoxemia. There was no significant difference in blood pressure between the dexmedetomidine and midazolam groups. Further, the dexmedetomidine group had a lower maximum visual analogue scale score and lower analgesic consumption postoperatively.

CONCLUSIONS

Dexmedetomidine has independent analgesia and systemically administered as an adjuvant agent has better analgesic efficacy than midazolam without severe side effects.

TRIAL REGISTRATION

clinicaltrial.gov Registry Identifier: NCT-04675372.Registered on 19/12 /2020.

Dexmedetomidine Continuous Infusion for Refractory Cancer Pain at End of Life: A Case Report

Refractory cancer-related pain at end-of-life (EoL) is multifaceted and may require utilizing medications with different mechanism of actions beyond opioids. We report the successful use of dexmedetomidine in a 63-year old female with recurrent breast cancer and intractable left arm pain and swelling admitted to University of California, San Diego, Health (UC San Diego Health), palliative care unit. Patient's pain and agitation continued to persist and she declined clinically despite efforts to start methadone, continuous infusion opioids, continuous infusion lidocaine and intravenous chlorpromazine by the palliative care team. On hospital day (HD) 11 patient was started on dexmedetomidine continuous infusion for refractory pain per our protocol at UC San Diego Health. The next day the patient appeared much improved in terms of pain and agitation with grimacing and moaning completely resolved. She was able to have some lucid periods and interacting with her family. With the addition of dexmedetomidine to her pain regiment, the patient was able to peacefully die 5 days later. This case report highlights the clinical utility of demedetomidine in a palliative care unit for refractory pain at EoL.

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

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

Effects of intraoperative dexmedetomidine infusion on renal function in elective living donor kidney transplantation: a randomized controlled trial

PURPOSE

Ischemia-reperfusion injury is inevitable during donor organ harvest and recipient allograft reperfusion in kidney transplantation, and affects graft outcomes. Dexmedetomidine, an α2-adrenoreceptor agonist, has renoprotective effects against ischemia-reperfusion injury. We investigated the effects of intraoperative dexmedetomidine infusion on renal function and the development of delayed graft function after elective living donor kidney transplantation in a randomized controlled trial.

METHODS

A total of 104 patients were randomly assigned to receive either an intraoperative infusion of dexmedetomidine 0.4 μg·kg^-1·hr^-1 or 0.9% saline. The primary outcome was the serum creatinine level on postoperative day (POD) 7. Secondary outcomes were renal function and the degree of inflammation and included the following variables: serum creatinine level and estimated glomerular filtration rate up to six months; incidence of delayed graft function; and levels of serum cystatin C, plasma interleukin (IL)-1β, and IL-18 during the perioperative period.

RESULTS

The mean (standard deviation) serum creatinine level on POD 7 was comparable between the groups (dexmedetomidine vs control: 1.11 [0.87] mg·dL^-1 vs 1.06 [0.73] mg·dL^-1; mean difference, 0.05; 95% confidence interval, -0.27 to 0.36; P = 0.77). Delayed graft function occurred in one patient in each group (odds ratio, 1.020; P > 0.99). There were no significant differences in the secondary outcomes between the groups (all P > 0.05).

CONCLUSIONS

Intraoperative dexmedetomidine infusion did not produce any beneficial effects on renal function or delayed graft function in patients undergoing elective living donor kidney transplantation.

STUDY REGISTRATION

www.ClinicalTrials.gov (NCT03327389); registered 31 October 2017.

Dexmedetomidine-induced hemodynamic instability in patients undergoing orthopedic upper limb surgery under brachial plexus block: a retrospective study

Background

Hemodynamic instability is a frequent adverse effect following administration of dexmedetomidine (DMED). In this study, we evaluated the incidence of DMED-induced hemodynamic instability and its predictive factors in clinical regional anesthesia practice.

Methods

One hundred sixteen patients who underwent orthopedic upper limb surgery under brachial plexus block with intravenous DMED administration were retrospectively identified. The primary outcome was the incidence of DMED-induced hemodynamic instability. The participants were allocated to a stable or unstable group by their hemodynamic instability status. Patients’ characteristics were compared between the groups. The relationship between the potential risk factors and development of DMED-induced hemodynamic instability was analyzed with a logistic regression model.

Results

DMED-induced hemodynamic instability was observed in 14.7% of patients (17/116). The unstable group had more women than the stable group (76.5% vs. 39.4%, P = 0.010). When patients were classified into four subgroup according to body mass index (underweight, normal weight, overweight, and obesity), there was significant difference in the composition of the subgroups in the two groups (P = 0.008). In univariate analysis, female sex, obesity, and pre-existing hypertension were significant predictors of DMED-induced hemodynamic instability. Multivariate analysis demonstrated that female sex (adjusted OR 3.86, CI 1.09; 13.59, P = 0.036) and obesity (adjusted OR 6.41, CI 1.22; 33.57, P = 0.028) were independent predictors of DMED-induced hemodynamic instability.

Conclusions

Female and obese patients are more likely to have hemodynamic instability following intravenous DMED administration in clinical regional anesthesia practice. This study suggests that DMED dose may be diminished to prevent hypotensive risk in these populations.

Trial registration

This article was retrospectively registered at WHO clinical trial registry platform (Trial number: KCT0005977).

Protein Binding and Population Pharmacokinetics of Dexmedetomidine after Prolonged Infusions in Adult Critically Ill Patients

PURPOSE

Dexmedetomidine (DEX) is a highly selective α₂-adrenoceptor agonist with high protein binding of 94%. Critical illness may affect protein binding and the pharmacokinetic (PK) parameters of many drugs, including DEX. In critically ill patients receiving prolonged infusions of DEX, there is little information documenting the relationship between key pathophysiologic factors and DEX protein binding or PK parameters. The purpose of this study was to characterize the protein binding and PK profile of prolonged DEX infusion in critically ill patients.

METHODS

Critically ill, adult intensive care unit patients at a university hospital in Hong Kong were studied. The association between the pathophysiologic changes of critical illness and protein binding was evaluated using a generalized estimating equation. A population pharmacokinetic model to establish the PK profile of DEX was developed, and key pathophysiologic covariate effects of severity of illness, organ dysfunction measures, and altered protein binding on DEX PK parameters in this critically ill population were evaluated.

FINDINGS

A total of 22 critically ill patients and 1 healthy control were included. Mean protein binding of DEX in the critically ill patients was 90.4% (95% CI, 89.1-91.7), which was 4% lower than that in the healthy control. The PK data were adequately described by a 2-compartment model. The estimated population mean (relative standard error [RSE]) values of systemic clearance (CL), volume of distribution of the central compartment (V2), intercompartmental clearance (Q), and V_d in the peripheral compartment (V3) were 38.6 (11.7) L/h, 32.1 (46.1) L, 114.5 (58.3) L/h and 95.1 (30.6) L, respectively. The corresponding estimated interindividual variability expressed as CV% (RSE) was 52.4 (23.8) for CL, 172.9 (19.3) for V2, 123.7 (33.7) for Q, and 106 (39.9) for V3. No significant explanatory pathophysiologic covariates were identified.

IMPLICATIONS

Although a marginally significant reduction of protein binding in critically ill patients was demonstrated, the magnitude of the difference was unlikely to be of clinical significance. Higher alanine aminotransferase concentration was associated with decreased protein binding. No significant pathophysiologic covariates were associated with the observed PK parameters. The high interindividual variability of PK parameters supports the current practice of dose titration to ensure the desired clinical effects of DEX infusion in the intensive care unit setting.

Population Pharmacokinetic Model of Dexmedetomidine in a Heterogeneous Group of Patients

Dexmedetomidine is a hepatically eliminated drug with sedative, anxiolytic, sympatholytic, and analgesic properties that has been increasingly used for various indications in the form of a short or continuous intravenous infusion. This study aimed to propose a population pharmacokinetic (PK) model of dexmedetomidine in a heterogeneous group of intensive care unit patients, incorporating 29 covariates potentially linked with dexmedetomidine PK. Data were collected from 70 patients aged between 0.25 and 88 years and treated with dexmedetomidine infusion for various durations at 1 of 4 medical centers. Statistical analysis was performed using a nonlinear mixed-effect model. Categorical and continuous covariates including demographic data, hemodynamic parameters, biochemical markers, and 11 single-nucleotide polymorphisms were tested. A 2-compartment model was used to describe dexmedetomidine PK. An allometric/isometric scaling was used to account for body weight difference in PK parameters, and the Hill equation was used to describe the maturation of clearance. Typical values of the central and peripheral volume of distribution and the systemic and distribution clearance for a theoretical adult patient were central volume of distribution = 22.50 L, peripheral volume of distribution  = 86.1 L, systemic clearance =  34.7 L/h, and distribution clearance = 40.8 L/h. The CYP1A2 genetic polymorphism and noradrenaline administration were identified as significant covariates for clearance. A population PK model of dexmedetomidine was successfully developed. The proposed model is well calibrated to the observed data. The identified covariates account for <5% of interindividual variability and consequently are of low clinical significance for the purpose of dose adjustment.

Anesthetic Considerations for Patients on Renal Replacement Therapy

The number of patients presenting for surgery with renal dysfunction requiring renal replacement therapy (RRT) is expected to increase as the population ages and improvements in therapy continue to be made. Every aspect of the perioperative period is affected by renal dysfunction, its associated comorbidities, and altered physiology secondary to RRT. Most alarming is the increased risk for perioperative cardiac morbidity and mortality seen in this population. Perioperative optimization and management aims to minimize these risks; however, few definite guidelines on how to do so exist.

Preventive Effects of Dexmedetomidine on Renal Dysfunction and Hemodynamic Stability in Malignant Obstructive Jaundice Patients During Peri-Operative Period

Background

This study aimed to investigate effects of intra-operative administration with dexmedetomidine (Dex) on hemodynamics and renal function in patients with malignant obstructive jaundice.

Material/Methods

Our randomized, double-blinded, placebo-controlled study was conducted among 40 patients with malignant obstructive jaundice between August 2009 and March 2011 in The Affiliated Hospital of Inner Mongolia Medical University. The 40 patients were randomly divided into 2 groups: the Dex group (receiving Dex 0.5 μg/kg 10-minutes before induction and then a 0.5 μg/kg/hour maintenance infusion until end of operation 30 minutes) and the Control group (receiving normal saline of same amount and at same rate). The adverse events, including incidence of cardiovascular complications and nausea and vomiting, and length of hospital stay were determined. The level of cystatin C (CysC), retinol-binding protein (RBP), creatinine (Scr), and blood urea nitrogen (BUN) were also evaluated.

Results

Dexmedetomidine administration significantly decreased heart rate (HR) and stroke volume variation (SVV) and significantly increased capital venous pressure (CVP) and mean arterial pressure (MAP) values compared to that in the Control group (P<0.05). Dexmedetomidine administration significantly upregulated urine volume and significantly downregulated atropine levels compared to the Control group (P<0.05). Dexmedetomidine administration significantly improved renal functions, by modulating CysC, RBP, Scr and BUN levels compared to the Control group (P<0.05). Dexmedetomidine administration demonstrated no additional side-effects. Dexmedetomidine administration significantly shortened length of hospitalization in the Dex group compared to the Control group (P<0.05).

Conclusions

Dexmedetomidine plays preventive effects on renal dysfunction and hemodynamic stability in malignant obstructive jaundice patients during peri-operative period.

Pharmacokinetics of Intranasally Administered Dexmedetomidine in Chinese Children

Background: Intranasal application is a comfortable, effective, nearly non-invasive, and easy route of administration in children. To date, there is, however, only one pharmacokinetic study on intranasal dexmedetomidine in pediatric populations and none in Chinese children available. Therefore, this study aimed to characterize the pharmacokinetics of intranasally administered dexmedetomidine in Chinese children.

Methods: Thirteen children aged 4 to 10 years undergoing surgery received 1 µg/kg dexmedetomidine intranasally. Arterial blood samples were drawn at various time points until 180 min after dose. Dexmedetomidine plasma concentrations were measured with high performance liquid chromatography (HPLC) and mass spectrometry. Pharmacokinetic modeling was performed by population analysis using linear compartment models with first-order absorption.

Results: An average peak plasma concentration of 748 ± 30 pg/ml was achieved after 49.6 ± 7.2 min. The pharmacokinetics of dexmedetomidine was best described by a two-compartment model with first-order absorption and an allometric scaling with estimates standardized to 70-kg body weight. The population estimates (SE) per 70 kg bodyweight of the apparent pharmacokinetic parameters were clearance CL/F = 0.32 (0.02) L/min, central volume of distribution V1/F = 34.2 (4.9) L, intercompartmental clearance Q2/F = 10.0 (2.2) L/min, and peripheral volume of distribution V2/F = 34.9 (2.3) L. The estimated absorption rate constant was Ka = 0.038 (0.004) min⁻¹.

Conclusions: When compared with studies in Caucasians, Chinese children showed a similar time to peak plasma concentration after intranasal administration, but the achieved plasma concentrations were about three times higher. Possible reasons are differences in age, ethnicity, and mode of administration.

The pharmacokinetics of dexmedetomidine in patients with obstructive jaundice: A clinical trial

OBJECTIVES

Dexmedetomidine, a highly selective central α2-agonist, undergoes mainly biotransformation in the liver. The pharmacokinetics of dexmedetomidine were significantly affected by hepatic insufficiency. The clearance of dexmedetomidine in patients with severe hepatic failure decreased by 50% compared with controls. We tested the hypothesis that the pharmacokinetics of dexmedetomidine would be affected by obstructive jaundice. The prospective registration number of clinical trial is ChiCTR-IPR-15007572.

METHODS

18 patients with obstructive jaundice and 12 non-jaundiced patient controls received dexmedetomidine, 1 μg/kg, over 10 min. Arterial blood samples were drawn before, during, and up to 5 h after the infusion. Plasma dexmedetomidine concentrations were determined by 1290 infinity high performance liquid chromatography coupled with 6470 tandem mass spectrometry. The relevant pharmacokinetic parameters were calculated by non-compartmental analysis using Phoenix WinNonlin 7.0.

RESULTS

Plasma clearance of dexmedetomidine was decreased by 33.3% in the obstructive jaundice group as compared with the control group (0.0068±0.0017 vs. 0.0102±0.0033 L/kg/min; P = 0.002). Volume of distribution was decreased by 29.2% in the obstructive jaundice group as compared with the control group (1.43±0.58 vs. 2.02±0.84 L/kg; P = 0.041).

CONCLUSIONS

This study demonstrates that the clearance and distribution volume of dexmedetomidine were decreased in patients with obstructive jaundice. It may be advisable to adjust the dose of dexmedetomidine in those patients.

Impact of CYP2A6 gene polymorphism on the pharmacokinetics of dexmedetomidine for premedication

BACKGROUND

Dexmedetomidine is a widely used sedative in clinic, which is mainly metabolized by cytochrome P450 2A6 (CYP2A6). Dexmedetomidine was rarely reported for off-label usage of premedication, but lacking relevant pharmacokinetic investigations. Therefore, our study determined the dexmedetomidine pharmacokinetics of CYP2A6*4 allele in Chinese patients pretreated with dexmedetomidine whose mutation frequency of CYP2A6*4 are high, in order to provide clinical references.

METHODS

Thirty-one elective surgery patients received premedication with 0.5 μg/kg dexmedetomidine via intravenous pump. Their plasma concentrations at multiple time-points and polymorphism of CYP2A6*4 were determined and statistically analyzed.

RESULTS

9 patients were *1/*4 or *4/*4, and 22 patients were *1/*1. The main pharmacokinetic parameters were area under curve (AUC) 1396.19 ± 332.47h· ng· l^-1, peak blood concentration (C_max) 495.50 ± 104.90ng· l^-1, distribution volume (V) 0.68 ± 0.20 L/kg, clearance (CL) 0.38 ± 0.11 L/h/kg, distribution half-life (t_1/2α) 0.05 ± 0.01h, elimination half-life (t_1/2β) 2.53 ± 0.04h. No significant pharmacokinetic differences were found among CYP2A6*1/*1, *1/*4, and *4/*4 patients.

CONCLUSIONS

In Chinese patients pretreated with dexmedetomidine, T_1/2β was consistent with that published, but T_1/2α, V and Cl were lower. It was unnecessary to consider the mutation when developing the precision regimen of dexmedetomidine.

Clinical Pharmacokinetics and Pharmacodynamics of Dexmedetomidine

Dexmedetomidine is an α₂-adrenoceptor agonist with sedative, anxiolytic, sympatholytic, and analgesic-sparing effects, and minimal depression of respiratory function. It is potent and highly selective for α₂-receptors with an α₂:α₁ ratio of 1620:1. Hemodynamic effects, which include transient hypertension, bradycardia, and hypotension, result from the drug’s peripheral vasoconstrictive and sympatholytic properties. Dexmedetomidine exerts its hypnotic action through activation of central pre- and postsynaptic α₂-receptors in the locus coeruleus, thereby inducting a state of unconsciousness similar to natural sleep, with the unique aspect that patients remain easily rousable and cooperative. Dexmedetomidine is rapidly distributed and is mainly hepatically metabolized into inactive metabolites by glucuronidation and hydroxylation. A high inter-individual variability in dexmedetomidine pharmacokinetics has been described, especially in the intensive care unit population. In recent years, multiple pharmacokinetic non-compartmental analyses as well as population pharmacokinetic studies have been performed. Body size, hepatic impairment, and presumably plasma albumin and cardiac output have a significant impact on dexmedetomidine pharmacokinetics. Results regarding other covariates remain inconclusive and warrant further research. Although initially approved for intravenous use for up to 24 h in the adult intensive care unit population only, applications of dexmedetomidine in clinical practice have been widened over the past few years. Procedural sedation with dexmedetomidine was additionally approved by the US Food and Drug Administration in 2003 and dexmedetomidine has appeared useful in multiple off-label applications such as pediatric sedation, intranasal or buccal administration, and use as an adjuvant to local analgesia techniques.

Pharmacokinetics of dexmedetomidine during analgosedation in ICU patients

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

Dexmedetomidine ameliorates the inflammatory immune response in rats with acute kidney damage

It has been demonstrated that dexmedetomidine (Dex) can protect patients with acute kidney injury from experiencing further tissue damage, however its mechanism of action remains unclear. The present study investigated the immune modulatory functions of Dex in rats with acute kidney injury (AKI) induced via injection of lipopolysaccharide into the tail vein. ELISA analysis showed that Dex reduced the levels of inflammatory cytokines in rats with AKI in a dose dependent manner. Furthermore, the regulatory effects of Dex on cytokine production disappeared when the α-2 adrenergic receptor antagonist Yohimbine (YOH) was added. For a detailed investigation on how Dex regulates the immune response in rats with AKI, the impact of Dex on the viability of splenocytes and lymphocytes was determined and it was determined that Dex did not influence splenocyte and lymphocyte viability. In addition, ELISA tests showed that Dex regulated the production of the T-helper (Th) 17 cytokines interleukin (IL)-17 and IL-23, but not the Th1 cytokine tumor necrosis factor α, in splenocytes and lymphocytes. To confirm whether Dex functioned as an α-2-adrenergic receptor in these immune regulations, YOH was administered together with Dex. When Dex and YOH were administered together, the regulatory functions of Dex were reduced, confirming that Dex acted as an agonist on the α-2-adrenergic receptor. Thus the results of the current study may provide novel insights regarding how Dex modulates immune functions in AKI.

Sedation After Cardiac Surgery: Is One Drug Better Than Another?

The classic high-dose narcotic-based cardiac anesthetic has been modified to facilitate a fast-track, rapid recovery in the intensive care unit (ICU). Postoperative sedation is consequently now an essential component in recovery of the patient undergoing cardiac surgery. It must facilitate the patient's unawareness of the environment as well as reduce the discomfort and anxiety caused by surgery, intubation, mechanical ventilation, suction, and physiotherapy. Benzodiazepines seem well suited for this role, but propofol, opioids, and dexmedetomidine are among other agents commonly used for sedation in the ICU. However, what is an ideal sedative for this application? When compared with benzodiazepine-based sedation regimens, nonbenzodiazepines have been associated with shorter duration of mechanical ventilation and ICU length of stay. Current sedation guidelines recommend avoiding benzodiazepine use in the ICU. However, there are no recommendations on which alternatives should be used. In postcardiac surgery patients, inotropes and vasoactive medications are often required because of the poor cardiac function. This makes sedation after cardiac surgery unique in comparison with the requirements for most other ICU patient populations. We reviewed the current literature to try to determine if 1 sedative regimen might be better than others; in particular, we compare outcomes of propofol and dexmedetomidine in postoperative sedation in the cardiac surgical ICU.

Prolonged infusion of sedatives and analgesics in adult intensive care patients: A systematic review of pharmacokinetic data reporting and quality of evidence

Although pharmacokinetic (PK) data for prolonged sedative and analgesic agents in intensive care unit (ICU) has been described, the number of publications in this important area appear relatively few, and PK data presented is not comprehensive. Known pathophysiological changes in critically ill patients result in altered drug PK when compared with non-critically ill patients. ClinPK Statement was recently developed to promote consistent reporting in PK studies, however, its applicability to ICU specific PK studies is unclear. In this systematic review, we assessed the overall ClinPK Statement compliance rate, determined the factors affecting compliance rate, graded the level of PK evidence and assessed the applicability of the ClinPK Statement to future ICU PK studies. Of the 33 included studies (n=2016), 22 (67%) were low evidence quality descriptive studies (Level 4). Included studies had a median compliance rate of 80% (IQR 66% to 86%) against the ClinPK Statement. Overall pooled compliance rate (78%, 95% CI 73% to 83%) was stable across time (P=0.38), with higher compliance rates found in studies fitting three compartments models (88%, P<0.01), two compartments models (83%, P<0.01) and one compartment models (77%, P=0.17) than studies fitting noncompartmental or unspecified models (69%) (P<0.01). Data unique to the interpretation of PK data in critically ill patients, such as illness severity (48%), organ dysfunction (36%) and renal replacement therapy use (32%), were infrequently reported. Discrepancy between the general compliance rate with ClinPK Statement and the under-reporting of ICU specific parameters suggests that the applicability of the ClinPK Statement to ICU PK studies may be limited in its current form.

Pharmacokinetics and pharmacodynamics of dexmedetomidine

Dexmedetomidine is an alpha-2 adrenoceptor agonist and has been used as a general anesthetic, sedative and analgesic for about 30 years. The aim of this paper is to review the pharmacokinetics and pharmacodynamics of dexmedetomidine, evaluate physiological factors that may affect the pharmacokinetics of dexmedetomidine, and summarize the pharmacodynamics of dexmedetomidine at different plasma levels. The pharmacokinetic parameters reported in previous studies according to noncompartmental analyses or population modeling results are compared. We concluded that the pharmacokinetic profile can be adequately described by a two-compartment model in population pharmacokinetic modeling. Body weight, height, albumin level, cardiac output, disease condition and other factors were considered to have significant influence on the clearance and/or distribution volume in different population pharmacokinetic models. The pharmacological effects of dexmedetomidine, such as sedation, heart rate reduction and biphasic change of blood pressure, vary at different plasma levels. These findings provide a reference for individualizing the dose of dexmedetomidine and achieving the desired pharmacological effects in clinical applications.

Clonidine as a First-Line Sedative Agent After Neonatal Cardiac Surgery: Retrospective Cohort Study

OBJECTIVES

To determine the cardiovascular tolerance of clonidine used as a first-line sedative after cardiac surgery in small infants.

DESIGN

Retrospective chart review.

SETTING

A tertiary and quaternary referral cardiac PICU.

PATIENTS

All infants younger than 2 months who received a clonidine infusion for sedation after cardiac surgery from October 2011 to July 2013.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

Heart rate, blood pressure, central venous and left atrial pressure, vasoactive inotropic score, volume of fluid bolus, and lactate and central mixed venous saturation were assessed. Preinfusion values were compared with postinfusion values. Of 224 potentially eligible patients, only 23 infants met inclusion criteria, as most patients only received high doses of morphine and some received midazolam instead of clonidine. Clonidine administration was started at a median of 12 hours after surgery (Q1-Q3, 5-23), and infusion rate was 0.5-2 μg/kg/hr for a median duration of 30 hours (Q1-Q3, 12-54). Heart rate decreased (maximal mean decrease: 12% [149 beats/min (SD, 17) to 131 beats/min (SD, 17)]; p < 0.0001). Apart from a transient and limited drop in diastolic blood pressure of 13% (maximal mean decrease: from 42.8 mm Hg [SD, 5.9] to 37.1 mm Hg [SD, 4.0]; p = 0.018), all other cardiovascular variables were stable or improved. A contemporaneous cohort of patients who received midazolam, did so sooner after surgery, stayed longer in the PICU and showed less favorable hemodynamics.

CONCLUSIONS

IV clonidine as sedative added to morphine in selected patients seems hemodynamically safe. The observed decrease in heart rate and diastolic blood pressure seems of minimal clinical importance as all other hemodynamic variables remained stable or improved. The safety of clonidine given early after cardiac surgery as alternative to midazolam merits further study.

IV and Perineural Dexmedetomidine Similarly Prolong the Duration of Analgesia after Interscalene Brachial Plexus Block

Background

Perineural and IV dexmedetomidine have each been suggested to prolong the duration of analgesia when administered in conjunction with peripheral nerve blocks. In the first randomized, triple-masked, placebo-controlled trial to date, the authors aimed to define and compare the efficacy of perineural and IV dexmedetomidine in prolonging the analgesic duration of single-injection interscalene brachial plexus block (ISB) for outpatient shoulder surgery.

Methods

Ninety-nine patients were randomized to receive ISB using 15 ml ropivacaine, 0.5%, with 0.5 μg/kg dexmedetomidine administered perineurally (DexP group), intravenously (DexIV group), or none (control group). The authors sequentially tested the joint hypothesis that dexmedetomidine prolongs the duration of analgesia and reduces the 24-h cumulative postoperative morphine consumption. Motor blockade, pain severity, hemodynamic variations, opioid-related side effects, postoperative neurologic symptoms, and patient satisfaction were also evaluated.

Results

Ninety-nine patients were analyzed. The duration of analgesia was 10.9 h (10.0 to 11.8 h) and 9.8 h (9.0 to 10.6 h) for the DexP and DexIV groups, respectively, compared with 6.7 h (5.6 to 7.8) for the control group (P &lt; 0.001). Dexmedetomidine also reduced the 24-h cumulative morphine consumption to 63.9 mg (58.8 to 69.0 mg) and 66.2 mg (60.6 to 71.8 mg) for the DexP and DexIV groups, respectively, compared with 81.9 mg (75.0 to 88.9 mg) for the control group (P &lt; 0.001). DexIV was noninferior to DexP for these outcomes. Both dexmedetomidine routes reduced the pain and opioid consumption up to 8 h postoperatively and did not prolong the duration of motor blockade.

Conclusion

Both perineural and IV dexmedetomidine can effectively prolong the ISB analgesic duration and reduce the opioid consumption without prolonging motor blockade.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care: Sedation, Analgesia and Muscle Relaxant

OBJECTIVE

This article reviews pharmacotherapies currently available to manage sedation, analgesia, and neuromuscular blockade for pediatric cardiac critical patients.

DATA SOURCES

The knowledge base of an expert panel of pharmacists, cardiac anesthesiologists, and a cardiac critical care physician involved in the care of pediatric cardiac critical patients was combined with a comprehensive search of the medical literature to generate the data source.

STUDY SELECTION

The panel examined all studies relevant to management of sedation, analgesia, and neuromuscular blockade in pediatric cardiac critical patients.

DATA EXTRACTION

Each member of the panel was assigned a specific subset of the studies relevant to their particular area of expertise (pharmacokinetics, pharmacodynamics, and clinical care) to review and analyze.

DATA SYNTHESIS

The panel members each crafted a comprehensive summary of the literature relevant to their area of expertise. The panel, as a whole, then collaborated to cohesively summarize all the available, relevant literature.

CONCLUSIONS

In the cardiac ICU, management of the cardiac patient requires an individualized sedative and analgesic strategy that maintains hemodynamic stability. Multiple pharmacological therapies exist to achieve these goals and should be selected based on the patient's underlying physiology, hemodynamic vulnerabilities, desired level of sedation and analgesia, and the projected short- or long-term recovery trajectory.

Dexmedetomidine for Sedation during Withdrawal of Support

Agents used to control end-of-life suffering are associated with troublesome side effects. The use of dexmedetomidine for sedation during withdrawal of support in pediatrics is not yet described. An adolescent female with progressive and irreversible pulmonary deterioration was admitted. Despite weeks of therapy, she did not tolerate weaning of supplemental oxygen or continuous bilevel positive airway pressure. Given her condition and the perception that she was suffering, the family requested withdrawal of support. Despite opioids and benzodiazepines, she appeared to be uncomfortable after support was withdrawn. Ketamine was initiated. Relief from ketamine was brief, and its use was associated with a "wide-eyed" look that was distressing to the family. Ketamine was discontinued and a dexmedetomidine infusion was initiated. The patient's level of comfort improved greatly. The child died peacefully 24 hours after initiating dexmedetomidine from her underlying disease rather than the effects of the sedative.

Dexmedetomidine Reduces Shivering during Mild Hypothermia in Waking Subjects

Background and Purpose

Reducing body temperature can prolong tolerance to ischemic injury such as stroke or myocardial infarction, but is difficult and uncomfortable in awake patients because of shivering. We tested the efficacy and safety of the alpha-2-adrenergic agonist dexmedetomidine for suppressing shivering induced by a rapid infusion of cold intravenous fluids.

Methods

Ten subjects received a rapid intravenous infusion of two liters of cold (4°C) isotonic saline on two separate test days, and we measured their core body temperature, shivering, hemodynamics and sedation for two hours. On one test day, fluid infusion was preceded by placebo infusion. On the other test day, fluid infusion was preceded by 1.0 μg/kg bolus of dexmedetomidine over 10 minutes.

Results

All ten subjects experienced shivering on placebo days, with shivering beginning at a mean (SD) temperature of 36.6 (0.3)°C. The mean lowest temperature after placebo was 36.0 (0.3)°C (range 35.7-36.5°C). Only 3/10 subjects shivered on dexmedetomidine days, and the mean lowest temperature was 35.7 (0.4)°C (range 35.0-36.3°C). Temperature remained below 36°C for the full two hours in 6/10 subjects. After dexmedetomidine, subjects had moderate sedation and a mean 26 (13) mmHg reduction in blood pressure that resolved within 90 minutes. Heart rate declined a mean 23 (11) bpm after both placebo and dexmedetomidine. Dexmedetomidine produced no respiratory depression.

Conclusion

Dexmedetomidine decreases shivering in normal volunteers. This effect is associated with decreased systolic blood pressure and sedation, but no respiratory depression.

Mechanism-based population pharmacokinetic and pharmacodynamic modeling of intravenous and intranasal dexmedetomidine in healthy subjects

PURPOSE

Dexmedetomidine is an α2-adrenoceptor agonist used for perioperative and intensive care sedation. This study develops mechanism-based population pharmacokinetic-pharmacodynamic models for the cardiovascular and central nervous system (CNS) effects of intravenously (IV) and intranasally (IN) administered dexmedetomidine in healthy subjects.

METHOD

Single doses of 84 μg of dexmedetomidine were given once IV and once IN to six healthy men. Plasma dexmedetomidine concentrations were measured for 10 h along with plasma concentrations of norepinephrine (NE) and epinephrine (E). Blood pressure, heart rate, and CNS drug effects (three visual analog scales and bispectral index) were monitored to assess the pharmacological effects of dexmedetomidine. PK-PD modeling was performed for recently published data (Eur J Clin Pharmacol 67: 825, 2011).

RESULTS

Pharmacokinetic profiles for both IV and IN doses of dexmedetomidine were well fitted using a two-compartment PK model. Intranasal bioavailability was 82%. Dexmedetomidine inhibited the release of NE and E to induce their decline in blood. This decrease in NE was captured with an indirect response model. The concentrations of the mediator NE served via a biophase/transduction step and nonlinear pharmacologic functions to produce reductions in blood pressure and heart rate, while a direct effect model was used for the CNS effects.

CONCLUSION

The comprehensive panel of two biomarkers and seven response measures were well captured by the population PK/PD models. The subjects were more sensitive to the CNS (lower EC 50 values) than cardiovascular effects of dexmedetomidine.

Effect of low dose dexmedetomidine premedication on propofol consumption in geriatric end stage renal disease patients

BACKGROUND AND OBJECTIVE

Sedation in dialysis dependent end-stage renal disease patients requires caution as a result of performing high doses of sedatives and its complications. Multidrug sedation regimens might be superior and advantage on lesser drug consumption and by the way adverse events which occur easily in end-stage renal disease patients. We evaluated the effects of dexmedetomidine premedication on propofol consumption, sedation levels with Observer's Assessment of Alertness and Sedation scores and the bispectral index and the hemodynamic changes, potential side effects in geriatric patients with end-stage renal disease who underwent hip fracture surgery under spinal anesthesia.

METHOD

In this randomized, controlled, double-blind study 60 elderly patients (age≥65 years) with end-stage renal disease and hip fracture scheduled for anterograde femoral intramedullary nailing were assigned to groups that received either intravenous saline infusion (Group C) or dexmedetomidine 0.5μg/kg/10min infusion for premedication (Group D). All the patients received propofol infusion after the induction of the spinal anesthesia.

RESULTS

Total propofol consumption, propofol dose required for targeted sedation levels according to Observer's Assessment of Alertness and Sedation scores and bispectral index levels, recovery times were significantly lower in Group D (p<0.001). The time to reach to Observer's Assessment of Alertness and Sedation score 4 and to achieve bispectral index≤80 was significantly lower in Group C compared with Group D (p<0.001). Adverse events were similar in both groups.

CONCLUSION

Dexmedetomidine premedication lowers intraoperative propofol consumption to maintain targeted level of sedation. Therefore low dose dexmedetomidine premedication in addition to propofol infusion might be an alternative in geriatric patients with end-stage renal disease for sedation.

Enzyme-inducing Anticonvulsants Increase Plasma Clearance of Dexmedetomidine

Background:

Dexmedetomidine is useful during mapping of epileptic foci as it facilitates electrocorticography unlike most other anesthetic agents. Patients with seizure disorders taking enzyme-inducing anticonvulsants appear to be resistant to its sedative effects. The objective of the study was to compare the pharmacokinetic and pharmacodynamic profile of dexmedetomidine in healthy volunteers with volunteers with seizure disorders receiving enzyme-inducing anticonvulsant medications.

Methods:

Dexmedetomidine was administered using a step-wise, computer-controlled infusion to healthy volunteers (n = 8) and volunteers with seizure disorders (n = 8) taking phenytoin or carbamazapine. Sedation and dexmedetomidine plasma levels were assessed at baseline, during the infusion steps, and after discontinuation of the infusion. Sedation was assessed by using the Observer’s Assessment of Alertness/Sedation Scale, Ramsay Sedation Scale, and Visual Analog Scale and processed electroencephalography (entropy) monitoring. Pharmacokinetic analysis was performed on both groups, and differences between groups were determined using the standard two-stage approach.

Results:

A two-compartment model was fit to dexmedetomidine concentration–time data. Dexmedetomidine plasma clearance was 43% higher in the seizure group compared with the control group (42.7 vs. 29.9 l/h; P = 0.007). In contrast, distributional clearance and the volume of distribution of the central and peripheral compartments were similar between the groups. No difference in sedation was detected between the two groups during a controlled range of target plasma concentrations.

Conclusion:

This study demonstrates that subjects with seizure disorders taking enzyme-inducing anticonvulsant medications have an increased plasma clearance of dexmedetomidine as compared with healthy control subjects.

Inflammatory Response in Patients under Coronary Artery Bypass Grafting Surgery and Clinical Implications: A Review of the Relevance of Dexmedetomidine Use

Despite the fact that coronary artery bypass grafting surgery (CABG) with cardiopulmonary bypass (CPB) prolongs life and reduces symptoms in patients with severe coronary artery diseases, these benefits are accompanied by increased risks. Morbidity associated with cardiopulmonary bypass can be attributed to the generalized inflammatory response induced by blood-xenosurfaces interactions during extracorporeal circulation and the ischemia/reperfusion implications, including exacerbated inflammatory response resembling the systemic inflammatory response syndrome (SIRS). The use of specific anesthetic agents with anti-inflammatory activity can modulate the deleterious inflammatory response. Consequently, anti-inflammatory anesthetics may accelerate postoperative recovery and better outcomes than classical anesthetics. It is known that the stress response to surgery can be attenuated by sympatholytic effects caused by activation of central (α-)2-adrenergic receptor, leading to reductions in blood pressure and heart rate, and more recently, that they can have anti-inflammatory properties. This paper discusses the clinical significance of the dexmedetomidine use, a selective (α-)2-adrenergic agonist, as a coadjuvant in general anesthesia. Actually, dexmedetomidine use is not in anesthetic routine, but this drug can be considered a particularly promising agent in perioperative multiple organ protection.

Population pharmacokinetics of dexmedetomidine in critically ill patients

Background and Objectives

Although the pharmacokinetics of dexmedetomidine in healthy volunteers have been studied, there are limited data about the pharmacokinetics of long-term administration of dexmedetomidine in critically ill patients.

Methods

This population pharmacokinetic analysis was performed to quantify the pharmacokinetics of dexmedetomidine in critically ill patients following infusions up to 14 days in duration. The data consisted of three phase III studies (527 patients with sparse blood sampling, for a total of 2,144 samples). Covariates were included in a full random-effects covariate model and the most important covariate relationships were tested separately. The linearity of dexmedetomidine clearance was evaluated by observing steady-state plasma concentrations acquired at various infusion rates.

Results

The data were adequately described with a one-compartment model. The clearance of dexmedetomidine was 39 (95 % CI 37–41) L/h and volume of distribution 104 (95 % CI 93–115) L. Both clearance and volume of distribution were highly variable between patients (coefficients of variation of 62 and 57 %, respectively), which highlights the importance of dose titration by response. Covariate analysis showed a strong correlation between body weight and clearance of dexmedetomidine. The clearance of dexmedetomidine was constant in the dose range 0.2–1.4 μg/kg/h.

Conclusions

The pharmacokinetics of dexmedetomidine are dose-proportional in prolonged infusions when dosing rates of 0.2–1.4 μg/kg/h, recommended by the Dexdor^® summary of product characteristics, are used.

Interpatient variability in dexmedetomidine response: a survey of the literature

Fifty-five thousand patients are cared for in the intensive care unit (ICU) daily with sedation utilized to reduce anxiety and agitation while optimizing comfort. The Society of Critical Care Medicine (SCCM) released updated guidelines for management of pain, agitation, and delirium in the ICU and recommended nonbenzodiazepines, such as dexmedetomidine and propofol, as first line sedation agents. Dexmedetomidine, an alpha-2 agonist, offers many benefits yet its use is mired by the inability to consistently achieve sedation goals. Three hypotheses including patient traits/characteristics, pharmacokinetics in critically ill patients, and clinically relevant genetic polymorphisms that could affect dexmedetomidine response are presented. Studies in patient traits have yielded conflicting results regarding the role of race yet suggest that dexmedetomidine may produce more consistent results in less critically ill patients and with home antidepressant use. Pharmacokinetics of critically ill patients are reported as similar to healthy individuals yet wide, unexplained interpatient variability in dexmedetomidine serum levels exist. Genetic polymorphisms in both metabolism and receptor response have been evaluated in few studies, and the results remain inconclusive. To fully understand the role of dexmedetomidine, it is vital to further evaluate what prompts such marked interpatient variability in critically ill patients.

Dexmedetomidine: an adjuvant making large inroads into clinical practice

The introduction of newer more selective α(-2) adrenergic agonist, dexmedetomidine has made a revolution in the field of anesthesia owing to its varied application. The aim of the current review is to highlight the various clinical and pharmacological aspects of dexmedetomidine in daily routine practice of anesthesiology and intensive care besides its potential role in other clinical specialties. This review of dexmedetomidine was carried out after searching the medical literature in Pubmed, Science direct, Scopus, Google scholar and various text books and journal articles using keywords anesthesia, dexmedetomidine, neurosurgery, pediatric surgery, regional dexmedetomidine, anesthesia, regional, neurosurgery, and pediatric surgery. Dexmedetomidine has made its application from a novel sedating agent in the intensive care unit to its use as an adjuvant in various regional anesthetic techniques because of its "cooperative sedation" without any respiratory depression. It has a favorable pharmacokinetic profile suitable to be used in the perioperative period to reduce the requirements of opioids and anesthetic drugs. There are few side-effects of dexmedetomidine, which should always be kept in mind before choosing the patients for its use. The various side-effects associated with dexmedetomidine include, but are not limited to hypotension, bradycardia, worsening of heart block, dry mouth, and nausea. However, large scale randomized controlled trials are still needed to establish various effects of dexmedetomidine and to clearly define its safety profile.

[Dexmedetomidine. Pharmacokinetics and pharmacodynamics]

Dexmedetomidine is a highly selective, potent α₂-adrenoceptor agonist which was approved in 2011 by the European Medicines Agency for sedation of patients in intensive care units (ICU). Dexmedetomidine exhibits sedative as well as analgesic and anxiolytic effects. Recent studies suggest that dexmedetomidine may be an alternative to midazolam in long-term ICU sedation. This review summarizes the pharmacokinetics and pharmacodynamics of dexmedetomidine particularly in ICU patients and with special regard to covariate effects. Although dexmedetomidine is currently approved only for use in adults the pharmacokinetics and pharmacodynamics in children will also be addressed as there are numerous studies on this off-label use.

[Dexmedetomidine and clonidine: a review of their pharmacodynamy to define their role for sedation in intensive care patients]

Alpha-2 adrenergic agonists ("alpha-2 agonists") present multiple pharmacodynamic effects: rousable sedation, decreased incidence of delirium in the setting of critical care, preservation of respiratory drive, decreased whole body oxygen consumption, decreased systemic and pulmonary arterial impedance, improved left ventricular systolic and diastolic function, preserved vascular reactivity to exogenous catecholamines, preserved vasomotor baroreflex with lowered set point, preserved kidney function, decreased protein catabolism. These pharmacodynamic effects explain the interest for these drugs in the critical care setting. However, their exact role for sedation in critically ill-patients remains open for further studies. Given the few double-blind randomized multicentric trials available, the present non exhaustive analysis of the literature aims at presenting the utilization of alpha-2 agonists as potential first-line sedative agents, in the critical care setting. Suggestions regarding the use of alpha-2 agonists as sedatives are detailed.

Effects of different loading doses of dexmedetomidine on bispectral index under stepwise propofol target-controlled infusion

BACKGROUND AND PURPOSE

Stepwise propofol target-controlled infusion (TCI) can achieve a less disturbed condition of hemodynamics and respiration. Its combination with dexmedetomidine may have some advantages for patients. We studied the effects of different loading doses of dexmedetomidine on the bispectral index (BIS) under stepwise propofol TCI.

METHODS

Forty patients were randomly assigned into groups D(1.0), D(0.5), D(0.25) and D(0), in which dexmedetomidine at 1.0, 0.5, 0.25 or 0 µg•kg(-1) was infused over 10 min followed by 0.5 µg•kg(-1)•h(-1) and stepwise propofol TCI, which was administered with target effect site concentration (Ce) at 0.5 µg•ml(-1), and increased until 2.5 µg•ml(-1) by 1.0 µg•ml(-1) after 5 min reaching target Ce. BIS, heart rate, MAP, pulse oxygen saturation, RR and end-tidal carbon dioxide pressure were recorded before loading dose (T(0)), at 5 min (T(5 min)) and 10 min (T(10 min)) after starting infusion, after 5 min reaching Ce of 0.5, 1.5 and 2.5 µg•ml(-1) (T(p0.5), T(p1.5) and T(p2.5)).

RESULTS

BIS values in group D(1.0) were significantly lower compared with those in group D(0) since T(10 min) and those in groups D(0.5) and D(0.25) since T(p0.5). In group D(1.0), heart rate decreased significantly at T(5 min) and T(10 min), heart rate at T(10 min) was significantly lower compared with that in group D(0). MAP remained stable during the loading dose infusion and decreased to some degree after propofol infusion in all groups. Changes in pulse oxygen saturation, RR and end-tidal carbon dioxide pressurewere similar among the groups without respiration depression.

CONCLUSION

A loading dose of dexmedetomidine of 1.0 µg•kg(-1), not 0.5 µg•kg(-1) or less, over 10 min followed by 0.5 µg•kg(-1)•h(-1) can definitely decrease the BIS under stepwise propofol TCI with clinically stable blood pressure and without respiration depression, while attention should be paid to decreased heart rate.

Dexmedetomidine: current role in anesthesia and intensive care

BACKGROUND AND OBJECTIVES

To update and review the application of dexmedetomidine in anesthesia and intensive care. This study is a comprehensive review of clinical uses, pharmacology, pharmacokinetics, mechanism of action and adverse effects of dexmedetomidine.

CONTENT

The effective use of sedative-hypnotic agents and analgesics is an integral part of comfort and safety of patients. Dexmedetomidine is a potent and highly selective α-2 adrenoceptor agonist with sympatholytic, sedative, amnestic, and analgesic properties, which has been described as a useful and safe adjunct in many clinical applications. It provides a unique "conscious sedation", analgesia, without respiratory depression. The current reviewed uses include sedation at Intensive Care Unit-ICU (both adult and pediatric), emergency department, regional and general anesthesia, neurosurgery, sedation for pediatric procedures, awake fiber-optic intubation, cardiac surgery and bariatric surgery.

CONCLUSIONS

Dexmedetomidine offers a unique ability of providing both sedation and analgesia without respiratory depression. It is a new agent with a wide safety margin, excellent sedative capacity and moderate analgesic properties. Although its wide use is currently in patients of surgical and non-surgical intensive care units, dexmedetomidine seems to have promising future applications in neuroprotection, cardioprotection and renoprotection. More detailed studies are required to define its role as sedative in critical, neurosurgical and pediatric patients, as anesthesia adjunct and sedative during procedures.