Receptor subtype and dose dependence of dexmedetomidine-induced accumulation of [14C]glutamine in astrocytes suggests glial involvement in its hypnotic-sedative and anesthetic-sparing effects

Efficacy of peritonsillar infiltration with dexmedetomidine versus tramadol in comparison to placebo for pain control and sedation after tonsillectomy in pediatric patients: A randomized clinical trial

Objective

This article aimed to assess the efficacy of peritonsillar infiltration with dexmedetomidine-ropivacaine versus tramadol-ropivacaine for pain control and sedation after tonsillectomy in pediatric patients.

Materials and Methods

This double-blind clinical trial recruited 99 eligible children (4-8 years old) undergoing tonsillectomy and assigned to three block-randomized groups, receiving dexmedetomidine-ropivacaine (group A), tramadol-ropivacaine (group B), or placebo-ropivacaine (group C). The vital signs included blood pressure, heart rate, and SaO2 before anesthesia induction, during surgery at regular intervals until 24 h after surgery. The duration of surgery and recovery, complications, and analgesic consumption were recorded and pain scores were measured by Children's Hospital of Eastern Ontario Pain Scale (CHEOPS) and Oucher scales as well as sedation scores by the Wilson sedation scale. Data were analyzed within SPSS 20 at a significance level of 0.05.

Results

The lowest pain scores were measured by the CHEOPS scale in the dexmedetomidine-ropivacaine group (P < 0.05). Statistically significant difference was observed in the CHEOPS pain score between the first two groups at 30 min, 1 h, 2 h, and 4 h after surgery (P < 0.01). The differences were revealed in the Oucher pain assessments among all groups from the time of recovery to four postoperative hours (P < 0.05), with the lowest in the dexmedetomidine-ropivacaine group whose sedation score was greater during recovery and 5 min after surgery (P < 0.05). Subjects in tramadol group had six cases of dizziness and nausea, while no side effects were observed in two other groups (P < 0.05). Only seven participants receiving dexmedetomidine required acetaminophen, but 29 in the tramadol group and all in the placebo group demanded to receive acetaminophen (P = 0.001).

Conclusion

The authors concluded that dexmedetomidine as an adjuvant to ropivacaine has better performance in local infiltration for intra- and post-tonsillectomy analgesia and postoperative sedation, without any special side effects (like the placebo group), and that it hence is recommended to be used for local infiltration during tonsillectomy.

Sedative Properties of Dexmedetomidine Are Mediated Independently from Native Thalamic Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel Function at Clinically Relevant Concentrations

Dexmedetomidine is a selective α₂-adrenoceptor agonist and appears to disinhibit endogenous sleep-promoting pathways, as well as to attenuate noradrenergic excitation. Recent evidence suggests that dexmedetomidine might also directly inhibit hyperpolarization-activated cyclic-nucleotide gated (HCN) channels. We analyzed the effects of dexmedetomidine on native HCN channel function in thalamocortical relay neurons of the ventrobasal complex of the thalamus from mice, performing whole-cell patch-clamp recordings. Over a clinically relevant range of concentrations (1-10 µM), the effects of dexmedetomidine were modest. At a concentration of 10 µM, dexmedetomidine significantly reduced maximal I_h amplitude (relative reduction: 0.86 [0.78-0.91], n = 10, and p = 0.021), yet changes to the half-maximal activation potential V_1/2 occurred exclusively in the presence of the very high concentration of 100 µM (-4,7 [-7.5--4.0] mV, n = 10, and p = 0.009). Coincidentally, only the very high concentration of 100 µM induced a significant deceleration of the fast component of the HCN activation time course (τ_fast: +135.1 [+64.7-+151.3] ms, n = 10, and p = 0.002). With the exception of significantly increasing the membrane input resistance (starting at 10 µM), dexmedetomidine did not affect biophysical membrane properties and HCN channel-mediated parameters of neuronal excitability. Hence, the sedative qualities of dexmedetomidine and its effect on the thalamocortical network are not decisively shaped by direct inhibition of HCN channel function.

Alpha and beta adrenoceptors activate interleukin-6 transcription through different pathways in cultured astrocytes from rat spinal cord

In brain astrocytes, noradrenaline (NA) has been shown to up-regulate IL-6 production via β-adrenoceptors (ARs). However, the underlying intracellular mechanisms for this regulation are not clear, and it remains unknown whether α-ARs are involved. In this study, we investigated the AR-mediated regulation of IL-6 mRNA levels in the cultured astrocytes from rat spinal cord. NA, the α1-agonist phenylephrine, and the β-agonist isoproterenol increased IL-6 mRNA levels. The phenylephrine-induced IL-6 increase was accompanied by an increase in ERK phosphorylation, and these effects were blocked by inhibitors of PKC and ERK. The isoproterenol-induced IL-6 increase was accompanied by an increase in CREB phosphorylation, and these effects were blocked by a PKA inhibitor. Our results indicate that IL-6 increases by α1- and β-ARs are mediated via the PKC/ERK and cAMP/PKA/CREB pathways, respectively. Moreover, conditioned medium collected from astrocytes treated with the α2-AR agonist dexmedetomidine, increased IL-6 mRNA in other astrocytes. In this study, we elucidate that α1- and α2-ARs, in addition to β-ARs, promote IL-6 transcription through different pathways in spinal cord astrocytes.

Effects of adding dexmedetomidine, fentanyl, and verapamil to 0.5% ropivacaine on onset and duration of sensory and motor block in forearm surgeries: a randomized controlled trial

This study was aimed to compare the onset and duration of axillary block with ropivacaine 0.5% plus either dexmedetomidine, fentanyl, or verapamil in forearm surgeries. This double-blind clinical trial enrolled three equal-sized block-randomized groups of patients (n = 105) scheduled for hand and forearm surgery at Arak, Iran in 2019, who received: (i) ropivacaine (40 mL/0.5%) + dexmedetomidine (1 μg/kg), (ii) ropivacaine (40 mL/0.5%) + fentanyl (1 μg/kg), and (iii) ropivacaine (40 mL/0.5%) + verapamil (2.5 mg), respectively. We recorded some vital signs such as mean arterial pressure, heart rate and oxygen saturation, onset of complete sensory and motor block, duration of the block, opioid use, as well as pain score at recovery and certain time points (2, 4, 6, 12, and 24 hours post-operation). Adding dexmedetomidine to ropivacaine (40 mL/0.5%) prolonged the duration of sensory (P = 0.001) and motor block (P = 0.001) in compared to adding fentanyl and verapamil and it also shortens the time to onset of sensory (P = 0.001) and motor block (P = 0.001). There is a significant difference between three groups in terms of visual analog scale mean and the lowest pain score was obtained in the dexmedetomidine group (P = 0.001), significant time trend (P = 0.001), as well as the time and groups interaction (P = 0.001). Dexmedetomidine was concluded to be associated with alleviated pain; reduced opioid use; short onset of sensory block; and prolonged duration of sensory and motor block. It hence is recommended to lengthen the duration of axillary block and to help relieve postoperative pain and ultimately to move to cut down the postoperative opioid use in forearm surgery. The study was approved by the Ethical Committee of Arak University of Medical Sciences (approval No. IR.ARAKMU. REC.1397.266), and registered on Iranian Registry of Clinical Trials (registration No. IRCT20141209020258N111) on May 9, 2019.

Abnormal Sleep, Circadian Rhythm Disruption, and Delirium in the ICU: Are They Related?

Delirium is a syndrome characterized by acute brain failure resulting in neurocognitive disturbances affecting attention, awareness, and cognition. It is highly prevalent among critically ill patients and is associated with increased morbidity and mortality. A core domain of delirium is represented by behavioral disturbances in sleep-wake cycle probably related to circadian rhythm disruption. The relationship between sleep, circadian rhythm and intensive care unit (ICU)-acquired delirium is complex and likely bidirectional. In this review, we explore the proposed pathophysiological mechanisms of sleep disruption and circadian dysrhythmia as possible contributing factors in transitioning to delirium in the ICU and highlight some of the most relevant caveats for understanding the relationship between these complex phenomena. Specifically, we will (1) review the physiological consequences of poor sleep quality and efficiency; (2) explore how the neural substrate underlying the circadian clock functions may be disrupted in delirium; (3) discuss the role of sedative drugs as contributors to delirium and chrono-disruption; and, (4) describe the association between abnormal sleep-pathological wakefulness, circadian dysrhythmia, delirium and critical illness. Opportunities to improve sleep and readjust circadian rhythmicity to realign the circadian clock may exist as therapeutic targets in both the prevention and treatment of delirium in the ICU. Further research is required to better define these conditions and understand the underlying physiologic relationship to develop effective prevention and therapeutic strategies.

Comparison of hemodynamic changes of magnesium sulfate and dexmedetomidine for an axillary brachial plexus block

Introduction:

Axillary brachial plexus block is used for anesthesia in hands and forearm surgery. The aim of this study was to compare the hemodynamic changes of magnesium sulfate and dexmedetomidine in axillary block.

Materials and Methods:

This randomized, double-blind clinical trial was conducted on 99 patients undergoing a forearm and hand surgery at the Vali-Asr Hospital. Patients were divided into three groups. Dexmedetomidine group consisted of lidocaine 1.5% plus 0.5 μg/kg dexmedetomidine, magnesium sulfate group included lidocaine 1.5% plus 100 mg magnesium sulfate, and the control group received lidocaine 1.5% with normal saline. The final volume was divided into 35 groups in three groups. Blood pressure, heart rate, and oxygen saturation were measured every 5 minutes during surgery, and data were analyzed by SPSS 23.

Results:

There was a statistically significant difference between the three groups in terms of the mean blood pressure during surgery (P < 0.05). At all times, blood pressure in the dexmedetomidine group was lower as compared to the other two groups. But in the 20^th and 25^th minutes, there was a relative increase in blood pressure. There was a significant difference between the three groups in terms of heart rate during surgery in minutes 20, 25, 65–100, and 110–120 (P < 0.05).

Conclusion:

The final result showed that the blood pressure and heart rate of the dexmedetomidine group patients at different times were less than the other two groups.

Neuroprotective role of dexmedetomidine pretreatment in cerebral ischemia injury via ADRA2A-mediated phosphorylation of ERK1/2 in adult rats

Neuroprotective effects of dexmedetomidine (Dex) have been reported in various models of brain injury. However, to our knowledge, the neuroprotective mechanism of Dex pretreatment in rats remains unknown. The aim of the present study was to detect the expression of the α2A adrenergic receptor (ADRA2A) in focal ischemic brain tissues and to investigate the protective role and corresponding mechanism of Dex pretreatment in cerebral ischemia in rats. A hypoxia/reoxygenation (H/R) cell model in primary cultured astrocytes and a focal cerebral ischemia/reperfusion (I/R) model in adult rats were used. The expression of ADRA2A and extracellular signal-regulated kinases 1 and 2 (ERK1/2) in the primary cultured astrocytes and rat brain ischemic tissues was detected in the different conditions prior to and following Dex pretreatment using western blotting. The H/R model of primary cultured astrocytes and the focal cerebral I/R model in adult rats were successfully constructed. Under the normal oxygen conditions, 500 ng/ml Dex pretreatment increased the expression of ADRA2A and phosphorylated (p)-ERK1/2 in the astrocytes compared with in the control group. Hypoxic culture for 6 h and then reoxygenation for 24 h decreased the levels of p-ERK1/2 in the astrocytes compared with those in control group. This decrease was prevented by Dex pretreatment for 3 h. The hypoxic culture and then reoxygenation increased the expression of ADRA2A. Similarly, compared with those prior to Dex treatment, the levels of ADRA2A and p-ERK1/2 in the brain ischemic tissues following Dex treatment were increased. The levels of ADRA2A and p-ERK1/2 were 0.72±0.23 and 0.66±0.25 following Dex treatment, compared with 0.76±0.22 and 0.31±0.18, respectively, prior to Dex treatment. The effect of Dex pretreatment increasing p-ERK1/2 expression was attenuated by AG1478 pretreatment. In summary, Dex appeared to promote phosphorylation of ERK1/2 in astrocytes under H/R. As a specific agonist of ADRA2A, Dex may activate phosphorylation of ERK1/2 via ADRA2A in astrocytes. Thus, the neuroprotective role of Dex pretreatment against cerebral ischemic injury may function via ADRA2A-mediated phosphorylation of ERK1/2.

Comparison of Magnesium Sulfate and Dexmedetomidine as an Adjuvant to 0.5% Ropivacaine in Infraclavicular Brachial Plexus Block

Background:

Magnesium sulfate and dexmedetomidine were used as adjuvants to local anesthesia to improve the quality of regional anesthesia.

Aims:

The aim of this study is to evaluate and compare the effects of magnesium sulfate and dexmedetomidine when added to ropivacaine on the quality of infraclavicular brachial plexus block (BPB).

Settings and Design:

This was a prospective randomized double-blinded controlled study.

Patients and Methods:

A total of 105 adult patients undergoing surgery in hands, wrist, and forearm using infraclavicular BPB were randomly assigned into three groups. Ultrasound-guided infraclavicular BPB was performed using 35 ml ropivacaine 0.5% diluted with 4 ml normal saline 0.9%. Magnesium sulfate 150 mg and dexmedetomidine 100 μg were added in the magnesium sulfate group and dexmedetomidine group, respectively. Duration of analgesia, onset times and durations of sensory block (SB) and motor block (MB), patient's satisfaction, and complications were recorded.

Statistical Analysis:

Statistical software SPSS 16 was used for statistical analysis.

Results:

Dexmedetomidine and magnesium sulfate provided longer duration of analgesia and lesser consumption of postoperative rescue analgesia than the control group (P = 0. 000); dexmedetomidine provided the longest duration of analgesia versus control and magnesium sulfate groups (P = 0.000). Dexmedetomidine provided the quickest onset times and the longest durations of both SB and MB than control and magnesium sulfate groups (P = 0.000). Dexmedetomidine group had higher incidences of bradycardia and hypotension.

Conclusions:

Magnesium sulfate or dexmedetomidine is a useful adjuvant to ropivacaine for infraclavicular BPB in lengthening the duration of analgesia. Dexmedetomidine provided quicker onset and longer duration of both SB and MB and longer duration of analgesia with lesser consumption of postoperative rescue analgesia; however, it showed a higher incidence of intraoperative hypotension and bradycardia than magnesium sulfate.

Controlled hypotension in day care functional endoscopic sinus surgery: A comparison between esmolol and dexmedetomidine: A prospective, double-blind, and randomized study

Background:

Functional endoscopic sinus surgery (FESS) is the cornerstone of therapeutic management for nasal pathologies. This study is to compare the ability of preoperative and intraoperative esmolol versus dexmedetomidine for producing induced hypotension during FESS in adults in a day care setting.

Materials and Methods:

Sixty patients (20-45 years) posted for FESS under general anesthesia were randomly divided into Group E (n = 30) receiving esmolol, loading dose 1 mg/kg over 1 min followed by 0.5 mg/kg/h infusion during maintenance and Group D (n = 30) receiving dexmedetomidine 1 μg/kg over 15 min before induction of anesthesia followed by 0.5 μg/Kg/h infusion during maintenance, respectively. Nasal bleeding and Surgeon's satisfaction score; amount and number of patients receiving fentanyl and nitroglycerine for analgesia and deliberate hypotension, Postanesthesia Care Unit (PACU) and hospital stay; hemodynamic parameters and side effects were recorded for each patient.

Results:

Significantly less number and dosage of nitroglycerine was required (P = 0.0032 and 0.0001, respectively) in Group D compared to that in Group E. Again the number and dosage of patients requiring fentanyl were significantly lower in Group D. However, the duration of controlled hypotension was almost similar in both the groups. Group D patients suffered from significantly less nasal bleeding, and surgeon's satisfaction score was also high in this group. Discharge from PACU and hospital were significantly earlier in Group D. Intraoperative hemodynamics were quite comparable (P > 0.05) without any appreciable side effects.

Conclusion:

Dexmedetomidine found to be providing more effectively controlled hypotension and analgesia and thus allowing less nasal bleeding as well as more surgeons’ satisfaction score.

The effect of dexmedetomidine added to preemptive (2% lignocaine with adrenaline) infiltration on intraoperative hemodynamics and postoperative pain after ambulatory maxillofacial surgeries under general anesthesia

BACKGROUND

Lignocaine + adrenaline; a local anesthetic agent; frequently used for perilesional infiltration, maintains the stable hemodynamics and decreases the postoperative pain after maxillofacial surgery. α2 agonists have peripheral analgesic effects. This prospective study was to evaluate the effectiveness of perilesional dexmedetomidine administered preincisionally in addition to conventional lignocaine adrenaline combinations for reconstructive maxillofacial surgery in an ambulatory care setting.

MATERIALS AND METHODS

76, American Society of Anesthesiologists I-II patients scheduled for unilateral traumatic maxillofacial surgeries were randomly allocated into group DL (n = 38) receiving 15 cc of 2% lignocaine + adrenaline (1:200,000) mixed with 1 μg/kg dexmedetomidine and group PL receiving 15 cc of 2% lignocaine + adrenaline with normal saline (placebo) via local wound infiltration 5 min prior to skin incision. Perioperative hemodynamics, time to first analgesic use, total analgesic need, bleeding, and side effects were recorded for each patient.

RESULTS

Dosage of supplemental propofol; total perioperative, postoperative, and postanesthesia care unit (PACU) fentanyl consumption was significantly lower (P = 0.0001, P= 0.0001, P= 0.0001, P= 0.004, respectively) in dexmedetomine treated group than placebo. Rescue analgesic requirement was significantly earlier in group PL than group DL. Group DL patients suffered from significantly less (P = 0.02) bleeding and surgeon's satisfaction score was also high in this group. Discharge from PACU was significantly earlier in group DL. Intraoperative hemodynamic parameters were significantly lower in group DL (P < 0.05) without any appreciable side effects.

CONCLUSION

Thus, prior dexmedetomidine local infiltration at the site of maxillofacial trauma has significantly reduced bleeding from wound site; perioperative fentanyl, propofol consumption, and subsequently ensured earlier discharge from PACU, better surgeon's satisfaction score with better hemodynamic control and lesser side effects.

Pain relief after ambulatory hand surgery: A comparison between dexmedetomidine and clonidine as adjuvant in axillary brachial plexus block: A prospective, double-blinded, randomized controlled study

BACKGROUND

For ages various adjuvants have been tried to prolong axillary brachial plexus block. We compared the effect of adding dexmedetomidine versus clonidine to ropivacaine for axillary brachial plexus blockade. The primary endpoints were the onset and duration of sensory and motor block and duration of analgesia.

MATERIALS AND METHODS

A total of 90 patients (20-40 years) posted for ambulatory elective hand surgery under axillary brachial plexus block were divided into two equal groups (groups ropivacaine dexmedetomidine [RD] and ropivacaine clonidine [RC]) in a randomized, double-blind fashion. In group RD (n = 45) 30 ml 0.5% ropivacaine + 100 μg of dexmedetomidine and group RC (n = 45) 30 ml 0.5% ropivacaine + 75 μg clonidine were administered in axillary plexus block. Sensory and motor block onset times and block durations, time to first analgesic use, total analgesic need, postoperative visual analog scale (VAS), hemodynamics and side-effects were recorded for each patient.

RESULTS

Though with similar demographic profile in both groups, sensory and motor block in group RD (P < 0.05) was earlier than group RC. Sensory and motor block duration and time to first analgesic use were significantly longer and the total need for rescue analgesics was lower in group RD (P < 0.05) than group RC. Postoperative VAS value at 18 h were significantly lower in group RD (P < 0.05). Intraoperative hemodynamics were insignificantly lower in group RD (P < 0.05) without any appreciable side-effects.

CONCLUSION

It can be concluded that adding dexmedetomidine to axillary plexus block increases the sensory and motor block duration and time to first analgesic use, and decreases total analgesic use with no side-effects.

Induced hypotension in ambulatory functional endoscopic sinus surgery: A comparison between dexmedetomidine and clonidine as premedication. A prospective, double-blind, and randomized study

Background:

Functional endoscopic sinus surgery (FESS) is the mainstay of a therapeutic technique for nasal pathologies. This study is to compare the ability of preoperative dexmedetomidine versus clonidine for producing controlled hypotensive anesthesia during FESS in adults in an ambulatory care setting.

Materials and Methods:

Sixty patients (25-50 years) posted for ambulatory FESS procedures under general anesthesia were randomly divided into Group C and D (n = 33 each) receiving dexmedetomidine 1 μg/kg and clonidine 1.5 μg/kg, respectively; both diluted in 100 ml saline solution 15 min before anesthetic induction. Nasal bleeding and surgeon's satisfaction score; amount and number of patients receiving fentanyl and nitroglycerine for analgesia and deliberate hypotension, duration of hypotension, post anesthesia care unit (PACU) and hospital stay; hemodynamic parameters and side effects were recorded for each patient.

Results:

Number and dosage of nitroglycerine used was significantly (P = 0.034 and 0.0001 respectively) lower in Group D compared to that in Group C. Similarly, number of patients requiring fentanyl and dosage of same was significantly lower in Group D. But, the duration of controlled hypotension was almost similar in both the groups. Group D patients suffered from significantly less nasal bleeding and surgeon's satisfaction score was also high in this group. Discharge from PACU was significantly earlier in Group D, but hospital discharge timing was quite comparable among two groups. Intraoperative hemodynamics was significantly lower in Group D (P < 0.05) without any appreciable side effects.

Conclusion:

Dexmedetomidine found to be providing more effectively controlled hypotension and analgesia, and thus, allowing less nasal bleeding as well as more surgeons’ satisfaction score.

Effect of Two Different Doses of Dexmedetomidine as Adjuvant in Bupivacaine Induced Subarachnoid Block for Elective Abdominal Hysterectomy Operations: A Prospective, Double-blind, Randomized Controlled Study

OBJECTIVES

Improvements in perioperative pain management for lower abdominal operations has been shown to reduce morbidity, induce early ambulation, and improve patients' long-term outcomes. Dexmedetomidine, a selective alpha-2 agonist, has recently been used intrathecally as adjuvant to spinal anesthesia to prolong its efficacy. We compared two different doses of dexmedetomidine added to hyperbaric bupivacaine for spinal anesthesia. The primary endpoints were the onset and duration of sensory and motor block, and duration of analgesia.  .

METHODS

A total of 100 patients, aged 35-60 years old, assigned to have elective abdominal hysterectomy under spinal anesthesia were divided into two equally sized groups (D5 and D10) in a randomized, double-blind fashion. The D5 group was intrathecally administered 3ml 0.5% hyperbaric bupivacaine with 5µg dexmedetomidine in 0.5ml of normal saline and the D10 group 3ml 0.5% bupivacaine with 10µg dexmedetomidine in 0.5ml of normal saline. For each patient, sensory and motor block onset times, block durations, time to first analgesic use, total analgesic need, postoperative visual analogue scale (VAS) scores, hemodynamics, and side effects were recorded.  .

RESULTS

Although both groups had a similar demographic profile, sensory and motor block in the D10 group (p<0.050) was earlier than the D5 group. Sensory and motor block duration and time to first analgesic use were significantly longer and the need for rescue analgesics was lower in the D10 group than the D5 group. The 24-hour VAS score was significantly lower in the D10 group (p<0.050). Intergroup hemodynamics were comparable (p>0.050) without any appreciable side effects.  .

CONCLUSION

Spinal dexmedetomidine increases the sensory and motor block duration and time to first analgesic use, and decreases analgesic consumption in a dose-dependent manner.

Dexmedetomidine Dose-Dependently Attenuates Ropivacaine-Induced Seizures and Negative Emotions Via Inhibiting Phosphorylation of Amygdala Extracellular Signal-Regulated Kinase in Mice

Ropivacaine (Ropi), one of the newest and safest amino amide local anesthetics, is linked to toxicity, including the potential for seizures, changes in behavior, and even cardiovascular collapse. Dexmedetomidine (Dex), an α2-adrenergic receptor agonist, has been widely used in anesthesia and critical care practice. To date, the underlying mechanisms of the effects of Dex premedication on Ropi-induced toxicity have not been clearly identified. In the current study, we investigated the effects of increasing doses of Dex premedication on 50% convulsive dose (CD50) of Ropi. With increasing doses of intraperitoneal (i.p.) Dex 10 min prior to each i.p. RopiCD50, the latency and duration of seizure activity were recorded. Open-field (OF) and elevated plus maze (EPM) test were used to measure negative behavioral emotions such as depression and anxiety. Immunohistochemistry and Western blot were utilized to investigate phosphorylation-extracellular regulated protein kinases (p-ERK) expression in the basolateral amygdala (BLA) on 2 h and in the central amygdala (CeA) on 24 h after convulsion in mice. The results of our investigation demonstrated that Dex dose-dependently increased RopiCD50, prolonged the latency and shortened the duration of each RopiCD50-induced seizure, improved the negative emotions revealed by both OF and EPM test, and inhibited p-ERK expression in the BLA and the CeA.

Emergence agitation prevention in paediatric ambulatory surgery: A comparison between intranasal Dexmedetomidine and Clonidine

Objective:

Emergence agitation (EA), a short-lived, self-limiting phenomenon, arises frequently after the use of inhalational agents and hampers the implementation of pediatric ambulatory surgery in spite of using so many drugs with variable efficacy.

Methods:

In this prospective, double-blinded, parallel group study (2008–2009), 80 children of both sex aged 3–7 years, with American Society of Anesthesiologists (ASA) physical status grade I-II, undergoing sevoflurane-based general anesthesia for elective day care surgery were randomly assigned into groups C or D. Group C received 4 μg/kg intranasal clonidine, whereas group D received 1 μg/kg intranasal dexmedetomidine, 45 min before induction of anesthesia. In postanesthesia care unit (PACU), the incidence of EA was assessed with Aonos four-point scale and the severity of EA was assessed with pediatric anesthesia emergence delirium scale upon admission (T0), after 5 min (T5), 15 min (T15), and 25 min (T25). Extubation time, emergence time, duration of PACU stay, dose and incidence of fentanyl use for pain control were noted.

Findings:

Based on comparable demographic profiles, the incidence and severity of EA were significantly lower in group D as compared to group C at T0, T5, T15, and T25. But time of regular breathing, awakening, extubation, and emergence were significantly delayed in group D than C. The number and dose of fentanyl used in group C were significantly higher than group D. PACU and hospital stay were quite comparable between groups.

Conclusion:

Intranasal dexmedetomidine 1 μg/kg was more effective than clonidine 4 μg/kg in decreasing the incidence and severity of EA, when administered 45 min before the induction of anesthesia with sevoflurane for pediatric day care surgery. Dexmedetomidine also significantly reduced fentanyl consumption in PACU.

Effect of dexmedetomidine as adjuvant in ropivacaine-induced supraclavicular brachial plexus block: A prospective, double-blinded and randomized controlled study

Background and Aims:

Different additives have been used to prolong brachial plexus block. We evaluated the effect of adding dexmedetomidine to ropivacaine for supraclavicular brachial plexus blockade. The primary endpoints were the onset and duration of sensory and motor block and duration of analgesia.

Materials and Methods:

A total of 84 patients (20-50 years) posted for elective forearm and hand surgery under supraclavicular brachial plexus block were divided into two equal groups (Group R and RD) in a randomized, double-blind fashion. In group RD (n = 42) 30 ml 0.5% ropivacaine +1 ml (100 μg) of dexmedetomidine and group R (n = 42) 30 ml 0.5% ropivacaine +1 ml normal saline were administered in supraclavicular block. Sensory and motor block onset times and block durations, time to first analgesic use, total analgesic need, postoperative visual analog scale (VAS), hemodynamics and side-effects were recorded for each patient.

Results:

Though with similar demographic profile in both groups, sensory and motor block in group RD (P < 0.05) was earlier than group R. Sensory and motor block duration and time to first analgesic use were significantly longer and the total need for rescue analgesics was lower in group RD (P < 0.05) than group R. Post-operative VAS value at 12 h were significantly lower in group RD (P < 0.05). Intra-operative hemodynamics were significantly lower in group RD (P < 0.05) without any appreciable side-effects.

Conclusion:

It can be concluded that adding dexmedetomidine to supraclavicular brachial plexus block increases the sensory and motor block duration and time to first analgesic use, and decreases total analgesic use with no side-effects.

Effect of different doses of dexmedetomidine as adjuvant in bupivacaine -induced subarachnoid block for traumatized lower limb orthopaedic surgery: a prospective, double-blinded and randomized controlled study

BACKGROUND AND AIMS

Improved pain management for blunt trauma to the lower extremity has shown to reduce morbidity, induce early ambulation and improve long-term outcomes. Dexmedetomidine; a selective α-2 agonist; has recently been used intrathecally in different doses to prolong spinal anaesthesia. We evaluated the effect of adding two different doses of dexmedetomidine to hyperbaric bupivacaine for spinal anaesthesia. The primary endpoints were the onset and duration of sensory, motor block and duration of analgesia.

MATERIALS AND METHODS

Eighty patients, (20-60yrs) posted for elective lower limb orthopedic surgery of traumatic origin under spinal anaesthesia were divided into 2 equal groups (Group D5&D10) in a randomized, double-blind fashion. In this prospective parallel group study, group D5(n=40) 3ml 0.5% hyperbaric bupivacaine+5μg dexmedetomidine in 0.5 ml of normal saline and group D10 (n=40) 3ml 0.5% bupivacaine+10μg dexmedetomidine in 0.5 ml of normal saline were administered intrathecally. Sensory and motor block onset times and block durations, time to first analgesic use, total analgesic need, postoperative VAS, hemodynamics and side effects were recorded for each patient.

RESULTS

Though with similar demographic profile in both groups, sensory and motor block in group D10(p<0.05) was earlier than group D5. Sensory, motor block duration and time to first analgesic use were significantly longer and the need for rescue analgesics was lower in group D10(p<0.05) than D5. 24 h VAS score was significantly lower in group D10(p<0.05). Intergroup hemodynamics was comparable (p>0.05) without any appreciable side effects.

CONCLUSION

Spinal dexmedetomidine increases the sensory, motor block duration and time to first analgesic use, and decreases analgesic consumption in a dose-dependent manner.

Dexmedetomidine suppresses interleukin-1β-induced interleukin-6 synthesis in rat glial cells

Dexmedetomidine, an α2-adrenoceptor agonist, is used as a sedative medication for criticalyl ill patients and is known to exert neuroprotective effects by direct action on neurons and indirect action on neurons through astrocytes. Interleukin (IL)-6 plays a key role in neuroinflammation, which accompanies infection, traumatic brain injury, ischemia, neurodegenerative disorders, as both a pro-inflammatory cytokine and an anti-inflammatory cytokine. Dexmedetomidine suppresses immune function. However, the effects of dexmedetomidine on cytokine synthesis in the central nervous system (CNS) remain elusive. We previously reported that IL-1β stimulates IL-6 synthesis in the rat C6 glioma cell line through the phosphorylation of p38 mitogen-activated protein (MAP) kinase, stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK) and IκB. In the present study, we investigated the effects of dexmedetomidine on the IL-1β-induced IL-6 synthesis in C6 cells. Dexmedetomidine inhibited the IL-1β-stimulated IL-6 release and mRNA expression in C6 cells. 8-Bromo-adenosine-3',5'-cyclic monophosphate, but not 8-bromo-guanosine 3',5'-cyclic monophosphate, significantly enhanced the IL-1β-induced IL-6 release and mRNA expression. However, dexmedetomidine failed to affect cAMP accumulation in the cells treated with IL-1β or forskolin, an activator of adenylyl cyclase. Yohimbine, an α2-adrenoceptor antagonist, did not reverse the suppressive effects of dexmedetomidine on the IL-1β-induced IL-6 release. Dexmedetomidine did not affect the IL-1β-induced phosphorylation of p38 MAP kinase, SAPK/JNK, IκB, nuclear factor (NF)-κB or c-Jun. Our findings strongly suggest that dexmedetomidine inhibits the IL-1β-induced IL-6 synthesis independently of the adenylyl cyclase-cAMP pathway through α2-adrenoceptors in C6 glioma cells. It is possible that dexmedetomidine may affect the immune system in the CNS by regulating the production of IL-6.

Pain relief after Arthroscopic Knee Surgery: A comparison of intra-articular ropivacaine, fentanyl, and dexmedetomidine: A prospective, double-blinded, randomized controlled study

Background:

Postoperative pain is very common distressing symptom after any surgical procedure. Different drugs in different routes have been used for controlling post-arthroscopic pain. No one proved to be ideal. We have compared the analgesic effect of ropivacaine, fentanyl, and dexmedetomidine when administered through the intra-articular route in arthroscopic knee surgery.

Materials and Methods:

From March 2008 to July 2010, 99 patients undergoing arthroscopic knee surgery were randomly assigned into three groups (A,B,C) in a prospective double-blinded fashion. Group A received 10 ml of 0.75% ropivacaine, where Group B received 50 μg fentanyl, and Group C received 100 μg of dexmedetomidine through the intra-articular route at the end of procedure. Pain assessed using visual analog scale and diclofenac sodium given as rescue analgesia when VAS >4. Time of first analgesia request and total rescue analgesic used in 24 hours were calculated.

Results:

Demographic profiles are quite comparable among the groups. Time for requirement of first postoperative rescue analgesia in Group A was 380.61 ± 22.973 min, in Group B was 326.82 ± 17.131 min and in Group C was 244.09 ± 20.096 minutes. Total rescue analgesia requirement was less in Group A (1.394 ± 0.496) compared to Group B (1.758 ± 0.435) and Group C (2.546 ± 0.546). Group A had higher mean VAS score at 6^th and 24^th postoperative hours. No side effects found among the groups.

Conclusion:

Therefore, it suggests that intra-articular ropivacaine gives better postoperative pain relief, with increased time of first analgesic request and decreased need of total postoperative analgesia compared to fentanyl and dexmedetomidine.

Inhibiting spinal neuron-astrocytic activation correlates with synergistic analgesia of dexmedetomidine and ropivacaine

Background

This study aims to identify that intrathecal (i.t.) injection of dexmedetomidine (Dex) and ropivacaine (Ropi) induces synergistic analgesia on chronic inflammatory pain and is accompanied with corresponding “neuron-astrocytic” alterations.

Methods

Male, adult Sprague-Dawley rats were randomly divided into sham, control and i.t. medication groups. The analgesia profiles of i.t. Dex, Ropi, and their combination detected by Hargreaves heat test were investigated on the subcutaneous (s.c.) injection of complete Freund adjuvant (CFA) induced chronic pain in rat and their synergistic analgesia was confirmed by using isobolographic analysis. During consecutive daily administration, pain behavior was daily recorded, and immunohistochemical staining was applied to investigate the number of Fos-immunoreactive (Fos-ir) neurons on hour 2 and day 1, 3 and 7, and the expression of glial fibrillary acidic protein (GFAP) within the spinal dorsal horn (SDH) on day 1, 3, 5 and 7 after s.c. injection of CFA, respectively, and then Western blot to examine spinal GFAP and β-actin levels on day 3 and 7.

Results

i.t. Dex or Ropi displayed a short-term analgesia in a dose-dependent manner, and consecutive daily administrations of their combination showed synergistic analgesia and remarkably down-regulated neuronal and astrocytic activations indicated by decreases in the number of Fos-ir neurons and the GFAP expression within the SDH, respectively.

Conclusion

i.t. co-delivery of Dex and Ropi shows synergistic analgesia on the chronic inflammatory pain, in which spinal “neuron-astrocytic activation” mechanism may play an important role.

Neuronal and glial localization of alpha(2A)-adrenoceptors in the adult zebrafish (Danio rerio) brain

The alpha(2A)-adrenoceptor (AR) subtype, a G protein-coupled receptor located both pre- and postsynaptically, mediates adrenaline/noradrenaline functions. The present study aimed to determine the alpha(2A)-AR distribution in the adult zebrafish (Danio rerio) brain by means of immunocytochemistry. Detailed mapping showed labeling of alpha(2A)-ARs, in neuropil, neuronal somata and fibers, glial processes, and blood vessels. A high density of alpha(2A)-AR immunoreactivity was found in the ventral telencephalic area, preoptic, pretectal, hypothalamic areas, torus semicircularis, oculomotor nucleus (NIII), locus coreruleus (LC), medial raphe, medial octavolateralis nucleus (MON), magnocellular octaval nucleus (MaON), reticular formation (SRF, IMRF, IRF), rhombencephalic nerves and roots (DV, V, VII, VIII, X), and cerebellar Purkinje cell layer. Moderate levels of alpha(2A)-ARs were observed in the medial and central zone nuclei of dorsal telencephalic area, in the periventricular gray zone of optic tectum, in the dorsomedial part of optic tectum layers, and in the molecular and granular layers of all cerebellum subdivisions. Glial processes were found to express alpha(2A)-ARs in rhombencephalon, intermingled with neuronal fibers. Medium-sized neurons were labeled in telencephalic, diencephalic, and mesencephlic areas, whereas densely labeled large neurons were found in rhombencephalon, locus coeruleus, reticular formation, oculomotor area, medial octavolateralis and magnocellular octaval nuclei, and Purkinje cell somata. The functional role of alpha(2A)-ARs on neurons and glial processes is not known at present; however, their strong relation to the ventricular system, somatosensory nuclei, and nerves supports a possible regulatory role of alpha(2A)-ARs in autonomic functions, nerve output, and sensory integration in adult zebrafish brain.

Alpha-adrenergic stimulation of ERK phosphorylation in astrocytes is alpha(2)-specific and may be mediated by transactivation

The highly specific alpha(2)-adrenergic agonist, dexmedetomidine, has hypnotic-sedative, anesthetic-sparing and analgesic effects, and it protects neurons against ischemia. The alpha(1)-adrenergic agonist, phenylephrine, does not share dexmedetomidine's pharmacological properties, although both dexmedetomidine and phenylephrine increase free cytosolic Ca(2+) ([Ca(2+)](i)) in astrocytes, and most of dexmedetomidine's actions in the brain are exerted on postjunctional receptors. alpha(2)-Adrenergic receptors are abundant on astrocytes. Dexmedetomidine-mediated 'down-streamn' signal transduction was therefore investigated in primary cultures of mouse astrocytes and contrasted with that of phenylephrine. The cultures were incubated with dexmedetomidine concentrations known to be pharmacologically active and to act specifically on alpha(2)-adrenergic receptors (25-100 nM). ERK(1/2) phosphorylation was measured using specific antibodies. Peak increases of ERK(1/2) phosphorylation occurred at 50 nM dexmedetomidine, with less effect at higher concentrations. Phenylephrine caused ERK phosphorylation only at a concentration high enough to exert non subtype-specific effects (10 microM), and this effect was counteracted by the alpha(2)-adrenergic antagonist atipamezole. The phosphorylation of ERK was reduced by tyrphostin AG1478, an inhibitor of phosphorylation of the epidermal growth factor receptor (EGFR), and by heparin, which neutralizes heparin-binding epithelial growth factor (HB-EGF), suggesting the involvement of a transactivation process, in which alpha(2)-adrenergic stimulation leads to proteolytic shedding of HB-EGF (and perhaps other EGFR agonists) from transmembrane-spanning precursors.

Alpha-2A-adrenergic receptors are present on neurons in the central nucleus of the amygdala that project to the dorsal vagal complex in the rat

The descending pathway between the central nucleus of the amygdala (CeA) and the dorsal vagal complex (DVC) is an important substrate for autonomic functions associated with emotion. Activity in this circuit is crucially modulated by catecholamines and agonists of the alpha-2A-adrenergic receptor (alpha(2A)-AR), which relieve cardiovascular and gastrointestinal symptoms associated with experience of aversive stimuli. The subcellular distribution of alpha(2A)-AR within the CeA, however, has not been characterized. It is also not known if any alpha(2A)-AR-expressing neurons in the CeA project to the dorsal vagal complex. In order to address these questions, we examined the immunocytochemical labeling of alpha(2A)-AR in the CeA of rats receiving microinjection of the retrograde tracer fluorogold (FG) into the dorsal vagal complex at the level of the area postrema, an area involved in cardiorespiratory and gastrointestinal functions. Of all alpha(2A)-AR-labeled profiles in the CeA, the majority were either dendrites (42%) or somata (24%). alpha(2A)-AR labeling was often present on the plasmalemma in dendrites and was mainly found in endosome-like organelles in somata. Of all alpha(2A)-AR immunoreactive somata, 62% also contained immunolabeling for FG and 23% of all dendrites also showed labeling for the retrograde tracer. The intracellular distribution of alpha(2A)-AR did not differ in somata or dendrites with or without detectable FG. The remaining singly labeled alpha(2A)-AR profiles consisted of axons (11%), axon terminals (12%), and glial processes (13%). In numerous instances, alpha(2A)-AR-labeled glia or axon terminals were apposed to DVC projecting neurons. Together, this evidence suggests that the principal site for alpha(2A)-AR activation is at extrasynaptic sites on dendrites of CeA neurons, many of which project to the DVC and also show endosomal receptor labeling. In addition, these results indicate that activation of alpha(2A)-AR in the CeA may influence the activity of DVC projecting neurons through indirect mechanisms, including changes in presynaptic transmitter release or glial function. These results suggest that alpha(2A)-AR agonists in the CeA may modulate numerous processes including stress-evoked autonomic reactions and feeding behavior.

Heterozygous alpha 2A-adrenergic receptor mice unveil unique therapeutic benefits of partial agonists

Genetic manipulation of the alpha(2A)-adrenergic receptor (alpha(2A)-AR) in mice has revealed the role of this subtype in numerous responses, including agonist-induced hypotension and sedation. Unexpectedly, alpha(2)-agonist treatment of mice heterozygous for the alpha(2A)-AR (alpha(2A)-AR(+/-)) lowers blood pressure without sedation, indicating that more than 50% of alpha(2A)-AR must be activated to evoke sedation. We postulated that partial activation of alpha(2A)-AR in wild-type alpha(2A)-AR(+/+) animals could be achieved with partial agonists, agents with variable ability to couple receptor occupancy to effector activation, and might elicit one versus another pharmacological response. In vitro assays reveal that moxonidine is a partial agonist at alpha(2A)-AR. Although moxonidine was developed to preferentially interact with imidazoline binding sites, it requires the alpha(2A)-AR to lower blood pressure because we observe no hypotensive response to moxonidine in alpha(2A)-AR-null (alpha(2A)-AR(-/-)) mice. Moreover, we observe that moxonidine lowers blood pressure without sedation in wild-type mice, consistent with the above hypothesis regarding partial agonists. Our findings suggest that weak partial agonists can evoke response-selective pathways and might be exploited successfully to achieve alpha(2A)-AR pharmacotherapy where concomitant sedation is undesirable, i.e., in treatment of depression or attention deficit hyperactivity disorder, in suppression of epileptogenesis, or enhancement of cognition. Furthermore, rigorous physiological and behavioral assessment of mice heterozygous for particular receptors provides a general strategy for elucidation of pathways that might be selectively activated by partial agonists, thus achieving response-specific therapy.

Amobarbital inhibits K(+)-stimulated glucose oxidation in cerebellar granule neurons by two mechanisms

The study aimed at determining mechanism(s) by which amobarbital (amytal) suppresses glucose oxidation in cerebellar granule neurons in primary cultures, a glutamatergic preparation. When challenged with a depolarizing K(+) concentration (55 mM), the cells doubled their rate of glucose oxidation (production of 14CO(2) from U-[14C]glucose) and glycolysis (lactate accumulation). At normal K(+) concentration, amobarbital reduced 14CO(2) production with half-maximum effect at 0.5-1 mM; at 55 mM K(+), the inhibition was more potent, with more than half of the K(+)-induced stimulation abolished at 50 microM. Dixon plot analysis showed a single inhibitory mechanism at 5.4 mM K(+), but at 55 mM K(+), two kinetically different mechanisms could be distinguished. A more pronounced compensatory amobarbital-induced increase in glycolysis at 5.4 than at 55 mM K(+) suggested that amobarbital in addition to its inhibition of mitochondrial respiration inhibited K(+)-induced increase in energy demand, probably by its known suppression of stimulated glutamate release.

Alpha(2A)-adrenergic receptors are present in mu-opioid receptor containing neurons in rat medial nucleus tractus solitarius

Agonists of the alpha-2A-adrenergic- (alpha(2A)-AR) and the mu-opioid-receptor (muOR) jointly affect autonomic functions that are also disregulated in animals undergoing withdrawal from chronic administration of the muOR agonist morphine. Cardiovascular and gastrointestinal reflexes are mediated, in part, by the medial nucleus of the solitary tract (mNTS) at caudal (cNTS) and intermediate (iNTS) subregions. Together, this evidence suggests that alpha(2A)-AR and muOR may be colocalized within many of the same neuronal profiles in both the intermediate and caudal mNTS. In order to examine whether alpha(2A)-AR and muOR are present within common somata, dendrites, or axon terminals in the mNTS, we used electron microscopic immunocytochemistry for the detection of antisera against each receptor at intermediate and caudal levels of this brain region. Most of the dually labeled profiles were somata and dendrites. Of all dual-labeled profiles in the iNTS 49% were somata and were 47% dendrites, whereas in the cNTS 61% were somata and 32% were dendrites. Within dual-labeled profiles, the intracellular distribution of alpha(2A)-AR and muOR differed. MuOR was more frequently associated with the plasmalemma, whereas alpha(2A)-AR was often affiliated with vesicular organelles. Few axon terminals, and even fewer glia, contained both markers. We also frequently observed single-labeled alpha(2A)-AR glia that apposed exclusively muOR-containing dendrites or axon terminals. These findings indicate that somata and dendrites contain functional sites for convergent muOR and alpha(2A)-AR activation. In addition, each receptor is positioned for involvement in intercellular signaling between apposed neurons and glia. Activation of alpha(2A)-AR on muOR-containing somata or dendrites, or on glia apposed to muOR-containing neurons, may help to account for the efficacy of alpha(2A)-AR agonists in relieving some of the autonomic symptoms of opiate withdrawal.

Signaling and gene expression in the neuron-glia unit during brain function and dysfunction: Holger Hydén in memoriam

Holger Hydén demonstrated almost 40 years ago that learning changes the base composition of nuclear RNA, i.e. induces an alteration in gene expression. An equally revolutionary observation at that time was that a base change occurred in both neurons and glia. From these findings, Holger Hydén concluded that establishment of memory is correlated with protein synthesis, and he demonstrated de novo synthesis of several high-molecular protein species after learning. Moreover, the protein, S-100, which is mainly found in glial cells, was increased during learning, and antibodies towards this protein inhibited memory consolidation. S-100 belongs to a family of Ca(2+)-binding proteins, and Holger Hydén at an early point realized the huge importance of Ca(2+) in brain function. He established that glial cells show more marked and earlier changes in RNA composition in Parkinson's disease than neurons. Holger Hydén also had the vision and courage to suggest that "mental diseases could as well be thought to depend upon a disturbance of processes in glia cells as in the nerve cells", and he showed that antidepressant drugs cause profound changes in glial RNA. The importance of Holger Hydén's findings and visions can only now be fully appreciated. His visionary concepts of the involvement of glia in neurological and mental illness, of learning being associated with changes in gene expression, and of the functional importance of Ca(2+)-binding proteins and Ca(2+) are presently being confirmed and expanded by others. This review briefly summarizes highlights of Holger Hydén's work in these areas, followed by a discussion of recent research, confirming his findings and expanding his visions. This includes strong evidence that glial dysfunction is involved in the development of Parkinson's disease, that drugs effective in mood disorders alter gene expression and exert profound effects on astrocytes, and that neuronal-astrocytic interactions in glutamate signaling, NO synthesis, Ca(2+) signaling, beta-adrenergic activity, second messenger production, protein kinase activities, and transcription factor phosphorylation control the highly programmed events that carry the memory trace through the initial, signal-mediated short-term and intermediate memory stages to protein synthesis-dependent long-term memory.