Anesthesiology
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Comparative Study
Effects of alpha(2)-adrenoceptor agonists on perinatal excitotoxic brain injury: comparison of clonidine and dexmedetomidine.
A growing number of children have severe neurologic impairment related to very premature birth. Experimental data suggest that overstimulation of cerebral N-methyl-d-aspartate (NMDA) receptors caused by excessive glutamate release may be involved in the genesis of perinatal hypoxic-ischemic brain injury. alpha(2)-Adrenoceptor agonists are protective in models of brain ischemia in adults. The authors sought to determine whether they prevent perinatal excitotoxic neuronal damage. ⋯ Clonidine and dexmedetomidine are potent neuroprotectors that act by stimulating the alpha(2) adrenoceptors. These results obtained in a murine model of perinatal excitotoxic injury may be relevant to some forms of neonatal brain damage in humans.
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The Bispectral Index (BIS) is an electroencephalogram-derived measure of anesthetic depth. A closed-loop anesthesia system was built using BIS as the control variable, a proportional-integral-differential control algorithm, and a propofol target-controlled infusion system as the control actuator. Closed-loop performance was assessed in 10 adult patients. ⋯ The system was able to provide clinically adequate anesthesia in 9 of 10 patients. Further studies are required to determine whether control performance can be improved by alterations to the gain factors or by using an effect site-targeted, target-controlled infusion propofol system.
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General anesthetics reduce neuronal death caused by focal cerebral ischemia in rodents and by in vitro ischemia in cultured neurons and brain slices. However, in intact animals, the protective effect may enhance neuronal survival for only several days after an ischemic injury, possibly because anesthetics prevent acute but not delayed cell death. To further understand the mechanisms and limitations of volatile anesthetic neuroprotection, the authors developed a rat hippocampal slice culture model of cerebral ischemia that permits assessment of death and survival of neurons for at least 2 weeks after simulated ischemia. ⋯ In an in vitro model of simulated ischemia, 1% isoflurane is of similar potency to 10 microm MK-801 in preventing delayed cell death. Modulation of glutamate excitotoxicity may contribute to the protective mechanism.
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Amitriptyline has been reported to be a more potent local anesthetic than bupivacaine. In keeping with the objective of identifying drugs for prolonged cutaneous analgesia, the authors compared the cutaneous analgesic effectiveness of amitriptyline and bupivacaine in rats. ⋯ Amitriptyline is a longer-acting local anesthetic compared with bupivacaine for cutaneous infiltration. Its analgesic effectiveness is significantly enhanced by epinephrine. Coinjection of amitriptyline and bupivacaine with epinephrine enhances the analgesic duration of both drugs.