Effect of dexmedetomidine on astrocytes in rats with focal cerebral ischemia-reperfusion

AIM: To investigate the effects of dexmedetomidine on astrocytes in rats with focal cerebral ischemia-reperfusion. METHODS: Sixty female SD rats, weighing 230~250 g, were randomly divided into sham operation group, ischemia-reperfusion group, dexmedetomidine preconditioning group 1 and dexmedetomidine preconditioning group 2. The model of middle cerebral artery occlusion (MCAO) was established by thread embolism of middle cerebral artery. In sham operation group, the carotid arteries were exposed without performing MCAO. In ischemia-reperfusion group, NS was injected intraperitoneally 30 min before focal cerebral ischemia-reperfusion. The rats in dexmedetomidine preconditioning group 1 and dexmedetomidine preconditioning group 2 received intraperitoneal injection of dexmedetomidine at doses of 20 μg/kg and 40 μg/kg, respectively. The neurological scores were studied, and the pathological changes were observed under microscope with HE staining. The expression of glial fibrillary acidic protein (GFAP) and tumor necrosis factor α (TNF-α) in astrocytes was detected by the methods of immunohistochemistry and immunoblotting 24 h after cerebral ischemia-reperfusion. RESULTS: No neurological change was observed in sham operation group. The neurological deficiency scores in ischemia-reperfusion group were markedly higher than those in dexmedetomidine preconditioning group 1 and group 2 (P<0.05). Compared with sham operation group, the expression of GFAP and TNF-α in astrocytes and the level of GFAP increased significantly 24 h after focal cerebral ischemia-reperfusion. Pretreatment with dexmedetomidine significantly attenuated the expression of GFAP and reduced the infarct size and inflammation. CONCLUSION: Dexmedetomidine has a neuroprotective effect on focal cerebral ischemia-reperfusion injury by inhibiting the astrocytes.     

Effect of sedation by infusion of dexmedetomidine on inflammatory factors in patients with severe trauma

AIM: To study the effect of short-term sedation by infusion of dexmedetomidine (DEX) on the inflammatory factors in the patients with severe trauma. METHODS: Sixty patients with severe trauma in ICU were randomly divided into 3 groups: DEX group (n=20), midazolam (MDZ) group (n=20) and control group (without any sedatives, n=20). Dexmedetomidine at an initial loading dose of 1~2 μg/kg was administered intravenously over 10 min to the patients in DEX group before the sedation procedure of continuous infusion at dose of 0.2~0.7 μg·kg^-1·h^-1 by a 50-mL infusion syringe was perform. Midazolam at dose of 0.03~0.3 mg/kg was also administered intravenously immediately before the procedure of a continuous infusion at dose of 0.03~0.2 mg·kg^-1·h^-1. The doses of DEX or MDZ for the patients receiving short-term (48 h) sedation were adjusted according to the Ramsay sedation scale scores. The serum levels of interleukins (IL-1 and IL-6), tumor necrosis factor α (TNF-α) and C-reactive protein (CRP) were measured at the time points of the baseline (before the start of the study), 24 h and 48 h of sedative infusion. RESULTS: The levels of TNF-α, IL-1, IL-6 and CRP in the 3 groups of severe traumatic patients at the time when they were admitted to the hospital were significantly higher than those of the normal values. The levels of TNF-α, IL-1, IL-6 and CRP in control group gradually increased at 24 h and 48 h, while those in DEX group and MDZ group significantly declined. No significant difference of TNF-α, IL-1, IL-6 and CRP levels between DEX group and MDZ group was observed at 24 h, but the changes were significantly different at 48 h. CONCLUSION: Dexmedetomidine reduces over-stress responses to a certain extent in the traumatic patients to prevent the further production and release of inflammatory mediators, thus contributing to the stability and recovery of the patients with severe trauma.     

Neurophysiological assessment of the sedative and analgesic effects of a constant rate infusion of dexmedetomidine in the dog

The sedative and analgesic effects of continuous rate infusion (CRI) of dexmedetomidine (DEX) were investigated in Beagle dogs (n = 8) using auditory and somatosensory evoked potentials (AEPs and SEPs) recorded before, during and after a CRI of saline or DEX (1.0, 3.0, 5.0 μg/kg bolus, followed by 1.0, 3.0, 5.0 μg/kg/h CRI, respectively).The results showed a significant reduction in AEP at doses of 1.0 μg/kg/h and above and a significant reduction of the SEP at doses of 3.0 and 5.0 μg/kg/h. Neither the AEP nor the SEP was further reduced at 5.0 μg/kg/h when compared to 3.0 μg/kg/h, although a slower return towards baseline values was observed at 5.0 μg/kg/h. The mean plasma levels (±SEM) of DEX during infusion were 0.533 ± 0.053 ng/mL for the 1.0 μg/kg/h dose, 1.869 ± 0.063 ng/mL for the 3.0 μg/kg/h dose and 4.017 ± 0.385 for the 5.0 μg/kg/dose. It was concluded that in adult dogs, a CRI of DEX had a sedative and analgesic effect that could be described quantitatively using neurophysiological parameters. Sedation was achieved at lower plasma levels than required for analgesia, and DEX had a longer (but not larger) effect with infusion rates above 3.0 μg/kg/h.     

Dexmedetomidine-induced pulmonary alterations in sheep

Alpha(2) agonist-induced pulmonary oedema in sheep might be related to alterations in pulmonary haemodynamics and/or activation of inflammatory processes. In seven sevoflurane-anaesthetized sheep pulmonary haemodynamics, arterial oxygen tensions, nitric oxide and prostaglandin E(2) concentrations were determined before and after intravenous dexmedetomidine (2microg kg(-1)). In a second trial, lung tissue was sampled for histopathology and quantitative real-time PCR for IL-1beta and iNOS mRNA in a control sheep and 2, 10 and 30min after dexmedetomidine. Computer tomography of the lung under sevoflurane anaesthesia before and after dexmedetomidine was performed. Two minutes after dexmedetomidine mean pulmonary artery pressure, pulmonary arterial occlusion pressure and estimated capillary pressurewere significantly increased to 34.5mmHg, 22.2mmHg and 27.1mmHg, respectively. On computer tomography, lung density increased immediately after dexmedetomidine, with maximal density occurring between 9 and 12min. Histopathology was consistent with vascular congestion followed by protein and erythrocyte extravasation into alveoli. Increased iNOS mRNA levels were detected in sevoflurane anaesthetized animals only. An IL-1beta signal occurred after morphological changes had occurred in lung tissue. These findings support hydrostatic stress as the underlying cause of alpha(2) agonist-induced pulmonary oedema in sheep.     

Dexmedetomidine attenuates acute kidney injury induced by hemorrhagic shock/resuscitation in rats

AIM: To investigate the effects of dexmedetomidine on hemorrhagic shock/resuscitation (HS/R)-induced acute kidney injury (AKI) in rats, and to explore the possible mechanisms. METHODS: Wistar rats (n=32) were randomly divided into 4 groups (n=8):normal saline control group (NS group), dexmedetomidine group (D group), HS/R group and HS/R+D group. The animals were sacrificed at 6 h after resuscitation. The levels of serum creatinine (Cr) and blood urine nitrogen (BUN) were examined. The kidneys of all rats were removed for evaluation of histological characteristics, and the levels of malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and superoxide dismutase (SOD) were measured. The expression of nuclear factor-κB (NF-κB) and hemeoxygenase-1 (HO-1) was determined by Western blot. RESULTS: Compared with NS group, the levels of Cr, BUN, MDA, TNF-α and IL-1β were obviously increased in HS/R group, which were obviously decreased in HS/R+D group (P<0.05). Compared with NS group, the SOD activity was obviously decreased in HS/R group, which was obviously increased in HS/R+D group (P<0.05). Compared with NS group, the protein expression of NF-κB was obviously increased in HS/R group, which was obviously decreased in HS/R+D group (P<0.05). Compared with NS group, the protein expression of HO-1 was increased in HS/R group. Compared with HS/R group, the protein expression of HO-1 was obviously increased in HS/R+D group. Compared with NS group, HS/R induced marked kidney histological injury, which was less pronounced in HS/R+D group.CONCLUSION: Dexmedetomidine effectively protects rats against AKI caused by HS/R, and its mechanism may be associated with the increase in HO-1 expression and the inhibition of NF-κB expression.     

Effect of intraoperative dexmedetomidine intervention on perioperative neurocognitive disorders in aged mice

AIM To investigate the effect of dexmedetomidine (DEX) on perioperative neurocognitive disorders (PND) in aged mice and its mechanism. METHODS The PND animal model was established by hepatic left lateral lobectomy in C57BL/6J aged mice, and the effects of intraoperative DEX intervention on postoperative cognitive behavior in aged mice were evaluated by Morris water maze and Y maze experiments. The effects of intraoperative DEX intervention on the changes of neurons in hippocampal CA1 region of aged mice were observed by Nissl staining and TUNEL staining. The effect of intraoperative DEX intervention on long-term potentiation in hippocampal CA1 region was recorded by patch-clamp technique. The effects of intraoperative DEX intervention on hippocampal astrocyte activation in aged mice were detected by immunofluorescence and immunohistochemistry. The effects of intraoperative DEX intervention on the protein levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and cleaved caspase-3 in hippocampal CA1 region of aged mice were determined by Western blot. RESULTS Intraoperative DEX intervention attenuated postoperative cognitive dysfunction in aged mice (P<0.01). Intraoperative DEX intervention significantly inhibited surgery-induced hippocampal neuron loss (P<0.01), reversed surgery-induced decrease in field excitatory postsynaptic potential amplitude, and reduced surgery-induced increases in the protein levels of TNF-α, IL-6 and cleaved caspase-3 in hippocampal CA1 region of aged mice (P<0.01). CONCLUSION Dexmedetomidine protects hippocampal neurons and improves postoperative cognitive function in aged mice by inhibiting hippocampal astrocyte activation and reducing neuronal inflammation and neuronal apoptosis.     

Dexmedetomidine and Bupivacaine Association in Caudal Epidural Injection in Mares

The objective of the study was to compare the effects of caudal epidural bupivacaine and dexmedetomidine (DEX) combination, with bupivacaine or DEX plain for perineal analgesia in mares. Six healthy saddle mares weighing 330–370 kg and aged 10–15 years were used in this study. Each mare was assigned to receive three treatments: 0.04 mg/kg 0.25% bupivacaine (BP), 2 μg/kg DEX (DX), or 0.02 mg/kg bupivacaine and 1 μg/kg DEX (BPDX). The order of treatments was randomized. All drugs were injected into the caudal epidural space (Co1-Co2) through a 16-G Tuohy epidural needle. After the epidural injections, heart rate, respiratory rate, arterial blood pressures (systolic, diastolic, and mean), and rectal temperature were measured at 5, 10, 15, 30, 60, 90, and 120 minutes, and after this time, every 60 minutes until the end of the experiments. A subjective score system was used to assess analgesia, behavioral and motor blockade at the same time points. The BPDX treatment produced analgesic action with twice the duration (200 minutes) of the BP treatment (97 minutes), but with an analgesic duration shorter than the DX treatment (240 minutes) in the regions of the tail, perineum, and upper hind limbs in mares. All treatments showed mild motor blockade. No behavioral changes were observed in any of the animals. There was hemodynamic stability without significant changes in respiratory rate for all treatments. Epidural analgesia using DEX alone or the combination of DEX and bupivacaine may be an option for painful obstetric and gynecological procedures in mares.