Anesthesiology
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Randomized Controlled Trial Comparative Study Clinical Trial
Rapid increase in desflurane concentration is associated with greater transient cardiovascular stimulation than with rapid increase in isoflurane concentration in humans.
Increases in desflurane and isoflurane concentrations can transiently increase arterial blood pressure or heart rate or both during induction of anesthesia. The current study tested the hypothesis that a rapid increase of desflurane concentration in humans increases sympathetic activity and hormonal variables and heart rate and arterial blood pressure more than does an equivalent increase in isoflurane concentration. ⋯ In healthy male volunteers, rapid increases of desflurane or isoflurane from 0.55 to 1.66 MAC increase sympathetic and renin-angiotensin system activity, and cause transient increases in arterial blood pressure and heart rate. Desflurane causes significantly greater increases than isoflurane, and also causes a transient increase in plasma AVP concentration. The temporal relationships suggest that the increased sympathetic activity increases mean arterial blood pressure and heart rate, with mean arterial blood pressure also increased by increased plasma AVP concentration, whereas the delayed, increased plasma renin activity is likely a response to the ensuing hypotension, or earlier inhibition by AVP, or both.
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Comparative Study
Irreversible conduction block in isolated nerve by high concentrations of local anesthetics.
Delivery of large doses of local anesthetics for spinal anesthesia by repeated injections or continuous infusion could expose the cauda equina to concentrations of drug that may be neurotoxic per se. We studied this possible neurotoxic effect by assessing recovery from conduction blockade of desheathed peripheral nerves after exposure to some of the local anesthetic solutions commonly used for spinal anesthesia. ⋯ Solutions of 5% lidocaine and 0.5% tetracaine that have been associated with clinical cases of cauda equina syndrome after continuous spinal anesthesia caused irreversible conduction block in desheathed amphibian nerve. Whether these in vitro actions also occur in mammalian nerves in vivo is an important, clinically relevant question now under investigation in our laboratory.
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Comparative Study
Spinal and systemic action of the alpha 2 receptor agonist dexmedetomidine in dogs. Antinociception and carbon dioxide response.
alpha 2 Agonists are powerful analgesics after spinal delivery. The current work characterizes the dose-dependent antinociception and effects upon respiratory function of dexmedetomidine after intrathecal, epidural, intravenous, and intracisternal delivery in chronically prepared dogs. ⋯ Dexmedetomidine, acting through an alpha 2-receptor, produces a powerful antinociceptive effect, mediated at the spinal level, while systemic redistribution of the drug leads to a hypnotic state with significant cardiorespiratory effects.
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Editorial Comment Review
Ventilation of the acute respiratory distress syndrome. Looking for Mr. Goodmode.
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Combinations of opioids and nonsteroidal antiinflammatory drugs (NSAIDs) are commonly used to control pain in the perioperative period, yet there are no quantitative evaluations of the interaction between opioids and nonsteroidal antiinflammatory drugs during visceral nociception. This study evaluated the interaction between morphine and ketorolac during visceral nociception in the rat. ⋯ Ketorolac is a powerful potentiator of morphine antinociception during visceral nociception in the rat. However, intravenous ketorolac alone did not demonstrate antinociceptive properties during colorectal distention, a model of acute visceral nociception without a major inflammatory component. These data suggest that ketorolac may have a central modulatory effect on opioid pharmacology and the synergistic effect may be separate from its peripheral antiinflammatory properties. This study encourages further basic as well as clinical evaluations of the improved antinociception provided by combination therapy of opioids and nonsteroidal antiinflammatory drugs.