Anesthesiology
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Randomized Controlled Trial Clinical Trial
Concentration-effect relations for intravenous lidocaine infusions in human volunteers: effects on acute sensory thresholds and capsaicin-evoked hyperpathia.
Preclinical studies have emphasized that persistent small afferent input will induce a state of central facilitation that can be regulated by systemically administered lidocaine. The authors extended these preclinical studies to human volunteers by examining the concentration-dependent effects of intravenous lidocaine on acute sensory thresholds and facilitated processing induced by intradermal capsaicin. ⋯ These studies suggest that the facilitated state induced by persistent small afferent input human pain models may predict the activity of agents that affect components of nociceptive processing that are different from those associated with the pain state evoked by "acute" thermal or mechanical stimuli. Such insight may be valuable in the efficient development of novel analgesics for both neuropathic and post-tissue-injury pain states.
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Randomized Controlled Trial Clinical Trial
Effects of concentration and volume of 2-chloroprocaine on epidural anesthesia in volunteers.
Effect of local anesthetic concentration and volume on the spread and density of epidural anesthesia is unclear. This study was performed to delineate effects of a threefold difference in concentration and volume of 2-chloroprocaine on epidural anesthesia. ⋯ Intensity of sensory and motor block from epidural anesthesia with 2-chloroprocaine appears to depend primarily on total milligram dose.
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Randomized Controlled Trial Clinical Trial
Hypoxic pulmonary vasoconstriction in nonventilated lung areas contributes to differences in hemodynamic and gas exchange responses to inhalation of nitric oxide.
Enhancement of hypoxic pulmonary vasoconstriction (HPV) in nonventilated lung areas by almitrine increases the respiratory response to inhaled nitric oxide (NO) in patients with acute respiratory distress syndrome (ARDS). Therefore the authors hypothesized that inhibition of HPV in nonventilated lung areas decreases the respiratory effects of NO. ⋯ In patients with ARDS, HPV in nonventilated lung areas modifies the hemodynamic and respiratory response to NO. The stronger the HPV in nonventilated lung areas the more pronounced is the NO-induced decrease in PAP-PAWP. In contrast, the NO-induced decrease in Q(S)/Q(T) is independent of PV(O2) over a wide range of PV(O2) levels. The effect of NO on the arterial oxygen tension varies with the level of PV(O2) by virtue of its location on the oxygen dissociation curve.
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Randomized Controlled Trial Clinical Trial
Alfentanil, but not amitriptyline, reduces pain, hyperalgesia, and allodynia from intradermal injection of capsaicin in humans.
Intradermal injection of capsaicin produces brief pain followed by hyperalgesia and allodynia in humans, and the latter effects are mediated by spinal N-methyl-D-aspartate mechanisms. Amitriptyline recently was shown to antagonize N-methyl-D-aspartate receptors, and in this study, the authors sought to determine the effect of amitriptyline alone and with the opioid alfentanil on hyperalgesia and allodynia produced by intradermal injection of capsaicin. ⋯ These data correspond with previous studies in volunteers demonstrating reduction in hyperalgesia and allodynia after intradermal injection of capsaicin by systemically administered opioids, and they suggest that this reduction may be secondary to reduced nociceptive input by acute analgesia. These data do not support the use of acute systemic administration of amitriptyline for acute pain, hyperalgesia, and allodynia, although the roles of chronic treatment and spinal administration are being investigated.
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Randomized Controlled Trial Comparative Study Clinical Trial
Xenon provides faster emergence from anesthesia than does nitrous oxide-sevoflurane or nitrous oxide-isoflurane.
Xenon, an inert gas with anesthetic properties (minimum alveolar concentration [MAC] = 71%), has an extremely low blood:gas partition coefficient (0.14). Therefore, we predicted that xenon would provide more rapid emergence from anesthesia than does N2O+isoflurane or N2O+sevoflurane of equivalent MAC. ⋯ Emergence from xenon anesthesia is two or three times faster than that from equal-MAC N2O+isoflurane or N2O+sevoflurane anesthesia.