The cardioprotective effect of dexmedetomidine on global ischaemia in isolated rat hearts

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

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

Neuroprotection of Dexmedetomidine against Cerebral Ischemia-Reperfusion Injury in Rats: Involved in Inhibition of NF-κB and Inflammation Response

Dexmedetomidine is an α2-adrenergic receptor agonist that exhibits a protective effect on ischemia-reperfusion injury of the heart, kidney, and other organs. In the present study, we examined the neuroprotective action and potential mechanisms of dexmedetomidine against ischemia-reperfusion induced cerebral injury. Transient focal cerebral ischemia-reperfusion injury was induced in Sprague-Dawley rats by middle cerebral artery occlusion. After the ischemic insult, animals then received intravenous dexmedetomidine of 1 µg/kg load dose, followed by 0.05 µg/kg/min infusion for 2 h. After 24 h of reperfusion, neurological function, brain edema, and the morphology of the hippocampal CA1 region were evaluated. The levels and mRNA expressions of interleukin-1β, interleukin-6 and tumor nevrosis factor-α as well as the protein expression of inducible nitric oxide synthase, cyclooxygenase-2, nuclear factor-κBp65, inhibitor of κBα and phosphorylated of κBα in hippocampus were assessed. We found that dexmedetomidine reduced focal cerebral ischemia-reperfusion injury in rats by inhibiting the expression and release of inflammatory cytokines and mediators. Inhibition of the nuclear factor-κB pathway may be a mechanism underlying the neuroprotective action of dexmedetomidine against focal cerebral I/R injury.

Dexmedetomidine attenuates hypoxia/reoxygenation injury in primary neonatal rat cardiomyocytes

Systemic administration of dexmedetomidine provides cardioprotection against ischemia/reperfusion (I/R) injury; however, the direct effects of dexmedetomidine on cardiomyocytes have not been clarified. The present study investigated the effects of dexmedetomidine on primary neonatal rat cardiomyocytes under hypoxic/reoxygenation (H/R) conditions. In order to simulate in vivo I/R injury, primary neonatal rat cardiomyocytes were cultured under hypoxic conditions for 1 h and subsequently reoxygenated for 24 h. The effects of preconditioning with dexmedetomidine 2 h before hypoxia and postconditioning during reoxygenation were also examined. Cellular viability and activity were analyzed by monitoring the dynamic response profile of living cells using a real-time cell analyzer system. A special scaled index, defined as the normalized cell index (NCI), was used to minimize the influence of inter-experimental variations. The dose-effect curve was generated from the area under the time-course curve values of NCI. H/R exposure markedly decreased cell viability and activity. Furthermore, no cytotoxicity was associated with a clinically relevant concentration of dexmedetomidine. Preconditioning with dexmedetomidine concentration-dependently ameliorated the reductions in NCI in cardiomyocytes following H/R injury. Additionally, postconditioning with dexmedetomidine improved the reductions in NCI at concentrations between 3 and 200 nM. Finally, the effect of 3–40 nM dexmedetomidine postconditioning was greater than preconditioning. These results indicated that preconditioning and postconditioning with dexmedetomidine attenuated H/R injury in primary neonatal rat cardiomyocytes at the cellular level.

Bidirectional Regulatory Effects of Dexmedetomidine on Porcine Coronary Tone In Vitro

Background

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

Material/Methods

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

Results

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

Conclusions

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

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

Introduction:

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

Methodology:

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

Results:

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

Conclusion:

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

Two Phase Modulation of [Formula: see text] Entry and Cl-/[Formula: see text] Exchanger in Submandibular Glands Cells by Dexmedetomidine

Dexmedetomidine (Dex), a highly selective α2-adrenoceptor agonist, attenuates inflammatory responses induced by lipopolysaccharide (LPS) and induces sedative and analgesic effects. Administration of Dex also reduces salivary secretion in human subjects and inhibits osmotic water permeability in rat cortical collecting ducts. However, little is known about the mechanisms underlying the effects of Dex on salivary glands fluid secretion. We demonstrated the α2-adrenoceptor expression in the basolateral membrane of mouse submandibular glands (SMG). To investigate fluid secretion upon treatment with Dex, we studied the effects of Dex on the activity of Na+-K+-2Cl- cotransporter1 (NKCC1) and Cl-/[Formula: see text] exchange (CBE), and on downstream pro-inflammatory cytokine expression in isolated primary mouse SMG cells. Dex acutely increased CBE activity and NKCC1-mediated and independent [Formula: see text] entry in SMG duct cells, and enhanced ductal fluid secretion in a sealed duct system. Dex showed differential effects on cholinergic/adrenergic stimulations and inflammatory mediators, histamine, and LPS, stimulations-induced Ca2+ in mouse SMG cells. Both, histamine- and LPS-induced intracellular Ca2+ increases were inhibited by Dex, whereas carbachol-stimulated Ca2+ signals were not. Long-lasting (2 h) treatment with Dex reduced CBE activity in SMG and in human submandibular glands (HSG) cells. Moreover, when isolated SMG cells were stimulated with Dex for 2 h, phosphodiesterase 4D (PDE4D) expression was enhanced. These results confirm the anti-inflammatory properties of Dex on LPS-mediated signaling. Further, Dex also inhibited mRNA expression of interleukin-6 and NADPH oxidase 4. The present study also showed that α2-adrenoceptor activation by Dex reduces salivary glands fluid secretion by increasing PDE4D expression, and subsequently reducing the concentration of cAMP. These findings reveal an interaction between the α2-adrenoceptor and PDE4D, which should be considered when using α2-adrenoceptor agonists as sedative or analgesics.

Dexmedetomidine preconditioning may attenuate myocardial ischemia/reperfusion injury by down-regulating the HMGB1-TLR4-MyD88-NF-кB signaling pathway

Aims

To investigate whether dexmedetomidine (DEX) preconditioning could alleviate the inflammation caused by myocardial ischemia/reperfusion (I/R) injury by reducing HMGB1-TLR4-MyD88-NF-кB signaling.

Methods

Seventy rats were randomly assigned into five groups: sham group, myocardial I/R group (I/R), DEX+I/R group (DEX), DEX+yohimbine+I/R group (DEX/YOH), and yohimbine+I/R group (YOH). Animals were subjected to 30 min of ischemia induced by occluding the left anterior descending artery followed by 120 min of reperfusion. Myocardial infarct size and histological scores were evaluated. The levels of IL-6 and TNF-α in serum and myocardium were quantified by enzyme-linked immunosorbent assay, and expression of HMGB1, TLR4, MyD88, IκB and NF-κB in the myocardial I/R area were determined with Western blot and immunocytochemistry.

Results

Myocardial infarct sizes, histological scores, levels of circulating and myocardial IL-6 and TNF-α, the expression of HMGB1, TLR4, MyD88 and NF-κB, and the degradation of IκB were significantly increased in the I/R group compared with the sham group (P<0.01). DEX preconditioning significantly reduced the myocardial infarct size and histological scores (P<0.01 vs. I/R group). Similarly, the serum and myocardial levels of IL-6 and TNF-α, the expression of HMGB1, TLR4, MyD88 and NF-κB, and the degradation of IκB were significantly reduced in the DEX group (P<0.01 vs. I/R group). These effects were partly reversed by yohimbine, a selective α₂-adrenergic receptor antagonist, while yohimbine alone had no significant effect on any of the above indicators.

Conclusion

DEX preconditioning reduces myocardial I/R injury in part by attenuating inflammation, which may be attributed to the downregulation of the HMGB1-TLR4-MyD88-NF-кB signaling pathway mediated by the α₂-adrenergic receptor activation.

Dexmedetomidine Attenuates Lipopolysaccharide Induced MCP-1 Expression in Primary Astrocyte

Background. Neuroinflammation which presents as a possible mechanism of delirium is associated with MCP-1, an important proinflammatory factor which is expressed on astrocytes. It is known that dexmedetomidine (DEX) possesses potent anti-inflammatory properties. This study aimed to investigate the potential effects of DEX on the production of MCP-1 in lipopolysaccharide-stimulated astrocytes. Materials and Methods. Astrocytes were treated with LPS (10 ng/ml, 50 ng/ml, 100 ng/ml, and 1000 ng/ml), DEX (500 ng/mL), LPS (100 ng/ml), and DEX (10, 100, and 500 ng/mL) for a duration of three hours; expression levels of MCP-1 were measured by real-time PCR. The double immunofluorescence staining protocol was utilized to determine the expression of α2-adrenoceptors (α2AR) and glial fibrillary acidic protein (GFAP) on astrocytes. Results. Expressions of MCP-1 mRNA in astrocytes were induced dose-dependently by LPS. Administration of DEX significantly inhibited the expression of MCP-1 mRNA (P < 0.001). Double immunofluorescence assay showed that α2AR colocalize with GFAP, which indicates the expression of α2-adrenoceptors in astrocytes. Conclusions. DEX is a potent suppressor of MCP-1 in astrocytes induced with lipopolysaccharide through α₂A-adrenergic receptors, which potentially explains its beneficial effects in the treatment of delirium by attenuating neuroinflammation.

Dexmedetomidine Protects Cardiomyocytes against Hypoxia/Reoxygenation Injury by Suppressing TLR4-MyD88-NF-κB Signaling

OBJECTIVE

We previously reported that dexmedetomidine (DEX) offers cardioprotection against ischemia/reperfusion injury in rats. Here, we evaluated the role of toll-like receptors 4- (TLR4-) myeloid differentiation primary response 88- (MyD88-) nuclear factor-kappa B (NF-κB) signaling in DEX-mediated protection of cardiomyocytes using in vitro models of hypoxia/reoxygenation (H/R).

METHODS

The experiments were carried out in H9C2 cells and in primary neonatal rat cardiomyocytes. Cells pretreated with vehicle or DEX were exposed to hypoxia for 1 h followed by reoxygenation for 12 h. We analyzed cell viability and lactate dehydrogenase (LDH) activity and measured tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-1β mRNA levels, TLR4, MyD88, and nuclear NF-κB p65 protein expression and NF-κB p65 nuclear localization. TLR4 knock-down by TLR4 siRNA transfection and overexpression by TLR4 DNA transfection were used to further confirm our findings.

RESULTS

DEX protected against H/R-induced cell damage and inflammation, as evidenced by increased cell survival rates, decreased LDH activity, and decreased TNF-α, IL-6, and IL-1β mRNA levels, as well as TLR4 and NF-κB protein expression. TLR4 knock-down partially prevented cell damage following H/R injury, while overexpression of TLR4 abolished the DEX-mediated protective effects.

CONCLUSIONS

DEX pretreatment protects rat cardiomyocytes against H/R injury. This effect is partly mediated by TLR4 suppression via TLR4-MyD88-NF-κB signaling.

Dexmedetomidine improves gastrointestinal motility after laparoscopic resection of colorectal cancer: A randomized clinical trial

BACKGROUND

To investigate the effects of intraoperative application of dexmedetomidine (Dex) on early gastrointestinal motility after laparoscopic resection of colorectal cancer.

METHODS

In this prospective, randomized double-blind investigation, 60 patients who underwent laparoscopic resection of colorectal cancer were randomly allocated to receive Dex (DEX group, n = 30) or saline (CON group, n = 30). In the DEX group, Dex was loaded (1 μg/kg) before anesthesia induction and was infused (0.3 μg/kg/h) during surgery. Time to postoperative first flatus (FFL) and first feces (FFE), and time to regular diet were recorded. Serum diamine oxidase (DAO) activity and intestinal fatty acid-binding protein (I-FABP) were detected.

RESULTS

Both the time to the FFL (44.41 ± 4.51 hours vs 61.03 ± 5.16 hours, P = 0.02) and the time to the FFE (60.67 ± 4.94 hours vs 82.50 ± 6.88 hours, P = 0.014) were significantly shorter in the DEX group than the CON group. Furthermore, the time to regular diet of the DEX group was shorter than that of the CON group (76.15 ± 4.11 hours vs 91.50 ± 5.70 hours, P = 0.037). Both DAO and I-FABP increased significantly from beginning of surgery to postoperative day 1 in the CON group (2.49 ± 0.41 ng/mL vs 4.48 ± 0.94 ng/mL for DAO, P = 0.028, 1.32 ± 0.09 ng/mL vs 2.17 ± 0.12 ng/mL for I-FABP, P = 0.045, respectively), whereas no significant change was observed in the DEX group. Furthermore, patients in the DEX group had stable hemodynamics and shorter hospital stay than those in the CON group.

CONCLUSION

Dex administration intraoperatively benefits recovery of gastrointestinal motility function after laparoscopic resection of colorectal cancer with stable hemodynamics during surgery though further studies are needed to explore the mechanisms of Dex on gastrointestinal motility.

Electrophysiological Effects of Dexmedetomidine on Sinoatrial Nodes of Rabbits

BACKGROUND

The purpose of this study was to investigate the electrophysiological effects of dexmedetomidine on pacemaker cells in sinoatrial nodes of rabbits.

METHODS

Healthy rabbits were anesthetized intravenously with sodium pentobarbital, and the hearts were quickly dissected and mounted in a tissue bath. Machine-pulled glass capillary microelectrodes which were connected to a high input impedance amplifier and impaled in dominant pacemaker cells. Thereafter, an intracellular microelectrode technique was used to record action potential.

RESULTS

The amplitude of action potential, velocity of diastolic (phase 4) depolarization, and rate of pacemaker firing in normal pacemaker cells in sinoatrial node were decreased by use of dexmedetomidine (0.5 ng/ml, 5 ng/ml, 50 ng/ml) in a concentration-dependent manner. Pretreatment with yohimbine (1 μM), did not alter the effects of dexmedetomidine (5 ng/ml) on sinoatrial node pacemaker cells. Pretreatment with CsCl (2 mmol/L), dexmedetomidine (5 ng/ml) decreased the amplitude of action potential, but had no significant effect on other parameters of action potential.

CONCLUSIONS

Dexmedetomidine exerts inhibitory electrophysiological effects on pacemaker cells in sinoatrial nodes of rabbits in a concentration-dependent manner, which may not be mediated by alpha 2-adrenoreceptor.

KEY WORDS

Action potential; Cardiology; Dexmedetomidine; Pacemaker activity; Sinoatrial node.

Dexmedetomidine Protects against Transient Global Cerebral Ischemia/Reperfusion Induced Oxidative Stress and Inflammation in Diabetic Rats

BACKGROUND

Transient global cerebral ischemia/reperfusion (I/R) is a major perioperative complication, and diabetes increases the response of oxidative stress and inflammation induced by I/R. The objective of this study was to determine the protective effect of dexmedetomidine against transient global cerebral ischemia/reperfusion induced oxidative stress and inflammation in diabetic rats.

METHODS

Sixty-four rats were assigned into four experimental groups: normoglycemia, normoglycemia + dexmedetomidine, hyperglycemia, and hyperglycemia + dexmedetomidine and all subsequent neurological examinations were evaluated by a blinded observer. Damage to the brain was histologically assessed using the TUNEL staining method while western blotting was used to investigate changes in the expression levels of apoptosis-related proteins as well as the microglia marker, ionized calcium-binding adapter molecule 1 (Iba1). Water content in the brain was also analyzed. In addition, hippocampal concentrations of malondialdehyde (MDA) and Nox2 (a member of the Nox family of NADPH oxidases), and the activity of superoxide dismutase and catalase were analyzed. Finally, changes in serum concentrations of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 were detected.

RESULTS

Results showed that diabetes increased brain water content, the number of apoptotic neurons, early neurological deficit scores, oxidative stress (MDA and Nox2) and inflammation (pro-inflammatory cytokines including TNF-α and IL-6) levels following transient global I/R injury, but that these symptoms were attenuated following administration of dexmedetomidine.

CONCLUSIONS

These findings suggest that dexmedetomidine can significantly alleviate damage resulting from I/R, and this mechanism may be related to a reduction in both oxidative stress and inflammation which is normally associated with I/R.

Cardiac and renal protective effects of dexmedetomidine in cardiac surgeries: A randomized controlled trial

BACKGROUND

Cardiac and renal injuries are common insults after cardiac surgeries that contribute to perioperative morbidity and mortality. Dexmedetomidine has been shown to protect several organs against ischemia/reperfusion-(I/R) induced injury. We performed a randomized controlled trial to assess the effect of dexmedetomidine on cardiac and renal I/R injury in patients undergoing cardiac surgeries.

MATERIALS AND METHODS

Fifty patients scheduled for elective cardiac surgeries were randomized to dexmedetomidine group that received a continuous infusion of dexmedetomidine initiated 5 min before cardiopulmonary bypass (1 μg/kg over 15 min, followed by 0.5 μg/kg/h) until 6 h after surgery, whereas the control group received an equivalent volume of physiological saline. Primary outcome measures included myocardial-specific proteins (troponin-I, creatine kinase-MB), urinary-specific kidney proteins (N-acetyl-beta-D-glucosaminidase, alpha-1-microglobulin, glutathione transferase-pi, glutathione transferase alpha), serum proinflammatory cytokines (tumor necrosis factor alpha and interleukin-1 beta), norepinephrine, and cortisol levels. They were measured within 5 min of starting anesthesia (T₀), at the end of surgery (T₁), 12 h after surgery (T₂), 24 h after surgery (T₃), 36 h postoperatively (T₄), and 48 h postoperatively (T₅). Furthermore, creatinine clearance and serum cystatin C were measured before starting surgery as a baseline, and at days 1, 4, 7 after surgery.

RESULTS

Dexmedetomidine reduced cardiac and renal injury as evidenced by lower concentration of myocardial-specific proteins, kidney-specific urinary proteins, and pro-inflammatory cytokines. Moreover, it caused higher creatinine clearance and lower serum cystatin C.

CONCLUSION

Dexmedetomidine provided cardiac and renal protection during cardiac surgery.

Neuroprotective effects of dexmedetomidine conditioning strategies: Evidences from an in vitro model of cerebral ischemia

AIMS

Dexmedetomidine is a selective agonist of α2-adrenergic receptors with clinical anesthetic and analgesic properties that has also shown neuroprotective effects on several models of brain injury. Because perioperative stroke and brain damage are frequent causes of death in critical care units, we aimed to investigate neuroprotective properties of dexmedetomidine using an in vitro model of cerebral ischemia.

MAIN METHODS

Primary mixed rat brain cortical cultures were subjected to oxygen and glucose deprivation and treated with different doses of dexmedetomidine in order to analyze three conditioning strategies: preconditioning, intraconditioning and postconditioning.

KEY FINDINGS

All dexmedetomidine pre-, intra- and postconditioning treatments showed neuroprotective effects reducing brain cell necrosis, although only preconditioning showed antiapoptotic effects. Dexmedetomidine treatments also reduced IL-6 and TNF-α levels, especially in the preconditioning groups. Oxidative stress was attenuated with all dexmedetomidine preconditioning treatments, but only with the higher dose in the intraconditioning group, and no effects were observed in the postconditioning. All conditioning strategies increased BDNF levels.

SIGNIFICANCE

Dexmedetomidine-mediated neuroprotective effects in an in vitro model of cerebral ischemia involve the attenuation of inflammation and oxidative stress and the increment of BDNF expression.

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

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

Protective effects of udenafil citrate, piracetam and dexmedetomidine treatment on testicular torsion/detorsion-induced ischaemia/reperfusion injury in rats

The aim of this study was to investigate the antioxidant properties of udenafil citrate (1.4 mg kg(-1) -2.8 mg kg(-1) ), dexmedetomidine 25 μg kg(-1) and piracetam 200 mg kg(-1) administered on ipsilateral/contralateral testes after ischaemia in a rat model of testicular torsion/detorsion (T/D) and define its protective effect histologically. Fifty-six Wistar albino rats were included and randomly assigned into 6 groups. No intervention was performed in control group (Group 1, n = 8) and in torsion/detorsion group, (Group 2, n = 8). Udenafil 1.4 mg kg(-1) was given to torsion/detorsion group (Group 3, n = 10), udenafil 2.8 mg kg(-1) was given to torsion/detorsion group (Group 4, n = 10), piracetam 200 mg kg(-1) was given to torsion/detorsion group (Group 5, n = 10) and dexmedetomidine 25 μg kg(-1) was given to torsion/detorsion group (Group 6, n = 10) intraperitoneally after 60 mins of testicular torsion. Biochemical and histopathological testicular injury were evaluated. When the tissue was examined by TOS values, Group 3, Group 4 and Group 5 were significantly lower than Group 2. In contrary Group 6 values were significantly higher than Group 2. The increasing doses of udenafil demonstrated antioxidant properties on the testis tissue and histopathological that protects the testicles.

Role of dexmedetomidine in IL-4 and IFN-γ expression in rats with multiple organ dysfunction syndrome induced by postpartum bleeding

Bleeding-induced multiple organ dysfunction syndrome (MODS) is one of the major causes of death in pregnant women. MODS is thought to result from an inappropriate generalized host inflammatory response to a variety of acute insults. In this study we established a MODS model in postpartum rats, in which MODS was induced by the combination of induced hypotension for 60 min and clamping of the superior mesenteric artery for a period of 40 min. We sacrificed all the rats 24 h after dexmedetomidine (DEX) treatment. Thymus, spleen, and mesenteric lymph node tissue were collected to detect interferon-γ (IFN-γ) and interleukin-4 (IL-4) protein expression; lung and intestine tissue were collected to measure IFN-γ and IL-4 gene expression. In the present study, IFN-γ and IL-4 mRNA were increased in the lungs and intestines of the MODS rats. DEX administration decreased IFN-γ and IL-4 mRNA expression. IFN-γ and IL-4 expression for the thymus, spleen, and mesenteric lymph nodes were higher in the MODS postpartum rats relative to control rats, and these expression levels decreased upon DEX administration, But there were no significant differences between DEX doses. In conclusion DEX administration appeared to reduce IFN-γ and IL-4 protein expression in thymus, spleen, and mesenteric lymph node tissue and reduce IFN-γ and IL-4 gene expression in the lungs and intestines in the MODS postpartum rats but was not dose-dependent.

Dexmedetomidine Modulates Histamine-induced Ca(2+) Signaling and Pro-inflammatory Cytokine Expression

Dexmedetomidine is a sedative and analgesic agent that exerts its effects by selectively agonizing α2 adrenoceptor. Histamine is a pathophysiological amine that activates G protein-coupled receptors, to induce Ca(2+) release and subsequent mediate or progress inflammation. Dexmedetomidine has been reported to exert inhibitory effect on inflammation both in vitro and in vivo studies. However, it is unclear that dexmedetomidine modulates histamine-induced signaling and pro-inflammatory cytokine expression. This study was carried out to assess how dexmedetomidine modulates histamine-induced Ca(2+) signaling and regulates the expression of pro-inflammatory cytokine genes encoding interleukin (IL)-6 and -8. To elucidate the regulatory role of dexmedetomidine on histamine signaling, HeLa cells and human salivary gland cells which are endogenously expressed histamine 1 receptor were used. Dexmedetomidine itself did not trigger Ca(2+) peak or increase in the presence or absence of external Ca(2+). When cells were stimulated with histamine after pretreatment with various concentrations of dexmedetomidine, we observed inhibited histamine-induced [Ca(2+)]i signal in both cell types. Histamine stimulated IL-6 mRNA expression not IL-8 mRNA within 2 hrs, however this effect was attenuated by dexmedetomidine. Collectively, these findings suggest that dexmedetomidine modulates histamine-induced Ca(2+) signaling and IL-6 expression and will be useful for understanding the antagonistic properties of dexmedetomidine on histamine-induced signaling beyond its sedative effect.

Intranasal dexmedetomidine in combination with patient-controlled sedation during upper gastrointestinal endoscopy: a randomised trial

BACKGROUND

Sedation using intranasal dexmedetomidine is a convenient and well-tolerated technique. This study evaluated the sedative efficacy of intranasal dexmedetomidine in combination with patient-controlled sedation (PCS) for upper gastrointestinal endoscopy.

METHODS

In this double-blind, randomised, controlled trial, 50 patients received either intranasal dexmedetomidine 1.5 μg/kg (dexmedetomidine group) or intranasal saline (placebo group) 1 h before the procedure. PCS with propofol and alfentanil was provided for rescue sedation. Additional sedative consumption, perioperative sedation scores using Observer's Assessment of Alertness/Sedation (OAA/S) scale, recovery, vital signs, adverse events and patient satisfaction were assessed.

RESULTS

Total consumption of PCS propofol and alfentanil was significantly less in the dexmedetomidine than placebo group with a mean difference of -13.8 mg propofol (95% confidence interval -27.3 to -0.3) and -34.5 μg alfentanil (95% confidence interval -68.2 to -0.7) at the completion of the procedure (P = 0.044). Weighted areas under the curve (AUCw ) of OAA/S scores were significantly lower in the dexmedetomidine group before, during and after procedures (P < 0.001, P = 0.024 and P = 0.041 respectively). AUCw of heart rate and systolic blood pressure were also significantly lower during the procedure (P = 0.007 and P = 0.022 respectively) with dexmedetomidine. There was no difference in recovery, side effects or satisfaction.

CONCLUSION

Intranasal dexmedetomidine with PCS propofol and alfentanil confers deeper perioperative clinical sedation with significantly less use of additional sedatives during upper gastrointestinal endoscopy.

Dexmedetomidine on renal ischemia-reperfusion injury in rats: assessment by means of NGAL and histology

BACKGROUND

Ischemic acute kidney injury is a common occurrence in the perioperative period and in critical patients admitted to intensive care units. The reestablishment of blood supply may worsen injury through the ischemia-reperfusion (I/R) mechanism. We investigated the effect of dexmedetomidine on the kidneys of rats subjected to an experimental I/R model.

METHODS

34 rats anesthetized with isoflurane was undergone right nephrectomy and randomly assigned to four groups: Control C (saline solution); Dexmedetomidine D (dexmedetomidine); Sham S (saline solution); Sham with Dexmedetomidine SD (dexmedetomidine). The serum levels of neutrophil gelatinase-associated lipocalin (NGAL) were measured at time-points T1 (following stabilization), T2 (ischemia), T3 (reperfusion), T4 (12 h after of I/R). The kidneys were subjected to histological examination.

RESULTS

The NGAL levels were significantly higher at T4 compared with T1. Upon histological examination, the left kidneys in groups C and D exhibited a similar extent of cell injury.

CONCLUSION

The levels of NGAL did not indicate either protection against or worsening of kidney injury. Histological examination for acute tubular necrosis showed that dexmedetomidine did not protect the kidneys from I/R.

Bradycardia in perspective-not all reductions in heart rate need immediate intervention

According to Wikipedia, the word 'bradycardia' stems from the Greek βραδύς, bradys, 'slow', and καρδία, kardia, 'heart'. Thus, the meaning of bradycardia is slow heart rate but not necessarily too slow heart rate. If looking at top endurance athletes they may have a resting heart rate in the very low thirties without needing emergent intervention with anticholinergics, isoprenaline, epinephrine, chest compressions or the insertion of an emergency pacemaker (Figure 1). In fact, they withstand these episodes without incident, accommodating with a compensatory increase in stroke volume to preserve and maintain cardiac output. With this in mind, it is difficult for the authors to fully understand and agree with the general sentiment amongst many pediatric anesthesiologists that all isolated bradycardia portends impending doom and must be immediately treated with resuscitative measures.

Mechanisms of testicular torsion and potential protective agents

Testicular torsion is a urological emergency most commonly seen in adolescence, involving a decrease in blood flow in the testis resulting from torsion of the spermatic cord that can result in gonad injury or even loss if not treated in time. Testicular ischaemia-reperfusion injury represents the principle pathophysiology of testicular torsion, with ischaemia caused by twisting of the spermatic cord, and reperfusion on its subsequent release. Many cellular and molecular mechanisms are involved in ischaemia-reperfusion injury following testicular torsion. Studies have investigated the use of pharmacological agents as supportive therapy to surgical repair in order to prevent the adverse effects of testicular torsion. Numerous substances have been proposed as important in the prevention of post-ischaemia-reperfusion testicular injury. A range of chemicals and drugs has been successfully tested in animal models for the purpose of mitigating the dangerous effects of ischaemia-reperfusion in testis torsion.

Dexmedetomidine: a review of applications for cardiac surgery during perioperative period

Cardiac surgery is associated with a high incidence of cardiovascular and other complications during the perioperative period that translate into increased mortality and prolonged hospital stays. Safe comprehensive perioperative management is required to eliminate these adverse events. Dexmedetomidine is a selective α2-adrenoreceptor agonist that has been described as an ideal medication in the perioperative period of cardiac surgery. The major clinical effects of dexmedetomidine in this perioperative period can be summarized as attenuating the hemodynamic response, cardioprotective effects, antiarrhythmic effects, sedation in the ICU setting, treatment of delirium, and procedural sedation. Although there are some side effects of dexmedetomidine, it is emerging as an effective therapeutic agent in the management of a wide range of clinical conditions with an efficacious, safe profile. The present review serves as an overview update in the diverse applications of dexmedetomidine for cardiac surgery during the perioperative period.

Dexmedetomidine: a review of applications for cardiac surgery during perioperative period

Cardiac surgery is associated with a high incidence of cardiovascular and other complications during the perioperative period that translate into increased mortality and prolonged hospital stays. Safe comprehensive perioperative management is required to eliminate these adverse events. Dexmedetomidine is a selective α2-adrenoreceptor agonist that has been described as an ideal medication in the perioperative period of cardiac surgery. The major clinical effects of dexmedetomidine in this perioperative period can be summarized as attenuating the hemodynamic response, cardioprotective effects, antiarrhythmic effects, sedation in the ICU setting, treatment of delirium, and procedural sedation. Although there are some side effects of dexmedetomidine, it is emerging as an effective therapeutic agent in the management of a wide range of clinical conditions with an efficacious, safe profile. The present review serves as an overview update in the diverse applications of dexmedetomidine for cardiac surgery during the perioperative period.

Molecular targets and mechanism of action of dexmedetomidine in treatment of ischemia/reperfusion injury

Dexmedetomidine (DEX), a highly specific α2-adrenergic agonist, which exhibits anaesthetic-sparing, analgesia and sympatholytic properties. DEX modulates gene expression, channel activation, transmitter release, inflammatory processes and apoptotic and necrotic cell death. It has also been demonstrated to have protective effects in a variety of animal models of ischemia/reperfusion (I/R) injury, including the intestine, myocardial, renal, lung, cerebral and liver. The broad spectrum of biological activities associated with DEX continues to expand, and its diverse effects suggest that it may offer a novel therapeutic approach for the treatment of human diseases with I/R involvement.

Dexmedetomidine reduces intestinal and hepatic injury after hepatectomy with inflow occlusion under general anaesthesia: a randomized controlled trial

BACKGROUND

We compared intestinal, hepatic, and other organ function after hepatic portal occlusion with or without dexmedetomidine administration under general anaesthesia.

METHODS

In this prospective, randomized double-blind investigation, 44 patients undergoing elective hepatectomy with inflow occlusion were randomized into a dexmedetomidine group or a control group. The dexmedetomidine group received an initial dexmedetomidine loading dose of 1 μg kg(-1) over 10 min followed by a maintenance dose of 0.3 μg kg(-1) h(-1). In the control group, 0.9% sodium chloride was administered. The primary outcome was serum diamine oxidase (DAO) activity reflecting intestinal injury. The secondary outcomes included variables reflecting intestinal, hepatic, kidney, and cardiopulmonary function, and biomarkers of oxidative stress and systemic inflammatory response.

RESULTS

DAO activity was lower in the dexmedetomidine group than in the control group at 6 and 24 h after liver reperfusion [9.77 (1.07) vs14.29 (1.43) units ml(-1), P=0.021; 9.67 (0.98) vs 13.97 (1.31) units ml(-1), P=0.017]. d-lactate acid levels were lower during 1-72 h after liver reperfusion compared with the control group (all P<0.05). Also, the intestinal injury severity grade was decreased by dexmedetomidine (P=0.038). The biomarkers reflecting liver injury increased over time, but were lower in the dexmedetomidine group (all P<0.05), while the variables reflecting cardiopulmonary and renal function showed no differences between the groups (all P>0.05).

CONCLUSIONS

Dexmedetomidine administered perioperatively attenuates intestinal and hepatic injury in patients undergoing elective liver resection with inflow occlusion without any potential risk.

CLINICAL TRIAL REGISTRATION

ChiCTR-TRC-11001530, September 2011.

Preconditionin effects of dexmedetomidine on myocardial ischemia/reperfusion injury in rats

BACKGROUND

Preconditioning might protect the myocardium against ischemia/ reperfusion injury by reducing infarct size and preventing arrhythmias. Dexmedetomidine (DEX) is a highly selective α2-agonist used for sedoanalgesia in daily anesthetic practice. The cardioprotective effects of DEX on infarct size and on the incidence of arrhythmias observed after regional ischemia/reperfusion injury in vivo have not been reported.

OBJECTIVE

The aim of this study was to determine whether DEX exhibits a preconditioning effect and reduces infarct size and the incidence and duration of arrhythmias in a regional cardiac ischemia/reperfusion model in rats.

METHODS

Adult male Sprague-Dawley rats were anesthetized with sodium thiopental and mechanically ventilated (0.9 mL/100 g at 60 strokes/min) through a cannula inserted into the trachea after tracheotomy. Cardiac ischemia was then produced by ligating the left main coronary artery for 30 minutes, followed by a reperfusion period of 120 minutes. Blood pressure (BP) and heart rate (HR) were monitored and echocardiograms (ECGs) were performed. Arrhythmia was scored based on incidence and duration. The animals were randomly divided into 3 groups. The ischemic preconditioning (IPC) group underwent 5 minutes of ischemia followed by 5 minutes of reperfusion before the 30-minute ischemia/120-minute reperfusion period. In the DEX group, intraperitoneal (IP) DEX 1 mL (100 μg/kg) was administered 30 minutes before the ischemia/ reperfusion period. In the control group, IP saline 1 mL was administered 30 minutes before the ischemia/reperfusion period. After reperfusion, the heart was excised, demarcated with saline and ethanol to identify the occluded and nonoccluded myocardium, and cut into slices ~2 mm thick, that were then stained and placed between 2 glass plates. The risk zone and the infarct zone were compared between groups. The investigator assessing the infarcts was blinded to the study group.

RESULTS

Twenty-one adult (aged 4-6 months) male Sprague-Dawley rats weighing 280 to 360 g were included in the study; 7 rats were assigned to each group. BP, HR, and ECG readings were not significantly different between groups and did not change during the study. Arrythmias occurred during ischemia and reperfusion in all groups. The duration of the arrhythmias was significantly shorter and the arrhythmia score was significantly lower in the IPC group (all, P<0.05), compared with the control group; however, they were not significantly different in the DEX group. During the ischemic period, duration of ventricular tachycardia (VT) and ventricular premature contractions (VPC) in the DEX group was significantly longer than that observed in the IPC group (all, P<0.05). The duration of VPC was also significantly shorter than that observed in the control group (both, P<0.05). Duration of VT during the reperfusion period in the DEX group was significantly longer than that observed in both IPC and control groups (both, P<0.05). The mean (SD) percentage of damage was significantly lower in the IPC group (44.1% [2.0%]) and the DEX group (26.7% [2.0%]) compared with the control group (69.0% [3.0%]; both, P<0.05). The percentage of damage in the DEX group was also significantly lower compared with the IPC group (P<0.05).

CONCLUSIONS

This small, experimental in vivo study found that DEX was associated with reduced infarct size in ischemia/reperfusion injury in regional ischemia in this rat model but had no effect on the incidence of arrhythmias. Future studies are needed to clarify these findings.

The effect of dexmedetomidine on oxidative stress during pneumoperitoneum

Purpose. This study was intended to investigate the effect of dexmedetomidine on oxidative stress response in pneumoperitoneum established in rats. Methods. Animals were randomized into three groups, group S: with no pneumoperitoneum, group P: with pneumoperitoneum established, and group D: given 100 mcg intraperitoneal dexmedetomidine 30 min before establishment of pneumoperitoneum. Plasma total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI) activity were measured 30 min after conclusion of pneumoperitoneum. Results. The mean TOS level was significantly higher in group P than in the other two groups, and the TOS level was significantly higher in group D than in group S (P < 0.05). Plasma TAS level was found to be lower in group P than in the other two groups, and the TAS level was lower in group D than in group S (P < 0.05). Consequently, the OSI was significantly higher in group P than in groups D and S (P < 0.05). Conclusions. Ischemia-reperfusion phenomenon that occurs during pneumoperitoneum causes oxidative stress and consumption of plasma antioxidants. Dexmedetomidine decreases oxidative stress caused by pneumoperitoneum and strengthens the antioxidant defense system.

Dexmedetomidine infusion for analgesia up to 48 hours after lung surgery performed by lateral thoracotomy

Patients undergoing a lateral thoracotomy for pulmonary resection have moderate to severe pain postoperatively that is often treated with opioids. Opioid side effects such as respiratory depression can be devastating in patients with already compromised respiratory function. This prospective double-blinded clinical trial examined the analgesic effects and safety of a dexmedetomidine infusion for postthoracotomy patients when administered on a telemetry nursing floor, 24 to 48 hours after surgery, to determine if the drug's known early opioid-sparing properties were maintained. Thirty-eight thoracotomy patients were administered dexmedetomidine intraoperatively and overnight postoperatively and then randomized to receive placebo or dexmedetomidine titrated from 0.1 to 0.5 μg·kg·h(-1) the day following surgery for up to 24 hours on a telemetry floor. Opioids via a patient-controlled analgesia pump were available for both groups, and vital signs including transcutaneous carbon dioxide, pulse oximetry, respiratory rate, and pain and sedation scores were monitored. The dexmedetomidine group used 41% less opioids but achieved pain scores equal to those of the placebo group. The mean heart rate and systolic blood pressure were lower in the dexmedetomidine group but sedation scores were better. The mean respiratory rate and oxygen saturation were similar in the two groups. Mild hypercarbia occurred in both groups, but periods of significant respiratory depression were noted only in the placebo group. Significant hypotension was noted in one patient in the dexmedetomidine group in conjunction with concomitant administration of a beta-blocker agent. The placebo group reported a higher number of opioid-related adverse events. In conclusion, the known opioid-sparing properties of dexmedetomidine in the immediate postoperative period are maintained over 48 hours.

Perioperative dexmedetomidine improves mortality in patients undergoing coronary artery bypass surgery

OBJECTIVE

This study retrospectively investigated the effect of dexmedetomidine on outcomes of patients undergoing coronary artery bypass graft (CABG) surgery.

DESIGN

Retrospective investigation.

SETTING

Patients from a single tertiary medical center.

PARTICIPANTS

A total of 724 patients undergoing CABG surgery met the inclusion criteria and were categorized into 2 groups: 345 in the dexmedetomidine group (DEX) and 379 in the nondexmedetomidine group (Non-DEX).

INTERVENTIONS

Perioperative dexmedetomidine was used as an intravenous infusion (0.24 to 0.6 µg/kg/hour) initiated after cardiopulmonary bypass and continued for less than 24 hours postoperatively in the intensive care unit.

MEASUREMENTS AND MAIN RESULTS

Major outcome measures of this study were in-hospital, 30-day and 1-year all-cause mortality, delirium and major adverse cardiocerebral events. Perioperative dexmedetomidine infusion was associated with significant reductions in in-hospital, 30-day, and 1-year mortalities, compared with the patients who did not received dexmedetomidine. In-hospital, 30-day, and 1-year mortalities were 1.5% and 4.0% (adjusted odds ratio [OR], 0.332; 95% CI, 0.155 to 0.708; p = 0.0044), 2.0% and 4.5% (adjusted OR, 0.487; 95% CI, 0.253 to 0.985; p = 0.0305), and 3.2% and 6.9% (adjusted OR 0.421; 95% CI, 0.247 to 0.718, p = 0.0015), respectively. Perioperative dexmedetomidine infusion was associated with a reduced risk of delirium from 7.9% to 4.6% (adjusted OR, 0.431; 95% CI, 0.265-0.701; p = 0.0007).

CONCLUSION

Dexmedetomidine infusion during CABG surgery was more likely to achieve improved in-hospital, 30-day, and 1-year survival rates, and a significantly lower incidence of delirium.

Post-bypass dexmedetomidine use and postoperative acute kidney injury in patients undergoing cardiac surgery with cardiopulmonary bypass

BACKGROUND

AND OBJECTIVES: The aim of this retrospective investigation was to study the relationships among chronic kidney disease, acute kidney injury (AKI), and potential benefits by post-bypass dexmedetomidine use in patients undergoing cardiac surgery.

METHODS

The patient data were reviewed from the institutional Society of Thoracic Surgeons National Adult Cardiac Surgery Database after IRB approval. 1,133 patients were identified and divided into two groups: those who received dexmedetomidine or those who did not during the post-bypass period. The postoperative outcomes include the incidence of AKI, any complication and all cause of mortality.

RESULTS

Post-bypass dexmedetomidine use was associated with significantly reduced the incidence of total AKI (26.1% vs. 33.75%; adjusted OR, 0.7033; 95%CI, 0.540 to 0.916; p=0.0089). In addition, post-bypass dexmedetomidine use was more likely to reduce the incidence of AKI in these patients with preoperative normal kidney function (Stage1; 32.8% to 22.8%; p=0.0233) and mild CKD (Stage 2; 32.8% to 24.7; p=0.0003) after cardiac surgery. Post-bypass infusion of dexmedetomidine was associated with significantly reduced incidence of any complication and 30-day mortalities.

CONCLUSIONS

Post-bypass dexmedetomidine use is associated with a significant reduction in the incidence of AKI, especially mild AKI in patients with preoperative normal renal function and mild CKD undergoing cardiac surgery.

Effect of dexmedetomidine pretreatment on lung injury following intestinal ischemia-reperfusion

Reperfusion injury is tissue damage caused by the re-supply of blood following a period of ischemia in tissues. Intestinal ischemia-reperfusion injury (IRI) is an extremely common clinical event associated with distant organ injury. The intestine serves as the initial organ of multi-system organ dysfunction syndrome. It is extremely important to identify a method to protect against IRI, as it is a key factor associated with morbidity and mortality in patients. In the present study, the protective effects of pretreatment with dexmedetomidine hydrochloride were investigated. Rats were divided into six groups and models of intestinal ischemia were created in the five groups. Certain groups were pretreated with dexmedetomidine hydrochloride. The levels of TNF-α and IL-6 were measured by enzyme-linked immunosorbent assay in order to evaluate the injury. Tissue sections were stained with hematoxylin and eosin to visualize the damage. qPCR and western blotting were performed to examine the inflammatory status. Pretreatment with various doses of dexmedetomidine hydrochloride significantly reduced the pathological scores and the inflammatory reaction. The levels of TNF-α, IL-6, TLR4 and MyD88 were decreased in the dexmedetomidine hydrochloride treatment groups compared with those in the sham control and untreated ischemia reperfusion groups. The results of the present study indicate that pretreatment with dexmedetomidine hydrochloride may be a useful method of reducing the damage caused by IRI.

Interruption of spinal cord microglial signaling by alpha-2 agonist dexmedetomidine in a murine model of delayed paraplegia

BACKGROUND

Despite investigation into preventable pharmacologic adjuncts, paraplegia continues to complicate thoracoabdominal aortic interventions. The alpha 2a adrenergic receptor agonist, dexmedetomidine, has been shown to preserve neurologic function and neuronal viability in a murine model of spinal cord ischemia reperfusion, although the mechanism remains elusive. We hypothesize that dexmedetomidine will blunt postischemic inflammation in vivo following thoracic aortic occlusion with in vitro demonstration of microglial inhibition following lipopolysaccharide (LPS) stimulation.

METHODS

Adult male C57BL/6 mice underwent 4 minutes of aortic occlusion. Mice received 25 μg/kg intraperitoneal dexmedetomidine (n = 8) or 0.9% normal saline (n = 7) at reperfusion and 12-hour intervals postoperatively until 48 hours. Additionally, sham mice (n = 3), which had aortic arch exposed with no occlusion, were included for comparison. Functional scoring was done at 6 hours following surgery and 12-hour intervals until 60 hours when spinal cords were removed and examined for neuronal viability and cytokine production. Additional analysis of microglia activation was done in 12 hours following surgery. Age- and sex-matched mice had spinal cord removed for microglial isolation culture. Cells were grown to confluence and stimulated with toll-like receptor-4 agonist LPS 100 ng/mL in presence of dexmedetomidine or vehicle control for 24 hours. Microglia and media were then removed for analysis of protein expression.

RESULTS

Dexmedetomidine treatment at reperfusion significantly preserved neurologic function with mice in treatment group having a Basso Score of 6.3 in comparison to 2.3 in ischemic control group. Treatment was associated with a significant reduction in microglia activation and in interleukin-6 production. Microglial cells in isolation when stimulated with LPS had an increased production of proinflammatory cytokines and markers of activation. Treatment with dexmedetomidine significantly attenuated microglial activation and proinflammatory cytokine production in vitro with a greater than twofold reduction in tumor necrosis factor-α.

CONCLUSIONS

Alpha 2a agonist, dexmedetomidine treatment at reperfusion preserved neurologic function and neuronal viability. Furthermore, dexmedetomidine treatment resulted in an attenuation of microglial activation and proinflammatory cytokine production both in vivo and in vitro following LPS stimulation. This finding lends insight into the mechanism of paralysis following thoracic aortic interventions and may guide future pharmacologic targets for attenuating spinal cord ischemia and reperfusion.

Dexmedetomidine reduced cytokine release during postpartum bleeding-induced multiple organ dysfunction syndrome in rats

Dexmedetomidine (DEX) is an α2-adrenergic agonist. It decreases the levels of norepinephrine release, resulting in a reduction of postsynaptic adrenergic activity. In the present study, the effects of DEX on postpartum bleeding-induced multiple organ dysfunction syndrome (BMODS) were studied in rats in which BMODS was induced by the combination of hypotension and clamping of the superior mesenteric artery. We evaluated the role of dexmedetomidine (DEX) in cytokine release during postpartum BMODS in rats. In summary, the present study demonstrated that DEX administration reduced IFN-r and IL-4 release and decreased lung injury during postpartum BMODS. It is possible that DEX administration decreased inflammatory cytokine production in BMODS by inhibiting inflammation and free radical release by leukocytes independent of the DEX dose.

Does dexmedetomidine provide cardioprotection in coronary artery bypass grafting with cardiopulmonary bypass? A pilot study

OBJECTIVE

The purpose of this pilot study was to evaluate whether dexmedetomidine has a cardioprotective effect during coronary artery bypass graft surgery with cardiopulmonary bypass (CPB).

DESIGN

A prospective, double-blind, randomized controlled trial.

SETTING

A university hospital.

PARTICIPANTS

Thirty-eight patients undergoing coronary artery bypass graft surgery.

INTERVENTIONS

Patients were randomized into 2 groups: dexmedetomidine and placebo groups. In the dexmedetomidine group, dexmedetomidine infusion was started by a loading dose of 0.5 μg/kg/10 min, followed by a continuous infusion of 0.5 μg/kg/h. The placebo group received the same volume of saline. Measurements of central venous pressure, mean pulmonary artery pressure (MPAP) and cardiac index were performed before and after dexmedetomidine loading dose and 2, 24 and 48 hours after CPB. Simultaneously, arterial blood was sampled for CK-MB, cardiac troponin T, and N-terminal probrain natriuretic peptide.

MEASUREMENTS AND MAIN RESULTS

CK-MB, cardiac troponin T and N-terminal probrain natriuretic peptide values were elevated in the periods after CPB in both groups (p<0.05) and there were no statistically significant differences between groups. MPAP was decreased in the dexmedetomidine group at the 2nd, 24th and 48th hour after CPB (p<0.001, p<0.001, p = 0.002, respectively). Higher cardiac index values were seen earlier in the dexmedetomidine group than in the placebo group (p< 0.05).

CONCLUSIONS

Myocardial damage was not reduced by administration of 0.5 μg/kg loading dose and 0.5 μg/kg/h infusion of dexmedetomidine. However MPAP tended to be lower in the dexmedetomidine group. Large-scale clinical outcome studies are indicated to confirm the effect of dexmedetomidine.

Use of dexmedetomidine to prevent pulmonary injury after pneumoperitoneum in ventilated rats

PURPOSE

This study examined the effectiveness of dexmedetomidine in preventing lung injury resulting from pneumoperitoneum in a ventilated rat model.

METHODS

Animals (n=18) were allocated randomly into 3 groups: control group, no pneumoperitoneum; sham group, pneumoperitoneum with intra-abdominal pressure of 12 mm Hg for 60 minutes; and dexmedetomidine group, dexmedetomidine administration 30 minutes before pneumoperitoneum. The rats were rested for 30 minutes after abdominal deflation. Then, blood samples were obtained for plasma malondialdehyde and ischemia-modified albumin (IMA) analyses. Tissue samples were taken for histopathologic examination and malondialdehyde analysis.

RESULTS

Compared with the control group, the sham group had a significantly higher level of plasma IMA. Pretreatment with dexmedetomidine significantly reduced the IMA level. Histopathologically, tissues from sham rats exhibited moderate or severe tissue damage, compared with control tissues. Dexmedetomidine-treated rats showed significantly less tissue damage than sham rats.

CONCLUSIONS

Dexmedetomidine prophylaxis resulted in significantly less IMA production and significantly less neutrophil infiltration, thereby helping to protect the lungs from injury after pneumoperitoneum.

Protective effects of dexmedetomidine in pneumoperitoneum-related ischaemia-reperfusion injury in rat ovarian tissue

OBJECTIVES

To determine the effects of dexmedetomidine on pneuomoperitoneum-related ischaemia-reperfusion (I/R) injury in rat ovarian tissue.

STUDY DESIGN

Animals were randomized into three groups: Group S (n=8), no pneumoperitoneum; Group C (n=8), pneumoperitoneum; and Group D (n=8), 100μg intraperitoneal dexmedetomidine 30min before pneumoperitoneum. Ovarian tissue was collected from all rats 30min after desufflation, and fresh frozen for histological and biochemical evaluation.

RESULTS

Body weight was similar in all three groups (202.62±28.86, 211.00±14.45 and 212.87±15.71g in Groups S, D and C, respectively). The mean malondialdehyde level was higher in Group C than the other groups (p<0.03). When the histological samples of ovarian tissue were compared, vascular congestion, haemorrhage, follicular cell degeneration and infiltrative cell infiltration scores were higher in Group C compared with the other groups (p<0.05). Significantly lower scores for the histological parameters were found in Group D compared with Group C (p<0.05). Similar scores for follicular cell degeneration and inflammatory cell infiltration were found in Group D and Group S (p>0.05). Although vascular congestion and haemorrhage scores were significantly lower compared with Group C, higher scores were found for Group D compared with Group S (p<0.05).

CONCLUSION

Pneumoperitoneum caused oxidative injury in rat ovarian tissue. Dexmedetomidine reduced oxidative stress and histological injury related to I/R.

Perioperative dexmedetomidine improves outcomes of cardiac surgery

BACKGROUND

Cardiac surgery is associated with a high risk of cardiovascular and other complications that translate into increased mortality and healthcare costs. This retrospective study was designed to determine whether the perioperative use of dexmedetomidine could reduce the incidence of complications and mortality after cardiac surgery.

METHODS AND RESULTS

A total of 1134 patients who underwent coronary artery bypass surgery and coronary artery bypass surgery plus valvular or other procedures were included. Of them, 568 received intravenous dexmedetomidine infusion and 566 did not. Data were adjusted with propensity scores, and multivariate logistic regression was used. The primary outcomes measured included mortality and postoperative major adverse cardiocerebral events (stroke, coma, perioperative myocardial infarction, heart block, or cardiac arrest). Secondary outcomes included renal failure, sepsis, delirium, postoperative ventilation hours, length of hospital stay, and 30-day readmission. Dexmedetomidine use significantly reduced postoperative in-hospital (1.23% versus 4.59%; adjusted odds ratio, 0.34; 95% confidence interval, 0.192-0.614; P<0.0001), 30-day (1.76% versus 5.12%; adjusted odds ratio, 0.39; 95% confidence interval, 0.226-0.655; P<0.0001), and 1-year (3.17% versus 7.95%; adjusted odds ratio, 0.47; 95% confidence interval, 0.312-0.701; P=0.0002) mortality. Perioperative dexmedetomidine therapy also reduced the risk of overall complications (47.18% versus 54.06%; adjusted odds ratio, 0.80; 95% confidence interval, 0.68-0.96; P=0.0136) and delirium (5.46% versus 7.42%; adjusted odds ratio, 0.53; 95% confidence interval, 0.37-0.75; P=0.0030).

CONCLUSION

Perioperative dexmedetomidine use was associated with a decrease in postoperative mortality up to 1 year and decreased incidence of postoperative complications and delirium in patients undergoing cardiac surgery.

CLINICAL TRIAL REGISTRATION

URL: www.clinicaltrials.gov. Unique identifier: NCT01683448.