Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2008
Comparative StudyThe effect of prolonged anesthesia with isoflurane, propofol, dexmedetomidine, or ketamine on neural cell proliferation in the adult rat.
Recent evidence indicates that new neurons are produced in the adult hippocampus, and play a functional role in cognitive processes such as learning and memory. In animals, new neuron production is suppressed by increasing age, gamma-aminobutyric acid receptor activity, reductions in basal forebrain activity and brain norepinephrine levels, and decreased environmental stimuli. Similarities between these effects and those of anesthetic administration suggest that anesthetics may modulate new cell production, and raise the possibility that postoperative cognitive dysfunction may result, in part, from anesthetic-induced suppression of adult neurogenesis. To test this hypothesis, we investigated the effects of prolonged anesthesia with four different anesthetics on hippocampal cell proliferation in young and older rats. ⋯ Despite using multiple, mechanistically distinct drugs, we found no effect of prolonged anesthesia on adult hippocampal cell proliferation in young rats, a slight suppressive effect of ketamine in older rats, and no circadian effect with isoflurane. These data indicate that anesthetics are unlikely to alter cell proliferation, and by extension that anesthetic-induced inhibition of cell proliferation is unlikely to play a major role in postoperative cognitive impairment. The contrast between our findings, current concepts of anesthetic action, and known modifiers of cell proliferation suggest an incomplete understanding of the pharmacological and behavioral factors governing new neuron production.
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Anesthesia and analgesia · Jun 2008
ReviewStrategies and experimental models for evaluating anesthetics: effects on the developing nervous system.
Advances in pediatric and obstetric surgery have resulted in an increase in the duration and complexity of procedures requiring anesthesia. It has been reported that anesthetic drugs cause widespread and dose-dependent apoptosis in the developing rat brain. The similarity of the physiology, pharmacology, metabolism, and reproductive systems of the nonhuman primate to that of the human, especially during pregnancy, make the monkey an exceptionally good animal model for assessing potential neurotoxic effects of anesthetics. ⋯ Although ketamine use in pediatric anesthesia is relatively limited, the findings of the studies are sufficiently strong to merit concern about the N-methyl-d-aspartate antagonist drugs as a class. Our focus on ketamine should not be construed as implying that the risk of neurodegeneration with ketamine is greater, or less, than with other anesthetics. We are simply describing the effects where we have the most preclinical data.
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Anesthesia and analgesia · Jun 2008
The effects of aromatic anesthetics on dorsal horn neuronal responses to noxious stimulation.
Gamma-aminobutyric acid type A receptor potentiation and/or N-methyl-d-aspartate (NMDA) receptor inhibition might explain the anesthetic properties of fluorinated aromatic compounds. We hypothesized that depression of dorsal horn neuronal responses to noxious stimulation would correlate with the magnitude of effect of benzene (BNZ), o-difluorobenzene, and hexafluorobenzene (HFB) on NMDA receptors. ⋯ The findings in intact rats suggest that NMDA blockade contributes to the depression of dorsal horn neurons to nociceptive stimulation by fluorinated aromatic anesthetics. These results, combined with the additional findings in decerebrate rats, suggest that supraspinal effects (perhaps on gamma-aminobutyric acid type A receptors) may have a supraspinal facilitatory effect on nociception for HFB.
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Anesthesia and analgesia · Jun 2008
Case ReportsDexmedetomidine sedation leading to refractory cardiogenic shock.
Dexmedetomidine is frequently used for deep sedation during electrophysiology procedures. We report a case where, presumably, the use of dexmedetomidine resulted in a patient's death. ⋯ We postulate that, in certain susceptible individuals, dexmedetomidine may lead to terminal complications. We therefore urge caution about using dexmedetomidine in the electrophysiology laboratory.
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Anesthesia and analgesia · Jun 2008
Expression of adenosine A 2A receptors in the rat lumbar spinal cord and implications in the modulation of N-methyl-d-aspartate receptor currents.
The presence of A(2A) receptors in the dorsal horn of the spinal cord remains controversial. At this level, activation of N-methyl-d-aspartate (NMDA) receptors induces wind-up, which is clinically expressed as hyperalgesia. Inhibition of NMDA receptor currents after activation of A(2A) receptors has been shown in rat neostriatal neurons. In this study, we sought to establish the presence of adenosine A(2A) receptors in the lamina II of the rat lumbar dorsal horn neurons and investigated whether the activation of A(2A) receptors is able to modulate NMDA receptor currents. ⋯ These results demonstrate the presence of A(2A) receptor on neurons from the substantia gelatinosa of the rat lumbar dorsal horn and the inhibition of NMDA-induced currents by the application of a selective A(2A) receptor agonist. Therefore, A(2A) receptor ligands could modulate pain processing at the spinal cord level.