The effect of intravenous dexmedetomidine premedication on the dose requirement of propofol to induce loss of consciousness in patients receiving alfentanil

The effects of propofol anaesthesia on molecular-enriched networks during resting-state and naturalistic listening

Placing a patient in a state of anaesthesia is crucial for modern surgical practice. However, the mechanisms by which anaesthetic drugs, such as propofol, impart their effects on consciousness remain poorly understood. Propofol potentiates GABAergic transmission, which purportedly has direct actions on cortex as well as indirect actions via ascending neuromodulatory systems. Functional imaging studies to date have been limited in their ability to unravel how these effects on neurotransmission impact the system-level dynamics of the brain. Here, we leveraged advances in multi-modal imaging, Receptor-Enriched Analysis of functional Connectivity by Targets (REACT), to investigate how different levels of propofol-induced sedation alter neurotransmission-related functional connectivity (FC), both at rest and when individuals are exposed to naturalistic auditory stimulation. Propofol increased GABA-A- and noradrenaline transporter-enriched FC within occipital and somatosensory regions respectively. Additionally, during auditory stimulation, the network related to the dopamine transporter showed reduced FC within bilateral regions of temporal and mid/posterior cingulate cortices, with the right temporal cluster showing an interaction between auditory stimulation and level of consciousness. In bringing together these micro- and macro-scale systems, we provide support for both direct GABAergic and indirect noradrenergic and dopaminergic-related network changes under propofol sedation. Further, we delineate a cognition-related reconfiguration of the dopaminergic network, highlighting the utility of REACT to explore the molecular substrates of consciousness and cognition.

Applications of Dexmedetomidine in Palliative and Hospice Care

Although the use of dexmedetomidine is currently approved by the US Food and Drug Administration in the adult population for monitored anesthesia care and sedation during mechanical ventilation, clinical experience suggests the potential application of dexmedetomidine in the palliative care arena. The medication can provide sedation with lower risk of delirium, control or minimize the adverse effects of other medications, and augment analgesia from opioids. We conducted a computerized bibliographic search of the literature regarding dexmedetomidine use for the treatment of pain and provision of sedation during palliative and hospice care in adult and pediatric patients. The objective was to provide a general descriptive account of the physiologic effects of dexmedetomidine and review its potential applications in the field of palliative and hospice care in adult and pediatric patients. The sedative and analgesic effects of dexmedetomidine have been well studied in animal and human models. Published experience from both single case reports and small case series has demonstrated the potential therapeutic applications of dexmedetomidine in palliative and hospice care. In addition to intravenous administration, case reports have demonstrated its successful use by both the intranasal and subcutaneous routes. Although these experiences have suggested its safety and efficacy, larger series and additional clinical experience with prospective comparison to other agents are needed to further define its efficacy and role in palliative and hospice care.

Efficacy and safety of dexmedetomidine in maintaining hemodynamic stability in pediatric cardiac surgery: a systematic review and meta-analysis

OBJECTIVES

Dexmedetomidine (DEX) is a highly selective alpha-2 adrenergic receptor agonist, which is the main sedative in the intensive care unit. This study aims to investigate the effectiveness and adverse events of DEX in maintaining hemodynamic stability in pediatric cardiac surgery.

SOURCES

Databases such as PubMed, Cochrane, Web of Science, WANFANG STATA and China National Knowledge Infrastructure were searched for articles about the application of DEX in maintaining hemodynamic stability during and after pediatric cardiac surgery up to 18th Feb. 2021. Only randomized controlled trials were included and random-effects model meta-analysis was applied to calculate the standardized mean deviation (SMD), odds ratio (OR) and 95% confidence interval (CI).

SUMMARY OF THE FINDINGS

Fifteen articles were included for this meta-analysis, and 9 articles for qualitative analysis. The results showed that preoperative prophylaxis and postoperative recovery of DEX in pediatric patients undergoing cardiac surgery were effective in maintaining systolic blood pressure (SBP), mean arterial pressure (MAP), diastolic blood pressure (DBP) and reducing heart rate (HR) (SBP: SMD = -0.35,95% CI: -0.72, 0.01; MAP: SMD = -0.83, 95% CI: -1.87,0.21; DBP: SMD = -0.79,95% CI: -1.66,0.08; HR: SMD = -1.71,95% CI: -2.29, -1.13). In addition, the frequency of Junctional Ectopic Tachycardia in the DEX treatment group was lower than that in the placebo group.

CONCLUSIONS

The application of DEX for preoperative prophylaxis and postoperative recovery in pediatric cardiac surgery patients are effective in maintaining hemodynamic stability, and the clinical dose of DEX is not significantly related to the occurrence of pediatric adverse events which may be related to individual differences.

Comparison of the Effect of Ketamine and Dexmedetomidine Combined with Total Intravenous Anesthesia in Laparoscopic Cholecystectomy Procedures: A Prospective Randomized Controlled Study

This randomized prospective clinical study aimed to investigate the effects of dexmedetomidine or ketamine administration to total intravenous anesthesia (TIVA) on postoperative analgesia in subjects undergoing elective laparoscopic cholecystectomy procedures. 90 adults, American Society of Anesthesiologists (ASA) physical status 1 and II patients, who underwent elective laparoscopic cholecystectomy procedures were included in the study and randomized into three groups equally. Remifentanil, propofol, and rocuronium infusions were used for TIVA guided by the bispectral index. In group KETA, 10 μg/kg/min ketamine was added to TIVA before surgery, and in group DEX, 0.5 μg/kg/h dexmedetomidine was added to TIVA before surgery. Normal saline infusions were infused in the control group. Postoperative analgesia was provided with intravenous patient-controlled analgesia (PCA) morphine (1 mg bolus morphine, 5 min lockout time). Hemodynamic parameters, scores of visual analogue scale (VAS) for pain, rescue morphine requirements, and side effects such as sedation, nausea, and vomiting were recorded for 48 hours after surgery. Postoperative first analgesic requirement time was longer in group KETA (P < 0.001), and it was longer in group DEX than in the control group (P < 0.001). Pain scores were lower in group KETA and group DEX than in the control group at all corresponding times throughout the 48 h period of observation. Intravenous PCA morphine consumptions were higher in the control group than in group KETA (P < 0.001 for all followed-up times), and they were higher in group DEX than in group KETA (P < 0.001 for all followed-up times). It is concluded that the use of dexmedetomidine or ketamine infusions can be suitable as an additive for TIVA in the intraoperative period. Furthermore, the addition of both drugs to the TIVA protocol may improve postoperative pain relief and decrease opioid consumption.

Electroencephalography-demonstrated mechanisms of dexmedetomidine-mediated deepening of propofol anesthesia: an observational study

BACKGROUND

Although dexmedetomidine (Dex) is known to reduce bispectral index (BIS) values and propofol dosage, there is little information regarding raw electroencephalography (EEG) changes related to Dex deepening of propofol general anesthesia (GA). This study investigated the Dex effects on propofol GA via analysis of EEG changes.

METHODS

A study cohort of 21 surgical patients (age range, 20-60 years) categorized as American Society of Anesthesiologists (ASA) class I or II was enrolled. We used time-varying spectral and bicoherence methods to compare electroencephalogram signatures 5 min before versus 10 min after intravenous Dex injection under propofol GA. The means and medians are reported with 95% confidence intervals (CIs) and inter-quartile ranges (IQRs), respectively.

RESULTS

Dex augmented the slow waves power and theta (θ) oscillation bicoherence peak from a mean (95% CI) of 22.1% (19.0, 25.2) to 25.2% (21.8, 28.6). Meanwhile, Dex reduced alpha (α) peak power and bicoherence from 3.5 dB (1.0, 6.0) and 41.5% (34.0, 49.0) to 1.7 dB (- 0.6, 4.0) and 35.4% (29.0, 41.8), respectively, while diminishing the median frequency of α oscillation peak values and the mean frequency of α peaks in bicoherence spectra from 12.0 Hz (IQR 11.2, 12.6) and 11.7 Hz (11.3, 12.2) to 11.1 Hz (IQR 10.3, 11.8) and 11.2 Hz (10.9, 11.6), respectively.

CONCLUSIONS

Profound EEG changes support the supposition that Dex enhances propofol-induced GA from a moderate to a deeper state. The present findings provide a theoretical basis and reference regarding protocols aimed at reducing anesthetic/sedative dosage while maintaining sufficient depth of GA.

CLINICAL TRIAL REGISTRATION

ChiCTR, ChiCTR1900026955 . Registered on 27 October 2019.

The Effect of Midazolam and Dexmedetomidine Sedation on Block Characteristic Following Spinal Bupivacaine: A Randomized Comparative Study

Background:

Dexmedetomidine is widely used as an adjunct to general as well as regional anesthesia.

Aims:

This study was conducted to compare and evaluate the synergistic effect of single intravenous (i.v.) bolus dose of dexmedetomidine with midazolam on spinal block duration, analgesia, and sedation in patients undergoing infra-umbilical surgeries.

Settings and Design:

Prospective, randomized, comparative, and double-blinded study.

Materials and Methods:

One hundred patients between 18 and 60 years of age of American Society of Anesthesiologists physical status I and II posted for elective infra-umbilical surgery under subarachnoid block were randomly divided into two groups (Group D and Group M). Patients of Group D received i.v. dexmedetomidine 0.5 μg.kg⁻¹ and of Group M received i.v. midazolam 0.05 mg.kg⁻¹ as premedication 5 min before spinal anesthesia over 10 min. Vital parameters, Ramsay sedation score, level of sensory and motor block, recovery time for sensory blockade, postoperative numerical rating scale, time of requirement of the first dose of postoperative rescue analgesic, and duration of analgesia were recorded and analyzed.

Statistical Analysis:

Chi-square test, t-test, and analysis of variance test were applied to analyze data using SPSS package for Windows.

Results and Conclusion:

Premedication with single i.v. dexmedetomidine prolonged the duration and increased the maximum upper level of only sensory component of spinal anesthesia (6.42 ± 3.21 vs. 4.8 ± 1.21 thoracic segments higher than with midazolam sedation). This property can be beneficial in preventing undesirable prolongation of motor block and facilitating early ambulation in shorter duration of infra-umbilical surgeries. In addition, dexmedetomidine slowed the regression of sensory block and increased the time of the first request of analgesic.

Dexmedetomidine or midazolam in combination with propofol for sedation in endoscopic retrograde cholangiopancreatography: a randomized double blind prospective study

Introduction

Interventional endoscopic procedures, such as endoscopic retrograde cholangiopancreatography (ERCP), often require sedation during the procedure. The most commonly used drugs for this purpose are midazolam and propofol, which are used as sedative and hypnotic agents with minimal analgesic potential.

Aim

To compare the analgesic sedative effects of midazolam-propofol and dexmedetomidine-propofol combinations and their influence on hemodynamic and respiratory variables in patients undergoing ERCP.

Material and methods

Forty adult patients aged 20-78 and undergoing ERCP were randomized to two groups. Patients were premedicated with midazolam (0.05 mg/kg 10 min before the procedure) in group M and with dexmedetomidine (1 μg/kg for 10 min) in group D. Propofol was used for maintenance. The sedation level was monitored using the bispectral index (BIS) to maintain a score between 70 and 80. Hemodynamic and respiratory variables, recovery time and adverse events were recorded.

Results

The hemodynamic and respiratory variables were similar in both groups. Total propofol consumption was significantly lower in the dexmedetomidine group (208.5 ±80.0 vs. 154.5 ±66.7 mg; p = 0.011). The recovery period was shorter in group D (time to achieve the Aldrete score 9 was 9.4 ±2.1 vs. 6.6 ±1.1 min; p < 0.001). Changes in hemodynamic and respiratory variables and adverse events were not different between the two groups.

Conclusions

We found a shorter recovery time and comparable sedative and adverse effects with the dexmedetomidine-propofol combination compared with the midazolam-propofol combination. Dexmedetomidine in combination with propofol may be a safe and useful alternative for sedation for ERCP patients.

Evaluation of retrograde intubation with different doses of dexmedetomidine infusion: A randomised controlled trial

Background

Retrograde intubation is one of the well-described and alternative methods of difficult airway management. It requires effective sedation and patient preparation. Study was done to evaluate intubating conditions during retrograde guided intubation with two different doses of dexmedetomidine.

Methods

This prospective randomized double blind parallel group trial was planned on 60 patients with difficult airway. Patients were divided in two groups to receive either dexmedetomidine 1.0 μg/kg (Group A) or dexmedetomidine 1.5 μg/kg (Group B) by intravenous (IV) route. The Modified Observer Assessment Awareness and Sedation (OAA/S) was measured as primary outcome and ease of intubation, facial grimace score, cough severity, hemodynamic response, patient recall and discomfort were assessed as secondary outcome during awake retrograde intubation.

Results

Groups were comparable in terms of demographic and baseline parameters. OAA/S (P = 0.001), cough severity (P < 0.001), facial grimace score (P < 0.001), grading of discomfort during procedure (P < 0.001) and recall of procedure scale (P = 0.038) were found significantly better/lower in Group B as compared to Group A. Hemodynamic parameters were better in Group B and showed significant difference during the retrograde intubation. However, ease of intubation scale, intubating time and complications were not significantly different (P > 0.05) between the two groups.

Conclusion

Retrograde intubation can be easily learned and performed with minimal complications. Dexmedetomidine in a dose of 1.5 μg/kg IV is optimum and safe for retrograde intubation with clinically manageable side effects.

Pharmacodynamic Interaction of Remifentanil and Dexmedetomidine on Depth of Sedation and Tolerance of Laryngoscopy

BACKGROUND

Dexmedetomidine is a sedative with modest analgesic efficacy, whereas remifentanil is an opioid analgesic with modest sedative potency. Synergy is often observed when sedative-hypnotics are combined with opioid analgesics in anesthetic practice. A three-phase crossover trial was conducted to study the pharmacodynamic interaction between remifentanil and dexmedetomidine.

METHODS

After institutional review board approval, 30 age- and sex- stratified healthy volunteers were studied. The subjects received consecutive stepwise increasing target-controlled infusions of dexmedetomidine, remifentanil, and remifentanil with a fixed dexmedetomidine background concentration. Drug effects were measured using binary (yes or no) endpoints: no response to calling the subject by name, tolerance of shaking the patient while shouting the name ("shake and shout"), tolerance of deep trapezius squeeze, and tolerance of laryngoscopy. The drug effect was measured using the electroencephalogram-derived "Patient State Index." Pharmacokinetic-pharmacodynamic modeling related the administered dexmedetomidine and remifentanil concentration to these observed effects.

RESULTS

The binary endpoints were correlated with dexmedetomidine concentrations, with increasing concentrations required for increasing stimulus intensity. Estimated model parameters for the dexmedetomidine EC50 were 2.1 [90% CI, 1.6 to 2.8], 9.2 [6.8 to 13], 24 [16 to 35], and 35 [23 to 56] ng/ml, respectively. Age was inversely correlated with dexmedetomidine EC50 for all four stimuli. Adding remifentanil did not increase the probability of tolerance of any of the stimuli. The cerebral drug effect as measured by the Patient State Index was best described by the Hierarchical interaction model with an estimated dexmedetomidine EC50 of 0.49 [0.20 to 0.99] ng/ml and remifentanil EC50 of 1.6 [0.87 to 2.7] ng/ml.

CONCLUSIONS

Low dexmedetomidine concentrations (EC50 of 0.49 ng/ml) are required to induce sedation as measured by the Patient State Index. Sensitivity to dexmedetomidine increases with age. Despite falling asleep, the majority of subjects remained arousable by calling the subject's name, "shake and shout," or a trapezius squeeze, even when reaching supraclinical concentrations. Adding remifentanil does not alter the likelihood of response to graded stimuli.

Dexmedetomidine: present and future directions

Dexmedetomidine is a potent, highly selective α-2 adrenoceptor agonist, with sedative, analgesic, anxiolytic, sympatholytic, and opioid-sparing properties. Dexmedetomidine induces a unique sedative response, which shows an easy transition from sleep to wakefulness, thus allowing a patient to be cooperative and communicative when stimulated. Dexmedetomidine may produce less delirium than other sedatives or even prevent delirium. The analgesic effect of dexmedetomidine is not strong; however, it can be administered as a useful analgesic adjuvant. As an anesthetic adjuvant, dexmedetomidine decreases the need for opioids, inhalational anesthetics, and intravenous anesthetics. The sympatholytic effect of dexmedetomidine may provide stable hemodynamics during the perioperative period. Dexmedetomidine-induced cooperative sedation with minimal respiratory depression provides safe and acceptable conditions during neurosurgical procedures in awake patients and awake fiberoptic intubation. Despite the lack of pediatric labelling, dexmedetomidine has been widely studied for pediatric use in various applications. Most adverse events associated with dexmedetomidine occur during or shortly after a loading infusion. There are some case reports of dexmedetomidine-related cardiac arrest following severe bradycardia. Some extended applications of dexmedetomidine discussed in this review are promising, but still limited, and further research is required. The pharmacological properties and possible adverse effects of dexmedetomidine should be well understood by the anesthesiologist prior to use. Moreover, it is necessary to select patients carefully and to determine the appropriate dosage of dexmedetomidine to ensure patient safety.

Comparative Evaluation of the Effects of Pregabalin, Dexmedetomidine, and Their Combination on the Hemodynamic Response and Anesthetic Requirements in Patients undergoing Laparoscopic Cholecystectomy: A Randomized Double-Blind Prospective Study

Background

In this study, we evaluated the efficacy of premedication with dexmedetomidine, pregabalin, and dexmedetomidine-pregabalin combination for attenuating the haemodynamic stress response to laryngoscopy and intubation and pneumoperitoneum (primary outcome), and for reducing anaesthetic requirement (secondary outcome) in patients undergoing laparoscopic cholecystectomy.

Methods

Ninety ASA physical status classes I-II patients, between 18 to 65 years of age, of either sex, scheduled to undergo laparoscopic cholecystectomy were included in this randomised double blind study. Morbidly obese patients and those with history of hypertension, cardiac, renal, hepatic, endocrine or pulmonary dysfunction were excluded. Patients were randomized to three groups - Group P- received oral pregabalin (150 mg) one hour before induction and 100 mL of i.v normal saline (0.9%) over 10 minutes, 10 minutes before induction; Group D- received i.v dexmedetomidine (1 μg.kg^-1) prepared in 100 mL of 0.9% normal saline and given over 10 minutes, 10 minutes before induction, and an oral placebo tablet one hour before induction; and Group C-received a combination of oral pregabalin 75 mg one hour before induction, and IV dexmedetomidine (0.5 μg.kg^-1) prepared in 100 mL of 0.9% normal saline over 10 minutes, 10 minutes before induction.

Results

Dexmedetomidine significantly attenuated the stress response to laryngoscopy and intubation and pneumoperitoneum and reduced anaesthetic requirement as compared to the other two groups. Dexmedetomidine was associated with significantly lower mean arterial pressures and higher sedation score in the preoperative and postoperative period and significantly lower heart rate and arterial pressures and reduced anaesthetic requirement in the intraoperative period as compared to the other groups.

Conclusion

Dexmedetomidine is a valuable adjunct to the technique of balanced anaesthesia for maintaining haemodynamic stability.

Clinical Pharmacokinetics and Pharmacodynamics of Propofol

Propofol is an intravenous hypnotic drug that is used for induction and maintenance of sedation and general anaesthesia. It exerts its effects through potentiation of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) at the GABAA receptor, and has gained widespread use due to its favourable drug effect profile. The main adverse effects are disturbances in cardiopulmonary physiology. Due to its narrow therapeutic margin, propofol should only be administered by practitioners trained and experienced in providing general anaesthesia. Many pharmacokinetic (PK) and pharmacodynamic (PD) models for propofol exist. Some are used to inform drug dosing guidelines, and some are also implemented in so-called target-controlled infusion devices, to calculate the infusion rates required for user-defined target plasma or effect-site concentrations. Most of the models were designed for use in a specific and well-defined patient category. However, models applicable in a more general population have recently been developed and published. The most recent example is the general purpose propofol model developed by Eleveld and colleagues. Retrospective predictive performance evaluations show that this model performs as well as, or even better than, PK models developed for specific populations, such as adults, children or the obese; however, prospective evaluation of the model is still required. Propofol undergoes extensive PK and PD interactions with both other hypnotic drugs and opioids. PD interactions are the most clinically significant, and, with other hypnotics, tend to be additive, whereas interactions with opioids tend to be highly synergistic. Response surface modelling provides a tool to gain understanding and explore these complex interactions. Visual displays illustrating the effect of these interactions in real time can aid clinicians in optimal drug dosing while minimizing adverse effects. In this review, we provide an overview of the PK and PD of propofol in order to refresh readers' knowledge of its clinical applications, while discussing the main avenues of research where significant recent advances have been made.

Propofol-sparing effect of different concentrations of dexmedetomidine : Comparison of gender differences

Background

The pharmacodynamics of propofol are closely linked to gender. Dexmedetomidine can decrease propofol needs during propofol anesthesia. The aim of this study was to compare the gender differences on the calculated effect site median effective concentration (EC₅₀) of propofol for loss of consciousness (LOC) after pretreatment with different concentrations of dexmedetomidine.

Methods

In this study 60 male and 60 female patients were randomly allocated to receive dexmedetomidine at target plasma concentrations of 0.0 ng/ml (0.0 group), 0.4 ng/ml (0.4 group), 0.6 ng/ml (0.6 group) and 0.8 ng/ml (0.8 group). Propofol was administered after dexmedetomidine had been intravenously infused for 15 min. The propofol infusion was targeted to provide an initial effect-site concentration of 1.0 μg/ml, followed by increments by 0.2 μg/ml when the effect-site concentration and target concentration of propofol were in equilibrium until LOC was established, where LOC was defined by the observer’s assessment of alertness/sedation scale (OAA/S) score < 2.

Results

The calculated effect-site EC₅₀ of propofol LOC was higher in males than in females in the 0.0, 0.4, 0.6, and 0.8 groups (2.43 vs. 2.17, 1.99 vs. 1.82, 1.72 vs. 1.56 and 1.50 vs. 1.32 μg/ml, respectively, all p < 0.05). The hypnotic interaction between dexmedetomidine and propofol could be described with an additive model of pharmacodynamic interaction.

Conclusion

Gender significantly influenced the calculated effect-site EC₅₀ of propofol for LOC after pretreatment with different concentrations of intravenous dexmedetomidine. It was concluded that an additive interaction could describe the results seen. Thus, gender has to be considered when these drugs are co-administered.

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.

Tramadol vs dexmedetomidine for emergence agitation control in pediatric patients undergoing adenotonsillectomy with sevoflurane anesthesia: prospective randomized controlled clinical study

Background

This study was designed to compare the efficacy of an intraoperative single dose administration of tramadol and dexmedetomidine on hemodynamics and postoperative recovery profile including pain, sedation, emerge reactions in pediatric patients undergoing adenotonsillectomy with sevoflurane anesthesia.

Methods

Seventy-seven patient, aged 2–12, undergoing adenotonsillectomy with sevoflurane anesthesia was enrolled in this study. Patients were randomly assigned to receive either intravenous 2 mg/kg tramadol (Group T; n = 39) or 1 μg/kg dexmedetomidine (Group D; n = 38) after intubation. Heart rates (HR), mean arterial pressure (MAP) were recorded before induction, at induction and every 5 min after induction. Observational pain scores (OPS), pediatric anesthesia emergence delirium (PAED) scores, percentage of patients with OPS ≥ 4 or PAED scale items 4 or 5 with an intensity of 3 or 4, and Ramsay sedation scores (RSS) were recorded on arrival to the postoperative care unit (PACU) and at 5, 10, 15, 30, 45, 60 min. Extubation time and time to reach Alderete score > 9 were recorded.

Results

Dexmedetomidine significantly decreased the HR and MAP 10 and 15 min after induction; increased the RSS 15, 30 and 45 min after arrival to PACU. OPS and PAED scores and percentage of patients with OPS ≥ 4 or PAED scale items 4 or 5 with an intensity of 3 or 4 in both groups did not show any significant difference. Extubation time and time to have Alderete score > 9 was significantly longer in Group D.

Conclusion

Both tramadol and dexmedetomidine were effective for controlling pain and emergence agitation. When compared with tramadol intraoperative hypotension, bradycardia and prolonged sedation were problems related with dexmedetomidine administration.

Trial registration

Retrospectively registered, registration number: ISRCTN89326952 registration date: 14.07.2016

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.

Dexmedetomidine in the Treatment of Withdrawal Syndromes in Cardiothoracic Surgery Patients

Dexmedetomidine (Precedex, Abbott Laboratories, Abbott Park, IL) is an• 2adrenergic agonist that possesses a high ratio of specificity for the• 2versus the• 1receptor. It is currently approved for the provision of sedation during mechanical ventilation in adults. Given previous experience with clonidine for the treatment of substance withdrawal and the preliminary anecdotal experience with dexmedetomidine, it appears that dexmedetomidine may be a useful agent for treatment of substance withdrawal in the intensive care setting. The authors present their experience with the use of dexmedetomidine to control withdrawal behavior in 3 patients following cardiothoracic surgery. Previous reports regarding the use of dexmedetomidine to treat withdrawal and its potential application in this clinical arena are reviewed.

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.

Comparison between dexmedetomidine and fentanyl on intubation conditions during awake fiberoptic bronchoscopy: A randomized double-blind prospective study

Background and Aims:

Various drugs are used for providing favorable intubation conditions during awake fiberoptic intubation (AFOI). However, most of them cause respiratory depression and airway obstruction leading to hypoxemia. The aim of this study was to compare intubation conditions, and incidence of desaturation between dexmedetomidine and fentanyl group during AFOI.

Material and Methods:

This randomized double-blind prospective study was conducted on a total of 60 patients scheduled for elective laparotomies who were randomly allocated into two groups: Group A received dexmedetomidine 1 mcg/kg and Group B received fentanyl 2 mcg/kg over 10 min. Patients in both groups received glycopyrrolate 0.2 mg intravenous, nebulization with 2% lidocaine 4 ml over 20 min and 10% lidocaine spray before undergoing AFOI. Adequacy of intubation condition was evaluated by cough score and post-intubation score. Incidence of desaturation, hemodynamic changes and sedation using Ramsay sedation scale (RSS) were noted and compared between two groups.

Results:

Cough Score (1-4), post-intubation Score (1-3) and RSS (1-6) were significantly favorable (P < 0.0001) along with minimum hemodynamic responses to intubation (P < 0.05) and less oxygen desaturation (P < 0.0001) in Group A than Group B.

Conclusion:

Dexmedetomidine is more effective than fentanyl in producing better intubation conditions, sedation along with hemodynamic stability and less desaturation during AFOI.

Does premedication with dexmedetomidine provide perioperative hemodynamic stability in hypertensive patients?

Background

Perioperative hemodynamic fluctuations are seen more often in hypertensive patients than in normotensive patients. The purpose of our study was to investigate the perioperative hemodynamic effects of dexmedetomidine and midazolam used for premedication in hypertensive patients relative to each other and in comparison to normotensive patients.

Methods

One-hundred-forty female, normotensive or hypertensive patients undergoing myomectomies or hysterectomies. They were randomly enrolled into the subgroups: Group ND (normotensive-dexmedetomidine); Group HD (hypertensive-dexmedetomine); Group NM (normotensive-midazolam); Group HM (hypertensive- midazolam). Dexmedetomidine was administered at a concentration of 0.5 μg.kg⁻¹, and midazolam was administered at a concentration of 0.025 μg.kg⁻¹ via intravenous (IV) infusion before the induction of anaesthesia. Haemodynamic parameters were recorded at several times (T_beginning, T_{preop5 min}, T_{preop 10 min}, T_induction, T_intubation, T_{intubation5 min}, T_{initial surgery}, T_{surgery 15 min}, T_{surgery 30 min}, T_extubation, T_{extubation 5 min}). Propofol amount for induction, time between induction and initial surgery, demand of antihypertensive therapy, rescue atropine were recorded. Quantitative clinical and demographic characteristics were compared using One Way ANOVA. The values were compared using One-way Analysis of Variance. Additionally periodic variations were examined by One way Repeated Measures Analysis of Variance for groups separately.

Results

SBP was significantly different between normotensive and hypertensive groups at the following time points: T_{preop 5 min}, T_{preop 10 min}, T_induction, T_intubation, T_{intubation 5 min} and T_{initial surgery}. MBP was significantly different in the hypertensive groups at T_induction, T_intubation, T_{intubation 5 min,} T_{initial surgery}, T_{surgery 15 min}, T_{surgery 30 min,} T_extubation and T_{extubation 5 min}. The perioperative requirements for antihypertensive drugs were significantly higher in Group HM.

Conclusion

In the hypertensive patients, dexmedetomidine premedication provides better hemodynamic stability compared with midazolam, and because it decreases the antihypertensive requirements, its use might be beneficial.

Trial registration

Trial registration: Clinicaltrials.gov identifier: NCT02058485.

Induced hypotension for functional endoscopic sinus surgery: A comparative study of dexmedetomidine versus esmolol

OBJECTIVE

A comparative study to evaluate the efficacy of dexmedetomidine as a hypotensive agent in comparison to esmolol in Functional Endoscopic Sinus Surgery (FESS).

METHODS

Forty patients ASA I or II scheduled for FESS were equally randomly assigned to receive either dexmedetomidine 1 μg/Kg over 10 min before induction of anesthesia followed by 0.4-0.8 μg/Kg/h infusion during maintenance (DEX group), or esmolol, loading dose 1mg/kg was infused over one min followed by 0.4-0.8 mg/kg/h infusion during maintenance (E group) to maintain mean arterial blood pressure (MAP) between (55-65 mmHg). General anesthesia was maintained with sevoflurane 2%-4%. The surgical field was assessed using Average Category Scale and average blood loss was calculated. Hemodynamic variables (MAP and HR); arterial blood gas analysis; plasma cortisol level; intraoperative fentanyl consumption; Emergence time and total recovery from anesthesia (Aldrete score ≥9) were recorded. Sedation score was determined at 15, 30, 60 min after tracheal extubation and time to first analgesic request was recorded.

RESULT

Both DEX group and E group reached the desired MAP (55-65 mmHg) with no intergroup differences in MAP or HR. The for the quality of the surgical filed in the range of MAP (55-65 mmHg) were <=2 with no significant differences between group scores during hypotensive period. Mean intraoperative fentanyl consumption was significantly lower in DEX group than E group. Cortisol level showed no significant changes between or within groups. No significant changes were observed in arterial blood gases. Emergence time and time to achieve Aldrete score ≥9 were significantly lower in E group compared with DEX group. The sedation score were significantly lower in E group compared with DEX group at 15 and 30 minutes postoperatively. Time to first analgesic request was significantly longer in DEX group.

CONCLUSION

Both dexmedetomidine or esmolol with sevoflurane are safe agents for controlled hypotension and are effective in providing ideal surgical field during FESS. Compared with esmolol, dexmedetomidine offers the advantage of inherent analgesic, sedative and anesthetic sparing effect.

Dexmedetomidine controls supraventricular tachycardia following cardiac surgery in a child

Dexmedetomidine is an α2-adrenergic agonist which initially received US Food and Drug Administration (FDA) approval in the United States in 1999 for the sedation of adults during mechanical ventilation and then in 2009 for monitored anesthesia care. Although generally viewed as an adverse effect, bradycardia and the negative chronotropic effects may be beneficial in certain patient populations and have occasionally been used as a therapeutic maneuver. We present a case summary describing intraoperative and postoperative use of dexmedetomidine to treat and control supraventricular tachycardia in a 5-year-old boy undergoing surgical repair of a large atrial septal defect. The specific effects of dexmedetomidine on the cardiac conduction system are reviewed and previous reports of its use as a therapeutic agent for the treatment of perioperative tachyarrhythmias are discussed.

Nasotracheal fiberoptic intubation: patient comfort, intubating conditions and hemodynamic stability during conscious sedation with different doses of dexmedetomidine

The study aims to evaluate the efficacy of two doses of dexmedetomidine for sedation during awake fiberoptic intubation (AFOI). The study was designed in a prospective, randomized, double-blinded manner and carried out in an academic medical university. Forty young co-operative patients aged 15–45 years of either sex belonging to ASA class I-II, planned for elective maxillo-facial surgery formed the study group. All patients received midazolam 0.05 mg/kg, glycopyrrolate 0.2 mg, ondansetron 4 mg, and ranitidine 50 mg IV 15 min before as premedication, oxygen by nasal cannula, and topical local anesthetics to the airway. Patients were randomly assigned to one of the groups; dexmedetomedine 1 μg/kg IV (Group L), or dexmedetomidine 1.5 μg/kg IV (Group H). Observer’s Assessment of Alertness/Sedation (OAA/S) was assessed. Primary outcome measurements were: HR, MAP, SpO₂ and EtCO₂ and secondary outcome measurements were: intubation scores by vocal cord movement, coughing and limb movement, fiberoptic intubation comfort score, nasotracheal intubation score and airway obstruction score. On the first post-operative day, recall, level of discomfort during fiberoptic intubation, adverse events and satisfaction score were also assessed. There were no significant hemodynamic differences between the two groups. OAA/S was significantly better with dexmedetomidine 1.5 μg/kg (p < 0.05) and patients were significantly calmer, more cooperative and satisfied during awake fiberoptic intubation with dexmedetomidine 1.5 μg/kg with fewer transient adverse effects. Dexmedetomidine 1.5 μg/kg proved to be more effective for sedation for awake fiberoptic intubation.

Isoflurane but not halothane minimum alveolar concentration-sparing response of dexmedetomidine is enhanced in rats chronically treated with selective α2-adrenoceptor agonist

Halothane minimum alveolar concentration (MAC)-sparing response is preserved in rats rendered tolerant to the action of dexmedetomidine. It has been shown that halothane and isoflurane act at different sites to produce immobility. The authors studied whether there was any difference between halothane and isoflurane MAC-sparing effects of dexmedetomidine in rats after chronic administration of a low dose of this drug. Twenty-four female Wistar rats were randomly allocated into four groups of six animals: two groups received 10 μg/kg intraperitoneal dexmedetomidine for five days (treated groups) and the other two groups received intraperitoneal saline solution for five days (naive groups) prior to halothane or isoflurane MAC determination (one treated and one naive group of halothane and one treated and one naive group of isoflurane). Halothane or isoflurane MAC determination was performed before (basal) and 30 min after an intraperitoneal dose of 30 μg/kg of dexmedetomidine (post-dex) from alveolar gas samples at the time of tail clamp. Administration of an acute dose of dexmedetomidine to animals that had chronically received dexmedetomidine resulted in a MAC-sparing effect that was similar to that seen in naive animals for halothane; however, the same treatment increased the MAC-sparing response of dexmedetomidine for isoflurane. Isoflurane but not halothane MAC-sparing response of acutely administered dexmedetomidine is enhanced in rats chronically treated with this drug.

Dexmedetomidine and hydroxyzine synergistically potentiate the hypnotic activity of propofol in mice

PURPOSE

Investigation into the characteristics of anesthetic interactions may provide clues to anesthesia mechanisms. Dexmedetomidine, an α(2)-adrenergic receptor agonist, has become a popular sedative in intensive care, and hydroxyzine, a histamine receptor antagonist, is well known as a tranquilizing premedication for anesthesia. However, no experimental or pharmacological evaluation has been reported concerning their combination with propofol. Thus, we studied their combined effect with a hypnotic dose of propofol in ddY mice.

METHODS

Male adult mice were intravenously administered either dexmedetomidine (30 μg/kg) or hydroxyzine (5 mg/kg) with propofol (3.75-10 mg/kg) to induce hypnosis, defined as a loss of the righting reflex (LRR). Other mice were intravenously administered propofol, dexmedetomidine (300 μg/kg), or hydroxyzine (50 mg/kg) alone, and subsequent behavioral changes were observed. The 50% effective dose (ED(50)) for LRR was calculated, and the duration of LRR was determined.

RESULTS

The hypnotic dose of propofol was 9.95 ± 1.04 mg/kg (ED(50) ± SEM) without combination. Dexmedetomidine and hydroxyzine reduced the ED(50) of propofol to 5.32 ± 0.57 and 5.63 ± 0.57 mg/kg, respectively. Coadministration of dexmedetomidine significantly extended LRR duration compared with propofol alone, whereas hydroxyzine significantly shortened LRR duration. A maximal dose of dexmedetomidine or hydroxyzine alone did not induce hypnosis.

CONCLUSIONS

Dexmedetomidine and hydroxyzine demonstrated no hypnotic action alone; however, their coadministration potentiated the hypnotic activity of propofol. Although reduction in the dose of propofol was similar, only dexmedetomidine prolonged the duration of hypnosis.

Dexmedetomidine: applications for the pediatric patient with congenital heart disease

This study aimed to provide a general description of the cardiovascular and hemodynamic effects of dexmedetomidine and an evidence-based review of the literature regarding its use in infants and children with congenital heart disease (CHD). A computerized bibliographic search of the literature on dexmedetomidine use in infants and children with CHD was performed. The cardiovascular effects of dexmedetomidine have been well studied in animal and adult human models. Adverse cardiovascular effects include occasional episodes of bradycardia, with rare reports of sinus pause or cardiac arrest. Both hypotension and hypertension also have been reported. The latter is related to peripheral α(2B) agonism leading to vasoconstriction. No adverse effects on the pulmonary vasculature have been noted even in patients with preexisting pulmonary hypertension. Although there are no direct effects on myocardial function, decreased cardiac output may result from changes in heart rate or increases in afterload. Although not currently Food and Drug Administration (FDA)-approved for the pediatric population, findings have shown dexmedetomidine to be effective in various clinical scenarios of patients with CHD including sedation during mechanical ventilation, prevention of procedure-related anxiety, prevention of emergence delirium and shivering after anesthesia, and treatment of withdrawal. Although dexmedetomidine may have limited utility for painful or invasive procedures, preliminary data suggest that the addition of ketamine to the regimen may offer benefits. When used during the perioperative period, additional benefits include blunting of the sympathetic stress response with a reduction of endogenous catecholamine release, a decrease in intraoperative anesthetic requirements, and a limitation of postoperative opioid requirements.

Acute hemodynamic changes after rapid intravenous bolus dosing of dexmedetomidine in pediatric heart transplant patients undergoing routine cardiac catheterization

BACKGROUND

Dexmedetomidine is a highly selective α(2)-adrenoceptor agonist with sedative, anxiolytic, and analgesic properties that has minimal effects on respiratory drive. Its sedative and hypotensive effects are mediated via central α(2A) and imidazoline type 1 receptors while activation of peripheral α(2B)-adrenoceptors result in an increase in arterial blood pressure and systemic vascular resistance. In this randomized, prospective, clinical study, we attempted to quantify the short-term hemodynamic effects resulting from a rapid i.v. bolus administration of dexmedetomidine in pediatric cardiac transplant patients.

METHODS

Twelve patients, aged 10 years or younger, weighing ≤40 kg, presenting for routine surveillance of right and left heart cardiac catheterization after cardiac transplantation were enrolled. After an inhaled or i.v. induction, the tracheas were intubated and anesthesia was maintained with 1 minimum alveolar concentration of isoflurane in room air, fentanyl (1 μg/kg), and rocuronium (1 mg/kg). At the completion of the planned cardiac catheterization, 100% oxygen was administered. After recording a set of baseline values that included heart rate (HR), systolic blood pressure, diastolic blood pressure, central venous pressure, systolic pulmonary artery pressure, diastolic pulmonary artery pressure, pulmonary artery wedge pressure, and thermodilution-based cardiac output, a rapid i.v. dexmedetomidine bolus of either 0.25 or 0.5 μg/kg was administered over 5 seconds. The hemodynamic measurements were repeated at 1 minute and 5 minutes.

RESULTS

There were 6 patients in each group. Investigation suggested that systolic blood pressure, diastolic blood pressure, systolic pulmonary artery pressure, diastolic pulmonary artery pressure, pulmonary artery wedge pressure, and systemic vascular resistance all increased at 1 minute after rapid i.v. bolus for both doses and decreased significantly to near baseline for both doses by 5 minutes. The transient increase in pressures was more pronounced in the systemic system than in the pulmonary system. In the systemic system, there was a larger percent increase in the diastolic pressures than the systolic pressures. Cardiac output, central venous pressure, and pulmonary vascular resistance did not change significantly. HR decreased at 1 minute for both doses and was, within the 0.5 μg/kg group, the only hemodynamic variable still changed from baseline at the 5-minute time point.

CONCLUSION

Rapid i.v. bolus administration of dexmedetomidine in this small sample of children having undergone heart transplants was clinically well tolerated, although it resulted in a transient but significant increase in systemic and pulmonary pressure and a decrease in HR. In the systemic system, there is a larger percent increase in the diastolic pressures than the systolic pressures and, furthermore, these transient increases in pressures were more pronounced in the systemic system than in the pulmonary system.

Dynamic assessment of baroreflex control of heart rate during induction of propofol anesthesia using a point process method

In this article, we present a point process method to assess dynamic baroreflex sensitivity (BRS) by estimating the baroreflex gain as focal component of a simplified closed-loop model of the cardiovascular system. Specifically, an inverse Gaussian probability distribution is used to model the heartbeat interval, whereas the instantaneous mean is identified by linear and bilinear bivariate regressions on both the previous R-R intervals (RR) and blood pressure (BP) beat-to-beat measures. The instantaneous baroreflex gain is estimated as the feedback branch of the loop with a point-process filter, while the RR-->BP feedforward transfer function representing heart contractility and vasculature effects is simultaneously estimated by a recursive least-squares filter. These two closed-loop gains provide a direct assessment of baroreflex control of heart rate (HR). In addition, the dynamic coherence, cross bispectrum, and their power ratio can also be estimated. All statistical indices provide a valuable quantitative assessment of the interaction between heartbeat dynamics and hemodynamics. To illustrate the application, we have applied the proposed point process model to experimental recordings from 11 healthy subjects in order to monitor cardiovascular regulation under propofol anesthesia. We present quantitative results during transient periods, as well as statistical analyses on steady-state epochs before and after propofol administration. Our findings validate the ability of the algorithm to provide a reliable and fast-tracking assessment of BRS, and show a clear overall reduction in baroreflex gain from the baseline period to the start of propofol anesthesia, confirming that instantaneous evaluation of arterial baroreflex control of HR may yield important implications in clinical practice, particularly during anesthesia and in postoperative care.

Comparison of patient-controlled analgesia with and without dexmedetomidine following spine surgery in children

STUDY OBJECTIVE

To evaluate the effect of dexmedetomidine as an adjunct to patient-controlled analgesia (PCA) with morphine.

DESIGN

Retrospective comparison.

SETTING

University-affiliated children's hospital.

MEASUREMENTS

The medical charts of 131 children with idiopathic scoliosis (IS) and NMS who had major spine surgery were reviewed. Out of 131, postoperatively 94 children received PCA with morphine alone (PCA group) and the remaining 37 children received PCA morphine and dexmedetomidine infusion at 0.4 mcg/kg/hour for 24 hours (PCA + Dex group). Preoperative, intraoperative, and postoperative morphine use data were collected.

MAIN RESULTS

Intraoperative use of morphine was similar in children with IS and NMS. However, patients with IS used more morphine than patients with NMS on the first, second and third postoperative days in both groups. In children with IS, use of morphine on the second postoperative day was significantly higher in the PCA + Dex group (73 mg [50.5, 110.5]) than the PCA alone group (54 mg [36, 69], P = 0.03). The overall frequency of all perioperative complications was more in the PCA alone group (40% vs. 32%) than the PCA + Dex group.

CONCLUSION

Postoperative 24-hour dexmedetomidine infusion as an adjunct to PCA with opioids might have a morphine-sparing effect as evidenced by the increase in morphine use on postoperative day 2 after the dexmedetomidine infusion was stopped.

Dexmedetomidine to Control Agitation and Delirium from Toxic Ingestions in Adolescents

Dexmedetomidine is an α2-adrenergic agonist that is approved by the Food and Drug Administration for the provision of short term (less than 24 hours) sedation of adults during mechanical ventilation. Given its beneficial physiologic effects including sedation and anxiolysis, various applications have been reported in the pediatric-aged patient. We report the use of dexmedetomidine to control the agitation and violent behavior which resulted from the ingestion of illicit drugs in 3 adolescents. The utility of dexmedetomidine in these scenarios is discussed and its potential beneficial effects on cardiovascular and respiratory function are reviewed.

Evaluation of Adverse Events Noted in Children Receiving Continuous Infusions of Dexmedetomidine in the Intensive Care Unit

OBJECTIVES

Dexmedetomidine is an α2-adrenergic receptor agonist with sedative and analgesic effects in mechanically ventilated adults and children. Safety and efficacy data are limited in children. The purpose of this study is to retrospectively identify the incidence and types of adverse events noted in children receiving continuous infusions of dexmedetomidine and evaluate potential risk factors for adverse events.

METHODS

Between July 1, 2006, and July 31, 2007, data were collected on all children (&lt; 18 years) who received continuous infusions of dexmedetomidine. Data collection included demographics, dexmedetomidine regimen, and type/number of adverse events. The primary endpoint was the total number of adverse events noted, including: transient hypertension, hypotension, neurological manifestations, apnea, and bradycardia. Secondary endpoints included categorization of each type of adverse event and an assessment of risk factors. A logistic regression model was used to assess the relationship of adverse events with independent variables including length of ICU stay, cumulative dose, peak infusion rate, duration of therapy, PRISM III score, and bolus dose.

RESULTS

Thirty-six patients received dexmedetomidine representing 41 infusions. The median age was 16 months (range, 0.1–204 months) and median PRISM III score was 2 (range, 0–18). Eighteen (43.9%) patients received a bolus dose of dexmedetomidine. The median cumulative dose (mcg/kg) and peak dose (mcg/kg/hr) were 8.5 (range, 2.2–193.7) and 0.5 (range, 0.2–0.7), respectively. Dexmedetomidine was continued for a median of 20 (range, 3–263) hours. Six (14.6%) patients were slowly tapered off the continuous infusions. Twenty-one adverse events were noted in 17 patients, including 4 neurologic manifestations. Fourteen patients required interventions for adverse events. ICU length of stay was the only independent risk factor (p=0.036) for development of adverse events.

CONCLUSIONS

Several potential adverse events were noted with dexmedetomidine continuous infusions including possible neurological manifestations. Further studies are needed looking at adverse events associated with dexmedetomidine use in the pediatric population.

Intravenous dexmedetomidine, but not midazolam, prolongs bupivacaine spinal anesthesia

PURPOSE

Midazolam has only sedative properties. However, dexmedetomidine has both analgesic and sedative properties that may prolong the duration of sensory and motor block obtained with spinal anesthesia. This study was designed to compare intravenous dexmedetomidine with midazolam and placebo on spinal block duration, analgesia, and sedation in patients undergoing transurethral resection of the prostate.

METHODS

In this double-blind randomized placebo-controlled trial, 75 American Society of Anesthesiologists' I and II patients received dexmedetomidine 0.5 microg . kg(-1), midazolam 0.05 mg . kg(-1), or saline intravenously before spinal anesthesia with bupivacaine 0.5% 15 mg (n = 25 per group). The maximum upper level of sensory block and sensory and motor regression times were recorded. Postoperative analgesic requirements and sedation were also recorded.

RESULTS

Sensory block was higher with dexmedetomidine (T 4.6 +/- 0.6) than with midazolam (T 6.4 +/- 0.9; P < 0.001) or saline (T 6.4 +/- 0.8; P < 0.001). Time for sensory regression of two dermatomes was 145 +/- 26 min in the dexmedetomidine group, longer (P < 0.001) than in the midazolam (106 +/- 39 min) or the saline (97 +/- 27 min) groups. Duration of motor block was similar in all groups. Dexmedetomidine also increased the time to first request for postoperative analgesia (P < 0.01 compared with midazolam and saline) and decreased analgesic requirements (P < 0.05). The maximum Ramsay sedation score was greater in the dexmedetomidine and midazolam groups than in the saline group (P < 0.001).

CONCLUSION

Intravenous dexmedetomidine, but not midazolam, prolonged spinal bupivacaine sensory blockade. It also provided sedation and additional analgesia.

Preliminary experience with dexmedetomidine for monitored anesthesia care during ENT surgical procedures

Dexmedetomidine is an alpha2-adrenergic agonist that produces anxiolysis, amnesia, sedation, potentiation of opioid analgesia, and sympatholysis. It is currently approved by the U.S. Food & Drug Administration for the sedation of adults in the intensive care setting for up to 24 hours during mechanical ventilation. Given its beneficial sedative and anxiolytic properties and limited adverse effect profile, it has been used in several other clinical scenarios. The authors present their experience using dexmedetomidine for monitored anesthesia care (MAC) during "awake" ENT procedures such as thyroplasty, a procedure requiring a patient to verbalize when requested but to otherwise remain immobile to allow for completion of the procedure, and in a patient with post-polio syndrome with poor pulmonary reserve requiring esophagoscopy with dilation and botulinum toxin injection for cricopharyngeal dysfunction. Our preliminary experience suggests that dexmedetomidine provides effective sedation as the primary agent for MAC during such procedures in adult patients. The end-organ effects of dexmedetomidine and previous reports of its use during MAC are reviewed.

Determination of the pharmacodynamic interaction of propofol and dexmedetomidine during esophagogastroduodenoscopy in children

OBJECTIVES

Propofol is a sedative-hypnotic drug commonly used to anesthetize children undergoing esophagogastroduodenoscopy (EGD). Dexmedetomidine is a highly selective alpha-2 adrenergic receptor agonist that has been utilized in combination with propofol to provide anesthesia. There is currently no information regarding the effect of intravenous dexmedetomidine on the propofol plasma concentration-response relationship during EGD in children. This study aimed to investigate the pharmacodynamic interaction of propofol and dexmedetomidine when used in combination for children undergoing EGD.

METHODS

A total of 24 children undergoing EGD, ages 3-10 years, were enrolled in this study. Twelve children received dexmedetomidine 1 microg x kg(-1) given over 10 min as well as a continuous infusion of propofol delivered by a computer-assisted target-controlled infusion (TCI) system with target plasma concentrations ranging from 2.8 to 4.0 microg x ml(-1) (DEX group). Another group of 12 children undergoing EGD also received propofol administered by TCI targeting comparable plasma concentrations without dexmedetomidine (control group). We used logistic regression to predict plasma propofol concentrations at which 50% of the patients exhibited minimal response to stimuli (EC50 for anesthesia).

RESULTS

The EC50 +/- SE values in the control and DEX groups were 3.7 +/- 0.4 microg x ml(-1) and 3.5 +/- 0.2 microg x ml(-1), respectively. There was no significant shift in the propofol concentration-response curve in the presence of dexmedetomidine.

CONCLUSION

The EC50 of propofol required to produce adequate anesthesia for EGD in children was unaffected by a concomitant infusion of dexmedetomidine 1 microg x kg(-1) given over 10 min.

Effects of dexmedetomidine on propofol and remifentanil infusion rates during total intravenous anesthesia for spine surgery in adolescents

INTRODUCTION

Total intravenous anesthesia with propofol and a synthetic opioid is a frequently chosen anesthetic technique for posterior spinal fusion. Despite its utility, adverse effects may occur with high or prolonged propofol dosing regimens including delayed awakening. The current study investigated the propofol-sparing effects of the concomitant administration of the alpha(2)-adrenergic agonist, dexmedetomidine, during spinal fusion surgery in adolescents.

METHODS

The surgical database of the department of orthopedic surgery was searched and patients (12-21 years of age) were identified who had undergone spinal fusion for either idiopathic or neuromuscular scoliosis during the past 24 months. Patients were assigned to two groups. Group 1 included patients anesthetized with propofol and remifentanil and group 2 included patients anesthetized with dexmedetomidine, propofol, and remifentanil. In the latter group, dexmedetomidine was administered as a continuous infusion of 0.5 microg.kg(-1).h(-1) started after the induction of anesthesia without a loading dose. Propofol was adjusted to maintain the bispectral index (BIS) number at 40-50 and remifentanil was adjusted to maintain the mean arterial pressure (MAP) at 50-65 mmHg. Labetolol or hydralazine was used if the MAP could not be maintained at 50-65 mmHg with remifentanil up to a maximum dose of 0.6 microg/kg/min. Statistical analysis included a nonpaired t-test for parametric data (age, weight, remifentanil/propofol infusion requirements, and heart rate/blood pressure values). A nonparametric statistical analysis (Dunn) was used to compare BIS numbers. Parametric data are presented as the mean +/- SD while nonparametric data are presented as the median and the 95th percentile confidence intervals.

RESULTS

Twelve patients received propofol-remifentanil-dexmedetomidine and 24 received propofol-remifentanil. There were no differences in the demographic data, BIS numbers or hemodynamic parameters between the two groups. There was a reduction in the propofol infusion requirements in patients who also received dexmedetomidine (71 +/- 11 microg.kg(-1).min(-1)) compared with those receiving only propofol-remifentanil (101 +/- 33 microg.kg(-1).min(-1), P = 0.0045). No difference was noted in the remifentanil infusion requirements or the use of supplemental agents (hydralazine and labetolol) to maintain controlled hypotension.

CONCLUSION

The concomitant use of dexmedetomidine in patients undergoing spinal fusion reduces propofol infusion requirements when compared with those patients receiving only propofol and remifentanil.

Effects of dexmedetomidine on intraoperative motor and somatosensory evoked potential monitoring during spinal surgery in adolescents

BACKGROUND

Dexmedetomidine may be a useful agent as an adjunct to an opioid-propofol total intravenous anesthesia (TIVA) technique during posterior spinal fusion (PSF) surgery. There are limited data regarding its effects on somatosensory (SSEPs) and motor evoked potentials (MEPs).

METHODS

The data presented represent a retrospective review of prospectively collected quality assurance data. When the decision was made to incorporate dexmedetomidine into the anesthetic regimen for intraoperative care of patients undergoing PSF, a prospective evaluation of its effects on SSEPs and MEPs was undertaken. SSEPs and MEPs were measured before and after the administration of dexmedetomidine in a cohort of pediatric patients undergoing PSF. Dexmedetomidine (1 microg x kg(-1) over 20 min followed by an infusion of 0.5 microg x kg(-1) x h(-1)) was administered at the completion of the surgical procedure, but prior to wound closure as an adjunct to TIVA which included propofol and remifentanil, adjusted to maintain a constant depth of anesthesia as measured by a BIS of 45-60.

RESULTS

The cohort for the study included nine patients, ranging in age from 12 to 17 years, anesthetized with remifentanil and propofol. In the first patient, dexmedetomidine was administered in conjunction with propofol at 110 microg x kg(-1) x min(-1) which resulted in a decrease in the bispectral index from 58 to 31. Although no significant effect was noted on the SSEPs (amplitude or latency) or the MEP duration, there was a decrease in the MEP amplitude. The protocol was modified so that the propofol infusion was incrementally decreased during the dexmedetomidine infusion to achieve the same depth of anesthesia. In the remaining eight patients, the bispectral index was 52 +/- 6 at the start of the dexmedetomidine loading dose and 49 +/- 4 at its completion (P = NS). There was no statistically significant difference in the MEPs and SSEPs obtained before and at completion of the dexmedetomidine loading dose.

CONCLUSION

Using the above-mentioned protocol, dexmedetomidine can be used as a component of TIVA during PSF without affecting neurophysiological monitoring.