Anesthesiology
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Comparative Study
Interaction of bupivacaine and tetracaine with the sarcoplasmic reticulum Ca2+ release channel of skeletal and cardiac muscles.
Although various local anesthetics can cause histologic damage to skeletal muscle when injected intramuscularly, bupivacaine appears to have an exceptionally high rate of myotoxicity. Research has suggested that an effect of bupivacaine on sarcoplasmic reticulum Ca2+ release is involved in its myotoxicity, but direct evidence is lacking. Furthermore, it is not known whether the toxicity depends on the unique chemical characteristics of bupivacaine and whether the toxicity is found only in skeletal muscle. ⋯ Bupivacaine's ability to enhance Ca2+ release channel-ryanodine receptor activity of skeletal muscle sarcoplasmic reticulum most likely contributes to the myotoxicity of this local anesthetic. Thus, the pronounced myotoxicity of bupivacaine may be the result of this specific effect on Ca2+ release channel-ryanodine receptor superimposed on a nonspecific action on lipid bilayers to increase the Ca2+ permeability of sarcoplasmic reticulum membranes, an effect shared by all local anesthetics. The specific action of tetracaine to inhibit Ca2+ release channel-ryanodine receptor activity may in part counterbalance the nonspecific action, resulting in moderate myotoxicity.
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Comparative Study
Mechanisms of bronchoprotection by anesthetic induction agents: propofol versus ketamine.
Propofol and ketamine have been purported to decrease bronchoconstriction during induction of anesthesia and intubation. Whether they act on airway smooth muscle or through neural reflexes has not been determined. We compared propofol and ketamine to attenuate the direct activation of airway smooth muscle by methacholine and limit neurally mediated bronchoconstriction (vagal nerve stimulation). ⋯ The local bronchoprotective effects of ketamine and propofol on airways is through neurally mediated mechanisms. Although the direct effects on airway smooth muscle occur at high concentrations, these are unlikely to be of primary clinical relevance.
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It is still unclear whether memory of intraoperative events results entirely from moments of inadequate anesthesia. The current study was designed to determine whether the probability of memory declines with increasing depth of the hypnotic state. ⋯ This study clearly indicates that memory is related to the depth of hypnosis. The observed memory performance should be interpreted in terms of implicit memory. Auditory information processing occurred at bispectral index levels between 60 and 40.
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Previous data have shown that postischemic brain hypothermia is protective. The authors evaluated the effect of postischemic spinal hypothermia on neurologic function and spinal histopathologic indices after aortic occlusion in the rat. ⋯ These findings indicate that the immediate period of reperfusion (0-15 min) represents a critical period that ultimately defines the degree of spinal neuronal degeneration. Hypothermia, when initiated during this period, showed significant protection, with the highest efficacy observed at 27 degrees C.
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Biography Historical Article
Vassily von Anrep, forgotten pioneer of regional anesthesia.